Kathleen ; Blondeau

Veerle Mertens

Lieven Dupont

Ans Pauwels

Ricard Farre

Anne Malfroot

Elke De Wachter

Iris De Schutter

Bruno Hauser

Yvan Vandenplas

Kuleuven

Mertens

De Wachter

De Schutter

Daniel Sifrim
email: daniel.sifrim@med.kuleuven.be

The relationship between gastroesophageal reflux and cough in children with chronic unexplained cough using combined impedance-pH-manometry recordings

Keywords: Non-acid gastroesophageal reflux, chronic cough, impedance-pH, manometry Children, gastroesophageal reflux, impedance-pH-manometry, cough

à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

INTRODUCTION

Both cough and gastroesophageal reflux (GER) in infants and children are common reasons for parents to seek medical attention. [START_REF] Bailey | Clinical pathways for chronic cough in children[END_REF] Although GER has been recognized as a cause for unexplained cough, diagnosing GER related cough in children is still challenging. The presence of symptoms suggestive for GER disease, e.g. regurgitation, vomiting, failure to thrive, is often a first indication [START_REF] Hassall | Decisions in diagnosing and managing chronic gastroesophageal reflux disease in children[END_REF] , but the absence of these symptoms cannot exclude GER as an underlying cause of the chronic cough.

Several diagnostic techniques, including proximal pH recording and detection of lipid laden macrophages in the Broncho-Alveolar Lavage Fluid (BALF) have been used for the diagnosis of proximal reflux and aspiration of gastric contents into the lungs. [START_REF] Conley | Proximal pH-metry for diagnosis of upper airway complications of gastroesophageal reflux[END_REF][START_REF] Koksal | Lipid-laden alveolar macrophage index in sputum is not useful in the differential diagnosis of pulmonary symptoms secondary to gastroesophageal reflux[END_REF][START_REF] Krishnan | Fat laden macrophages in tracheal aspirates as a marker of reflux aspiration: a negative report[END_REF] However, proximal reflux is not required as the presence of gastric contents in the distal esophagus might induce a vagal reflex leading to cough. 6;7 Ambulatory esophageal pH-metry has long been considered an important tool for the detection of acid reflux. More recently, combined esophageal impedance-pH recordings have shown that not only acid but also non-acid reflux might be associated with respiratory symptoms such as cough. [START_REF] Blondeau | Improved diagnosis of gastrooesophageal reflux in patients with unexplained chronic cough[END_REF][START_REF] Blondeau | Gastro-oesophageal reflux and aspiration of gastric contents in adult patients with cystic fibrosis[END_REF][START_REF] Rosen | The importance of multichannel intraluminal impedance in the evaluation of children with persistent respiratory symptoms[END_REF][START_REF] Thilmany | Acid and non-acid gastro-esophageal refluxes in children with chronic pulmonary diseases[END_REF][START_REF] Wenzl | Association of apnea and nonacid gastroesophageal reflux in infants: Investigations with the intraluminal impedance technique[END_REF] Symptom association analysis requires an accurate registration of symptoms, which previously has been performed using an event marker. 10;13 . Since in children symptom recording is mostly controlled by the parents, the use of an event marker may imply that the timing of registration might be delayed compared to the actual occurrence of the symptom and that symptoms might be missed. Moreover, especially in patients with cough, an accurate timing of symptom recording is important since reflux may not only induce cough, but cough might also induce reflux. 6;14 To which extent the latter is important in children with chronic cough remains unknown. Ambulatory 24 hours esophageal manometry has been proven a useful tool for objective recognition of cough in patients undergoing 24 hours reflux testing and for establishing the exact time relationship between reflux and cough events. 8;15;16 .

The aim of the current study was therefore to use combined ambulatory 24 hours impedance-pH-manometry recordings to study acid and non-acid GER and its relationship to cough in children with chronic unexplained cough.

METHODS

Subjects

Simultaneous 24 hours ambulatory esophageal manometric-impedance-pH monitoring was performed in 26 children with chronic unexplained cough (12 boys; median age 4 years, range 1-10.5 years). The patients were recruited at the outpatient clinic of the Universitair Ziekenhuis Brussel, and presented daily cough of unclear etiology for at least 8 weeks. Those with an alternative diagnosis, such as clinical suspected asthma responding to a treatment trial during at least 4 weeks, underlying ENT problems or upper airway cough syndrome, pertussis, cystic fibrosis, tuberculosis, cardiac disease, chromosomal or humoral immunological deficiency were excluded from the study after workup as listed in Table1. [START_REF] Merchant | Evaluation and Outcome of Young Children With Chronic Cough[END_REF] None of the children received acid suppressing therapy. The study was approved by the local ethical committee. Informed consent was given prior to inclusion.

Recording equipment and technique

Cough and GER were monitored simultaneously using an ambulatory manometricimpedance-pH system. Manometry was used for accurate cough recognition whereas impedance-pH monitoring allowed detection of acid, weakly acidic and weakly alkaline reflux.

A manometric catheter with 2 solid-state pressure sensors (15 cm apart) (Sandhill Scientific, Inc; Highlands Ranch, CO, USA) (1.3 mm external diameter) was passed transnasally. The catheter was positioned so that one pressure channel was located in the esophageal body and the other in the stomach. Esophageal impedance-pH was recorded with a 2.1mm diameter catheter that comprised six electrode pairs to measure intraluminal impedance and 2 antimony pH sensors (Sandhill Scientific, Inc; Highlands Ranch, CO, USA). Two different types of age appropriate catheters were used: infant (< 75 cm of height) and pediatric (> 75 cm of height).The impedance-pH and manometric

Study protocol

The study was performed after an overnight fast. The catheters were passed transnasally and positioned to record pressures and pH in the stomach and pressure pH and impedance in the esophageal body. Impedance-pH catheter was positioned so that the esophageal pH sensor was at the third vertebral body above the diaphragmatic angle.

The patients were encouraged to maintain normal activities, sleep schedule, and eat their usual meals at their normal times. Event markers on the data logger recorded meal times and posture changes. Between meals, patients abstained from snacks and beverages with a pH< 5. Before the study, parents were instructed to keep a careful diary and trained to use a dedicated event marker in the data logger, to record cough episodes and other events.

Data analysis

The manometric-impedance-pH recordings were uploaded into a personal computer and were manually analysed using dedicated software (Bioview, Sandhill Scientific, USA ).

Cough detection

The manometric tracing was independently analysed for cough episodes. Cough was defined according to Paterson et al. as phasic, short duration, rapid pressure rises (time to peak <1sec) occurring simultaneously and with the same pressure configuration at both manometric recording sites. [START_REF] Paterson | Combined ambulatory esophageal manometry and dualprobe pH-metry in evaluation of patients with chronic unexplained cough[END_REF] A "cough burst" was defined as two or more rapid simultaneous pressure peaks within 3 seconds. Only "cough bursts" were considered in the further analysis. The cough events marked in the data logger and diary information were used for comparison with objective detection of cough bursts by manometry.

Reflux detection

The impedance-pH recording was analysed for GER, independently of the pressure recordings. The impedance recording was analysed using criteria described in a recent consensus report on detection and definitions of acid, non-acid, and gas reflux. [START_REF] Sifrim | Gastro-oesophageal reflux monitoring: review and consensus report on detection and definitions of acid, non-acid, and gas reflux[END_REF] GER was defined as a sequential orally progressing drop in impedance to less than 50 % of the baseline values starting at the most distal channel and propagating retrograde to at least the next more proximal measuring segment. According to the corresponding pH change, impedance-detected reflux was classified as acid if pH fell below 4 for at least 4 seconds, if pH was already below 4, as a decrease of at least 1 pH unit sustained for more than 4 seconds. Weakly acidic reflux was defined as a pH drop of at least 1 pH unit sustained for more than 4 seconds with the basal pH remaining between 7 and 4. Reflux was judged to be weakly alkaline when there was impedance evidence of reflux but the pH did not drop below 7.

Acid only events were defined as a drop in the esophageal pH below 4 for at least 4 sec without a characteristic reflux pattern in the impedance tracing.

For each reflux episode determined by pH-impedance, the associated gas-liquid pattern was classified as: (i) mixed reflux of liquid and gas or (ii) liquid reflux. Only gas reflux episodes (belches) were not included in the analysis. The proximal extent of each reflux event was evaluated from the impedance tracings. For each patient, the total number of reflux events (acid, weakly acidic and weakly alkaline), the number of episodes reaching the proximal esophagus (nr of episodes reaching impedance channel 1) and the exposure of the esophageal body to acid and volume were calculated.

Total 24 hours acid exposure was calculated as the percentage of time that the esophageal pH was below 4 and was considered increased if > 6% of the total recording time. [START_REF] Rudolph | Guidelines for evaluation and treatment of gastroesophageal reflux in infants and children: recommendations of the North American Society for Pediatric Gastroenterology and Nutrition[END_REF] This parameter included all pH drops either related or not related to bolus reflux.

For each reflux episode detected by impedance, volume exposure in impedance channel 5, was calculated as the time (sec) between the 50% drop in impedance until the 50% recovery of the impedance baseline. Total volume exposure/24 hours was obtained by addition of the volume exposures of all individual reflux events.

Association reflux-cough

A 2 minute time interval following the start of a reflux episode was used to delimitate the time window for reflux-cough association. A 2 minute period was chosen based on previous analysis of acid reflux-chest pain association. [START_REF] Lam | What is the optimal time window in symptom analysis of 24-hour esophageal pressure and pH data?[END_REF] Thus, if a cough episode occurred in the 2 minute time period after the start of a reflux event, cough was considered "associated to reflux". (Figure 1) If cough fell outside the 2 minutes time window after reflux, it was considered to have occurred "independent" of reflux. We calculated for each patient the symptom association probability (SAP) between cough and different types of reflux (acid and weakly acidic). (software Dr Tutuian) The entire recording was subdivided into consecutive 2 minute time intervals. Each time interval was evaluated for the presence of reflux. When reflux was detected at any point during the 2 minute period, the period was considered positive for reflux (R+). In a second step, the 2 minute periods containing a reflux episode followed by cough (R+S+), those with only cough but no reflux (R-S+) and those with neither cough nor reflux (R-S-) were counted. A contingency table was constructed containing the number of the four different types of 2 minute periods. Fisher's exact test was used to calculate the probability (P value) that the observed association between reflux and cough occurred by chance. The SAP was calculated as (1.0-p)*100%. SAP values greater than 95% were considered statistically significant. 21;22 Association cough-reflux Cough episodes preceding a reflux event were evaluated separately.

A reflux event was considered "induced by" cough if cough occurred in the 30 seconds preceding reflux. [START_REF] Paterson | Combined ambulatory esophageal manometry and dualprobe pH-metry in evaluation of patients with chronic unexplained cough[END_REF] (Figure 2) The total esophageal acid and volume exposures due to cough were calculated by adding the acid and volume exposures (sec) at 5 cm above the LES from the individual reflux events "induced by" cough, divided by the total recording time.

Statistical analysis

Data are presented as median (range) unless otherwise stated. If data were normally distributed the paired Student's t test was used for comparison. If data were not normally distributed a non-parametric Mann-Whitney test was applied. Fisher's exact test was used to calculate SAP. Statistical significance was accepted when p<0.05.

RESULTS

Gastroesophageal reflux

4 patients had symptoms suggesting GER. Two children had heartburn and/or regurgitation, 1 had abdominal pain and 1 child had frequent vomiting.

Impedance recordings detected 967 reflux events. From the total amount of reflux detected, 55.2% was acid, 41.5% was weakly acidic and 3.3% was weakly alkaline.

Overall, 32% of the reflux episodes were mixed (liquid+gas) and 68% were liquid. Of all reflux events detected by impedance, 26% reached the proximal esophagus. Reflux characteristics are displayed in table 2.

In addition to the reflux events detected by impedance, 59 acid only events were identified [1(0-21)/patient]. From the total esophageal acid exposure 6.0(2.4-62.3)% was due to acid only events. Overall, 3/26 children had an increased esophageal acid exposure. None of these children had symptoms suggesting GER. There was a significant correlation between age and the nocturnal esophageal acid exposure (r=0.77, p<0.0001), total number of reflux events (r=0.77, p<0.0001), number of acid reflux events (r=0.74, p<0.0001) and the esophageal volume exposure (r=0.79, p<0.0001).

Cough

Gastroesophageal manometry detected 47 (5-203) There was a significant correlation between the number of coughs recorded by manometry and the number of event markers (r=0.73, p=0.001). In 9 children no cough markers were recorded. (Table 3)

F o r P e e r R e v i e

w

From the 464 cough markers recorded, 388 (84%) corresponded to a cough burst identified by manometry. The event marker was pressed, 19(5-92) seconds after the start of the actual cough burst.

From the 78 event markers that did not correspond to a cough burst identified by manometry, 65 occurred in the same child. These 65 cough markers corresponded to single pressure spikes, probably representing single cough episodes.

There was no correlation between age and the number of coughs detected either by manometry or indicated by the event marker.

Gastroesophageal reflux and cough

There was no correlation between any of the reflux parameters (acid exposure, volume exposure, number of reflux events and number of proximal reflux events) and the number of coughs.

Reflux-cough

From the 1404 cough bursts detected by manometry, 140 were preceded by impedance reflux (58 acid, 77 weakly acidic and 5 weakly alkaline reflux). Only 5 cough bursts were preceded by an "acid only" event.

Ten patients had a positive SAP for reflux-cough, of which 1 exclusively for acid reflux, 6 exclusively for weakly acidic and 3 patients for both acid and weakly acidic reflux.

One of the 10 patients with a +SAP had an increased esophageal acid exposure. (Figure 3) One of the patients with a +SAP (acid reflux) had symptoms suggesting reflux (abdominal pain).

Patients with a +SAP were significantly older than patients with a -SAP [Mean 5.9± SD exposure, number of reflux events and proximal extent of reflux) and the number of cough bursts were similar in patients with and without a +SAP.

Six out of the 10 patients with a +SAP using objective cough detection had a +SAP using the event marker for cough recognition operated by the parents. In contrast to the SAP based on the manometric recordings, 4 of these patients had a +SAP for acid reflux and only 2 patients for weakly acidic reflux. One patient had a +SAP using the cough event marker but a -SAP using manometry. (table 3)

Cough-reflux

Cough-reflux sequences were found in 18/26 patients [3(0-7)/patient]. From the reflux events "induced by" cough, 43% were acid, 41% weakly acidic, 4.5% weakly alkaline and 11.5% were acid only events. From the total esophageal acid 9.6% (0.4-31.8%) and bolus exposure 2.1% (0.0-28.0%) was secondary to cough.

The majority of cough-reflux events occurred during the upright period, whereas 24% occurred during a recumbent period. Thirty six percent of the cough-reflux events occurred in the first hour after the meal.

DISCUSSION

GER is recognized as an important cause of respiratory symptoms in children, including chronic cough. [START_REF] Tolia | Systematic review: the extra-oesophageal symptoms of gastro-oesophageal reflux disease in children[END_REF] Reflux-symptom association during 24 hours reflux recording is an important tool for the diagnosis of GER related cough. However, in children when symptom registration is performed by the parents, the use of an event marker for cough registration might lack accuracy and the reflux-cough relationship might be misinterpreted.

The aim of the current study was to study reflux and its relationship to cough using objective techniques for both reflux (impedance-pH recording) and cough (gastroesophageal manometry) detection.

Our main findings were the following: 1) Independent of an increased esophageal acid exposure, a group of children had a statistical and clinical significant association between reflux and cough. 2) Acid reflux may precede cough. However, more frequently cough was preceded by weakly acidic reflux. Weakly alkaline reflux is rare and is unlikely to precede cough. 3) Acid only events are present in children with chronic unexplained cough and contribute to the total esophageal acid exposure. However, they were not associated with cough 4) An objective technique for cough recording is important to identify the correct time relationship between reflux and cough events. 5) Cough does not provoke reflux in children with chronic unexplained cough.

Both in adults and in children, GER has been implicated in the pathophysiology of a wide variety of respiratory symptoms and diseases including chronic unexplained cough. 1;8;10- 12;23-25 Ambulatory 24 hours esophageal pH recording has demonstrated an increased acid exposure in a subgroup of children with respiratory symptoms such as cough 10;11;23 . However, 24 hours pH-metry is limited to the detection of acid reflux. In conditions during which the gastric contents is neutralized, e.g. in the postprandial period, reflux events of non-acid pH may be missed. Esophageal impedance recording allows detection all types of reflux, independent of the pH. Combining impedance with pH recording allows to classify reflux events based on their pH. 18;26 The role of non-acid reflux in children with respiratory complications remains unclear. [START_REF] Tolia | Systematic review: the extra-oesophageal symptoms of gastro-oesophageal reflux disease in children[END_REF] Rosen et al. previously studied acid and non-acid reflux using combined impedance pH recording in a group of children with persistent respiratory symptoms "on" PPI therapy. In patients studied during PPI treatment, 50% of the reflux events detected by pHimpedance recordings were non-acidic [START_REF] Rosen | The importance of multichannel intraluminal impedance in the evaluation of children with persistent respiratory symptoms[END_REF] . Thilmany et al. performed a similar study in children "off" PPI therapy. They found that from the total amount of reflux detected, only 5.1% was non-acidic. [START_REF] Thilmany | Acid and non-acid gastro-esophageal refluxes in children with chronic pulmonary diseases[END_REF] In contrast to these findings we found that 44.8% of all reflux episodes was non-acidic. The reason for this large difference in prevalence of non-acid reflux remains uncertain. However, whereas our study included only children with chronic cough of unknown origin, the study of Thilmany et al included patients with different respiratory diseases including patients with cystic fibrosis. [START_REF] Thilmany | Acid and non-acid gastro-esophageal refluxes in children with chronic pulmonary diseases[END_REF] The high prevalence of especially acid reflux in this population together with inclusion of other respiratory pathologies might be related to the higher proportion of acid reflux.

In the current study non-acidic reflux was sub classified into weakly acidic (pH 4-7) and weakly alkaline (pH≥7). Our results showed that as in adults with chronic cough, weakly alkaline is rare and the majority of non-acidic events has a weakly acidic pH. 8;16 .

An absence of increased reflux does not exclude an association between reflux and symptoms. Moreover, since in children normal values for impedance-pH recording are lacking, it is impossible to judge whether non-acid reflux is increased. Simultaneous symptom and reflux recording allows to determine the time association between individual reflux and cough events and to identify whether a cough is preceded, followed by or not-associated with reflux.

Thilmany et al. previously studied the time association, using a 2 min time interval, between reflux events and episodes of oxygen desaturation. They found that overall 37.7% of all desaturation episodes were preceded by a reflux event of which the majority (92%) were acid. [START_REF] Thilmany | Acid and non-acid gastro-esophageal refluxes in children with chronic pulmonary diseases[END_REF] Rosen et al. also studied the time association between reflux and a variety of respiratory symptoms including a subgroup of children with chronic cough. They used combined impedance-pH recording, a patient diary for cough registration and a 2 minute time window for reflux-cough association. They found that overall, 37.6% of the cough events recorded were associated with reflux. Per patient analysis showed a significant association between reflux and cough in 33.3% of patients using combined impedance-pH analysis and in 5.6% of patients using only pH probe analysis. [START_REF] Rosen | The importance of multichannel intraluminal impedance in the evaluation of children with persistent respiratory symptoms[END_REF] The use of an event marker for cough registration has a major limitation since the accuracy of this method depends largely on the patient's cooperation. This may even be Symptoms episodes may be missed (e.g. during sleep) or may be recorded later than they actually occurred. The use of an objective technique for cough recording may overcome this limitation. Gastroesophageal pressure recording has been demonstrated as a useful tool for objective cough registration and has been previously used by our group and others to study the time relationship between reflux and cough events in adult patients with chronic cough. 8;15;16 In the current study we demonstrated in children with chronic cough that, as in adult patients, the use an objective technique for cough detection significantly increased the number of coughs recorded compared to the use of an event marker. The mean delay between the cough bursts and the event marker was approximately 20 seconds.

Overall 84% of the event markers corresponded to a manometric cough bursts. Although 78/464 event markers did not correspond to a typical cough bursts, 65 of these were recorded in a single patient. All of the 65 markers corresponded to a single pressure spike in manometry. Since single spikes in manometry cannot be distinguished from phenomena such as sneezing, they were included in the analysis. Nevertheless, these single coughs were associated with event markers in only one child, suggesting that their clinical importance might be limited.

The most important aim of the current study was to evaluate the exact time relationship between reflux and cough events using objective techniques for both reflux and cough recordings. First of all we confirmed that not only acid but also weakly acidic reflux may precede cough. We remind that Rosen et al previously reported similar findings, but their study was performed in patients "on" PPI treatment and without the use of objective cough detection. [START_REF] Rosen | The importance of multichannel intraluminal impedance in the evaluation of children with persistent respiratory symptoms[END_REF] Our study showed for the first time, using an objective technique for cough recording that weakly acidic reflux may "induce" cough in children "off" PPI. A significant association between reflux and cough (+SAP) was found in 10/26 (38%) of the children, which is comparable what has been previously reported for other respiratory symptoms. Remarkable is that only 1 child had a +SAP for acid reflux, whereas all other patients had a +SAP for weakly acidic reflux either alone or in combination with acid. This finding is in line with previous observations describing that the presence of non-acid reflux was associated with an increase in reflux-symptom association. [START_REF] Rosen | The importance of multichannel intraluminal impedance in the evaluation of children with persistent respiratory symptoms[END_REF] Weakly alkaline reflux was rare and hardly ever preceded a cough event.

The reason why weakly acidic reflux is more likely to be associated with cough might be Six out of the ten patients with a positive SAP for reflux-cough using manometry were also identified as SAP+ using the event marker. Interestingly, using the event marker most of these patients had an association between acid reflux and cough whereas with the manometry, cough was associated with weakly acidic reflux. The reason for this difference is unclear. Possibly acid reflux is more clearly perceived by the child and may lead to a change in behaviour (e.g. crying). This in term might make the parents more aware of the symptom and may stimulate them of pressing the event marker.

One child had a +SAP using the event marker but a -SAP using manometry, this was the child with the multiple single coughs.

Although impedance recording provides a high sensitivity of reflux detection, pH drops may occur without the typical reflux impedance pattern. These "acid only" events are found to be common, particularly in young children. In contrast to previous studies which reported a very high prevalence of acid only events, their prevalence in the current study was much lower. [START_REF] Rosen | The importance of multichannel intraluminal impedance in the evaluation of children with persistent respiratory symptoms[END_REF][START_REF] Thilmany | Acid and non-acid gastro-esophageal refluxes in children with chronic pulmonary diseases[END_REF][START_REF] Wenzl | Association of apnea and nonacid gastroesophageal reflux in infants: Investigations with the intraluminal impedance technique[END_REF] Moreover, although acid only events may contribute to the total esophageal acid exposure, our study showed that only 4/59 acid only events preceded cough, suggesting that they do not contribute to the reflux-cough relationship.

The relationship between reflux and cough is complex, since reflux may not only induce cough but it has been suggested that cough, by increasing the abdomino-thoracic pressure gradient, can also provoke reflux. Whether and to what extent, cough provokes reflux in children is unknown. Our study is the first to report that cough is not an important cause of reflux in children with chronic unexplained cough, since only a very small proportion of the total esophageal acid and volume exposure were secondary to cough, confirming our findings in adult patients. The current study has some limitations, including the small number of children studied.

Our study focussed primarily on children with unexplained chronic cough without clear signs of excessive reflux. In children with severe reflux, the objective relationship between reflux and cough will need to be investigated.

In order to have an optimal detection of cough, a thin catheter crossing the LES was used to record both abdominal and thoracic pressures. Although the overall prevalence of reflux in the current study was low, previous studies have reported that a catheter crossing the LES might slightly enhance reflux in children and this effect cannot be excluded from our study. [START_REF] Rudolph | Guidelines for evaluation and treatment of gastroesophageal reflux in infants and children: Recommendations of the North American Society for pediatric gastroenterology and Nutrition[END_REF] Previous studies have shown a suboptimal reproducibility of reflux measurements using 24hrs pH-recordings. Hence, it is likely that the reflux-cough association as assessed in the current study is subject to a day-to-day variability. [START_REF] Mahajan | Reproducibility of 24houur intraesophageal pH monitoring in pediatric patients[END_REF] Although we could establish the objective relationship between reflux and cough in this group of children with chronic unexplained cough, intervention studies will need to confirm the clinical relevance of this reflux-cough association in these patients.

In summary we can conclude that using objective techniques for reflux and cough detection, results in the observation that reflux may precede cough in a subgroup of children with chronic unexplained cough. Although acid reflux may precede cough, in most children cough was preceded by weakly acidic reflux. Weakly alkaline and acid only events are not important for the reflux-cough relationship. The use of an objective technique for cough detection increases the prevalence and accuracy of cough registration and may improve symptom association analysis. In contrast to what is often suggested, cough does not provoke a significant amount of reflux in children with chronic cough.

These findings may have important diagnostic and therapeutic implications for patients with reflux related respiratory problems. First of all our results suggested that combined impedance-pH testing is superior to pH testing alone. Secondly, other treatment strategies might need to be considered to treat patients with reflux related cough. In most of these patients reflux is treated with anti-acid medications, which insufficiently reduce weakly acidic reflux. [START_REF] Tutuian | Nonacid reflux in patients with chronic cough on acid-suppressive therapy[END_REF] Anti-reflux treatments affecting all types of reflux may need to be considered. However, so far pharmacological options are limited to baclofen, Impedance shows a retrograde flow of liquid up to channel 1, with the esophageal pH remaining above 4 (weakly acidic reflux). 45 seconds after the reflux, event, the manometry shows a cough burst, characterized by a rapid increase in pressure.

  to a single ambulatory device containing their respective amplifiers (Sleuth, Sandhill Scientific, Inc; Highlands Ranch, CO, USA). The impedance amplifier delivered ultra-low current in a range of 1-2 KHz with resulting current flow variations in response to intraluminal impedance changes. The impedance, pH and manometric signals were digitized at 50Hz and stored in the data logger. Before the start of the recording, the pH electrodes were calibrated using pH 4.0 and pH 7.0 buffer solutions.

  cough bursts/patient, of which 4(0-65) occurred during the night. Overall 464 cough markers were recorded in 17/26 children [8(0-75) markers/child].

3. 3

 3 vs. Mean 3.6± SD 1.7 years, p=0.03]. All reflux parameters (acid exposure, volume

  in children where symptom registration is performed by the parents.

  different composition of the weakly acidic refluxate. The presence of specific chemical components (e.g. unconjugated bile acids) or an increased volume of the refluxate might promote stimulation of the vagal reflex associated with the reflux-cough pathway or might be more harmful when aspirated into the lungs.

8

 8

  agonist reducing the number of transient relaxations of the lower esophageal sphincter (LES).[30][31][32] In some patients anti-reflux surgery may be considered. Intervention studies will need to confirm the clinical relevance of weakly acidic reflux in children with unexplained chronic cough. GH, Sifrim D, Lerut T, Janssens J, Tack J. Effect of the GABA(B) agonist baclofen in patients with symptoms and duodeno-gastro-oesophageal reflux refractory to proton pump inhibitors. Gut 2003 Oct;52(10):1397-402. 31. Lidums I, Lehmann A, Checklin H, Dent J, Holloway RH. Control of transient lower esophageal sphincter relaxations and reflux by the GABA(B) agonist baclofen in normal subjects. Gastroenterology 2000 Jan;118(1):7-13. 32. Sifrim D, Tack J, Arts J, Caenepeel P, Zhang X, Silny J, et al. Baclofen reduces weakly acidic reflux in ambulant patients with GERD. Gastroenterology 2005 Apr;128(4):A531. .

Figure 1 :

 1 Figure 1: Example of cough "induced" by weakly acidic reflux.

Figure 2 :

 2 Figure 2: Example of cough provoking reflux. The manometry tracing shows a cough burst, immediately followed by a retrograde flow of liquid in the impedance tracing. During reflux, the esophageal pH drops below 4 (acid reflux). * acid exposure provoked by coughing (13 sec). ** volume exposure provoked by coughing (9 sec).

Figure 3 :-

 3 Figure 3: Flow chart displaying the different subgroups of patients identified by the study. From the patients without increased esophageal acid exposure, we identified a subgroup (n=9) that had a +SAP for reflux-cough.

  Figure 2 150x172mm (96 x 96 DPI)

Table 1 :

 1 Work-up performed in all patients before the impedance-pH recording. Work-up showed no underlying etiological diagnosis for chronic cough, or in case of clinical suspected asthmatic cough, there was no response to a correct treatment trial of at least 4 weeks.

Table 2 :

 2 Reflux characteristics in children with chronic unexplained cough during the total study period and in the recumbent position.Results are expressed as median (range).

	Page 24 of 28

Table 3 :

 3 Comparison of cough events indicated in the patient diary and objectively recorded with gastroesophageal manometry

	Page 25 of 28

John Wiley & Sons, Inc.

John Wiley & Sons, Inc.Pediatric Pulmonology

John Wiley & Sons, Inc.

Pediatric Pulmonology


Marieke G Peetsold

Hugo Heij

Ad F Nagelkerke

Jacqueline A Deurloo

Reinoud Gemke
email: rjbj.gemke@vumc.nl

Gastro-Esophageal For

Disease Reflux

Prof. dr R J B J Gemke

PULMONARY FUNCTION IMPAIRMENT AFTER TRACHEA-ESOPHAGEAL FISTULA: A MINOR ROLE FOR GASTRO-ESOPHAGEAL REFLUX DISEASE

Keywords: trachea-esophageal fistula, gastro-esophageal reflux disease, pulmonary function, thoracoscopic repair esophageal atresia, gastroesophageal reflux disease, pulmonary function, thoracoscopic repair esophageal atresia, gastroesophageal reflux disease, pulmonary function, thoracoscopic repair

published or not. The documents may come

INTRODUCTION

Trachea-esophageal fistula (TEF) is a congenital anomaly affecting 1 in 2400 to 4500 newborns. (1;2) The most common variant is esophageal atresia (EA) with a distal fistula (type C). Other types are isolated EA without a fistula (type A) and EA with a proximal fistula (type B).(3) Many patients with TEF have associated congenital malformations. Since the first successful primary repair in 1941 by Haight and Towsley, there has been a dramatic improvement of survival,(4) due to improved neonatal care, which has resulted in an increased awareness of long term complications of TEF.

Many TEF patients experience respiratory problems due to recurrent pneumonia, EA associated tracheomalacia (TM) and gastro-esophageal reflux disease (GERD).( 5) Pulmonary function studies have shown obstructive impairment in 10-70% of the patients (6-9), while 18-36% had restrictive impairment. (7;8) It has been suggested that prolonged micro-aspiration of gastric contents in the first years of life may cause chronic pulmonary inflammation and fibrosis. (7) Surgical complications such as pleural scarring from empyema after anastomotic rupture and multiple thoracotomies may lead to restrictive lung disease. (7) Data concerning maximal exercise capacity in TEF patients are lacking. Only one study including 8 TEF patients has been published, in which a reduced level of physical fitness, expressed in exercise duration and V'O 2 max, was found. (10) TEF patients with a history of GERD were more likely to have pulmonary function abnormalities and many authors have suggested that GERD in the first years after TEF repair may play a major role in TEF-associated pulmonary pathology. (7;8;11-13) The purpose of this study was to assess the influence of GERD on pulmonary function and exercise capacity in a group of patients aged 8-18 years, who had undergone neonatal surgical repair of TEF. We categorized TEF in two groups: those who had undergone anti-reflux surgery (and consequently were considered to have had severe GERD (s-GERD)) and those who had not (considering to have had mild GERD). In order to examine the effect of TEF and its surgical treatment on cardiopulmonary function we compared these two groups to a control group consisting of otherwise healthy patients who had undergone an antireflux procedure because of isolated s-GERD. We hypothesized that pulmonary function of TEF patients with s-GERD is comparable to control patients with s-GERD who did not have TEF. TEF patients without s-GERD were expected to have better lung function than TEF patients with s-GERD.

METHODS

Patients

All patients born with TEF who underwent thoracotomy at the Pediatric Surgical Centre of Amsterdam between 1988 and 1997 were considered eligible, if their age was over 8 year at the time of the study, i.e. the minimum needed to adequately perform lung function tests and CPET. TEF patients were divided in 2 groups: TEF patients who had s-GERD requiring antireflux surgery (group TEF+GERD), and TEF patients who had not undergone antireflux surgery (group TEF-GERD.

The control group consisted of patients, born between 1988 and 1997, without TEF but with isolated s-GERD requiring antireflux surgery. All children underwent a Boerema anterior gastropexy, which was the standard antireflux procedure at that time. The following exclusion criteria were used: incapable of following instructions, physically not able to perform the tests, (partial) pneumonectomy, severe non-TEF related disease (e.g. bronchopulmonary dysplasia, cystic fibrosis etc), cardiac surgery, chromosomal anomaly, prematurity (≤ 34 weeks).

Indications for antireflux surgery were based on clinical findings in combination with results of diagnostic studies (upper gastrointestinal series, pH-studies and/or endoscopy). The patient's history was reviewed with specific attention to birth weight, gestational age, type of atresia, associated malformations, length of stay in the hospital (LOS), duration of ventilation, (GERD) and surgical complications including pleural injury (as reported by the surgeon in the operative report) . The local Ethics Committee approved the study protocol. Written informed consent was obtained from each patient and their parent(s) prior to participation.

Study design

Patients who provided informed consent, then received a detailed medical history including information concerning respiratory complaints and physical performance was obtained.

Pulmonary function testing included spirometry, lung volume measurements and measurement of diffusion capacity followed by cardiopulmonary exercise testing (CPET). All measurements were performed by experienced respiratory lab technicians according to the guidelines of the European Respiratory Society.( 14)

Pulmonary function

Subjects performed standard spirometry and lung volume measurements.( 14) All medication was discontinued 24 hours prior to testing. Forced expiratory volume (FEV 1 ), forced vital capacity (FVC), maximum midexpiratory flow (MMEF) and peak expiratory flow (PEF) were determined from the largest of three reproducible manoeuvres using a mass flow sensor (Vmax 229, Sensormedics, Yorba Linda, CA, USA). Spirometry was repeated after inhalation of 4x100 μg of salbutamol dose aerosol by metered dose inhaler to evaluate reversibility of potential bronchial obstruction and in order to prevent exercise-induced bronchoconstriction. A change of the FEV 1 ≥ 12%, expressed as percentage of the predicted value, was considered as a significant response. (14) Lung volume measurements were carried out after bronchodilation. Functional residual capacity (FRC), total lung capacity (TLC) and residual volume (RV) were determined by whole body plethysmography. The mean of three reproducible manoeuvres was used for analysis.

Diffusion capacity for carbon monoxide (DL,CO ) was measured by the single breath method using a multigasanalazyer (Sensor Medics) in combination with the mass flow sensor (Vmax 229, Results of the spirometry and the lung volume measurements were expressed as z-scores calculated as the difference between the observed and the predicted value divided by the standard deviation for normal reference values. (15)(16)(17) RV/TLC ratio was expressed as a percentage.

Cardiopulmonary exercise testing

Maximal exercise capacity was assessed using the Bruce treadmill test. Briefly summarized, the Bruce test protocol comprises three minute stages of increasing belt speed and percent grade on a treadmill (Marquette, 2000 treadmill). (18) Children were always tested in the presence of their parent(s). Each patient was allowed to familiarise with the mouth piece and the treadmill, enabled by starting every test with 3 minutes of rest. Each child was urged to continue to the point of severe fatigue. Heart rate and oxygen saturation were monitored by finger pulse oximetry.

Parameters measured during CPET were minute ventilation (V'E), oxygen uptake (V'O 2, max ), oxygen pulse (O 2 -pulse; i.e. oxygen uptake divided by the heart rate), respiratory quotient (RQ), ratio of ventilation to CO 2 output (V'E,CO 2 ), respiratory rate and duration of the exercise test.

Respiratory gases were monitored on a breath-by-breath basis using a flow sensor (Vmax 229, Sensormedics, Yorba Linda, CA, USA).

The CPET was considered adequate if one or more of the following conditions were achieved: at least 80% of the maximal predicted heart rate (determined as 220 minus age in years) , RQ >1.0 for one minute or exhaustion of the subject. (19) The V'O 2, max and the V'O 2, max/kg were expressed as z-scores calculated from reference values. Statistical analysis was performed using the unpaired t-test for normally distributed continuous data.

Non parametric tests were used for non normally distributed continuous data. The Fisher exact test or the Chi-square were used for comparing categorical data.

To compare the three groups of patients, linear regression analysis was used with pulmonary function parameters and CPET results as dependent variables. The following variables were added as potential confounders to the model for pulmonary function parameters: atopy (defined as having eczema and/or allergic rhinitis), parental smoking and family history of asthma (1 st degree relatives).

For the CPET results we corrected for the frequency of participating in sports besides the other variables mentioned above. Statistical significance was defined as p < 0.05. SPSS 15.0 was used for data analysis.

RESULTS

Patient characteristics

Trachea-esophageal fistula

Eighty-four patients were treated for TEF in the Pediatric Surgical Centre of Amsterdam between 1988 and 1997. One patient died at the age of three years. Twenty-nine patients were excluded for the following reasons: prematurity (n = 18), type E atresia (n = 4), severe mental retardation (n = 1), cardiac surgery (n = 3), spinal tethered cord (n = 1), severe pulmonary infections (n =1) and paralysis of the recurrent laryngeal nerve (n =1).

Of the 54 eligible TEF patients 33 agreed to participate. Ten patients refused, nine patients could not be contacted and two patients had emigrated. Two of the 33 patients gave consent but did not show up (figure 1).

A comparison of the basic characteristics of 31 participating patients with those who were did not participate did not show significant differences (table 1).

One patient (3%) had EA without TEF. All patients underwent thoracotomy for TEF repair. Fourteen participants (45%) had at least one congenital anomaly including a cardiac anomaly (5 patients), imperforate anus (5 patients), limb anomalies (2 patients) and renal anomalies (2 patients).

Participants with a cardiac anomaly had a patent ductus arteriosus with an atrial septal defect (n = 3) or without an atrial septal defect (n = 2). Since their cardiac situation had been stable for years, none of them were being followed by a pediatric cardiologist.

Clinically relevant tracheomalacia was diagnosed in 4 participants (13%) by bronchoscopy. Two of them underwent aortopexy.

In 14 participants (45%) GERD had been demonstrated in the first four years after TEF repair by upper gastro-intestinal series (UGI), pH-metry and/or endoscopy (table 2). Eleven patients (35%) underwent a Boerema anterior gastropexy (TEF+GERD group) 18 ± 15 months after birth (range 1-70 months) (table 3). These children underwent antireflux surgery because of an ALTE (apparently lifethreatening event) (n=3) growth restriction (n=3) or a combination. All patients had had recurrent respiratory infections in the first years of life.

At the time of the study none of these patients was treated for current GERD.

TEF participants (with and without s-GERD) who had current symptoms of tracheomalacia had significantly more respiratory infections (1.3 vs 2.8x/yr; p = 0.002) and episodes of bronchitis (0.0 vs 1.4x/yr; p = 0.001) than TEF patients who did not have current symptoms of tracheomalacia. Six TEF patients (27% in TEF+GERD group vs 14% in TEF-GERD group; p = 0.41) had current gastrointestinal symptoms such as heartburn and regurgitation. None of the patients used antireflux medication. At follow-up none of the patients had a scoliosis.

Control group

An age matched control group was recruited from 46 GERD patients who were operated in the Pediatric Surgical Centre of Amsterdam for isolated s-GERD.

Of these, 16 could not be located and of the 30 remaining patients 17 refused to participate. Hence 13 otherwise healthy controls were included. Reasons for surgery in the GERD group were ALTE (n

Pulmonary function

In one TEF patient pulmonary function was not assessed because of a serious respiratory infection at follow-up visit. Spirometry and lung volume measurements of four patients (three with TEF) could not be reproduced despite detailed instructions and were therefore excluded from analysis.

All pulmonary function results were normally distributed. Five patients (1 group TEF-GERD; 4 group GERD) had an obstructive impairment (z-score FEV 1 /FVC < -1.64), none of the patients responded adequately to bronchodilation (i.e. improvement of FEV 1 ≥ 12%) (table 4).

FVC was significantly lower in patient with TEF (with and without s-GERD) when compared to patients with isolated s-GERD (z-score FVC TEF+GERD -1.57±0.92; TEF-GERD -1.09±0.92; GERD 0.05±1.00).TLC was also significantly lower in patients with TEF (with and without s-GERD) when compared to group GERD (z-score TLC TEF+GERD -0.88±0.85, TEF-GERD -0.68±0.47; GERD 0.01±0.77) (table 4). Among all TEF patients, TLC was similar in those with or without a history of pleural injury (TLC zscore -0.73 vs -0.70; p = 0.91). Similarly, among all TEF patients, TLC was similar in those with or without a history of post-operative pneumonia (TLC z-score -0.79 vs -0.34; p = 0.35).

TEF patients with and without current gastrointestinal symptoms had similar lung function.

The differences we found remained significant after adjustment for potential confounders in regression analysis.

Exercise Capacity

Three patients did not perform CPET because of serious respiratory infection at time of follow-up (n = 1, group TEF-GERD) and technical problems (n = 2; group TEF+GERD) respectively. Forty-one patients and/or RQ > 1.00 during one minute. Results of three patients were excluded from analysis, because they had to stop early and did therefore not reach the level of maximal exercise: in two patients (both group TEF-GERD) this was due to painful legs and in one patient (group TEF+GERD) this was due to shortness of breath. FEV 1 /FVC before and after BD and MMEF before and after BD were significantly lower in the six patients that did not perform or not complete the CPET. None of the children desaturated during exercise.

Reliable exercise data could be obtained in 38 patients and showed that only one patient (group TEF-GERD) had an abnormally low V'O 2, max score (< -1.96), probably because of airway obstruction (FEV 1 /FVC z-score -2.14). V'O 2, max and V'O 2, max/kg were similar in group TEF+GERD, TEF-GERD and GERD (table 5) when corrected for atopy, asthma family (1 st grade), parental smoking habits and frequency of sport practise. We found mild to moderate, mainly restrictive, pulmonary function abnormalities in TEF patients, years after surgical correction. Results of the CPET were normal and similar for all groups after correction for potential confounders (e.g. atopy, parental smoking and family history of asthma).

Previous studies of lung function in TEF patients have demonstrated obstructive impairment in 10-70% of the TEF patients and many studies document a relation between obstructive impairment and GERD in the early years after TEF repair. (6;8;9;21) The largest study, from Chetcuti et al, described 154 patients born with TEF, and found a significantly lower FEV 1 and FEF50% in TEF patients with early radiologically proven GERD in comparison to TEF patients without GERD 6-37 years after TEF repair.( 7) In contrast we did not find obstructive impairment in TEF patients with s-GERD. The lower values for FEV 1 and MMEF we found, were most likely due to relative restrictive impairment since the reduction in FVC was proportionally greater than that in FEV 1 .

Almost all patients had a TLC within normal range, but mean TLC was significantly lower in TEF patients (with and without s GERD) when compared to isolated GERD controls. In the literature in 18-36% of the TEF patients restrictive pulmonary function was seen, especially when TEF patients had GERD. (7;8) In our study, differences between TEF patients with and without surgically treated GERD were not significant, suggesting a minor role for GERD. In addition antireflux surgery could have a protective effect if it avoids long-term damage from GERD.

There are several possible explanation for relative restrictive lung function impairment in TEF. First of all, it could result from suboptimal lung growth in the early years of life due to recurrent infection. (6) This might be due to an ineffective cough technique due to tracheomalacia resulting in recurrent pneumonia. (22) Furthermore recurrent (micro-)aspiration due to GERD in the first years after TEF repair may contribute to early epithelial damage and consequently increased risk for infection.

Together this may result in impaired or altered lung growth. Since isolated GERD patients have less episodes of bronchitis and normal pulmonary function parameters, TEF-associated factors such as tracheomalacia may play a more prominent role than GERD itself. Secondly, it has been suggested 13 that pleural scarring from empyema after anastomotic rupture may lead to mild restrictive disease. (7;23) In our group of TEF patients we did not find a relation between postoperative pneumonia and restrictive impairment. Thirdly, previous research has suggested a correlation between scoliosis, which is more common in TEF, (24) and pulmonary function impairment. (25) However in our study none of the patients had a scoliosis. Fourthly, thoracotomy itself may also result in restrictive impairment. In adolescents with scoliosis it has been demonstrated that thoracoscopic approach leads to a smaller decline in pulmonary function one year after surgery in comparison to the more invasive technique of open thoracotomy.( 26) Thoracoscopic approach to treatment of TEF is becoming increasingly accepted. Long term effects on pulmonary function are not yet available, but are expected to be less with the open thoracotomy technique. (27) We hypothesized that patients with TEF and s-GERD would have a reduced diffusion capacity and V'O 2, max when compared to TEF patients without s-GERD, since prolonged micro-aspiration of gastric acid in the airways and potentially into the alveoli may cause chronic pulmonary inflammation and pulmonary fibrosis. (28) It has been documented that adult patients with severe GERD have a reduced level of DL,CO and K'CO compared to patients without GERD. (28) We did not find evidence for damage of the alveolar membrane and subsequent gas exchange impairment reflected by the normal diffusion capacity, since almost all patients achieved maximal exercise and V'O 2, max was similar for all groups after correction for confounders. Mean z-scores for V'O 2, max, DL,CO and KCO were approximately 0, indicating that our patients are probably comparable to the healthy population. Our results therefore do not concord with Zaccara et al who reported a reduced exercise capacity in TEF patients. This could probably be attributed to a lower degree of physical fitness since almost all patients in the study of Zaccara et al reported reduced level of physical activity generally because of parental anxiety and a strict Italian law that regulates sports activities.

The respiratory symptoms we observed are common after TEF repair.(5;6) Daily functioning does not seem affected since frequency of sport practise and exercise-related symptoms did not differ between TEF patients and GERD patients. Except for three TEF patients, all patients practised sports 14 at the same level as their peers. This might be due to the willingness of TEF patients to accept symptoms that they assume are due to the congenital abnormality as well as the fact that many patients have been living with airway pathology since birth and might therefore not fully appreciate their respiratory limitations.

We are aware that a major limitation of this study is the small sample size. This could result in the inability to demonstrate differences between groups e.g. in pulmonary function. It was expected that many GERD controls could not be traced because the majority of these patients did not receive medical treatment for many years. Despite a clear informed consent letter the willingness of GERD controls to participate was low, probably because most GERD controls felt healthy for many years and therefore might lack motivation. Another limitation is the possible positive selection of CPET participants, since non-CPET participants had reduced pulmonary function parameters. Another limitation is the definition of severe GERD. We choose to define severe GERD as GERD which needed antireflux surgery. Patients with severe GERD eventually responding to medication are not included in this group. We assumed that patients with most severe GERD (i.e. many symptoms and/or prolonged duration of symptoms) will eventually undergo surgery, increasing the likelihood of finding of long-term damage of GERD in these patients. It was expected that if GERD has an effect on pulmonary function, it will be most pronounced in these patients. We agree realize that, on the other hand, patients with severe GERD eventually responding to medication are not included in the GERD group. This is the first study that compares lung function of TEF patients with patients who had isolated s-GERD. TEF patients with and without s-GERD had mild relative restrictive impairment when compared to GERD controls. TEF patients with s-GERD had a significantly lower FEV 1 when compared to TEF patients without s-GERD suggesting that GERD may affect large airway function in TEF patients. Diffusion capacity and exercise capacity were normal in nearly all patients. Since GERD controls did not have any pulmonary function impairment, other factors such as tracheomalacia or thoracotomy might play a more important role. We speculate that TEF patients undergoing In order to examine the effect of TEF and its surgical treatment on cardiopulmonary function we compared these two groups to a control group consisting of otherwise healthy patients who had undergone an antireflux procedure because of isolated s-GERD. We hypothesized that pulmonary function of TEF patients with s-GERD is comparable to control patients with s-GERD who did not have TEF. TEF patients without s-GERD were expected to have better lung function than TEF patients with s-GERD.

METHODS

Patients

All patients born with TEF who underwent thoracotomy at the Pediatric Surgical Centre of Amsterdam between 1988 and 1997 were considered eligible, if their age was over 8 year at the time of the study, i.e. the minimum needed to adequately perform lung function tests and CPET.

TEF patients were divided in 2 groups: TEF patients who had s-GERD requiring antireflux surgery (group TEF+GERD), and TEF patients who had not undergone antireflux surgery (group TEF-GERD.

The control group consisted of patients, born between 1988 and 1997, without TEF but with isolated s-GERD requiring antireflux surgery. All children underwent a Boerema anterior gastropexy, which was the standard antireflux procedure at that time. The following exclusion criteria were used: incapable of following instructions, physically not able to perform the tests, (partial) pneumonectomy, severe non-TEF related disease (e.g. bronchopulmonary dysplasia, cystic fibrosis etc), cardiac surgery, chromosomal anomaly, prematurity (≤ 34 weeks).

Indications for antireflux surgery were based on clinical findings in combination with results of diagnostic studies (upper gastrointestinal series, pH-studies and/or endoscopy). The patient's history was reviewed with specific attention to birth weight, gestational age, type of atresia, associated malformations, length of stay in the hospital (LOS), duration of ventilation, (GERD) and surgical complications including pleural injury (as reported by the surgeon in the operative report) . The local Ethics Committee approved the study protocol. Written informed consent was obtained from each patient and their parent(s) prior to participation.

Study design

Patients who provided informed consent, then received a detailed medical history including information concerning respiratory complaints and physical performance was obtained.

Pulmonary function testing included spirometry, lung volume measurements and measurement of diffusion capacity followed by cardiopulmonary exercise testing (CPET). All measurements were performed by experienced respiratory lab technicians according to the guidelines of the European Respiratory Society.( 14)

Pulmonary function

Subjects performed standard spirometry and lung volume measurements.( 14) All medication was discontinued 24 hours prior to testing. Forced expiratory volume (FEV 1 ), forced vital capacity (FVC), maximum midexpiratory flow (MMEF) and peak expiratory flow (PEF) were determined from the largest of three reproducible manoeuvres using a mass flow sensor (Vmax 229, Sensormedics, Yorba Linda, CA, USA). Spirometry was repeated after inhalation of 4x100 μg of salbutamol dose aerosol by metered dose inhaler to evaluate reversibility of potential bronchial obstruction and in order to prevent exercise-induced bronchoconstriction. A change of the FEV 1 ≥ 12%, expressed as percentage of the predicted value, was considered as a significant response.( 14)

Lung volume measurements were carried out after bronchodilation. Functional residual capacity (FRC), total lung capacity (TLC) and residual volume (RV) were determined by whole body plethysmography. The mean of three reproducible manoeuvres was used for analysis.

Diffusion capacity for carbon monoxide (DL,CO ) was measured by the single breath method using a multigasanalazyer (Sensor Medics) in combination with the mass flow sensor (Vmax 229, Results of the spirometry and the lung volume measurements were expressed as z-scores calculated as the difference between the observed and the predicted value divided by the standard deviation for normal reference values.(15-17) RV/TLC ratio was expressed as a percentage.

Cardiopulmonary exercise testing

Maximal exercise capacity was assessed using the Bruce treadmill test. Briefly summarized, the Bruce test protocol comprises three minute stages of increasing belt speed and percent grade on a treadmill (Marquette, 2000 treadmill).( 18)

Children were always tested in the presence of their parent(s). Each patient was allowed to familiarise with the mouth piece and the treadmill, enabled by starting every test with 3 minutes of rest. Each child was urged to continue to the point of severe fatigue. Heart rate and oxygen saturation were monitored by finger pulse oximetry.

Parameters measured during CPET were minute ventilation (V'E), oxygen uptake (V'O 2, max ), oxygen pulse (O 2 -pulse; i.e. oxygen uptake divided by the heart rate), respiratory quotient (RQ), ratio of ventilation to CO 2 output (V'E,CO 2 ), respiratory rate and duration of the exercise test.

Respiratory gases were monitored on a breath-by-breath basis using a flow sensor (Vmax 229, Sensormedics, Yorba Linda, CA, USA).

The CPET was considered adequate if one or more of the following conditions were achieved: at least 80% of the maximal predicted heart rate (determined as 220 minus age in years) , RQ >1.0 for one minute or exhaustion of the subject. (19) The V'O 2, max and the V'O 2, max/kg were expressed as z-scores calculated from reference values. Statistical analysis was performed using the unpaired t-test for normally distributed continuous data.

Non parametric tests were used for non normally distributed continuous data. The Fisher exact test or the Chi-square were used for comparing categorical data.

To compare the three groups of patients, linear regression analysis was used with pulmonary function parameters and CPET results as dependent variables. The following variables were added as potential confounders to the model for pulmonary function parameters: atopy (defined as having eczema and/or allergic rhinitis), parental smoking and family history of asthma (1 st degree relatives).

For the CPET results we corrected for the frequency of participating in sports besides the other variables mentioned above. Statistical significance was defined as p < 0.05. SPSS 15.0 was used for data analysis.

RESULTS

Patient characteristics

Trachea-esophageal fistula

Eighty-four patients were treated for TEF in the Pediatric Surgical Centre of Amsterdam between 1988 and 1997. One patient died at the age of three years. Twenty-nine patients were excluded for the following reasons: prematurity (n = 18), type E atresia (n = 4), severe mental retardation (n = 1), cardiac surgery (n = 3), spinal tethered cord (n = 1), severe pulmonary infections (n =1) and paralysis of the recurrent laryngeal nerve (n =1).

Of the 54 eligible TEF patients 33 agreed to participate. Ten patients refused, nine patients could not be contacted and two patients had emigrated. Two of the 33 patients gave consent but did not show up (figure 1).

A comparison of the basic characteristics of 31 participating patients with those who were did not participate did not show significant differences (table 1).

One patient (3%) had EA without TEF. All patients underwent thoracotomy for TEF repair. Fourteen participants (45%) had at least one congenital anomaly including a cardiac anomaly (5 patients), imperforate anus (5 patients), limb anomalies (2 patients) and renal anomalies (2 patients).

Participants with a cardiac anomaly had a patent ductus arteriosus with an atrial septal defect (n = 3)

or without an atrial septal defect (n = 2). Since their cardiac situation had been stable for years, none of them were being followed by a pediatric cardiologist.

Clinically relevant tracheomalacia was diagnosed in 4 participants (13%) by bronchoscopy. Two of them underwent aortopexy.

In 14 participants (45%) GERD had been demonstrated in the first four years after TEF repair by upper gastro-intestinal series (UGI), pH-metry and/or endoscopy (table 2). Eleven patients (35%) underwent a Boerema anterior gastropexy (TEF+GERD group) 18 ± 15 months after birth (range 1-70 months) (table 3). These children underwent antireflux surgery because of an ALTE (apparently lifethreatening event) (n=3) growth restriction (n=3) or a combination. All patients had had recurrent respiratory infections in the first years of life.

At the time of the study none of these patients was treated for current GERD.

TEF participants (with and without s-GERD) who had current symptoms of tracheomalacia had significantly more respiratory infections (1.3 vs 2.8x/yr; p = 0.002) and episodes of bronchitis (0.0 vs 1.4x/yr; p = 0.001) than TEF patients who did not have current symptoms of tracheomalacia. Six TEF patients (27% in TEF+GERD group vs 14% in TEF-GERD group; p = 0.41) had current gastrointestinal symptoms such as heartburn and regurgitation. None of the patients used antireflux medication. At follow-up none of the patients had a scoliosis.

Control group

An age matched control group was recruited from 46 GERD patients who were operated in the Pediatric Surgical Centre of Amsterdam for isolated s-GERD.

Of these, 16 could not be located and of the 30 remaining patients 17 refused to participate. Hence 13 otherwise healthy controls were included. Reasons for surgery in the GERD group were ALTE (n

Pulmonary function

In one TEF patient pulmonary function was not assessed because of a serious respiratory infection at follow-up visit. Spirometry and lung volume measurements of four patients (three with TEF) could not be reproduced despite detailed instructions and were therefore excluded from analysis.

All pulmonary function results were normally distributed. Five patients (1 group TEF-GERD; 4 group GERD) had an obstructive impairment (z-score FEV 1 /FVC < -1.64), none of the patients responded adequately to bronchodilation (i.e. improvement of FEV 1 ≥ 12%) (table 4).

FVC was significantly lower in patient with TEF (with and without s-GERD) when compared to patients with isolated s-GERD (z-score FVC TEF+GERD -1.57±0.92; TEF-GERD -1.09±0.92; GERD 0.05±1.00).TLC was also significantly lower in patients with TEF (with and without s-GERD) when compared to group GERD (z-score TLC TEF+GERD -0.88±0.85, TEF-GERD -0.68±0.47; GERD 0.01±0.77) (table 4).

Among all TEF patients, TLC was similar in those with or without a history of pleural injury (TLC zscore -0.73 vs -0.70; p = 0.91). Similarly, among all TEF patients, TLC was similar in those with or without a history of post-operative pneumonia (TLC z-score -0.79 vs -0.34; p = 0.35).

TEF patients with and without current gastrointestinal symptoms had similar lung function.

The differences we found remained significant after adjustment for potential confounders in regression analysis.

Exercise Capacity

Three patients did not perform CPET because of serious respiratory infection at time of follow-up (n = 1, group TEF-GERD) and technical problems (n = 2; group TEF+GERD) respectively. Forty-one patients and/or RQ > 1.00 during one minute. Results of three patients were excluded from analysis, because they had to stop early and did therefore not reach the level of maximal exercise: in two patients (both group TEF-GERD) this was due to painful legs and in one patient (group TEF+GERD) this was due to shortness of breath. FEV 1 /FVC before and after BD and MMEF before and after BD were significantly lower in the six patients that did not perform or not complete the CPET. None of the children desaturated during exercise.

Reliable exercise data could be obtained in 38 patients and showed that only one patient (group TEF-GERD) had an abnormally low V'O 2, max score (< -1.96), probably because of airway obstruction (FEV 1 /FVC z-score -2.14). V'O 2, max and V'O 2, max/kg were similar in group TEF+GERD, TEF-GERD and GERD (table 5) when corrected for atopy, asthma family (1 st grade), parental smoking habits and frequency of sport practise. 154 patients born with TEF, and found a significantly lower FEV 1 and FEF50% in TEF patients with early radiologically proven GERD in comparison to TEF patients without GERD 6-37 years after TEF repair.( 7) In contrast we did not find obstructive impairment in TEF patients with s-GERD. The lower values for FEV 1 and MMEF we found, were most likely due to relative restrictive impairment since the reduction in FVC was proportionally greater than that in FEV 1 .

Almost all patients had a TLC within normal range, but mean TLC was significantly lower in TEF patients (with and without s GERD) when compared to isolated GERD controls. In the literature in 18-36% of the TEF patients restrictive pulmonary function was seen, especially when TEF patients had GERD. (7;8) In our study, differences between TEF patients with and without surgically treated GERD were not significant, suggesting a minor role for GERD. In addition antireflux surgery could have a protective effect if it avoids long-term damage from GERD.

There are several possible explanation for relative restrictive lung function impairment in TEF. First of all, it could result from suboptimal lung growth in the early years of life due to recurrent infection. (6) This might be due to an ineffective cough technique due to tracheomalacia resulting in recurrent pneumonia. (22) Furthermore recurrent (micro-)aspiration due to GERD in the first years after TEF repair may contribute to early epithelial damage and consequently increased risk for infection. 14 at the same level as their peers. This might be due to the willingness of TEF patients to accept symptoms that they assume are due to the congenital abnormality as well as the fact that many patients have been living with airway pathology since birth and might therefore not fully appreciate their respiratory limitations.

We are aware that a major limitation of this study is the small sample size. This could result in the inability to demonstrate differences between groups e.g. in pulmonary function. It was expected that many GERD controls could not be traced because the majority of these patients did not receive medical treatment for many years. Despite a clear informed consent letter the willingness of GERD controls to participate was low, probably because most GERD controls felt healthy for many years and therefore might lack motivation. Another limitation is the possible positive selection of CPET participants, since non-CPET participants had reduced pulmonary function parameters. Another limitation is the definition of severe GERD. We choose to define severe GERD as GERD which needed antireflux surgery. Patients with severe GERD eventually responding to medication are not included in this group. We assumed that patients with most severe GERD (i.e. many symptoms and/or prolonged duration of symptoms) will eventually undergo surgery, increasing the likelihood of finding of long-term damage of GERD in these patients. It was expected that if GERD has an effect on pulmonary function, it will be most pronounced in these patients. We agree realize that, on the other hand, patients with severe GERD eventually responding to medication are not included in the GERD group.

This is the first study that compares lung function of TEF patients with patients who had isolated s-GERD. TEF patients with and without s-GERD had mild relative restrictive impairment when compared to GERD controls. TEF patients with s-GERD had a significantly lower FEV Group TEF+GERD (I): TEF patients with surgically treated GERD; Group TEF-GERD (II): TEF patients without surgically treated GERD; Group GERD (III): GERD patients who had antireflux surgery.

Bronchitis was defined as a an episode of productive cough lasting for more than 5 days.

Tracheamalacia was defined as persistent barking cough.

F

  Linda, CA, USA). Mean value of two measurements was used to determine DL,CO, alveolar volume (Va) and DL,CO corrected for Va (KCO).

  growth restriction (n=8), recurrent respiratory tract infections (n=2) or a combination. None of the patients had current gastrointestinal symptoms.

  38 patients achieved maximal exercise defined as a predicted heart rate > 80%

  fistula (TEF) is a congenital anomaly affecting 1 in 2400 to 4500 newborns.(1;2) The most common variant is esophageal atresia (EA) with a distal fistula (type C). Other types are isolated EA without a fistula (type A) and EA with a proximal fistula (type B).(3) Many patients with TEF have associated congenital malformations. Since the first successful primary repair in 1941 by Haight and Towsley, there has been a dramatic improvement of survival,(4) due to improved neonatal care, which has resulted in an increased awareness of long term complications of TEF.Many TEF patients experience respiratory problems due to recurrent pneumonia, EA associated tracheomalacia (TM) and gastro-esophageal reflux disease (GERD).(5) Pulmonary function studies have shown obstructive impairment in 10-70% of the patients (6-9), while 18-36% had restrictive impairment.(7;8) It has been suggested that prolonged micro-aspiration of gastric contents in the first years of life may cause chronic pulmonary inflammation and fibrosis.(7) Surgical complications such as pleural scarring from empyema after anastomotic rupture and multiple thoracotomies may lead to restrictive lung disease.(7) Data concerning maximal exercise capacity in TEF patients are lacking. Only one study including 8 TEF patients has been published, in which a reduced level of physical fitness, expressed in exercise duration and V'O 2 max, was found.(10) TEF patients with a history of GERD were more likely to have pulmonary function abnormalities and many authors have suggested that GERD in the first years after TEF repair may play a major role in TEF-associated pulmonary pathology.(7;8;11-13) The purpose of this study was to assess the influence of GERD on pulmonary function and exercise capacity in a group of patients aged 8-18 years, who had undergone neonatal surgical repair of TEF. We categorized TEF in two groups: those who had undergone anti-reflux surgery (and consequently were considered to have had severe GERD (s-GERD)) and those who had not (considering to have had mild GERD).

  Linda, CA, USA). Mean value of two measurements was used to determine DL,CO, alveolar volume (Va) and DL,CO corrected for Va (KCO).

  growth restriction (n=8), recurrent respiratory tract infections (n=2) or a combination. None of the patients had current gastrointestinal symptoms.

  38 patients achieved maximal exercise defined as a predicted heart rate > 80%

12 DISCUSSION

 12 We found mild to moderate, mainly restrictive, pulmonary function abnormalities in TEF patients, years after surgical correction. Results of the CPET were normal and similar for all groups after correction for potential confounders (e.g. atopy, parental smoking and family history of asthma).Previous studies of lung function in TEF patients have demonstrated obstructive impairment in 10-70% of the TEF patients and many studies document a relation between obstructive impairment and GERD in the early years after TEF repair.(6;8;9;21) The largest study, from Chetcuti et al, described

  15 thoracoscopic repair of TEF will have reduced restrictive pulmonary function impairment in comparison to patients undergoing a thoracotomy. To improve pulmonary outcome in TEF patients further research comparing both treatment modalities is recommended.

	Sp,O 2 PULMONARY FUNCTION IMPAIRMENT AFTER TRACHEA-ESOPHAGEAL FISTULA: A MINOR ROLE Transcutaneous oxygen saturation
	LIST OF ABBREVIATIONS FOR GASTRO-ESOPHAGEAL REFLUX DISEASE.
	TEF	Tracheo-esophageal fistula
	CO 2 Peetsold MG(1), Heij HA (2), Nagelkerke A F (1), Deurloo JA (2), Gemke RJBJ(1) Carbon dioxide
	TLC	Total lung capacity
	CPET	Cardiopulmonary exercise testiing
	TM	Tracheomalacia
	DL,CO Running title: Cardiopulmonary function after trachea-esophageal fistula Diffusion capacity carbon monoxide
	Va	Alveolar volume
	EA	Esophageal atresia
	VC	Vital capacity
	F o r F o r F o r F o r F o r F o r (1) VU University Medical Centre, Amsterdam, The Netherlands, Department of Pediatrics FEV 1 Forced expiratory volume in one second FRC Forced residual volume V'E Minute ventilation V'E,CO Ratio of ventilation to carbon dioxide output F (2) Pediatric Surgical Centre of Amsterdam (VU University Medical Centre and Emma Children's o r Hospital/AMC), the Netherlands
	FVC GERD GI V'O 2 Correspondence to: Prof. dr. R.J.B.J. Gemke	P e e r P e e r Forced vital capacity Gastroesophageal reflux disease Gastrointestinal P e e r P P P P Maximal oxygen uptake e e r e e r e e r e e r
	R e v i e w R e v i e w R R R R Department of Pediatrics, VU University Medical Centre KCO R Diffusion capacity corrected for alveolar volume LOS Length of stay in hospital MMEF e v i e e v i e e v i e e v i e e PO Box 7057 v i 1007 MB Amsterdam e Maximum midexpiratory flow w w w w w The Netherlands
	PEF	Peak expiratory flow
	Tel + 31-20-4443319
	RQ	Respiratory quotient
	Fax + 31-20-4442918
	RV	Residual volume
	RJBJ.Gemke@vumc.nl
	SD	Standard deviation
	SPSS	Statistical package social siences
		16 17 1

  Together this may result in impaired or altered lung growth. Since isolated GERD patients have less episodes of bronchitis and normal pulmonary function parameters, TEF-associated factors such as tracheomalacia may play a more prominent role than GERD itself. Secondly, it has been suggested In our group of TEF patients we did not find a relation between postoperative pneumonia and restrictive impairment. Thirdly, previous research has suggested a correlation between scoliosis, which is more common in TEF,(24) and pulmonary function impairment.(25) However in our study none of the patients had a scoliosis. Fourthly, thoracotomy itself may also result in restrictive impairment. In adolescents with scoliosis it has been demonstrated that thoracoscopic approach leads to a smaller decline in pulmonary function one year after surgery in comparison to the more invasive technique of open thoracotomy.(26) Thoracoscopic approach to treatment of TEF is becoming increasingly accepted. Long term effects on pulmonary function are not yet available, but are expected to be less with the open thoracotomy technique.(27) We hypothesized that patients with TEF and s-GERD would have a reduced diffusion capacity and V'O 2, max when compared to TEF patients without s-GERD, since prolonged micro-aspiration of gastric acid in the airways and potentially into the alveoli may cause chronic pulmonary inflammation and pulmonary fibrosis.(28) It has been documented that adult patients with severe GERD have a reduced level of DL,CO and K'CO compared to patients without GERD.(28) We did not find evidence for damage of the alveolar membrane and subsequent gas exchange impairment reflected by the normal diffusion capacity, since almost all patients achieved maximal exercise and V'O 2, max was similar for all groups after correction for confounders. Mean z-scores for V'O 2, max, DL,CO and KCO were approximately 0, indicating that our patients are probably comparable to the healthy population. Our results therefore do not concord with Zaccara et al who reported a reduced exercise capacity in TEF patients. This could probably be attributed to a lower degree of physical fitness since almost all patients in the study of Zaccara et al reported reduced level of physical activity generally because of parental anxiety and a strict Italian law that regulates sports activities.

	that pleural scarring from empyema after anastomotic rupture may lead to mild restrictive
	F o r P e e r R e v i e w F o r P e e r R e v i e disease.(7;23) The respiratory symptoms we observed are common after TEF repair.(5;6) Daily functioning does not w
	seem affected since frequency of sport practise and exercise-related symptoms did not differ
	between TEF patients and GERD patients. Except for three TEF patients, all patients practised sports
	13

Table 1 .

 1 15 thoracoscopic repair of TEF will have reduced restrictive pulmonary function impairment in comparison to patients undergoing a thoracotomy. To improve pulmonary outcome in TEF patients further research comparing both treatment modalities is recommended. Comparison of basic characteristics of participants and non-participants with trachea-

	1 when compared

Table 2 .

 2 Diagnosis of GERD in all 3 patient groups. Numbers indicate number of patients. With regard to pH-metry patients were considered to have pathologic acid GERD when the reflux index was ≥10% or with nocturnal episodes of acid reflux. Esophagitis was histologically graded according to the ESPGHAN-criteria21 .

	Diagnosis	Group TEF-GERD	Group TEF+GERD	Group GERD (n =13)
		(n = 20)	(n =11)
	pH-metry	3/19	8/11	11/12 (1 unknown)
	Histology	1/1	5/9	12/13
	(esophagitis)
	UGIS		5/8	6/9

Table 3 .

 3 Patient characteristics and results of the follow-up visit.

Table 4 .

 4 Baseline pulmonary function results of TEF patients with surgically treated GERD (group TEF+GERD (I)), TEF patients without surgically treated GERD (group TEF-GERD (II)) and surgically treated GERD controls (group GERD (III)). Results are expressed as z-scores (SD) calculated from a reference population according to Stanojevic et al (FEV 1 , FVC, FEV 1 /FVC and MMEF),(16) Stocks et al (FRC, RV, TLC and RV/TLC) (17) and Zapletal (PEF, VC, DL,CO and DL,CO/V'a).(15) * p < 0.05 Before BD -1.67 (1.04) -0.89 (0.82) 0.18 (1.22) -0.52 --0.05* 0.86 -2.83* 0.28 -1.86* After BD -1.22 (1.07) -0.81 (0.76) 0.65 (1.21) -1.14 -0.31 0.88 -2.86* 0.69-2.22* FVC Before BD -1.57 (0.92) -1.09 (0.92) 0.05 (1.00) -1.21 -0.27 0.79 -2.46* 0.40 -1.90* DL,CO -0.80 (1.05) -0.62 (0.71) -0.21 (0.75) -0.90 -0.54 -0.26 -1.43 -0.17 -0.99 DL,CO /V'a 0.03 (0.21) 0.04 (0.15) -0.04 (0.19) -0.15 -0.14 -0.24 -0.11 -0.21 -0.06 BD: bronchodilation; CI : confidence interval.

	(mean ± SD)
	Daily coughing	1 (9%)	2 (10%)	0 (0%)	1.0	0.46	0.51
	Wheezing	2 (18%)	7 (35%)	2 (15%)	0.43	1.00	0.26
	Respiratory	2.5 ± 1.9	2.2 ± 1.3	1.5 ± 1.9	0.74	0.25	0.21
	infections/year (mean ±
	SD
	Bronchitis/year (mean ±	1.6 ± 2.0	0.6 ± 1.0	0.2 ± 0.6	0.15	0.06	0.31
	SD)
		o r
		P
		e
			e r
			R
			e
				v i e
				w

Table 5 .

 5 Results of the CPET. Numbers are expressed as mean ± SD. Group TEF+GERD (I): TEF patients with surgically treated GERD; Group TEF-GERD (II): TEF patients without surgically treated GERD; Group GERD (III): GERD patients who had antireflux surgery.

	Parameter	Group	Group TEF-	Group GERD (III)	p-value
		TEF+GERD	GERD (II)	n = 13
		(I)	n= 17
		n = 8
		Mean ± SD Mean ± SD	Mean ± SD	I vs II I vs III II vs III
	Heart rate max (%	95.4 ± 4.3	94.1 ± 4.5	94.0 ± 5.0	0.51 0.53 0.99
	predicted)
	Respiratory rate (x/min)	48.1 ± 10.4 48.6 ± 7.7	47.8 ± 7.6	0.90 0.94 0.30
	Respiratory Quotient	1.09 ± 0.07 1.11 ± 0.08	1.12 ± 0.05	0.56 0.33 0.66
	V'e max (L/min)	76.5 ± 24.7 65.3 ± 16.1** 92.6 ± 15.3**	0.20 0.08 <0.001
	z-score V'O 2, max	0.46 ± 1.86 -0.27 ± 1.60** 0.73 ± 1.14**	0.34 0.68 0.05
	z-score V'O 2, max/kg	0.54 ± 0.96 -0.08 ± 1.68	-0.07 ± 1.32	0.34 0.70 0.96
	O 2 -pulse (% predicted)	116.3 ± 19.2 109.9 ± 18.1 114.4 ± 13.6	0.44 0.81 0.42
	V'E,CO 2	26.9 ± 3.3	28.9 ± 2.3	27.9 ± 3.0	0.09 0.46 0.22
	SpO 2 (%)	95.8 ± 2.7	96.7 ± 1.9	96.0 ± 1.7	0.33 0.80 0.40

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