MD Thomas Metterlein
email: tom.metterlein@gmx.net

Matthias Frommer

Pingling Kwok

Stefan Lyer

Bernhard M Graf

Barbara Sinner

Metterlein

Sinner

Emergency cricothyrotomy in infantsevaluation of a novel device in an animal model

Keywords: infant < Age, difficult < Airway, devices < techniques Pediatric airway management, emergency, cricothyrotomy, Quicktrach baby™ Pediatric airway management, emergency, cricothyrotomy, Quicktrach baby™

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

Introduction

The "difficult airway" algorithm of the American Society of Anesthesiologists (ASA) recommends a surgical approach as the final step in managing an otherwise inaccessible airway. 1 Cricothyrotomy is an easy, quick, and potentially life-saving surgical procedure in adult patients. 2;3 If performed correctly, the complication rate is very low since the technique itself is straightforward. However, most physicians, even those who are regularly involved in airway management, have limited experience with this technique. 4 Its emergency character means it is rarely used, and generally, when it is implemented, is in a life-threatening situation.

As alternatives to an open surgical procedure, less invasive techniques have been introduced. For adults, two alternatives for a minimally invasive cricotyrotomy exist: the Seldiger method, using a guide-wire to insert the cannula, and the catheter-over-needle technique for direct puncture. For both approaches, various sets are commercially available and have been evaluated in prior studies.

In contrast, for infants, only one device is commercially available -the Quicktrach baby™ (VBM Medizintechnik GmbH, Sulz am Neckar, Germany) (Figure 1). It is a smaller version of the same set used for adults and utilizes the catheter-over-needle technique.

In adults, the catheter-over-needle technique has a complication rate of about 40%. Only in about 70 to 80% of the cases sufficient ventilation is possible. Damage to surrounding structures can be seen in about 60% of the procedures.

In infants the anatomic structures of the anterior neck are less defined. The tissue of the larynx and the trachea is softer and more vulnerable, leading to a higher risk for traumatic complications.

Methods

After information of the local ethics committee, two anesthesiologists (a first and a fourth year resident) performed this randomized trial. The two participants were familiar with the set, and had the chance to practice the technique on manikins one month prior to the investigation. For the study, cadavers of ten female adult rabbits (New Zealand White Rabbits) were used. The rabbits were euthanized (T61, Intervet, Unterschleißheim, Germany) while under deep anesthesia (intravenous thiopenthal;

Nykomed, Konstanz, Germany). After their death the whole anterior neck region was shaved, and the animals were placed in a supine position. The weight of the rabbits was documented. For each of the participants the rabbits were randomly allocated.

We then evaluated Quicktrach baby™ (VBM Medizintechnik GmbH, Sulz am Neckar, Germany), a commercially available device for emergency cricothyrotomy in infants. The set consists of a syringe, a curved needle, a plastic 1.2 mm (inner diameter) cannula and a stopper. The stopper is intended to prevent the needle from being inserted to deeply. The risk of a posterior wall perforation is supposed to be reduced with this device.

Two time intervals were defined. The first time interval was started with the "decision" to gain a surgical airway and ended with the actual beginning of the cricothyrotomy. While the participant examined the anatomical structures and identified the puncture site, a second person opened and prepared the set by filling the syringe with liquid. The second time interval started with the puncture and ended with the first successful ventilation, or when the time limit of 180 seconds was reached.

This time limit was set because three minutes are considered to be the maximum accepted time to achieve a proper surgical airway, in case of a total airway obstruction. 8;9 Exceeding this time limit was considered as failure.

Puncture site was the cricothyriod membrane between the palpable thyroid and cricoid's cartilage. The procedure was performed standing behind the head with one hand marking the insertion site and the other hand guiding the device. In all approaches the needle was advanced at an angle of 45° to the prelaryngeal skin, in caudal direction. Air could be aspirated as soon as the needle entered the larynx.

The device was then advanced a little further and the cannula was placed over the mandarin. After insertion of the cannula, and removal of the metal needle, the device was connected to a breathing bag. Successful manual ventilation was confirmed clinically by inspection and auscultation.

Finally an otorhinolaryngologist (P.K.), who had not been present during the cricothyrotomy, opened the larynx and the trachea allowing complete inspection of the involved structures. Damage to the

Results

The weight of the animals was 4.1 [3.5 -5.4] kg, and the tracheal diameter had a median of 5.5 [5.1 -6.0] mm. Proper placement of the cannula was achieved in all ten attempts. (Figure 2) The time for the preparation of the device was 12 [9 -14] seconds. The actual placement of the cannula lasted 31 [23 -43] seconds from penetration of the skin, until the connection with the breathing bag. Successful ventilation was possible in all ten cases.

After preparation of the larynx, fractures of the cricoid's cartilage and small hematoma of the cricothyroid muscle were seen in two animals. In one animal, injury to the posterior wall mucosa was observed. (Figure 3)

There was no difference in the complication rates between the two operators. Damage to the cricoid cartilage was not operator dependent.

Both participants stated they would consider using this device in a real emergency. There were minor complications in 33% of procedures carried out, which had no impact on the success of the technique.

Several studies have already been published on minimal invasive cricothyrotomy in adults.

8-12

Performance time of the wire-guided technique, compared to a standard surgical technique in human cadavers is similar at about 100 seconds. Also, no difference in complication rate (about 15%) could be seen. 8;10 Various studies have been performed to evaluate the catheter-over-needle technique in adults. Depending on the individual design, various conclusions could be drawn. In general, the catheter-over-needle technique is faster to perform than other minimally invasive cricothrotomy techniques. However, relatively high complication rates were documented in two studies involving human adult manikins. Damage to surrounding structures occurred in 30 and 20% of cases respectively, and involved mainly the posterior larynx wall. 13;14 Ventilation was possible in 100% of cases in both trials, and the procedure time was less than 60 seconds. 13;14 A further study evaluated the cannula-over-needle method on prepared adult pig larynxes. Anesthesiology and ENT residents found again, that the technique was fast to perform (48 seconds), and had an even lower complication rate (5%). 15 In this setting, the catheter-over-needle technique was subjectively easier to perform than other methods and would, therefore, be the preferred technique in a real emergency situation. A recent study with a more realistic model, using whole adult sheep cadavers, revealed a relatively high complication rate. In 37%, no successful ventilation was possible because of an incorrect placement of the cannula, and damage to the surrounding structures occurred in 60%.

5

So far, the cannula-over-needle method has never been evaluated in a model for infants. Compared to the adult model, a higher complication rate has been suspected for infants, because the anatomical structures are more difficult to identify with palpation. In addition, the tissue of the anterior neck in infants is softer than in adults, allowing an easier compression of larynx and trachea.

4;6

The results of this study, however, demonstrate a complication rate similar to the studies on the adult model. Damage to surrounding structures occurred in 33%, but did not impair ventilation. The explanation for this might be the force that is needed to place the cannula. The needle of the adult Quicktrach™ is large and conically shaped. The necessary force for insertion of the cannula is higher and leads to a compression of the trachea due to the compliant anterior wall. The risk of an injury of the posterior wall increases with the decreased anterior-posterior diameter of the trachea. This could be shown fiberoptically with a similar device in an in vivo study. 16 Because of the small and sharp needle of the Quicktrach baby™, no excessive force is needed for an accurate placement of the cannula. The risk for potential trauma to surrounding structures is therefore minimized, and the success rate increased. In two cases, the cricoid cartilage was fractured. This is potentially due to less distinct anatomic landmarks and a smaller larynx. However, in both cases ventilation was possible.

The injury to the posterior wall mucosa occurred most likely because the device was advanced too far into the larynx. Early detection (no air could be aspirated) in this case prevented an esophageal misplacement.

The included stopper does not, necessarily, prevent damage to the posterior wall. Depending on the angle in which the needle is forwarded, penetration, even into the esophagus, is still possible. The use of the stopper cannot compensate the risks of a careless performance of the procedure.

A clear advantage of the small size of the needle is the limited trauma to the tissue. After the device is removed complications such as delayed healing, or excessive scarring, should be less frequent compared to open surgical approaches. Additionally, the small diameter allows the placement of the cannula through the cricothyroid membrane. Larger devices can only be placed below the cricoids cartilage, the narrowest part of the upper airway in infants. 17

Quicktrach baby™ is a commercially available device that allows a facilitated needle cricothyrotomy in an emergency situation. This technique is mentioned as preferred method for smaller children, but detailed information about success and complication rates is missing. 18 The device primarily designed for cricothyrotomy can however also be place directly into the trachea as "needle tracheotomy".

Theoretically, the "needle airway" avoids an acute desaturation, and gains time before a definite airway can be established. The exact length of the created time interval is unknown and depends on the method of oxygen delivery. A prior study could show that both bag ventilation as well as the delivery of a constant flow of over 6 L/min of oxygen resulted in sufficient minute volumes. The connection to a jet ventilation device resulted in the highest amounts of oxygen delivered. prevent aspiration, and the quality of carbon dioxide elimination is not known. Compared to a standard intravenous needle, Quicktrach baby™ has various advantages. The bend shape facilitates puncture.

After successful placement, the shape allows easy fixation to the neck.

A clear advantage of the technique is the short performance time. Placement is very straightforward similar to a standard intravascular catheter. Once placed the device is ready to use without any further steps involved.In prior publications, three minutes was considered the maximal acceptable time for the establishment of a surgical airway in the case of a total obstruction of the upper airway. 8;9 Even the longest attempt for placing the device in this study took just 67 seconds, including preparation of the device. It is, therefore, well within tolerable limits. The device is easy and quick to prepare because only the included syringe has to be filled with liquid.

Both participants had never performed the procedure on a patient before, and were therefore motivated and unbiased. The time for establishing the emergency airway did not differ between the two physicians, despite various levels of experience. Previous knowledge and training might not have an extensive influence on the performance. There was also not a substantial discrepancy in performance time between the first and the following attempts, indicating that the plateau of the learning curve was already reached after just one practice session. In prior studies, with other sets for emergency cricothyrotomy, such a plateau could only be reached after at least five attempts. 20 Human cadavers are a good teaching model for procedures like a cricothyrotomy and thus, would be an ideal study object. However human corpses are not widely available. Trials on formalin-prepared corpses are less realistic and the interpretation of the results is, therefore, again limited. 21 Certain animals can be used as a realistic model for airway studies. Prior trials found no significant differences in insertion and penetration force between human cadavers and various animal models. 22 Rabbit skin resembles human skin more than the skin of many other animals. 23 Patients with edema of the head and neck region often have altered skin conditions. The anatomical structures of the neck region of rabbit and human infants are very similar, but of course not identical. Size and shape of the thyroid's, cricoid's cartilage and cricothyroid membrane are comparable. The cricothyroid membrane faces slightly cephalad and the airway narrows at the cricoid's cartilage. Both aspects are not as distinct as in human infants but resemble the pediatric airway more than the adult larynx. Palpable landmarks of the anterior neck region are also very similar.

However, the real life scenario of a "cannot intubate, cannot ventilate" situation mainly occurs in patients with unfavorable anatomy. Therefore, the heterogeneity of a rabbit neck is probably more practical than the uniform design of a human simulator.

Both involved physicians felt confident using this device in an emergency. A reason for this might be that anesthesiologists are comfortable with the cannula-over-needle technique. Whether involvement of surgeons or otolaryngologists, who are more familiar with open surgical procedures, would lead to different results has to be investigated in further trials.

Conclusion

It could be proven that the cannula-over-needle technique is a reliable method for emergency cricothyrotomy in infants. Within a reasonable time sufficient ventilation was achieved. The observed complication rate was within an acceptable range.

We thank Miss Elise Palmer for proofreading the manuscript. Quicktrach babyTM set containing the cannula, a metal mandarin, a rubber stopper and a syringe. A: assembled as contained in the set; B: dissembled after its use.

Introduction

The "difficult airway" algorithm of the American Society of Anesthesiologists (ASA) recommends a surgical approach as the final step in managing an otherwise inaccessible airway. 1 Cricothyrotomy is an easy, quick, and potentially life-saving surgical procedure in adult patients. 2;3 If performed correctly, the complication rate is very low since the technique itself is straightforward. However, most physicians, even those who are regularly involved in airway management, have limited experience with this technique. 4 Its emergency character means it is rarely used, and generally, when it is implemented, is in a life-threatening situation.

As alternatives to an open surgical procedure, less invasive techniques have been introduced. For adults, two alternatives for a minimally invasive cricotyrotomy exist: the Seldiger method, using a guide-wire to insert the cannula, and the catheter-over-needle technique for direct puncture. For both approaches, various sets are commercially available and have been evaluated in prior studies.

In contrast, for infants, only one device is commercially available -the Quicktrach baby™ (VBM Medizintechnik GmbH, Sulz am Neckar, Germany) (Figure 1). It is a smaller version of the same set used for adults and utilizes the catheter-over-needle technique.

In adults, the catheter-over-needle technique has a complication rate of about 40%. Only in about 70 to 80% of the cases sufficient ventilation is possible. Damage to surrounding structures can be seen in about 60% of the procedures.

5

In infants the anatomic structures of the anterior neck are less defined. The tissue of the larynx and the trachea is softer and more vulnerable, leading to a higher risk for traumatic complications. performed this randomized trial. The two participants were familiar with the set, and had the chance to practice the technique on manikins one month prior to the investigation. For the study, cadavers of ten female adult rabbits (New Zealand White Rabbits) were used. The rabbits were euthanized (T61, Intervet, Unterschleißheim, Germany) while under deep anesthesia (intravenous thiopenthal;

Nykomed, Konstanz, Germany). After their death the whole anterior neck region was shaved, and the animals were placed in a supine position. The weight of the rabbits was documented. For each of the participants the rabbits were randomly allocated.

We then evaluated Quicktrach baby™ (VBM Medizintechnik GmbH, Sulz am Neckar, Germany), a commercially available device for emergency cricothyrotomy in infants. The set consists of a syringe, a curved needle, a plastic 1.2 mm (inner diameter) cannula and a stopper. The stopper is intended to prevent the needle from being inserted to deeply. The risk of a posterior wall perforation is supposed to be reduced with this device.

Two time intervals were defined. The first time interval was started with the "decision" to gain a surgical airway and ended with the actual beginning of the cricothyrotomy. While the participant examined the anatomical structures and identified the puncture site, a second person opened and prepared the set by filling the syringe with liquid. The second time interval started with the puncture and ended with the first successful ventilation, or when the time limit of 180 seconds was reached.

This time limit was set because three minutes are considered to be the maximum accepted time to achieve a proper surgical airway, in case of a total airway obstruction. 8;9 Exceeding this time limit was considered as failure.

Puncture site was the cricothyriod membrane between the palpable thyroid and cricoid's cartilage. The procedure was performed standing behind the head with one hand marking the insertion site and the other hand guiding the device. In all approaches the needle was advanced at an angle of 45° to the prelaryngeal skin, in caudal direction. Air could be aspirated as soon as the needle entered the larynx.

The device was then advanced a little further and the cannula was placed over the mandarin. After insertion of the cannula, and removal of the metal needle, the device was connected to a breathing bag. Successful manual ventilation was confirmed clinically by inspection and auscultation.

Finally an otorhinolaryngologist (P.K.), who had not been present during the cricothyrotomy, opened the larynx and the trachea allowing complete inspection of the involved structures. Damage to the After the study, both participants were asked to indicate if they felt confident in using the device in case of a real emergency.

Because of the small number of animals, data were supposed to be non-parametrically distributed and are, therefore, shown as median with interquartile range.

Results

The weight of the animals was 4.1 [3.5 -5.4] kg, and the tracheal diameter had a median of 5.5 [5.1 -6.0] mm. Proper placement of the cannula was achieved in all ten attempts. (Figure 2) The time for the preparation of the device was 12 [9 -14] seconds. The actual placement of the cannula lasted 31 [23 -43] seconds from penetration of the skin, until the connection with the breathing bag. Successful ventilation was possible in all ten cases.

After preparation of the larynx, fractures of the cricoid's cartilage and small hematoma of the cricothyroid muscle were seen in two animals. In one animal, injury to the posterior wall mucosa was observed. (Figure 3)

There was no difference in the complication rates between the two operators. Damage to the cricoid cartilage was not operator dependent.

Both participants stated they would consider using this device in a real emergency.

Discussion

This is the first animal study that evaluates success rate, procedure time, and complication rate of a novel emergency cricothyrotomy device for infants -the Quicktrach baby™. The major finding is that the technique had a 100% success rate. It could be performed quickly within 31 [23 -43] seconds. There were minor complications in 33% of procedures carried out, which had no impact on the success of the technique.

Several studies have already been published on minimal invasive cricothyrotomy in adults.

8-12

Performance time of the wire-guided technique, compared to a standard surgical technique in human cadavers is similar at about 100 seconds. Also, no difference in complication rate (about 15%) could be seen. 8;10 Various studies have been performed to evaluate the catheter-over-needle technique in adults. Depending on the individual design, various conclusions could be drawn. In general, the catheter-over-needle technique is faster to perform than other minimally invasive cricothrotomy techniques. However, relatively high complication rates were documented in two studies involving human adult manikins. Damage to surrounding structures occurred in 30 and 20% of cases respectively, and involved mainly the posterior larynx wall. 13;14 Ventilation was possible in 100% of cases in both trials, and the procedure time was less than 60 seconds. 13;14 A further study evaluated the cannula-over-needle method on prepared adult pig larynxes. Anesthesiology and ENT residents found again, that the technique was fast to perform (48 seconds), and had an even lower complication rate (5%). 15 In this setting, the catheter-over-needle technique was subjectively easier to perform than other methods and would, therefore, be the preferred technique in a real emergency situation. A recent study with a more realistic model, using whole adult sheep cadavers, revealed a relatively high complication rate. In 37%, no successful ventilation was possible because of an incorrect placement of the cannula, and damage to the surrounding structures occurred in 60%.

5

So far, the cannula-over-needle method has never been evaluated in a model for infants. Compared to the adult model, a higher complication rate has been suspected for infants, because the anatomical structures are more difficult to identify with palpation. In addition, the tissue of the anterior neck in infants is softer than in adults, allowing an easier compression of larynx and trachea.

4;6

The results of this study, however, demonstrate a complication rate similar to the studies on the adult model. Damage to surrounding structures occurred in 33%, but did not impair ventilation. The explanation for this might be the force that is needed to place the cannula. The needle of the adult Quicktrach™ is large and conically shaped. The necessary force for insertion of the cannula is higher and leads to a compression of the trachea due to the compliant anterior wall. The risk of an injury of the posterior wall increases with the decreased anterior-posterior diameter of the trachea. This could be shown fiberoptically with a similar device in an in vivo study. 16 Because of the small and sharp needle of the Quicktrach baby™, no excessive force is needed for an accurate placement of the cannula. The risk for potential trauma to surrounding structures is therefore minimized, and the success rate increased. In two cases, the cricoid cartilage was fractured. This is potentially due to less distinct anatomic landmarks and a smaller larynx. However, in both cases ventilation was possible.

The injury to the posterior wall mucosa occurred most likely because the device was advanced too far into the larynx. Early detection (no air could be aspirated) in this case prevented an esophageal misplacement.

The included stopper does not, necessarily, prevent damage to the posterior wall. Depending on the angle in which the needle is forwarded, penetration, even into the esophagus, is still possible. The use of the stopper cannot compensate the risks of a careless performance of the procedure.

A clear advantage of the small size of the needle is the limited trauma to the tissue. After the device is removed complications such as delayed healing, or excessive scarring, should be less frequent compared to open surgical approaches. Additionally, the small diameter allows the placement of the cannula through the cricothyroid membrane. Larger devices can only be placed below the cricoids cartilage, the narrowest part of the upper airway in infants. 17

Quicktrach baby™ is a commercially available device that allows a facilitated needle cricothyrotomy in an emergency situation. This technique is mentioned as preferred method for smaller children, but detailed information about success and complication rates is missing. 18 The device primarily designed for cricothyrotomy can however also be place directly into the trachea as "needle tracheotomy".

Theoretically, the "needle airway" avoids an acute desaturation, and gains time before a definite airway can be established. The exact length of the created time interval is unknown and depends on the method of oxygen delivery. A prior study could show that both bag ventilation as well as the delivery of a constant flow of over 6 L/min of oxygen resulted in sufficient minute volumes. The connection to a jet ventilation device resulted in the highest amounts of oxygen delivered. prevent aspiration, and the quality of carbon dioxide elimination is not known. Compared to a standard intravenous needle, Quicktrach baby™ has various advantages. The bend shape facilitates puncture.

After successful placement, the shape allows easy fixation to the neck.

A clear advantage of the technique is the short performance time. Placement is very straightforward similar to a standard intravascular catheter. Once placed the device is ready to use without any further steps involved.In prior publications, three minutes was considered the maximal acceptable time for the establishment of a surgical airway in the case of a total obstruction of the upper airway. 8;9 Even the longest attempt for placing the device in this study took just 67 seconds, including preparation of the device. It is, therefore, well within tolerable limits. The device is easy and quick to prepare because only the included syringe has to be filled with liquid.

Both participants had never performed the procedure on a patient before, and were therefore motivated and unbiased. The time for establishing the emergency airway did not differ between the two physicians, despite various levels of experience. Previous knowledge and training might not have an extensive influence on the performance. There was also not a substantial discrepancy in performance time between the first and the following attempts, indicating that the plateau of the learning curve was already reached after just one practice session. In prior studies, with other sets for emergency cricothyrotomy, such a plateau could only be reached after at least five attempts. 20 Again a possible indication for the practicability of Quicktrach baby TM . The design of the device is very similar to familiar intravascular catheters allowing easy handling.

To draw further conclusions from the mentioned results is, of course, limited by the design of the study protocol. The produced setting reflects a real-life situation only to a certain degree. The stress of a real emergency can not be simulated with artificial time-pressure. No other distracting factors like obvious trauma, restlessness of the patient or agitated personnel were generated. Whether a proper oxygenation would be possible with this device is subject to further studies. Other relevant complications like infection or tracheal stenosis were not examined.

Prospective randomized trials in humans for emergency procedures are impossible -both ethically and logistically.

Human cadavers are a good teaching model for procedures like a cricothyrotomy and thus, would be an ideal study object. However human corpses are not widely available. Trials on formalin-prepared corpses are less realistic and the interpretation of the results is, therefore, again limited. 21 Certain animals can be used as a realistic model for airway studies. Prior trials found no significant differences in insertion and penetration force between human cadavers and various animal models. 22 Rabbit skin resembles human skin more than the skin of many other animals. 23 Patients with edema of the head and neck region often have altered skin conditions. The anatomical structures of the neck region of rabbit and human infants are very similar, but of course not identical. Size and shape of the thyroid's, cricoid's cartilage and cricothyroid membrane are comparable. The cricothyroid membrane faces slightly cephalad and the airway narrows at the cricoid's cartilage. Both aspects are not as distinct as in human infants but resemble the pediatric airway more than the adult larynx. Palpable landmarks of the anterior neck region are also very similar.

However, the real life scenario of a "cannot intubate, cannot ventilate" situation mainly occurs in patients with unfavorable anatomy. Therefore, the heterogeneity of a rabbit neck is probably more practical than the uniform design of a human simulator.

Both involved physicians felt confident using this device in an emergency. A reason for this might be that anesthesiologists are comfortable with the cannula-over-needle technique. Whether involvement of surgeons or otolaryngologists, who are more familiar with open surgical procedures, would lead to different results has to be investigated in further trials.

Conclusion

It could be proven that the cannula-over-needle technique is a reliable method for emergency cricothyrotomy in infants. Within a reasonable time sufficient ventilation was achieved. The observed complication rate was within an acceptable range.

We thank Miss Elise Palmer for proofreading the manuscript. Table 1: Anterior view:

Rabbit: Weight [kg]

6 ; 7

 67 This is the first study that examines the catheter-over-needle technique in a model for infants. An animal model was used to investigate whether this novel device would allow the successful establishment of an emergency airway. Procedure time and complication rate were evaluated.

19 Cricothyrotomy

 19 has to be considered an emergency procedure only in a life or death situation. The cannula must be replaced by a definite airway as soon as possible. Needle cricothyrotomy does not Deleted: cricothyrotomy Deleted: Therefore, c

  Again a possible indication for the practicability of Quicktrach baby TM . The design of the device is very similar to familiar intravascular catheters allowing easy handling. To draw further conclusions from the mentioned results is, of course, limited by the design of the study protocol. The produced setting reflects a real-life situation only to a certain degree. The stress of a real emergency can not be simulated with artificial time-pressure. No other distracting factors like obvious trauma, restlessness of the patient or agitated personnel were generated. Whether a proper oxygenation would be possible with this device is subject to further studies. Other relevant complications like infection or tracheal stenosis were not examined. Prospective randomized trials in humans for emergency procedures are impossible -both ethically and logistically.

  Figures:

Figure 2 :

 2 Figure 2: Proper placement of the device in the cricothyroid membrane: A lateral view of the intact neck; B anterior view of the larynx and trachea.

Figure 3 :

 3 Figure 3: Posterior wall of larynx and trachea: A: no injury B: injury to the posterior wall (circle) (Arrow: entry wound at cricothyroid membrane)

6 ; 7 Methods

 67 This is the first study that examines the catheter-over-needle technique in a model for infants. An animal model was used to investigate whether this novel device would allow the successful establishment of an emergency airway. Procedure time and complication rate were evaluated. After information of the local ethics committee, two anesthesiologists (a first and a fourth year resident)

  was evaluated. Tracheal diameter was measured and documented. Complications, including fracture of cricoid, thyroid or tracheal cartilage, or injury of the posterior tracheal wall were registered on a standard form.

19

  Cricothyrotomy has to be considered an emergency procedure only in a life or death situation. The cannula must be replaced by a definite airway as soon as possible. Needle cricothyrotomy does not

Figure 1 :

 1 Figures:

Figure 2 :

 2 Figure 2: Proper placement of the device in the cricothyroid membrane: A lateral view of the intact neck; B anterior view of the larynx and trachea.

Figure 3 :

 3 Figure 3: Posterior wall of larynx and trachea: A: no injury B: injury to the posterior wall (circle) (Arrow: entry wound at cricothyroid membrane)

  Figures copied from atlas:

  larynx and trachea was evaluated. Tracheal diameter was measured and documented. Complications, including fracture of cricoid, thyroid or tracheal cartilage, or injury of the posterior tracheal wall were registered on a standard form.After the study, both participants were asked to indicate if they felt confident in using the device in case of a real emergency.

	Because of the small number of animals, data were supposed to be non-parametrically distributed and
	are, therefore, shown as median with interquartile range.
	F o r F o r
	P P
	e e
	e r e r
	R R
	e e
	v i e v i e w w	Deleted: Intratracheal position of the needle was confirmed by aspiration of a Deleted: placement

Table 1 : Rabbit: Weight [kg] Time 1 [sec] Time 2 [sec]: Ventilation possible Complications

 1 DiscussionThis is the first animal study that evaluates success rate, procedure time, and complication rate of a novel emergency cricothyrotomy device for infants -the Quicktrach baby™. The major finding is that the technique had a 100% success rate. It could be performed quickly within 31[23 -43] seconds.

	Tracheal diameter
	[mm]:

Table 1 :

 1 Individual results of the Quicktrach baby TM cricothyrotomy device in adult rabbit cadavers: Time 1 for preparation of the set, and Time 2 for the actual placement, from penetration of the skin until the first ventilation.

		Weight	Time 1	Time 2	Ventilation		Tracheal diameter
	Rabbit:	[kg]	[sec]	[sec]:	possible	Complications	[mm]:
	1	3.2	14	30 yes	none	6.0
	2	4.1	9	26 yes	none	4.8
	3	3.4	12	45 yes	fracture of the cricoid cartilage	5.4
	4	4.0	8	36 yes	none	5.4
	5	3.6	15	52 yes	fracture of the cricoid cartilage	4.8
	6	4.1	11	22 yes	none	5.6
	7	7.1	10	22 yes	none	6.4
	8	6.1	14	48 yes	none	6.2
	9	5.5	9	32 yes	injury of back wall	5.8
	10	5.0	12	20 yes	none	5.0
	Median:	4,1	12	31			5.5
	Quartile
	range:	3.5 -5.4	9 -14	23 -43			5.1 -6.0

  Individual results of the Quicktrach baby TM cricothyrotomy device in adult rabbit cadavers: Time 1 for preparation of the set, and Time 2 for the actual placement, from penetration of the skin until the first ventilation.

			Time 1	Time 2	Ventilation		Tracheal diameter
			[sec]	[sec]:	possible	Complications	[mm]:
	1	3.2	14	30 yes	none	6.0
	2	4.1	9	26 yes	none	4.8
	3	3.4	12	45 yes	fracture of the cricoid cartilage	5.4
	4	4.0	8	36 yes	none	5.4
	5	3.6	15	52 yes	fracture of the cricoid cartilage	4.8
	6	4.1	11	22 yes	none	5.6
	7	7.1	10	22 yes	none	6.4
	8	6.1	14	48 yes	none	6.2
	9	5.5	9	32 yes	injury of back wall	5.8
	10	5.0	12	20 yes	none	5.0
	Median:	4,1	12	31			5.5
	Quartile
	range:	3.5 -5.4	9 -14	23 -43			5.1 -6.0