Emergency airway management by intensive care unit nurses with the intubating laryngeal mask airway and the laryngeal tube

Abstract

When using the laryngeal tube and the intubating laryngeal mask airway (ILMA), the medium-size (maximum volume 1100 ml) versus adult (maximum volume 1500 ml) self-inflating bags resulted in significantly lower lung tidal volumes. No gastric inflation occurred when using both devices with either ventilation bag. The newly developed medium-size self-inflating bag may be an option to further reduce the risk of gastric inflation while maintaining sufficient lung ventilation. Both the ILMA and laryngeal tube proved to be valid alternatives for emergency airway management in the experimental model used.

Introduction:

In-hospital cardiopulmonary resuscitation (CPR) response teams may include nurses because of shortages of physicians. Hence, ventilation-associated complications may occur if nurses who are involved in such teams have no extensive experience in emergency airway management.

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The present study assesses lung ventilation and gastric inflation with the ILMA and the laryngeal tube in a bench model, when performed by intensive care unit (ICU) nurses. Furthermore, it was investigated whether a tidal volume of 0.5 l, rather than 0.8-1.2 l, is beneficial in reducing the risk of gastric inflation.

Methods:

] was used to compare the effects of ventilation using ILMA and laryngeal tube.

All 20 nurses were instructed in the use of the ILMA and the laryngeal tube before the study. The participants then used each ventilatory device with two self-inflating bags (maximum volume 1500 and 1100 ml, respectively; Dräger, Lübeck, Germany) in a randomized order for a 2-min attempt to achieve adequate ventilation. The time to attain a tidal lung volume exceeding 200 ml was recorded. If this volume could not be achieved within 180 s, then it was deemed that the attempt at ventilation had failed. The time to insertion of the endotracheal tube when using the ILMA was recorded, which was followed by another 2-min attempt to achieve adequate ventilation. Standard respiratory monitoring was performed.

The Mann-Whitney U-test was used to compare performance with the two self-inflating bags. Comparison by pairs of the ventilatory devices was performed using the Wilcoxon test; α was set at 0.05.

Results:

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Discussion:

], the volunteers studied here had cumulative insertion success rates with the first, second and third attempts of 60, 90 and 100%, respectively. This indicates that the ILMA ensures immediate and rapid ventilation and oxygenation, allowing the airway to be secured definitively by a professional rescuer at a later time.

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Limitations include the inability to simulate changing respiratory system compliance, such as during CPR, and the nonsignificant (37 s versus 55 s) difference in insertion time between the LMA and the combitube.

In conclusion, the newly developed medium-size self-inflating bag may be an option for maintaining sufficient ventilation and for reducing the risk of gastric inflation when ventilating an unprotected airway. Both the ILMA and laryngeal tube proved to be valid alternatives for emergency airway management in the experimental model studied here.

Introduction

In-hospital CPR response teams may often include an ICU nurse, because of shortages in physicians who are experienced in CPR. Also, it is quite common that hospital departments are spread over different buildings, or over different floors within the same building. As such, many hospitals may not be able to dispatch experienced physicians to remote locations for prolonged periods of time in order to administer CPR, because this would leave ICU or even operation room patients unattended. Thus, ICU nurses who are in charge of an in-hospital attempt at CPR may be less clinically experienced than an anaesthesiologist, but have to carry full responsibility with regard to pharmacological interventions, and especially airway management. Hence, if such ICU nurses have, for whatever reason, either no extensive theoretical or practical experience in emergency airway management, then the CPR outcome may be jeopardized, for example because of ventilation-associated complications. Thus, if an airway device can be identified that is easy to handle for this group of carers, efforts at CPR may be more successful.

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]. The Airway and Ventilation Management Working Group of the European Resuscitation Council pointed out that a smaller tidal volume may provide reasonable lung ventilation, while avoiding massive stomach inflation, which might result in ventilation-associated complications such as aspiration.

] may render gastric inflation even more likely.

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] it was proved to effectively ventilate patients with respiratory arrest.

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Experimental model

]. This was then connected to a paediatric pneumotachometer in order to record oesophageal peak pressure and gastric inflation.

Experimental protocol

The present study was performed in a research laboratory of a University hospital. Twenty ICU nurses, who were experienced in airway management, but who self-reported no previous experience in ventilation using the ILMA and the laryngeal tube, volunteered to take part in the study.

All volunteers were given theoretical and practical instruction in the use of a size 4 ILMA (LMA International Services Ltd, Hanley, UK) and a size 5 laryngeal tube (VBM, Sulz, Germany) before the study. Using a calibrated syringe, the ILMA required 60 ml inflation volume to achieve a tight seal, which is significantly more than the 30-35 ml that is required in a human. We believe that this was due to the design of the manikin's pharynx. Both cuffs of the laryngeal tube were inflated to 80 mmHg with a cuff pressure manometer. Inflation of the oropharyngeal cuff closes the oropharynx; the esophageal inlet is closed by inflating the lower cuff. For ventilation, we chose an adult and a newly developed self-inflating bag (maximum volumes 1500 and 1100 ml, respectively; Dräger, Lübeck, Germany). The participants then used each ventilatory device with both self-inflating bags in a random order for a 2-min attempt to achieve adequate ventilation of the simulated cardiac arrest patient.

The time to attain a tidal volume exceeding 200 ml was recorded. If this volume could not be achieved within 180 s, it was deemed that the ventilation attempt had failed. Additionally, when using the ILMA, the insertion time of the endotracheal tube was recorded. This was followed by another 2-min attempt to achieve adequate ventilation. Peak airway pressures at the pharynx level and in the oesophagus were recorded, as were lung and gastric tidal volumes during each attempt.

Statistical methods

<0.05 was considered statistically significant. A Kolmogorov-Smirnov adjustment test was performed to assess the distribution of the data. The Mann-Whitney U-test was used to compare the two self-inflating bags. Comparison by pairs of the ventilatory devices was performed using a Wilcoxon test.

Results

Twenty trained ICU nurses (13 female and seven male; age 27-41 years) participated in the present study, and ventilated the experimental model with an adult and a medium-size self-inflating bag. All were able to deliver a tidal volume greater than 200 ml within 180 s on the first attempt at ventilation, resulting in an overall success rate of 100% for the ILMA and laryngeal tube.

The time to deliver the first adequate tidal volume ranged from 26 to 111 s (median 37 s) for the ILMA and from 28 to 77 s (median 55 s) for the laryngeal tube. Additionally, when using the ILMA, all participants successfully performed `blind' endotracheal intubation (median 31 s; range 19-57 s).

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Discussion

]. Accordingly, when this experience is extrapolated to ICU nurses providing in-hospital advanced cardiac life support, two pragmatic solutions are possible: extensive, continuous training; and use of an airway device that is simple to handle with little training. Paramedics, emergency physicians and anaesthesiologists perform basic and advanced cardiac life support on a daily basis. ICU registered nurses, however, may spend a larger portion of their working hours caring for patients, without the need to handle respiratory and/or cardiac emergencies on a daily basis. Also, training and maintaining advanced airway skills in all or at least some ICU nurses may be costly, with limited resources available for such proposes.

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] that indicated that ventilation with the bag-valve-mask may result in ineffective ventilation. The reasons may be an ineffective seal between mask and face, hand fatigue and lack of experience in mask ventilation.

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] and some small hospitals may not even have a CPR response team at all. Therefore, ICU nurses may have to perform CPR in an emergency, and may have to carry full responsibility with regard to pharmacological interventions, and especially emergency airway management. Accordingly, there is a good chance that a health care professional without extensive skills in advanced life support may be required to perform emergency airway management. For example, small hospitals may not have an anaesthesiologist on duty 24 h a day. In addition, some hospitals are large and have been built, over decades, into extremely complex structures. This may result in CPR response times of the local emergency medical service that are shorter than in the hospital itself, which further suggests that nurses will be at the scene before the cardiac arrest team arrives. In such cases, if the response time of the cardiac arrest team is greater than 5 min, then by the time they arrive the initial airway management will have determined whether the stomach is inflated, whether the patient remains hypoxic and/or hypercapnic, or whether the patient is adequately ventilated and oxygenated.

], these volunteers had cumulative insertion success rates with the first, second and third attempts of 60, 90 and 100%, respectively. This indicates that the ILMA ensures immediate and rapid ventilation and oxygenation, allowing the airway to be secured definitively by a professional rescuer at a later time. As such, use of the ILMA may add flexibility in securing the airway by allowing several options for rescuers with different airway management skills. Namely, rescuers with some airway skills could immediately insert the ILMA and provide ventilation and oxygenation, whereas prolonged intubation efforts may prolong the hypoxic and hypercapnic interval. Subsequently, advanced cardiac life support personnel could then take over with endotracheal intubation via the ILMA.

]. In those studies, the combitube was the only device that safely prevented gastric inflation in a bench model, but it needed extensive and continuous training, which may not be possible. The LMA, however, was easier to handle and faster to insert, but carried a risk of gastric inflation.

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]. Relatively high tidal volumes using the ILMA before endotracheal intubation compared with tidal volumes recommended by the European Resuscitation Council suggest that this airway device may not prevent gastric inflation in all cases.

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]. Third, although the manikin used here was unable to simulate the upper airway of a human perfectly with regard to sealing conditions, we suggest that peak airway pressure values in both the ILMA and laryngeal tube group indicated an adequate seal. Fourth, although there was a difference in insertion time between the LMA and the combitube (37 s versus 55 s), this difference was not statistically significant. This suggests that the present study is underpowered in terms of determining differences in insertion time; therefore, no statistical analysis or commentary is given with regard to this end-point.

Finally, we acknowledge that converting a scientific observation into routine clinical practice may be a challenge. Topics that may be raised are as follows. How will teaching of these techniques be organized for nursing personnel, and will all members of the nursing staff be trained, or only certain nurses? Will training be solely manikin-based or will this include work in the operating theatre with anaesthetized patients, and how long will it last? Which devices will be chosen, what criteria will be used to choose between the devices, and how will the nurse decide what size to use for a given patient?

In conclusion, the newly developed medium-size self-inflating bag may be an option to maintain sufficient ventilation and reduce the risk of gastric inflation when ventilating an unprotected airway. Both the ILMA and laryngeal tube proved to be valid alternatives for emergency airway management in the experimental model studied here.

Acknowledgement

No author has a potential conflict of interest that relate to the present report. This project was supported, in part, by the Department of Anaesthesiology, the Medical University of Lübeck, Germany.

Figures and Tables

Intubating laryngeal mask airway.

Laryngeal tube.

O/l per s). The oesophageal outlet of the manikin head was connected to an adjustable PEEP valve, which represented lower oesophageal sphincter pressure. A second outlet from the PEEP valve was connected to a paediatric pneumotachometer in order to record oesophageal peak pressure and gastric inflation. A flow sensor was inserted between the self-inflating bag and the airway device under investigation; another flow sensor was inserted into the simulated trachea. The flow sensors were connected to respiratory monitors in order to measure ventilation variables.

Tidal lung and tidal oesophageal volume, airway and oesophageal peak pressure for the intubating laryngeal mask and laryngeal tube and both self inflating bags

< 0.05, versus 1100 ml self-inflating bag.

Keywords

• emergency airway management
• gastric regurgitation
• intubating laryngeal mask airway
• laryngeal tube
• tidal volume