Marcelo Rodrigues
email: marcelorodrigues@uvigo.es

Ángel Guerra

Jesús S Troncoso

The embryonic

Keywords: Cephalopoda, Sepiola atlantica, reproduction, development, hatchling

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

Introduction

Development and reproductive trait analysis provide examples for most adaptive relationships and responses to intrinsic and extrinsic forces of selection acting throughout the life cycle [START_REF] Sv | Development and reproduction in the evolutionary biology of cephalopoda[END_REF]Boletzky 2003a). In natural populations, offspring size and egg size are classical life history traits which identify effects on hatchling size and competitive performance [START_REF] Sv | Developmental constraints and heterochrony: a new look at offspring size in cephalopod molluscs[END_REF]Boletzky 2003b;[START_REF] Marshall | The evolutionary ecology of offspring size in marine invertebrates[END_REF]. However, most data is from empirical studies provided from laboratory observations, since field studies are lacking due to the logistical difficulties of experimentally manipulating population densities in natural settings [START_REF] Svensson | Experimental excursions on adaptive landscapes: density-dependent selection on egg size[END_REF].

In marine invertebrates, a change in hatchling size can be obtained by the adoption of intracapsular feeding on stored nutritive material or by the production of larger eggs [START_REF] Sv | Developmental constraints and heterochrony: a new look at offspring size in cephalopod molluscs[END_REF]. Larger hatchlings are supposed to reduce susceptibility to predation [START_REF] Steer | Are bigger calamary Sepioteuthis australis hatchlings more likely to survive? A study based on statolith dimensions[END_REF] and starvation due to enhanced swimming ability and predatory competence in comparison to smaller hatchlings. This trade-off has been identified in different animal taxa, such as lizards [START_REF] Svensson | Experimental excursions on adaptive landscapes: density-dependent selection on egg size[END_REF], many marine invertebrates (Marshall and Keough 2007 a review) and cephalopods [START_REF] Laptikhovsky | Egg size, fecundity, and spawning in females of the genus Illex (Cephalopoda: Ommastrephidae)[END_REF]Rodrigues et al. in press;[START_REF] Steer | Are bigger calamary Sepioteuthis australis hatchlings more likely to survive? A study based on statolith dimensions[END_REF]2004; see also Boletzky 2003b and Villanueva and Norman 2008 for reviews). Moreover, differences in egg size and hatchling size seem to reflect ecosystem fluctuations, mainly temperature and food availability, such as those found during different spawning groups in the squid Illex argentines [START_REF] Laptikhovsky | Egg size, fecundity, and spawning in females of the genus Illex (Cephalopoda: Ommastrephidae)[END_REF].

In cephalopods, the duration of embryonic development is dependent not only on species but on temperature, as documented for several species (Boletzky 2003a;[START_REF] Villanueva | Biology of the planktonic stages of benthic octopuses[END_REF]. In contrast to many other marine invertebrates (references in [START_REF] Marshall | The evolutionary ecology of offspring size in marine invertebrates[END_REF], there is very little information on how maternal conditions affect the hatchling condition in cephalopods (Boletzky 2003b; Rodrigues et al. in press;[START_REF] Steer | The role of temperature and maternal ration in embryo survival: using the dumpling squid Euprymna tasmanica as a model[END_REF]). Therefore, it is beneficial to investigate whether egg size is a determinant of hatchling size in S. atlantica and if temperature has an effect on this trait.

During embryonic development, prevailing environmental conditions may affect the physiological state of the developing larva [START_REF] Giménez | Larval growth in the estuarine crab Chasmagnathus granulate: the importance of salinity experienced during embryonic development, and the initial biomass[END_REF], particularly in cephalopod paralarvae where the inner yolk sac provides energy for metabolism in learning activities such as predation [START_REF] Sv | The "larvae" of cephalopoda: a review[END_REF][START_REF] Sv | Development and reproduction in the evolutionary biology of cephalopoda[END_REF]. Several authors have suggested that the transition from yolk utilization to active predation represents a critical period in the early life history of cephalopods (Boletzky 2003a; [START_REF] Vidal | Influence of temperature and food availability on survival, growth and yolk utilization in hatchling squid[END_REF][START_REF] Villanueva | Biology of the planktonic stages of benthic octopuses[END_REF]. In paralarvae of chokka squid, Loligo reynaudii, rates of inner yolk utilization may be influenced by environmental temperature [START_REF] Martins | Effects of temperature on yolk utilization by chokka squid (Loligo reynaudii d`Orbigny, 1839) paralarvae[END_REF].

As observed in other sepiolids, Sepiola atlantica d'Orbigny, 1839-1842, transfers spermatophores to the female, who stores them in the bursa copulatrix, a large pouch lying on the visceral mass that allows the spermatangia to become attached [START_REF] Rodrigues | Mating behaviour of the Atlantic bobtail squid Sepiola atlantica (Cephalopoda: Sepiolidae)[END_REF]). This species is an intermittent terminal spawner (see [START_REF] Rocha | A review of reproductive strategies in cephalopods[END_REF]) and this spawning strategy comprises group-synchronous ovary maturation, multiple egg laying and deposition of egg clutches in different locations.

Furthermore, the egg size shows a positive correlation with maternal size, and the female does not take parental care of its progeny (Rodrigues et al. in press).

The goals of this study were to evaluate the influence of temperature on development in S. atlantica and to determine if hatchling size is dependent on the duration of development, along with providing new information on post-hatching behaviour and condition.

Material and Methods

A total of twelve mated adult females were obtained during dedicated dives in the Ría of Vigo (NW Iberian Peninsula) (42º 14' N; 8º 47' W). The field collection and laboratory study were carried out between January and September 2009. Live specimens were immediately with care to the Marine Station of the University of Vigo in Toralla Island (ECIMAT-UVIGO). Collection depth was between 3 to 6 m in sandy substrate with no algae present.

Each individual was placed in a 20.2 l (30 cm long x 27 cm wide x 25 cm deep) glass tank with an open system of running seawater (16.4 ± 1.1ºC). The bottom of the tanks was covered with 0.5-1 cm of fine sand from the type locality. The system received a natural photoperiod according to the season, roughly: spring 12:12 LD, summer 15:9 LD, autumn 12:12 LD, winter 9:15 LD. Sepiolid squids were fed daily ad libitum with freshly collected adult mysid shrimps, Siriella armata and Leptomysis mediterranea. Females were always kept in isolation in the tanks and were never exposed to males in captivity, but all of them produced eggs that initiated development, thus indicating that spermatangia were present in the females.

Twelve spawns in aquaria were obtained (753 eggs) from the captive females.

Eggs were laid during the night or early morning, and were removed upon observation. Each clutch was divided into three groups exposed to different temperatures: 13 ± 0.4 º C (N= 247), 18 ± 0.3 º C (N= 251) and natural variation (NV= 255) 16.4 ± 1.1 º C. Eggs from each female were maintained in small nylex mesh bags (0.5 mm mesh) where the spawning date, egg volume and "mother" were recorded.

Bagged eggs were checked daily in routine controls at 8:00 -9:00 a.m. and p.m., allowing us to record roughly from each clutch the emergence of the first hatchling, the diel hatching time and rate of successful hatchings for each female at the different temperatures.

After hatching, following [START_REF] Messenger | Magnesium chloride as an anaesthetic for cephalopods[END_REF], a total of 721 specimens were anesthetized using a 1/1 ASW-MgCl2 (7.14 %) solution for one minute in order to reduce their mobility. Dorsal mantle length (ML) and total length (TL= from posterior tip of the mantle to tip of the longest arm) were measured to 0.01 mm accuracy and weighed (BW) to 0.001 g immediately after being anesthetized. The same measurements were made on each female immediately after death. Once measured, hatchlings were maintained in the same conditions as the adults and juveniles of the mysid shrimps mentioned above were offered.

All measurements were made using a stereomicroscope (Nikon SMZ-1500).

The image was calibrated on a video monitor and measurements were taken directly from the screen utilizing an image analyzer (Nikon, NIS-Elements).

Egg volume (EV) was approximated using the formula for the volume of a prolate ellipsoid, (4/3) LW 2 (within 0.01 mm 3 ) (see Rodrigues et al. in press), where L= egg length (mm) and W= egg width (mm). All statistical analyses were performed using SPSS software (SPSS statistics 17.0).

In addition, a number of hatchlings (Fig. 1) were fixed in Bouin´s fixative and preserved in 70 % EtOH (25 replicas in total). These specimens were dehydrated in a graded series of ethanol, cleared with toluene and embedded in paraffin. Cross and frontal sections of 7 µm were mounted on slides and stained with haematoxylin and eosin.

Results

Egg laying began between 67 and 104 days after females were collected. Of the twelve females, five deposited four egg clutches. The number of laid eggs per clutch was highly variable ranging between 2 and 86 eggs, with an apparent decrease in the number of eggs laid with time. The individual egg volume varied between 47.81 and 182.45 mm 3 (53.29 ± 27.12 mm 3 ; mean ± standard deviation).

The embryonic development in terms of time duration was strictly dependent on temperature (Fig. 2). The slowest rate in developmental time occurred with samples incubated at 13 º C (N= 247), 61.8 ± 3.8 days. Eggs at 16.4 ± 1.1 º C (N= 251) hatched after 40.1 ± 4.8 days. At 18 º C (N= 251) hatching occurred after 22.6 ± 1.7 days. Successful hatching was recorded in 98.5 to 100 % of all the eggs laid.

Hatchling`s ML varied from 1.1 to 1.7 mm (1.5 ± 0.3 mm), and TL ranged between 2.6 and 3.6 mm (3.2 ± 0.5 mm). BW was 0.077 up to 0.098 g (0.081 ± 0.02 g).

There was no relationship between hatchling length and weight (r 2 = 0.36, n= 721, p>0.05).

Hatchling ML was positively related to EV (r 2 = 0.69, n= 721, P<0.001), which is represented by the following linear equation: ML=0.904+0.007EV (Fig. 3). However, hatchling ML was not affected by temperature, nor corresponding developmental time duration (F= 1.34, n= 721, p>0.05).

Hatching and post-hatching behaviour

Of the 721 successful hatchings obtained, 96.3 % took place during the night or early morning, and the rest during daylight or early evening. Hatching was achieved with vigorous mantle contractions. To leave the egg case the hatchling possibly utilized the terminal spine as auxiliary equipment along with the hatching gland (see [START_REF] Sv | The terminal spine of sepiolid hatchlings: its development and functional morphology (Mollusca, Cephalopoda)[END_REF].

Newly hatched individuals showed expanded chromatophores of dark brown colour on a yellowish background along the whole body, and they often assumed a "flamboyant" arm display (as shown in [START_REF] Mauris | Colour patterns and body postures related to prey capture in Sepiola affinis (Mollusca: Cephalopoda)[END_REF], figure 2-PB1). This posture consisted of the following arm patterns: i) the dorsal and laterodorsal arms were stretched upwards perpendicularly to the body axis; ii) the lateroventral and ventral arms together were stretched downward on either side; and iii) the tips of all the arms were rolled in.

Hatchlings were generally less active during daylight hours, and juveniles remained at the bottom of the tank attempting to bury themselves in the sand.

However, after a few hours (4 -6 hours) all the animals tried to bury in the substrate (sand grain size between 0.25 -0.125 mm), but with varying levels of success. These attempts consisted in contractions and expansions of the mantle while the animal was sitting on the substrate (first phase, cf. Boletzky and Boletzky 1970). Subsequent attempts consisted of the juveniles gathering sand particles (second phase) with outstretched laterodorsal arms, with varying success. A complete burying sequence (see [START_REF] Rodrigues | Burying behaviour of the, Atlantic bobtail squid Sepiola atlantica (Cephalopoda: Sepiolidae)[END_REF]) was observed after four days.

Although hatchlings possess yolk reserves (inner yolk sac) (Figure 4), they are poised to hunt mysid shrimp of the equal size one hour post-hatching. This initial innate predatory response was not always successful but gradually improved.

Hatchlings showed expanded dark brown chromatophores when directing attention to the prey. Afterwards, they moved quickly toward the prey in order to attain appropriate attacking distance [START_REF] Messenger | The visual attack of the cuttlefish Sepia officinalis[END_REF]). Prior to attack, hatchlings contracted all chromatophores and consequently turned virtually transparent. Arms were spread to form a circular crown, to enable the tentacles to be rapidly shot out (generally to the dorsal side in the middle of the mysid shrimp). If the attack was successful, the tentacles were quickly retracted with the prey. When the tentacles were retracted (with or without prey), the animals resumed a dark brown colour.

Although most hatchlings had eaten mysid shrimp within the first few days post hatch, 97 % died between 3 to 6 days after hatching. One individual survived to 24 days old.

Histological analyses demonstrated that yolk was present in all hatchlings between 0-6 days old (N= 14). From 7 to 9 days old only 2 of 6 replicas (N=6) showed traces of yolk. The hatchlings 10 and 11 days old (N=4) had no traces of yolk.

Nevertheless, the single juvenile that reached 24 days old showed traces of yolk (Fig. 4).

Discussion

Spawning behaviour observed in this study was similar to those shown in previous studies (Rodrigues et al. in press). As in others coleoid cephalopods, S. atlantica showed an inverse relationship between temperature and developmental duration (Boletzky 2003a). The duration of development was similar to that observed by [START_REF] Sv | Sepiola robusta[END_REF] in Sepiola robusta. However, the mean time was 50 % lower than in the sepiolidae Euprymna tasmanica reared at the same temperature (18 ºC, [START_REF] Steer | The role of temperature and maternal ration in embryo survival: using the dumpling squid Euprymna tasmanica as a model[END_REF]). Hatching lasted for 23 days in S. atlantica at a mean temperature of 14.4 ºC in northern Welsh waters [START_REF] Jones | Laboratory culture, growth, and the life cycle of the little cuttlefish Sepiola atlantica (Cephalopoda: Sepiolidae)[END_REF], which is comparable to our results at 18 ºC.

Our comparison between the three tested temperatures did not show apparent differences in hatching success (98.5 -100 %). Since high hatching rates were obtained at all temperatures examined (with no malformations), our results suggest that S. atlantica is adapted to living in waters ranging between 13.0-18.0 ºC. On the other hand, [START_REF] Steer | The role of temperature and maternal ration in embryo survival: using the dumpling squid Euprymna tasmanica as a model[END_REF] observed in E. tasmanica that hatching success is positively correlated with offspring size.

We do not have direct evidence relating to how long the female can store sperm in the bursa copulatrix. This is mainly because we do not know when the females in our experiments mated in the wild. However, we have evidence that female S. atlantica can store viable sperm for at least 104 days, which was the maximum time fertilized eggs were spawned in our experiment.

This study revealed a positive effect of egg size on hatchling size in captive S. atlantica. This result is supported by the positive trade-off between maternal fitness, which determines egg size and trade-offs previously identified by Rodrigues et al. (in press) in the same laboratory conditions. Such features are normally found in direct marine developers which have no parental care [START_REF] Marshall | The evolutionary ecology of offspring size in marine invertebrates[END_REF]. However, as observed in the brighteye darters, Etheostoma lynceum, egg quality and size varies in successive spawning events [START_REF] Heins | Seasonal and interannual components of intrapopulation variation in clutch size and egg size of a darter[END_REF]). Thus, the basis of the trade-off between female fitness and hatchling size could be influenced by other factors (such as temperature, food availability and salinity) in the field (Boletzky 1997; [START_REF] Heins | Seasonal and interannual components of intrapopulation variation in clutch size and egg size of a darter[END_REF][START_REF] Laptikhovsky | Egg size, fecundity, and spawning in females of the genus Illex (Cephalopoda: Ommastrephidae)[END_REF][START_REF] Marshall | The evolutionary ecology of offspring size in marine invertebrates[END_REF][START_REF] Steer | The role of temperature and maternal ration in embryo survival: using the dumpling squid Euprymna tasmanica as a model[END_REF][START_REF] Svensson | Experimental excursions on adaptive landscapes: density-dependent selection on egg size[END_REF].

S. atlantica hatchling ML was similar to that observed in other sepiolid hatchling species [START_REF] Sv | Sepiola robusta[END_REF][START_REF] Jones | Laboratory culture, growth, and the life cycle of the little cuttlefish Sepiola atlantica (Cephalopoda: Sepiolidae)[END_REF][START_REF] Nabhitabhata | Life cycle of cultured bobtail squid, Euprymna hyllebergi Nateewathana, 1997[END_REF], which ranged between 1.1 and 2.5 mm ML, with the exception of Rossia macrossoma where hatching ML was around 5 mm (Boletzky 1973).

Hatching and post-hatching behaviour

Apparently in most cephalopod species, a decrease in natural light triggers hatching, but why this occurs in one particular is due at the physiological state that is attained by the animal (Boletzky 1974). [START_REF] Summers | Ecological implications of life stage timing determined from the cultivation of Rossia pacifica (Mollusca: Cephalopoda)[END_REF] observed laboratory hatching in Rossia pacifica that showed the same diel hatching cycle as S. atlantica. This type of "hatching strategy" is a form of minimizing vulnerability to predators. We have now additional evidence which suggests that two new traits occur during the hatching strategy. This includes the presence of a dark brown pattern, and the flamboyant arm display. The flamboyant posture especially allows the hatchling to convey a confounding picture to a potential predator. This posture is perhaps not only related to prey capture [START_REF] Mauris | Colour patterns and body postures related to prey capture in Sepiola affinis (Mollusca: Cephalopoda)[END_REF]. Both traits may improve camouflage, and may constitute part of the primary defence strategy of the juvenile sepiolid squid [START_REF] Hanlon | Cephalopod behaviour[END_REF].

This study provides additional observations for the behavioural fitness of S. atlantica hatchlings without previous experience in burying and hunting. Juvenile cephalopods have a remarkable repertoire of actions that correspond to some "innate responses" similar to adult behaviour [START_REF] Sv | The "larvae" of cephalopoda: a review[END_REF][START_REF] Villanueva | Biology of the planktonic stages of benthic octopuses[END_REF].

Although very vulnerable to predation, sepiolid hatchlings mainly behave in a defensive way by burying into the sand and by showing body patterns and displays adapted for concealment in the given environment [START_REF] Sv | Observations on the embryonic and early postembryonic development of Rossia macrossoma (Mollusca, Cephalopoda)[END_REF][START_REF] Sv | The "larvae" of cephalopoda: a review[END_REF]. Although kept in a tank without sand for weeks, occasional observations demonstrated that sepiolid hatchlings of several Sepiola and Sepietta species [START_REF] Sv | Sepiola robusta[END_REF]2003a;[START_REF] Sv | Observations on the embryonic and early postembryonic development of Rossia macrossoma (Mollusca, Cephalopoda)[END_REF] bury when sand is present using similar techniques observed in our study.

This study demonstrates that S. atlantica possesses the innate predatory attack response one hour post-hatching while still possessing yolk reserves. This result is in disagreement with that observed in the same species by [START_REF] Jones | Laboratory culture, growth, and the life cycle of the little cuttlefish Sepiola atlantica (Cephalopoda: Sepiolidae)[END_REF], who found that individuals began hunting at six days old. In contrast, other studies have shown that newly hatched cuttlefish (Sepia officinalis) began their predatory attacks at 24-48 hours post hatching [START_REF] Wells | Factors affecting reactions to Mysis by newly hatched Sepia[END_REF], with the precise sequence of motor actions observed in mature adults [START_REF] Messenger | The visual attack of the cuttlefish Sepia officinalis[END_REF]).

High mortality was still observed, despite traces of yolk in juvenile S. atlantica (Fig. 4). This suggests the existence of a critical period (cf. [START_REF] Vidal | Influence of temperature and food availability on survival, growth and yolk utilization in hatchling squid[END_REF] in the early life history in S. atlantica. Based on juvenile mortality, [START_REF] Jones | Laboratory culture, growth, and the life cycle of the little cuttlefish Sepiola atlantica (Cephalopoda: Sepiolidae)[END_REF] suggested that the first 40 days are critical in the life cycle of the species, although in their study no inner yolk was observed after 20 days old. The phenomenon of critical period was also observed in some squid species reared in laboratory up to date (eg. Loligo opalescens, [START_REF] Vidal | Influence of temperature and food availability on survival, growth and yolk utilization in hatchling squid[END_REF]. However some extrinsic factors can be affecting in this aspect, like food availability, substrate type and light cycle [START_REF] Hanlon | Laboratory culture of the Sepiolid squid Euprymna scolopes: A model system for bacteria-animal symbiosis[END_REF][START_REF] Vidal | Influence of temperature and food availability on survival, growth and yolk utilization in hatchling squid[END_REF].

Post-hatch conditions were similar for all hatchlings, despite being raised at different developmental temperatures. This may have changed the physiological consumption of the yolk [START_REF] Giménez | Larval growth in the estuarine crab Chasmagnathus granulate: the importance of salinity experienced during embryonic development, and the initial biomass[END_REF]. Unfortunately, we had no individual temperature information and, consequently, we cannot prove this. Yolk consumption was studied in crabs (Chasmagnathus granulate), with salinity as the variable factor and although salinity stress resulting in an increase in egg size [START_REF] Giménez | Relationships among salinity, egg size, embryonic development and larval biomass in the estuarine crab Chasmagnathus granulate, Dana 1851[END_REF] it was demonstrated that changes in salinity may have negative consequences in the growth rates at early juvenile stages [START_REF] Giménez | Larval growth in the estuarine crab Chasmagnathus granulate: the importance of salinity experienced during embryonic development, and the initial biomass[END_REF]. Future projects would need to address the variability in yolk consumption in S. atlantica hatchlings under various environmental conditions.

Although this is one of the first ecological trade-off investigations in the family Sepiolidae, our data and the previously reported correlation in maternal fitness and egg size (Rodrigues et al. in press), support the idea that maternal fitness is a determinant of hatchling size in S. atlantica. Moreover, the current results indicate

Figure Caption Fig. 1

 Caption1 Figure CaptionFig.1Scheme of the fixed post-hatching Sepiola atlantica (N= 25) to make histological

Figure Caption Fig. 2 S

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Figure Caption Fig. 3 S

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Figure Caption Fig. 4

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Acknowledgements

The authors are greatly indebted to Prof. Sigurd von Boletzky (Observatoire Océanologique de Banyuls sur mer, Laboratoire Arago) for his attention, time, and fruitful advice, as well as the hosting facilities offered in his institute. We are also grateful to Manuel E. Garcí and Jose M. Antonio of ECOBIOMAR (IIM, CSIC) for their assistance in the sample collections and histology.

Thanks to Katharine Ni Mhurchú and Fiona Read for their cordial help with the English. The first author was supported by a financial grant Estadías en Centros de Investigación from the "Universidade de Vigo" and a fellowship from the program Axudas Predoutorais from the same institution.

future areas of research in sepiolid squids, which may be fruitful towards understanding the innate behavioural response and the costs of metabolism during the transition from yolk utilization to active prey ingestion.


Farah ; Al-Khalidi

John Wiley

F Q Al-Khalidi

R Saatchi

D Burke

Heather E Elphick
email: heather.elphick@sch.nhs.uk

S Tan

F Q Al-Khalidi

Respiration Rate Monitoring Methods: A Review

Keywords: respiratory, thermal imaging, non-contact Respiratory, thermal imaging, noncontact Respiratory, thermal imaging, noncontact

Respiration rate is an important indicator of a person's health, and thus it is monitored when performing clinical evaluations. There are different approaches for respiration monitoring, but generally they can be classed as contact or noncontact.

For contact methods, the sensing device (or part of the instrument containing it) is attached to the subject's body. For noncontact approaches the monitoring is performed by an instrument that does not make any contact with the subject.

In this paper a review of respiration monitoring approaches (both contact and noncontact) is provided. Concerns related to the patient's recording comfort, recording hygiene, and the accuracy of respiration rate monitoring have resulted in the development of a number of noncontact respiration monitoring approaches.

A description of thermal imaging based and vision based noncontact respiration monitoring approaches we are currently developing is provided.

Introduction

Breathing is an important physiological task in living organisms. For humans, this process results in air containing oxygen being inhaled into the lungs, where gas exchange occurs across the alveolar-capillary membrane [START_REF] Lausted | Respiratory system[END_REF]. Carbon Dioxide is excreted as part of the process, in the air released through the nose or mouth. The entire process from the inhalation to exhalation is known as a breathing (or respiration) cycle.

Respiratory rate is a vital sign used to monitor the progression of illness and an abnormal respiratory rate is an important marker of serious illness. There is substantial evidence that alterations in respiratory rate can be used to predict potentially serious clinical events such as cardiac arrest or admission to the intensive care unit (2)(3)(4)(5). These studies have shown respiratory rate to be better than other vital measurements such as pulse and blood pressure in discriminating between stable patients and patient at risk (3). Using changes in respiratory rate measurements patients could have been identified as high risk up to 24 hours before the event with a specificity of 95% (5). Hospital systems such as the Paediatric Early Warning System (PEWS) have been developed to encourage appropriate responses to abnormal vital signs including an elevated respiratory rate.

Evidence from a recent audit of febrile children in our unit suggests that in both the emergency department and the acute medical admissions unit, respiratory rate was only measured in around two thirds of children on arrival. Reasons for omission were given as "crying" or "unsettled" and in many of these children experienced nursing staff were unable to obtain an accurate reading. However, it is in these children that this measurement would potentially be most useful and important.

According to Murthy (6), existing devices for monitoring respiratory rate only estimate the actual breathing rate due to their limitations. These devices can be classified in different ways, depending on the manner in which they operate and how they are used. In this paper, respiration rate monitoring devices are grouped as either contact or noncontact. In contact respiration rate monitoring, the instrument makes direct contact with the subject's body. However, in noncontact monitoring, the respiration rate is measured without the instrument making contact with the subject's body.

There are clear advantages to noncontact respiration monitoring methods. These include improved patient comfort (especially for long term monitoring) as the subject is not tied to an instrument and improved accuracy as distress caused by a contact device may alter the respiration rate.

There have been several studies reporting developments in both contact and noncontact respiration monitoring. A review of non-invasive respiratory monitoring in medical care was provided by Folke et al. (7). This paper aims to review the literature on contact and non-contact methods of respiratory rate monitoring, including two methods currently being developed by our unit.

Contact Based Respiration Monitoring

Contact respiration rate monitoring instruments are usually based on measuring one of the following parameters: respiratory sounds, respiratory airflow, respiratory

Acoustic Based Methods

Respiratory sound can be measured using a microphone placed either close to the respiratory airways or over the throat to detect the variation of sound. Then a frequency analysis and estimation of the loudness of the sound can be carried out (8).

Werthammer et al. (9) reported a respiratory sounds measurement system to detect sleep apnea in infants. The system depended on recording a signal derived from breathing sounds from the nose. This method was applied to eight premature infants. Snorting, speaking, crying, coughing etc had a negative effect on the operation of the system.

Corbishley and Rordriguez-Villegas (10) proposed a miniaturised and wearable respiration monitoring respiration system. It used a microphone mounted on the neck to obtain the largest breathing acoustic.

Airflow Based Methods

Airflow can be detected because exhaled air is warmer, has higher humidity and contains more CO 2 than inhaled air. These variations can be used for indicating the respiratory rate. Most airflow-sensing methods need a sensor, attached to the airways (7). The measurement of the airflow can be achieved by using a nasal or oronasal thermistor which detects changes in temperature between the inhaled and exhaled air. This gives a semi-quantitative estimate of airflow, but the method is limited due to a high incidence of thermistor displacement (11).

The nasal pressure transducer is another sensor used to measure respiration rate.

Nasal pressure is a more accurate measure of airflow than others as it based on the actual volume of the air exhaled (8,12). It can be measured via nasal cannulae, mouthpiece or facemask. A problem with airflow measurement is that some patients may not feel comfortable with the sensor (13). The collector can also affect respiratory activity by increasing deadspace.

Folke et al. ( 14) have reported a CO 2 sensor to measure respiration rate. Their study also indicated that subtle design changes in the collecting device could introduce large differences in sensor performance.

Chest and Abdominal Movement Detection

Chest and abdominal wall movements can best be measured by either mercury strain gauges or impedance methods. Respiratory inductance plethysmography is a non-invasive technique whereby two bands measure the respiration rate, the thoracic band which is placed around the rib cage and the abdominal band which is placed over the abdomen at the level of the umbilicus. The bands are made from an extendible/deformable conducting material, either a very fine wire or thin foil such that the conductivity can be maintained during the stretching process (12,15). The principle of the strain gauge sensor is based on increase in the resistance of a conductor when the area of the conductor is increased during the respiration process. However, if the upper airway is partially obstructed, there may be a change in the phase angle and timing of the movements of the thorax and abdomen (16). The movements become asynchronous, ie the thorax moves inwards, and the abdomen outwards. During expiration this pattern is then reversed. Thoraco-abdominal asynchrony is a normal finding in infants in whom chest wall compliance is greater (17) and is exacerbated by respiratory disease or respiratory muscle weakness [START_REF] Stromberg | Thoracoabdominal asynchrony in small children with lung disease--methodological aspects and the relationship to lung mechanics[END_REF].

Nepal et al. (19) studied the abdominal strain gauge transducer for measuring respiration rate. The strain gauge was strapped around the patient's chest and changes in thoracic or abdominal circumference during breathing were measured.

The method involved a classification algorithm to separate respiratory signals as apnoea, respiration, or respiration with motion, by using a second order autoregressive modelling and zero cross algorithm.

Transcutaneous CO 2 Monitoring

In transcutaneous CO 2 monitoring a heated electrode (about 42° C) is applied to the skin (usually an arm). This method relies on the diffusion of gas to the skin and provides an overall estimate of change in CO 2 level rather than minute by minute readings. The electrode is surrounded by a solution to provide conductivity. Care needs to be taken to avoid skin burning on sensitive and neonatal skin (12).

Transcutaneous CO 2 monitoring therefore allows measurements of consequences of abnormal ventilation rather than a measure of the respiratory rate itself. Blood-Oxygen saturation (SpO 2 ) measurement is another technique for monitoring the consequences of abnormal ventilation. When air enters the lungs its oxygen binds to the haemoglobin in red blood cells. The oxygen is then transported throughout the body in arterial blood. A pulse oximeter uses the red and infrared frequencies to determine the percentage of haemoglobin in the blood that is saturated with oxygen. This percentage is called blood saturation, or SpO 2 (20). An oximeter simultaneously displays the SpO 2 level as well as the pulse rate and plethysmogram.

There have been studies indicating that respiration rate can be extracted from plethysmograms. Plethysmograms from ten healthy adults were processed using wavelet transforms (21). Respiration waveform was observed in the plots of the wavelet transforms. In another study involving 14 infants, of median age 2 days, the feasibility of extracting respiratory information from the plethsmogram traces was also demonstrated (22). The magnitude frequency spectra of the plethsmogram traces showed peaks associated with respiration rate.

Electrocardiogram (ECG) Derived Respiration Rate

This method is based on the fact that respiration has a modulating effect on the ECG. In this respiration rate monitoring approach, ECG electrodes are attached to the subject in order to record an ECG. By measuring the fluctuation in ECG, the respiration rate can be derived. This technique is called ECG-Derived Respiration (EDR) and is based on a process known as sinus arrhythmia, i.e. the modulation of ECG by the breathing process (23). EDR is believed to be based on small ECG morphology changes during the respiratory cycle caused by movement of the heart position relative to the electrodes and the change in lung volume. Principal component analysis has been used to identify which ECG lead was most effective before extracting the respiration rate (24).

EDR monitoring has also been performed by using a single-channel that did not have to be a precordial lead (25). In contrast to a number of other studies that used ECG characteristic waves (e.g. QRS complex), this study used the higher order statistics of ECG recording (such as the 4th order cumulant).

A study carried out a quantitative comparison of EDR monitoring techniques based on direct measurement of the modulation components versus techniques based on calculation of the mean electrical axis variation (26). The study concluded that single lead respiration rate estimates are more robust than the methods based on the mean electrical axis.

Optical Based Respiration Rate Monitoring

Aoki et al. ( 29) reported a non-restrictive visual sensing method to detect the respiration pattern by using a Fiber Grating (FG) vision sensor and processor unit.

Their system consisted of two parts. The first was the Fibre Grating projecting device. This provided an array of invisible infra-red light spots (wavelength 810nm).

The

Thermal Sensor and Thermal Imaging Based Respiration Rate Monitoring

Hsu and Chow (32) have reported a thermal sensor based respiration rate monitoring system. In this approach there was no contact with the child's skin. The sensor could detect temperature changes induced by respiration and then the data were corrected and analysed simultaneously by a personal computer that was linked to a central nursery room. To avoid missing the breathing signals, an ellipsoidshaped mask was made and the thermo sensors were placed on the mask so that breathing could be detected when the child's head turned. The problem with this method was that a mask had to be placed close to the child's face. In a study carried out by our group, the FLIR A40 thermal camera was used to monitor respiration related skin surface temperature variation in area centred on the tip of the nose (35). The thermal sensitivity of the camera is 0.08 Kelvin. The camera was fixed on a tripod in front of the subject at a distance of about one meter. The image capture rate was 50 frames per second, thus providing 3000 images per minute. The recording time was two minutes. The images were segmented and then an algorithm was used to locate and track a circular area centred on the tip of the nose. The segmentation and tracking algorithms are described Al-Khalidi et al. [START_REF] Saatchi | Facial tracking method for noncontact respiration rate monitoring[END_REF].

The chosen area was divided into eight equal concentric segments as shown in providing the least clear signal. This result indicated that for respiration monitoring, it would be advisable to consider all the eight segments and then to select the segments that provide the clearest respiration signal. An algorithm was produced to automatically extract the respiration rate from the recorded signal.

Discussion

Respiration rate monitoring has evolved from the days when it could only be measured by placing the back of the hand close to the nose to monitor exhaled air. It (11). A semi-quantitative measure of airflow and tidal volume can be derived from respiratory inductance plethysmography (RIP). The technique has been demonstrated to work well in measuring tidal volume in infants [START_REF] Hershenson | Changes in the contribution of the rib cage to tidal breathing during infancy[END_REF].

F
However, from a clinical perspective the main disadvantage of these methods is that they require connection to the child, some to the facial area, which disturbs many children and may be poorly tolerated. In addition, in infants and children, the added dead space of the equipment required for some of these techniques may have an influence on breathing patterns [START_REF] Brooks | Assessment of tidal volume over time in preterm infants using respiratory inductance plethysmography, The CHIME Study Group. Collaborative Home Infant Monitoring Evaluation[END_REF].

Conclusions

Monitoring respiration rate is an important task when evaluating a subject's health.

Respiration rate monitoring devices can be classified by a number of ways depending on the manner of their use and their operation. In this review paper, they were grouped into contact and noncontact. This review has highlighted the advances made to improve the effectiveness of respiration monitoring.

Introduction

Breathing is an important physiological task in living organisms. For humans, this process results in air containing oxygen being inhaled into the lungs, where gas exchange occurs across the alveolar-capillary membrane [START_REF] Lausted | Respiratory system[END_REF]. Carbon Dioxide is excreted as part of the process, in the air released through the nose or mouth. The entire process from the inhalation to exhalation is known as a breathing (or respiration) cycle.

Respiratory rate is a vital sign used to monitor the progression of illness and an abnormal respiratory rate is an important marker of serious illness. There is substantial evidence that alterations in respiratory rate can be used to predict potentially serious clinical events such as cardiac arrest or admission to the intensive care unit (2-5). These studies have shown respiratory rate to be better than other vital measurements such as pulse and blood pressure in discriminating between stable patients and patient at risk (3). Using changes in respiratory rate measurements patients could have been identified as high risk up to 24 hours before the event with a specificity of 95% (5). Hospital systems such as the Paediatric Early

Warning System (PEWS) have been developed to encourage appropriate responses to abnormal vital signs including an elevated respiratory rate.

Evidence from a recent audit of febrile children in our unit suggests that in both the emergency department and the acute medical admissions unit, respiratory rate was only measured in around two thirds of children on arrival. Reasons for omission were given as "crying" or "unsettled" and in many of these children experienced nursing staff were unable to obtain an accurate reading. However, it is in these children that this measurement would potentially be most useful and important.

According to Murthy (6), existing devices for monitoring respiratory rate only estimate the actual breathing rate due to their limitations. These devices can be classified in different ways, depending on the manner in which they operate and how they are used. In this paper, respiration rate monitoring devices are grouped as either contact or noncontact. In contact respiration rate monitoring, the instrument makes direct contact with the subject's body. However, in noncontact monitoring, the respiration rate is measured without the instrument making contact with the subject's body.

There are clear advantages to noncontact respiration monitoring methods. These include improved patient comfort (especially for long term monitoring) as the subject is not tied to an instrument and improved accuracy as distress caused by a contact device may alter the respiration rate.

There have been several studies reporting developments in both contact and noncontact respiration monitoring. A review of non-invasive respiratory monitoring in medical care was provided by Folke et al. (7). This paper aims to review the literature on contact and non-contact methods of respiratory rate monitoring, including two methods currently being developed by our unit.

Contact Based Respiration Monitoring

Contact respiration rate monitoring instruments are usually based on measuring one of the following parameters: respiratory sounds, respiratory airflow, respiratory

Acoustic Based Methods

Respiratory sound can be measured using a microphone placed either close to the respiratory airways or over the throat to detect the variation of sound. Then a frequency analysis and estimation of the loudness of the sound can be carried out (8).

Werthammer et al. ( 9) reported a respiratory sounds measurement system to detect sleep apnea in infants. The system depended on recording a signal derived from breathing sounds from the nose. This method was applied to eight premature infants. Snorting, speaking, crying, coughing etc had a negative effect on the operation of the system.

Corbishley and Rordriguez-Villegas (10) proposed a miniaturised and wearable respiration monitoring respiration system. It used a microphone mounted on the neck to obtain the largest breathing acoustic.

Airflow Based Methods

Airflow can be detected because exhaled air is warmer, has higher humidity and contains more CO 2 than inhaled air. These variations can be used for indicating the respiratory rate. Most airflow-sensing methods need a sensor, attached to the airways (7). The measurement of the airflow can be achieved by using a nasal or oronasal thermistor which detects changes in temperature between the inhaled and exhaled air. This gives a semi-quantitative estimate of airflow, but the method is limited due to a high incidence of thermistor displacement (11).

The nasal pressure transducer is another sensor used to measure respiration rate.

Nasal pressure is a more accurate measure of airflow than others as it based on the actual volume of the air exhaled (8,12). It can be measured via nasal cannulae, mouthpiece or facemask. A problem with airflow measurement is that some patients may not feel comfortable with the sensor (13). The collector can also affect respiratory activity by increasing deadspace.

Folke et al. ( 14) have reported a CO 2 sensor to measure respiration rate. Their study also indicated that subtle design changes in the collecting device could introduce large differences in sensor performance.

Chest and Abdominal Movement Detection

Chest and abdominal wall movements can best be measured by either mercury strain gauges or impedance methods. Respiratory inductance plethysmography is a non-invasive technique whereby two bands measure the respiration rate, the thoracic band which is placed around the rib cage and the abdominal band which is placed over the abdomen at the level of the umbilicus. The bands are made from an extendible/deformable conducting material, either a very fine wire or thin foil such that the conductivity can be maintained during the stretching process (12,15). The principle of the strain gauge sensor is based on increase in the resistance of a conductor when the area of the conductor is increased during the respiration process. However, if the upper airway is partially obstructed, there may be a change in the phase angle and timing of the movements of the thorax and abdomen (16). The movements become asynchronous, ie the thorax moves inwards, and the abdomen outwards. During expiration this pattern is then reversed. Thoraco-abdominal asynchrony is a normal finding in infants in whom chest wall compliance is greater (17) and is exacerbated by respiratory disease or respiratory muscle weakness [START_REF] Stromberg | Thoracoabdominal asynchrony in small children with lung disease--methodological aspects and the relationship to lung mechanics[END_REF].

Nepal et al. (19) studied the abdominal strain gauge transducer for measuring respiration rate. The strain gauge was strapped around the patient's chest and changes in thoracic or abdominal circumference during breathing were measured.

The method involved a classification algorithm to separate respiratory signals as apnoea, respiration, or respiration with motion, by using a second order autoregressive modelling and zero cross algorithm.

Transcutaneous CO 2 Monitoring

In transcutaneous CO 2 monitoring a heated electrode (about 42° C) is applied to the skin (usually an arm). This method relies on the diffusion of gas to the skin and provides an overall estimate of change in CO 2 level rather than minute by minute readings. The electrode is surrounded by a solution to provide conductivity. Care needs to be taken to avoid skin burning on sensitive and neonatal skin (12).

Transcutaneous CO 2 monitoring therefore allows measurements of consequences of abnormal ventilation rather than a measure of the respiratory rate itself. Blood-Oxygen saturation (SpO 2 ) measurement is another technique for monitoring the consequences of abnormal ventilation. When air enters the lungs its oxygen binds to the haemoglobin in red blood cells. The oxygen is then transported throughout the body in arterial blood. A pulse oximeter uses the red and infrared frequencies to determine the percentage of haemoglobin in the blood that is saturated with oxygen. This percentage is called blood saturation, or SpO 2 (20). An oximeter simultaneously displays the SpO 2 level as well as the pulse rate and plethysmogram.

There have been studies indicating that respiration rate can be extracted from plethysmograms. Plethysmograms from ten healthy adults were processed using wavelet transforms (21). Respiration waveform was observed in the plots of the wavelet transforms. In another study involving 14 infants, of median age 2 days, the feasibility of extracting respiratory information from the plethsmogram traces was also demonstrated (22). The magnitude frequency spectra of the plethsmogram traces showed peaks associated with respiration rate.

Electrocardiogram (ECG) Derived Respiration Rate

This method is based on the fact that respiration has a modulating effect on the ECG. In this respiration rate monitoring approach, ECG electrodes are attached to the subject in order to record an ECG. By measuring the fluctuation in ECG, the respiration rate can be derived. This technique is called ECG-Derived Respiration (EDR) and is based on a process known as sinus arrhythmia, i.e. the modulation of ECG by the breathing process (23). EDR monitoring has also been performed by using a single-channel that did not have to be a precordial lead (25). In contrast to a number of other studies that used ECG characteristic waves (e.g. QRS complex), this study used the higher order statistics of ECG recording (such as the 4th order cumulant).

A study carried out a quantitative comparison of EDR monitoring techniques based on direct measurement of the modulation components versus techniques based on calculation of the mean electrical axis variation (26). The study concluded that single lead respiration rate estimates are more robust than the methods based on the mean electrical axis.

Radar Based Respiration Rate Monitoring

Greneker [START_REF] Greneker | Radar sensing of heartbeat and respiration at a distance with applications of the technology[END_REF] reported one of the first noncontact respiration rate monitoring systems. The system was called the Radar Vital Signs Monitor (RVSM). It was developed to monitor the performance of Olympic athletes at distances exceeding 10 meters. The RVSM detected breathing-induced movements of the chest using the Doppler phenomenon. A limitation of this method was motion artefact which corrupted the breathing signals. There have been no published studies describing the use of this method in children.

Optical Based Respiration Rate Monitoring

Aoki et al. ( 29) reported a non-restrictive visual sensing method to detect the respiration pattern by using a Fiber Grating (FG) vision sensor and processor unit.

Their system consisted of two parts. The first was the Fibre Grating projecting device. This provided an array of invisible infra-red light spots (wavelength 810nm).

The second part was a Charge-Coupled Device (CCD) camera with an optical bandpass filter. Infrared light was used to project a set of bright spots on the subject, while the CCD camera was used to capture the scene of bright spots. The moving distances of bright spots in each image were extracted and analysed to monitor respiration. ). The value of td was determined practically. An increase in the value of td caused faster algorithm operation, but decreased the resolution of the algorithm in detecting movements. In this study a value of 0.5 second was used for td as it was observed to provide an acceptable compromise between the resolution and speed.

The resulting difference images (img diff ) were then thresholded to produce binary images (img x ). The sum of pixel values in each binary image was determined to produce a set of data values (x). The magnitude of each data value in x represented the movement between the time t and t-td. These values were then plotted against time to obtain a respiration signal.

A plot of the values of x during exhalation and inhalation is provided in Fig. 1. The vertical axis of the plot represents chest and abdominal movements. Two lobes were observed, the lobe representing inhalation being larger. During exhalation, the chest's wall initially moves slowly inward, its movement increases with time, reaching a peak and then, the amount of movement decreases. A similar process occurs during inhalation, but this time the chest's wall moves outward. Fig. 2 shows the plot of x(t) during three respiration cycles. An algorithm was developed to extract the respiration rate from the recorded signal in real-time. Hsu and Chow (32) have reported a thermal sensor based respiration rate monitoring system. In this approach there was no contact with the child's skin. The sensor could detect temperature changes induced by respiration and then the data were corrected and analysed simultaneously by a personal computer that was linked to a central nursery room. To avoid missing the breathing signals, an ellipsoidshaped mask was made and the thermo sensors were placed on the mask so that breathing could be detected when the child's head turned. The problem with this method was that a mask had to be placed close to the child's face. In a study carried out by our group, the FLIR A40 thermal camera was used to monitor respiration related skin surface temperature variation in area centred on the tip of the nose (35). The thermal sensitivity of the camera is 0.08 Kelvin. The camera was fixed on a tripod in front of the subject at a distance of about one meter. The image capture rate was 50 frames per second, thus providing 3000 images per minute. The recording time was two minutes. The images were segmented and then an algorithm was used to locate and track a circular area centred on the tip of the nose. The segmentation and tracking algorithms are described Al-Khalidi et al. [START_REF] Saatchi | Facial tracking method for noncontact respiration rate monitoring[END_REF].

The chosen area was divided into eight equal concentric segments as shown in providing the least clear signal. This result indicated that for respiration monitoring, it would be advisable to consider all the eight segments and then to select the segments that provide the clearest respiration signal. An algorithm was produced to automatically extract the respiration rate from the recorded signal.

Discussion

Respiration rate monitoring has evolved from the days when it could only be measured by placing the back of the hand close to the nose to monitor exhaled air. It (11). A semi-quantitative measure of airflow and tidal volume can be derived from respiratory inductance plethysmography (RIP). The technique has been demonstrated to work well in measuring tidal volume in infants [START_REF] Hershenson | Changes in the contribution of the rib cage to tidal breathing during infancy[END_REF].

However, from a clinical perspective the main disadvantage of these methods is that they require connection to the child, some to the facial area, which disturbs many children and may be poorly tolerated. In addition, in infants and children, the added dead space of the equipment required for some of these techniques may have an influence on breathing patterns [START_REF] Brooks | Assessment of tidal volume over time in preterm infants using respiratory inductance plethysmography, The CHIME Study Group. Collaborative Home Infant Monitoring Evaluation[END_REF].

Conclusions

Monitoring respiration rate is an important task when evaluating a subject's health.

Respiration rate monitoring devices can be classified by a number of ways depending on the manner of their use and their operation. In this review paper, they were grouped into contact and noncontact. This review has highlighted the advances made to improve the effectiveness of respiration monitoring. The potential for noncontact respiration monitoring is emphasised. Noncontact respiration rate

  abdominal movements, respiratory CO 2 emission and oximetry probe SpO2. Respiration rate can also be derived from the electrocardiogram (ECG).

7

 7 Normally the inspiratory thoracic and abdominal expansion is almost synchronous.

  second part was a Charge-Coupled Device (CCD) camera with an optical bandpass filter. Infrared light was used to project a set of bright spots on the subject, while the CCD camera was used to capture the scene of bright spots. The moving distances of bright spots in each image were extracted and analysed to monitor respiration.Nakajima et al.(30) used a static camera to detect thoracic movements to determine respiration rate. The projection of the surface of the thorax was represented as a region with a range of brightness intensities. Respiration was monitored by quantifying the variations of the locations of the image intensities over time. optical methods have not previously been described in children, however, in a study carried out by our group, a high speed desktop computer connected to a video camera (webcam) was used to record respiration related chest and abdominal movements in children in a sleep unit(31). The video consisted of a series of sequential images, each marked with an individual time stamp (t), corresponding to the time of the recording. An algorithm was designed to subtract the current image at time t (i.e. img t ) and the image a few time frames before at time t-td (i.e. img t-td ). The value of td was determined practically. An increase in the value of td caused faster algorithm operation, but decreased the resolution of the algorithm in detecting movements. In this study a value of 0.5 second was used for td as it was observed to provide an acceptable compromise between the resolution and speed.The resulting difference images (img diff ) were then thresholded to produce binary images (img x ). The sum of pixel values in each binary image was determined to produce a set of data values (x). The magnitude of each data value in x represented the movement between the time t and t-td. These values were then plotted against time to obtain a respiration signal.A plot of the values of x during exhalation and inhalation is provided in Fig.1. The vertical axis of the plot represents chest and abdominal movements. Two lobes were observed, the lobe representing inhalation being larger. During exhalation, the chest's wall initially moves slowly inward, its movement increases with time, reaching a peak and then, the amount of movement decreases. A similar process occurs during inhalation, but this time the chest's wall moves outward. Fig.2shows the plot of x(t) during three respiration cycles. An algorithm was developed to extract the respiration rate from the recorded signal in real-time.

  Zhu et al.(33) developed an infrared imaging based respiration rate monitoring method. They designed a tracking algorithm that could follow facial features related to respiration. These features were selected manually from a reference image (i.e. the first image in the video) by specifying three windows. Two of these windows covered the areas between the bridge of nose and the inner corner of the eyes (i.e. the periorbital regions) and represented the warmest facial areas. Another window was placed on the apex of nose to represent the coolest facial area. Their algorithm tracked these three windows in the following recorded images. The respiration signal was obtained from a rectangular region under the nose.Instead of using a focal plane array of mid-wave infra-red sensors, Chekmenev, et al.(34) used a thermal camera consisting of a focal plane array for a long-wave infra-red (6-15 µm) sensor. They measured the temperature changes around the neck region, carotid vessel complex, and the nasal region. The selection of these regions was carried out manually. A wavelet analysis technique was developed to extract the ECG and the respiration rate.

Fig. 3 .

 3 Fig.3. The pixel values within each of the eight segments were averaged to obtain a single value representing the skin temperature in that segment. The process was repeated for each image. Plots of the average temperature against time for the segments were obtained (see Fig.4). These plots represented the respiration signal associated with the segments. The respiration signal reduces in amplitude during inhalation and increases in amplitude during exhalation. The clarity of the signals varied, with segments 3 and 7 providing the most clear signals and segment 1

  There are extensive opportunities to further improve noncontact respiration monitoring schemes. Radar, infrared imaging and optical imaging have all been used to monitor respiration rate. Advances in computing technology have resulted in algorithms for respiration monitoring. For example, it has been possible to use 3-dimentional vision algorithms and two web cameras to monitor respiration in manikins[START_REF] Saatchi | Facial tracking method for noncontact respiration rate monitoring[END_REF].Currently noncontact respiration monitoring methods have not yet reached the level of maturity that can be used routinely in clinical environments. Concerns related to patient safety, electromagnetic interference with existing medical equipments, complexity of using the systems have been factors in their slow take up in clinical environments. With further development, noncontact methods will gradually become more and more viable and will effectively complement contact based respiration rate monitoring methods.We have developed two novel methods for non contact respiratory rate monitoring in children which, whilst currently are sophisticated, high technology devices are undergoing further evaluation in acute clinical settings and will serve as a basis for future development to produce an inexpensive, user friendly device for use in the clinical environment.

  abdominal movements, respiratory CO 2 emission and oximetry probe SpO2. Respiration rate can also be derived from the electrocardiogram (ECG).

7

 7 Normally the inspiratory thoracic and abdominal expansion is almost synchronous.

9 EDR

 9 is believed to be based on small ECG morphology changes during the respiratory cycle caused by movement of the heart position relative to the electrodes and the change in lung volume. Principal component analysis has been used to identify which ECG lead was most effective before extracting the respiration rate(24).

  Tarassenko et al.(27) looked at three methods: The EDR, the electrical impedance pneumography (IP) signal across the chest, and the ECG or the changes in light absorption which is known as photoplethysmogram (PPG) across a finger. They obtained estimates of the breathing rate by adding the individual estimated outputs for both the IP and PPG channels after applying the Kalman filters for both waveforms. A limitation of these methods is that movement artefacts introduce errors in estimating the breathing rates.

12 3. 3

 123 Thermal Sensor and Thermal Imaging Based Respiration Rate Monitoring

  Zhu et al.(33) developed an infrared imaging based respiration rate monitoring method. They designed a tracking algorithm that could follow facial features related to respiration. These features were selected manually from a reference image (i.e. the first image in the video) by specifying three windows. Two of these windows covered the areas between the bridge of nose and the inner corner of the eyes (i.e. the periorbital regions) and represented the warmest facial areas. Another window was placed on the apex of nose to represent the coolest facial area. Their algorithm tracked these three windows in the following recorded images. The respiration signal was obtained from a rectangular region under the nose.Instead of using a focal plane array of mid-wave infra-red sensors, Chekmenev, et al.(34) used a thermal camera consisting of a focal plane array for a long-wave infra-red (6-15 µm) sensor. They measured the temperature changes around the neck region, carotid vessel complex, and the nasal region. The selection of these regions was carried out manually. A wavelet analysis technique was developed to extract the ECG and the respiration rate.

Fig. 3 .

 3 Fig.3. The pixel values within each of the eight segments were averaged to obtain a

  There are extensive opportunities to further improve noncontact respiration monitoring schemes. Radar, infrared imaging and optical imaging have all been used to monitor respiration rate. Advances in computing technology have resulted in algorithms for respiration monitoring. For example, it has been possible to use 3-dimentional vision algorithms and two web cameras to monitor respiration in manikins[START_REF] Saatchi | Facial tracking method for noncontact respiration rate monitoring[END_REF]. Currently noncontact respiration monitoring methods have not yet reached the level of maturity that can be used routinely in clinical environments. Concerns related to patient safety, electromagnetic interference with existing medical equipments, complexity of using the systems have been factors in their slow take up in clinical environments. With further development, noncontact methods will gradually become more and more viable and will effectively complement contact based respiration rate monitoring methods. We have developed two novel methods for non contact respiratory rate monitoring in children which, whilst currently are sophisticated, high technology devices are undergoing further evaluation in acute clinical settings and will serve as a basis for future development to produce an inexpensive, user friendly device for use in the clinical environment.

A

  a distinct advantage over contact methods, especially in children, as they cause least disturbance to the patient. Studies are still ongoing to produce more effective respiration monitoring devices. plot of values of x during inhalation and exhalation. 128x68mm (96 x 96 DPI) Plot x(t) against time during three respiration cycles. 154x69mm (96 x 96 DPI) A thermal image with tip of the nose represented by a circle, (b) the eight segments of the selected respiration region. 110x65mm (96 x 96 DPI) Respiration signals obtained from segments 1 to 8 (from top to bottom respectively). 148x116mm (96 x 96 DPI)

10 3 Noncontact Respiratory Monitoring Methods 3.1 Radar Based Respiration Rate Monitoring

	Greneker (28) reported one of the first noncontact respiration rate monitoring
	systems. The system was called the Radar Vital Signs Monitor (RVSM). It was
	developed to monitor the performance of Olympic athletes at distances exceeding
	10 meters. The RVSM detected breathing-induced movements of the chest using
	the Doppler phenomenon. A limitation of this method was motion artefact which
	corrupted the breathing signals. There have been no published studies describing
	r o F the use of this method in children.
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	Tarassenko et al. (27) looked at three methods: The EDR, the electrical impedance pneumography (IP) signal across the chest, and the ECG or the changes in light e r
	absorption which is known as photoplethysmogram (PPG) across a finger. They R
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  to develop a reliable, accurate and objective method of monitoring respiratory rate in children which is non-invasive and therefore will not cause distress to the child which may lead to inaccuracies in the measurement. The gold standard is still to place a thermistor in a nostril to monitor exhaled air. However, a variety of contact and noncontact respiration monitoring devices have been developed.

	is very important Several techniques are available for measurement of respiratory rate via nasal
	prongs, masks, thermistor or respiratory impedance plethysmography. These
	methods all involve some contact with the child. A pneumotachograph has the
	advantage that it gives quantitative assessments of flows, from which respiratory rate
	can be derived, and may be important in a research setting. The thermistor is a
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commonly used technique to detect temperature changes breath by breath at the nostril, thereby giving the number of breaths per minute. This technique has been formally validated in the measurement of respiratory rate for the purposes of sleep studies

  a distinct advantage over contact methods, especially in children, as they cause least disturbance to the patient. Studies are still ongoing to produce more effective respiration monitoring devices.

	Pediatric Pulmonology monitoring devices have Page 16 of 46 28. Greneker EF. Radar sensing of heartbeat and respiration at a distance with Surface Centred on the Tip of the Nose for Respiration Monitoring. ICEDSP
	applications of the technology. Radar 1997; 97:150:154. International Conference on Computer Systems and Applications, Manipal, India,
	2009.
	36. Al-Khalidi FQ, Saatchi R, Burke D, Elphick H. Facial tracking method for
	noncontact respiration rate monitoring, IEEE, IET International Symposium on
	Communication Systems, Networks and Digital Signal Processing, Newcastle, UK.
	21-23 July, 2010; 827-830. ISBN-Hardcopy: 978-1-86135-370-2
	37. Hershenson MB, Colin AA, Wohl ME, Stark AR. Changes in the contribution of
	the rib cage to tidal breathing during infancy. American Review of Respiratory
	F o r F o r F o r F o r F o r r o F Disease. 1990;141:922-5.
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	noncontact respiration monitoring is emphasised. Noncontact respiration rate
	16 20 21
	John Wiley & Sons, Inc.

38. Brooks LJ, DiFiore JM, Martin RJ. Assessment of tidal volume over time in preterm infants using respiratory inductance plethysmography, The CHIME Study Group. Collaborative Home Infant Monitoring Evaluation. Pediatr Pulmonol. 1997;23:429-33.

  to develop a reliable, accurate and objective method of monitoring respiratory rate in children which is non-invasive and therefore will not cause distress to the child which may lead to inaccuracies in the measurement. The gold standard is still to place a thermistor in a nostril to monitor exhaled air. However, a variety of contact and noncontact respiration monitoring devices have been developed.Several techniques are available for measurement of respiratory rate via nasal prongs, masks, thermistor or respiratory impedance plethysmography. These methods all involve some contact with the child. A pneumotachograph has the advantage that it gives quantitative assessments of flows, from which respiratory rate can be derived, and may be important in a research setting. The thermistor is a commonly used technique to detect temperature changes breath by breath at the nostril, thereby giving the number of breaths per minute. This technique has been formally validated in the measurement of respiratory rate for the purposes of sleep studies

	is very important
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John Wiley & Sons, Inc.Pediatric Pulmonology