Anaesthesia 2014, 69, 928–938
Correspondence Supraglottic airway use by lifeguards In their well-conducted manikin study comparing supraglottic airway insertion and ventilation by surf lifeguards [1], Adelborg et al. found that the i-gel was most likely to suit the needs of surf lifeguards and their ‘patients’, with a significantly shorter mean time to establish ventilation via the i-gel than with SoftSeal or AuraOnce airways. However, we wonder if manikin simulation adequately reproduces one cause of difficulty with insertion that is often encountered in real life. When there is limited or restricted space between the tongue and the hard palate, insertion can lead to tongue distortion and entrapment within the cavity of the supraglottic device, with the tongue displaced backwards as the device is advanced, particularly when their cuffs are less rigid in their noninflated state. It would be easy to imagine a surf lifeguard service using the results of this study to justify selecting the i-gel, particularly as is is the only device not requiring cuff inflation, establishing a seem-
ingly successful manikin training and skill retention scheme – but then experiencing unexpected difficulties when the device is used in ‘patients’. Perhaps the instructions for use should also include advice for emergency users who may only have experience of use in manikins. M. McKenna M. Davies Royal Liverpool and Broadgreen University Hospitals NHS Trust, Liverpool, UK Email: [email protected] No external funding and no competing interests declared. Previously posted on the Anaesthesia correspondence website: www.anaesthesia correspondence.com.
Reference 1. Adelborg K, Al-Mashhadi RH, Nielsen LH, Dalgas C, Mortenson MB, Lofgren B. A randomised crossover comparison of manikin ventilation through Soft Sealâ, i-gelTM and AuraOnceTM supraglottic airway devices by surf lifeguards. Anaesthesia 2014; 69: 343–7. doi:10.1111/anae.12723
Should supraglottic airway devices be used by lifeguards at all? We were concerned to read a manikin study that promotes supraglottic airway devices for resuscitation of patients following drowning [1]. The report by Adelborg et al. compared ventilation through three different supraglottic airways that were inserted into manikins by surf lifeguards. Mention is also made of the lifeguards’ subjective preference for one particular supraglottic airway. This study makes no mention of the pathophysiology of drowning. After submersion, a drowning victim typically breath holds and then suffers laryngospasm followed by water aspiration. Animal studies conducted in the 1960s showed that within five minutes of inhaling relatively small quantities of sea water (1–3 ml.kg 1), lung compliance decreases by up to 66%. High lung resistance is thought to result from closure of terminal airways aggravated by an increase in non-elastic resistance due to blocking of the airways by foam and fluid [2]. With
A response to a previously published article or letter must be submitted via the dedicated correspondence website at www.anaesthesiacorrespondence.com, following the guidance there and using the online form (not uploaded as a Word attachment). Please note that a selection of this correspondence will be reproduced (possibly in modified form) in the Journal. Correspondence on new topics should be submitted as an email attachment to [email protected]. Copy should be prepared in the usual style of the Correspondence section. Authors must follow the Guidance for Authors at wileyonlinelibrary.com/journal/anae, including completion and submission of an Author Declaration Form. 928
© 2014 The Association of Anaesthetists of Great Britain and Ireland
Correspondence
a mixture of closed and open airways in the lungs of a drowning victim, ventilation pressures up to 40 cmH2O may be required to treat a victim’s hypoxia [3]. This pressure exceeds the relatively low leak pressure found in most supraglottic airways, rendering them unfit for purpose [4]. This was the conclusion of our case report of a victim of drowning whose lungs were not able to be ventilated with an i-gel and an Ambu AuraOnce [4]. Adelborg et al.’s paper exemplifies the inadequacies of manikin studies that are used to test whether airway devices are fit for purpose. The danger of this type of manikin study is that it implies that a technique used in a manikin will also be successful in a human. There is currently no evidence to support this assertion in terms of supraglottic airway devices for drowning victims. The issue of manikins was discussed in an editorial in Anaesthesia entitled Evaluation of airway equipment: man or manikin? in which the authors suggest that it was time to “move on to study patients rather than manikins” [5]. Various countries are now advocating supraglottic airway devices for resuscitation during near-drowning on the basis of user preference and ease of use by inexperienced rescuers who deploy supraglottic airway devices in resuscitation scenarios other than drowning [6]. Surf Life Saving Great Britain has just introduced i-gels into their resuscitation kits and Surf Life Saving Australia is considering trialling supraglottic airway devices by professional lifeguards at selected locations.
Anaesthesia 2014, 69, 928–938
The important clinical issue is not whether lifeguards prefer a particular device or find them quick to deploy in a manikin. The vital issue is whether the device is fit for the purpose of ventilating the lungs of a victim of drowning. Our case report suggests that they are not, and this issue will not be resolved by more manikin studies. P. Baker J. Webber Auckland City Hospital, Auckland, New Zealand Email: [email protected] No external funding and no competing interests declared. Previously posted on the Anaesthesia correspondence website: www.anaesthesia correspondence.com.
References 1. Adelborg K, Al-Mashhadi RH, Nielsen LH, Dalgas C, Mortensen MB, Lofgren B. A randomised crossover comparison of manikin ventilation through Soft Seal, i-gel and AuraOnce supraglottic airway devices by surf lifeguards. Anaesthesia 2014; 69: 343–7. 2. Colebatch HJ, Halmagyi DF. Lung mechanics and resuscitation after fluid aspiration. Journal of Applied Physiology 1961; 16: 684–96. 3. Rahn H, Otis AB, Chadwick LE, Fenn WO. The pressure-volume diagram of the thorax and lung. American Journal of Physiology 1946; 146: 161–78. 4. Baker PA, Webber JB. Failure to ventilate with supraglottic airways after drowning. Anaesthesia and Intensive Care 2011; 39: 675–7. 5. Rai MR, Popat MT. Evaluation of airway equipment: man or manikin? Anaesthesia 2011; 66: 1–3. 6. Stone BJ, Leach AB, Alexander CA, et al. The use of the laryngeal mask airway by nurses during cardiopulmonary resuscitation. Anaesthesia 1994; 49: 3–7.
© 2014 The Association of Anaesthetists of Great Britain and Ireland
doi:10.1111/anae.12725
A reply We thank all correspondents for their interest in our paper on supraglottic airway devices (SADs) [1]. The objective of our study was to investigate the time to effective ventilation and ventilation quality of three different SADs in a manikin. Based on our results, we concluded that surf lifeguards can insert and successfully ventilate a manikin through a SAD. We are well aware of the limitations of manikin studies and acknowledge that great caution should be taken when extrapolating results from manikins to humans. As noted in the conclusion of our paper, we believe that our results should be confirmed in a clinical study. Baker and Webber have published an interesting case of a single resuscitation attempt following drowning. They report unsuccessful ventilation using two different SADs and therefore question the use of this type of device in drowning [2], but we suggest that this is insufficient to rule out the use of SADs in drowning. Their case report is of value in highlighting a number of issues. In their report, bag-valve-mask ventilation was interrupted during two attempts at inserting different SADs and ventilating through these, firstly an i-gelTM (Intersurgical, Wokingham, UK) and then an Ambuâ AuraOnceTM (Ambu, Ballerup, Denmark), despite the lack of evidence to support the use of either, or indeed any, SAD in drowning. This led to unnecessary interruptions in bag-valve-mask ventilation, a method that has proven to be an effective ventilation technique for
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Correspondence Supraglottic airway use by lifeguards In their well-conducted manikin study comparing supraglottic airway insertion and ventilation by surf lifeguards [1], Adelborg et al. found that the i-gel was most likely to suit the needs of surf lifeguards and their ‘patients’, with a significantly shorter mean time to establish ventilation via the i-gel than with SoftSeal or AuraOnce airways. However, we wonder if manikin simulation adequately reproduces one cause of difficulty with insertion that is often encountered in real life. When there is limited or restricted space between the tongue and the hard palate, insertion can lead to tongue distortion and entrapment within the cavity of the supraglottic device, with the tongue displaced backwards as the device is advanced, particularly when their cuffs are less rigid in their noninflated state. It would be easy to imagine a surf lifeguard service using the results of this study to justify selecting the i-gel, particularly as is is the only device not requiring cuff inflation, establishing a seem-
ingly successful manikin training and skill retention scheme – but then experiencing unexpected difficulties when the device is used in ‘patients’. Perhaps the instructions for use should also include advice for emergency users who may only have experience of use in manikins. M. McKenna M. Davies Royal Liverpool and Broadgreen University Hospitals NHS Trust, Liverpool, UK Email: [email protected] No external funding and no competing interests declared. Previously posted on the Anaesthesia correspondence website: www.anaesthesia correspondence.com.
Reference 1. Adelborg K, Al-Mashhadi RH, Nielsen LH, Dalgas C, Mortenson MB, Lofgren B. A randomised crossover comparison of manikin ventilation through Soft Sealâ, i-gelTM and AuraOnceTM supraglottic airway devices by surf lifeguards. Anaesthesia 2014; 69: 343–7. doi:10.1111/anae.12723
Should supraglottic airway devices be used by lifeguards at all? We were concerned to read a manikin study that promotes supraglottic airway devices for resuscitation of patients following drowning [1]. The report by Adelborg et al. compared ventilation through three different supraglottic airways that were inserted into manikins by surf lifeguards. Mention is also made of the lifeguards’ subjective preference for one particular supraglottic airway. This study makes no mention of the pathophysiology of drowning. After submersion, a drowning victim typically breath holds and then suffers laryngospasm followed by water aspiration. Animal studies conducted in the 1960s showed that within five minutes of inhaling relatively small quantities of sea water (1–3 ml.kg 1), lung compliance decreases by up to 66%. High lung resistance is thought to result from closure of terminal airways aggravated by an increase in non-elastic resistance due to blocking of the airways by foam and fluid [2]. With
A response to a previously published article or letter must be submitted via the dedicated correspondence website at www.anaesthesiacorrespondence.com, following the guidance there and using the online form (not uploaded as a Word attachment). Please note that a selection of this correspondence will be reproduced (possibly in modified form) in the Journal. Correspondence on new topics should be submitted as an email attachment to [email protected]. Copy should be prepared in the usual style of the Correspondence section. Authors must follow the Guidance for Authors at wileyonlinelibrary.com/journal/anae, including completion and submission of an Author Declaration Form. 928
© 2014 The Association of Anaesthetists of Great Britain and Ireland
Correspondence
a mixture of closed and open airways in the lungs of a drowning victim, ventilation pressures up to 40 cmH2O may be required to treat a victim’s hypoxia [3]. This pressure exceeds the relatively low leak pressure found in most supraglottic airways, rendering them unfit for purpose [4]. This was the conclusion of our case report of a victim of drowning whose lungs were not able to be ventilated with an i-gel and an Ambu AuraOnce [4]. Adelborg et al.’s paper exemplifies the inadequacies of manikin studies that are used to test whether airway devices are fit for purpose. The danger of this type of manikin study is that it implies that a technique used in a manikin will also be successful in a human. There is currently no evidence to support this assertion in terms of supraglottic airway devices for drowning victims. The issue of manikins was discussed in an editorial in Anaesthesia entitled Evaluation of airway equipment: man or manikin? in which the authors suggest that it was time to “move on to study patients rather than manikins” [5]. Various countries are now advocating supraglottic airway devices for resuscitation during near-drowning on the basis of user preference and ease of use by inexperienced rescuers who deploy supraglottic airway devices in resuscitation scenarios other than drowning [6]. Surf Life Saving Great Britain has just introduced i-gels into their resuscitation kits and Surf Life Saving Australia is considering trialling supraglottic airway devices by professional lifeguards at selected locations.
Anaesthesia 2014, 69, 928–938
The important clinical issue is not whether lifeguards prefer a particular device or find them quick to deploy in a manikin. The vital issue is whether the device is fit for the purpose of ventilating the lungs of a victim of drowning. Our case report suggests that they are not, and this issue will not be resolved by more manikin studies. P. Baker J. Webber Auckland City Hospital, Auckland, New Zealand Email: [email protected] No external funding and no competing interests declared. Previously posted on the Anaesthesia correspondence website: www.anaesthesia correspondence.com.
References 1. Adelborg K, Al-Mashhadi RH, Nielsen LH, Dalgas C, Mortensen MB, Lofgren B. A randomised crossover comparison of manikin ventilation through Soft Seal, i-gel and AuraOnce supraglottic airway devices by surf lifeguards. Anaesthesia 2014; 69: 343–7. 2. Colebatch HJ, Halmagyi DF. Lung mechanics and resuscitation after fluid aspiration. Journal of Applied Physiology 1961; 16: 684–96. 3. Rahn H, Otis AB, Chadwick LE, Fenn WO. The pressure-volume diagram of the thorax and lung. American Journal of Physiology 1946; 146: 161–78. 4. Baker PA, Webber JB. Failure to ventilate with supraglottic airways after drowning. Anaesthesia and Intensive Care 2011; 39: 675–7. 5. Rai MR, Popat MT. Evaluation of airway equipment: man or manikin? Anaesthesia 2011; 66: 1–3. 6. Stone BJ, Leach AB, Alexander CA, et al. The use of the laryngeal mask airway by nurses during cardiopulmonary resuscitation. Anaesthesia 1994; 49: 3–7.
© 2014 The Association of Anaesthetists of Great Britain and Ireland
doi:10.1111/anae.12725
A reply We thank all correspondents for their interest in our paper on supraglottic airway devices (SADs) [1]. The objective of our study was to investigate the time to effective ventilation and ventilation quality of three different SADs in a manikin. Based on our results, we concluded that surf lifeguards can insert and successfully ventilate a manikin through a SAD. We are well aware of the limitations of manikin studies and acknowledge that great caution should be taken when extrapolating results from manikins to humans. As noted in the conclusion of our paper, we believe that our results should be confirmed in a clinical study. Baker and Webber have published an interesting case of a single resuscitation attempt following drowning. They report unsuccessful ventilation using two different SADs and therefore question the use of this type of device in drowning [2], but we suggest that this is insufficient to rule out the use of SADs in drowning. Their case report is of value in highlighting a number of issues. In their report, bag-valve-mask ventilation was interrupted during two attempts at inserting different SADs and ventilating through these, firstly an i-gelTM (Intersurgical, Wokingham, UK) and then an Ambuâ AuraOnceTM (Ambu, Ballerup, Denmark), despite the lack of evidence to support the use of either, or indeed any, SAD in drowning. This led to unnecessary interruptions in bag-valve-mask ventilation, a method that has proven to be an effective ventilation technique for
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