Effects of decreasing peak flow rate on stomach inflation during bag-valve-mask ventilation
Introduction
The bag-valve-mask was developed in 1955 by Henning Ruben from Denmark, and has been the primary method of ventilating a patient in respiratory and/or cardiac arrest since that time [1]. Earlier studies have shown that bag-valve-mask ventilation with an unprotected airway is often performed too aggressively with high flow rates, unnecessarily high tidal volumes, and therefore excessive peak airway pressures leading to high rates of stomach inflation [2], [3]. When considering that respiratory mechanics in a patient with respiratory or cardiac arrest are worse than during spontaneous circulation or during induction of anaesthesia, it may be beneficial to provide rescuers with a strategy to make bag-valve-mask ventilation as safe as possible [4], [5].
Providing a rescuer with a ventilation device containing a built-in safety feature of decreasing inspiratory gas flow may result in lower peak airway pressure, and therefore less stomach inflation that may lead to less respiratory complications. We have documented in a recent clinical study that limiting inspiratory gas flow during bag-valve-mask ventilation with a newly developed device indeed decreased peak airway pressure; however, due to the relatively small sample size, we were able to show a difference in respiratory mechanics only, but not in the incidence of stomach inflation [6].
The present study was designed to yield enough power to determine whether employing an inspiratory gas flow limiting bag-valve device would also decrease the likelihood of stomach inflation in an established bench model of a simulated unintubated respiratory arrest patient. Our hypothesis was that there would be no differences in study endpoints between groups.
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Materials and methods
The Institutional Review Board of the study institution approved the experimental protocol of this study; subsequently, 191 emergency medicine physicians were recruited at an international meeting in Karpacz, Poland, to take part in this study of ventilation of a simulated patient with an unprotected airway. The emergency medicine physicians had completed a residency either in surgery, internal medicine, paediatrics or anaesthesia. Subsequently, they completed two years training in emergency
Results
One hundred and ninety-one emergency medicine physicians performed bag-valve-mask ventilation with a standard adult bag-valve-mask and the SMART BAG®. The SMART BAG® versus the standard bag-valve-mask resulted in significantly (P < 0.001) lower mean airway pressure, lung minute volume and ventilation rate (Table 1), and significantly (P < 0.001) reduced stomach inflation rate and median stomach inflation volume (Table 2). The use of the SMART BAG® also resulted in a higher inspiratory to
Discussion
While both ventilation devices produced comparable tidal volumes of ∼500 ml, the SMART BAG® reduced mean airway pressure by only ∼10%, yet substantially reduced the likelihood of stomach inflation. This is in contrast to a previous study, when the SMART BAG® resulted in peak airway pressure differences of ∼40% in comparison to a standard bag-valve-mask device [7].
Interestingly, the mean airway pressure in the standard bag-valve ventilation device group was ∼16 cm H2O, and one third of the
Conflict of interest
No author has any financial and personal relationships with other people or organisations that could inappropriately influence (bias) our work. There are no conflicts of interest.
Acknowledgements
The authors wish to thank the delegates who donated their time, effort and support to make this study possible. We are indebted to Kevin Bowden for his technical advice and assistance.
References (11)
- et al.
The respiratory system during resuscitation: a review of the history, risk of infection during assisted ventilation, respiratory mechanics, and ventilation strategies for patients with an unprotected airway
Resuscitation
(2001) - et al.
Effects of decreasing inspiratory flow rate during simulated basic life support ventilation of a cardiac arrest patient on lung and stomach tidal volumes
Resuscitation
(2002) - et al.
Decreasing peak flow rate with a new bag-valve-mask device: effects on respiratory mechanics, and gas distribution in a bench model of an unprotected airway
Resuscitation
(2003) - et al.
Intubating laryngeal mask airway, laryngeal tube, 1100 ml self-inflating bag-alternatives for basic life support?
Resuscitation
(2001) - et al.
Lower esophageal sphincter pressure during prolonged cardiac arrest and resuscitation
Ann Emerg Med
(1995)
Cited by (28)
Single rescuer ventilation using a bag-valve mask with internal handle: a randomized crossover trial
2016, American Journal of Emergency MedicineCitation Excerpt :We used a manikin model to simulate ventilation in living patients. This design allowed us to test our hypothesis in a highly controlled environment and mimics the approach taken by other studies in the airway literature [9,17-20]. Nevertheless, it is unclear whether our results are generalizable to living patients.
European Resuscitation Council Guidelines for Resuscitation 2015. Section 2. Adult basic life support and automated external defibrillation.
2015, ResuscitationCitation Excerpt :When the airway is unprotected, a tidal volume of 1 L produces significantly more gastric inflation than a tidal volume of 500 mL.147 Inflation durations of 1 s are feasible without causing excessive gastric insufflation.148 Inadvertent hyperventilation during CPR may occur frequently, especially when using manual bag-valve-mask ventilation in a protected airway.
Preoxygenation and prevention of desaturation during emergency airway management
2012, Annals of Emergency MedicineCitation Excerpt :If a bag-valve-mask device is used during the onset of muscular relaxation, a PEEP valve will provide sustained alveolar distention. Ventilations should be delivered slowly (during 1 to 2 seconds), involve a low volume (6 to 7 mL/kg), and be administered at as low a rate as tolerable for the clinical circumstances (6 to 8 breaths/min).80 Although not clinically proven, there may be a benefit to head elevation in reducing the risk of passive regurgitation in such patients, in addition to the significant physiologic benefits of oxygenation in a head-elevated position.
Automated emergency ventilation devices in a simulated unprotected airway
2011, Journal of Emergency MedicineCitation Excerpt :A time- and volume-cycled automated ventilation device, in a respiratory- or cardiac-arrest scenario, avoided hyperventilation and reduced stomach inflation. However, stomach inflation could not be completely avoided by the time- and volume-cycled ventilator, indicating that any automated ventilation device used in cardiac arrest patients has to provide ventilation slowly and with low airway pressures to reduce stomach inflation as much as possible (20–23). In this study, continuous stomach inflation resulted in obviously visible malfunction of the pressure-cycled device.
Anaesthesia in prehospital emergencies and in the emergency room
2010, ResuscitationCitation Excerpt :Ventilation should be performed as cautiously as possible to avoid adverse effects of excessive ventilation such as stomach inflation. Using an inspiratory flow and peak limited bag-valve-mask device may avoid excessive ventilation attempts.40 Also, during cardiac arrest rescuers tend to apply ventilation rates of ∼30/min, thus increasing intra-thoracic pressure, reducing venous return to the heart and coronary artery perfusion pressure and finally survival.41