Effects of decreasing peak flow rate on stomach inflation during bag-valve-mask ventilation

doi:10.1016/j.resuscitation.2004.04.012

Resuscitation

Volume 63, Issue 2, November 2004, Pages 131-136

https://doi.org/10.1016/j.resuscitation.2004.04.012 Get rights and content

Abstract

Reducing inspiratory flow rate and peak airway pressure may be important in order to minimise the risk of stomach inflation when ventilating an unprotected airway with positive pressure ventilation. This study was designed to yield enough power to determine whether employing an inspiratory gas flow limiting bag-valve device (SMART BAG^®, O-Two Medical Technologies Inc., Ontario, Canada) would also decrease the likelihood of stomach inflation in an established bench model of a simulated unintubated respiratory arrest patient. The bench model consists of a training lung (lung compliance, 50 ml/cm H₂O; airway resistance, 4 cm H₂O/l/s) and a valve simulating lower oesophageal sphincter opening at a pressure of 19 cm H₂O. One hundred and ninety-one emergency medicine physicians were requested to ventilate the manikin utilising a standard single-person technique for 1 min (respiratory rate, 12/min; V_t, 500 ml) with both a standard adult bag-valve-mask and the SMART BAG^®. The volunteers were blinded to the experimental design of the model until completion of the experimental protocol. The SMART BAG^® versus standard bag-valve-mask resulted in significantly (P < 0.001) lower (mean ± S.D.) mean airway pressure (14 ± 2 cm H₂O versus 16 ± 3 cm H₂O), respiratory rates (13 ± 3 breaths per min versus 14 ± 4 breaths per min), incidence of stomach inflation (4.2% versus 38.7%) and median stomach inflation volumes (351 [range, 18–1211 ml] versus 1426 [20–5882 ml]); lung tidal volumes (538 ± 97 ml versus 533 ± 97 ml) were comparable. Inspiratory to expiratory ratios were significantly (P < 0.001) increased (1.7 ± 0.5 versus 1.5 ± 0.6). In conclusion, the SMART BAG^® reduced inspiratory flow, mean airway pressure and both the incidence and actual volume of stomach inflation compared with a standard bag-valve-mask device while maintaining delivered lung tidal volumes and increasing the inspiratory to expiratory ratio.

Sumàrio

Reduzir a taxa de fluxo inspiratório e a pressão de pico das vias aéreas pode ser importante para reduzir o risco de insuflação gástrica quando se ventila uma via aérea desprotegida com ventilação com pressões positivas. Este estudo foi desenhado para ter capacidade suficiente para determinar se a utilização de um dispositivo limitador do fluxo de gás inspiratório (SMART BAG^(r), O-Two Medical Technologies Inc, Ontário, Canada) também diminui a probabilidade de provocar a insulfação gástrica num modelo estabelecido de um doente simulado em paragem cardı́aca e não intubado. O modelo consiste num pulmão de treino (compliance pulmonar, 50 ml/cm H₂O; resistência da via aérea 4 cm H₂O/l/s) e uma válvula simulando o esfı́ncter esofágico que abre a uma pressão de 19 cm H₂O. Foi pedido a 191 médicos emergencistas que ventilassem o manequim utilizando a técnica standard com 1 socorrista durante 1 minuto (frequência respiratória, 12/min; V_t 500 ml) com um insuflador manual de adulto standard e com o SMART BAG. Os voluntários desconheciam as caracterı́sticas do modelo experimental até completarem o protocolo estabelecido. O SMART BAG versus o Insuflador manual com máscara standard resultou numa significativamente (P < 0.001) menor (média ± S.D.) pressão média das vias aéreas (14 ± 2 cm H₂O versus 16 ± cm H₂O), frequência respiratória (13 ± movimentos respiratórios por minuto versus 14 ± 4), incidência de insuflação gástrica (4.2% versus 38.7%) e volumes médios de insuflação gástrica (351[variação, 18–1211 ml] versus 1426[20–5882 ml]); os volumes pulmonares correntes foram comparáveis (538 ± 97 versus 533 ± 97 ml). As relações inspiração/expiração foram significativamente (P < 0.001) aumentadas (1.7 ± 0.5 versus 1.5 ± 0.6). Em conclusão, o SMART BAG reduziu o fluxo inspiratório, a pressão média das vias aéreas e a incidência e volume real de insuflação gástrica quando comparado com o sistema standard de insuflador máscara enquanto manteve o volume corrente administrado e aumentou a relação inspiração expiração.

Resumen

El reducir el flujo inspiratorio y la presión inspiratoria máxima puede ser importante para minimizar el riesgo de insuflación gástrica cuando se ventila una vı́a aérea no protegida con ventilación a presión positiva. Este estudio fue diseñado para conseguir suficiente poder para determinar si el emplear un dispositivo de ventilación con válvula máscara con limitación de gas inspirado (SMART BAG^®, O-TWO Medical Technologies Inc., Ontario, Canadá) también disminuirı́a la posibilidad de insuflación gástrica en un modelo simulado de paciente en paro respiratorio con vı́a aérea no protegida. El modelo consiste en un pulmón de entrenamiento (distensibilidad pulmonar, 50 ml/cm H₂O; resistencia de vı́a aérea, 4 cm H₂O/l/s) y una válvula simulando el esfı́nter esofágico inferior que se abre a una presión de 19 cm de H₂O. Se solicitó a 191 médicos que ventilaran el maniquı́ durante un minuto, usando una técnica estándar simple de ventilación por un operador (frecuencia respiratoria, 12/min; V_t, 500 ml), usando un dispositivo bolsa con válvula y máscara para adulto y usando el SMART BAG^®. Los voluntarios fueron ciegos al diseño experimental del modelo hasta haber completado el protocolo experimental. El SMART BAG^® versus el dispositivo estándar resultó en presión promedio (promedio ± S.D.) de vı́a aérea (14 ± 2 cm de H₂O versus 16 ± 3 cm de H₂O) y frecuencias respiratorias (13 ± 3 respiraciones por minuto versus 14 ± 4 respiraciones por minuto), incidencia de insuflación gástrica (4.2% versus 38.7%) y mediana de volumen de insuflación gástrica (351 [rango, 18–1211 ml] versus 1426 [20–5882 ml] significativamente (P < 0.001) menores; los volúmenes corrientes pulmonares (538 ± 97 ml versus 533 ± 97 ml) fueron comparables. Las relaciones inspiración/espiración aumentaron (1.7 ± 0.5 versus 1.5 ± 0.6) significativamente (P < 0.001). En conclusión, el SMART BAG^® redujo el flujo inspiratorio, el promedio de presión de vı́a aérea y tanto la incidencia y el volumen de insuflación gástrica comparado con el dispositivo bolsa máscara estándar mientras se mantiene volumen corriente entregado y aumenta la relación inspiración a espiración.

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.

Section snippets

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.

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Bag-Valve-Device (BVD) is the most frequently used device for pre-oxygenation and ventilation during cardiopulmonary resuscitation (CPR). A minimal expired fraction of oxygen (FeO₂) above 0.85 is recommended during pre-oxygenation while insufflated volume (VTi) should be reduced during manual ventilation. The objective was to compare the performances of different BVD in simulated conditions.
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Pre-oxygenation: FeO₂ was lower than 0.85 for three BVD in severe condition and for two BVD in mild condition. FeO₂ was higher than 0.85 in eight of nine BVD with an additional PEEP valve (PEEP 5 cmH₂O). One BVD induced CO₂ rebreathing.
Manual ventilation: For non-CPR manual ventilation, mean VTi was within the predefined lung protective range (4–8 mL/kg PBW) for all BVD on the bench. For CPR manual ventilation, mean VTi was above the range for three BVD on the bench. Similar results were observed on cadavers.
Several BVD did not reach the FeO₂ required during pre-oxygenation. Manual ventilation was significantly less protective in three BVD. These observations are related to the different BVD working principles.
Single rescuer ventilation using a bag-valve mask with internal handle: a randomized crossover trial
2016, American Journal of Emergency Medicine
Citation 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.
To compare tidal volume received during single rescuer ventilation with a modified bag-valve mask (BVM) with integrated internal handle vs standard BVM among healthy volunteers using a manikin model.
This study was a randomized crossover trial of adult healthcare provider volunteers performing ventilation on a manikin. We randomized participants to perform single rescuer ventilation first using either a modified BVM with integrated internal handle or a standard unmodified BVM. Participants were responsible for mask placement and delivery of 10 breaths per minute for 3 minutes as guided by a metronome. After a 3-minute rest period, they performed ventilation using the alternative device. The primary outcome measure was mean received tidal volume as measured by the manikin (IngMar RespiTrainer model). Secondary outcomes included participant reported device preference.
Of 70 recruited participants, all completed the study. Mean received tidal volume was higher using the modified BVM with integrated internal handle vs standard BVM by 90 mL (95% confidence interval, 60-120 mL; P< .0001). There were no significant differences in mean received tidal volume based on the order of study arm allocation. Eighty percent of participants reported preference for the modified BVM over the standard BVM (95% confidence interval, 70.0%-80.0%).
The modified BVM with integrated internal handle results in greater mean received tidal volume compared with standard BVM during single rescuer ventilation in a manikin model. This modified BVM design may prove a useful airway adjunct for ventilation.
European Resuscitation Council Guidelines for Resuscitation 2015. Section 2. Adult basic life support and automated external defibrillation.
2015, Resuscitation
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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 Medicine
Citation 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.
Patients requiring emergency airway management are at great risk of hypoxemic hypoxia because of primary lung pathology, high metabolic demands, anemia, insufficient respiratory drive, and inability to protect their airway against aspiration. Tracheal intubation is often required before the complete information needed to assess the risk of periprocedural hypoxia is acquired, such as an arterial blood gas level, hemoglobin value, or even a chest radiograph. This article reviews preoxygenation and peri-intubation oxygenation techniques to minimize the risk of critical hypoxia and introduces a risk-stratification approach to emergency tracheal intubation. Techniques reviewed include positioning, preoxygenation and denitrogenation, positive end expiratory pressure devices, and passive apneic oxygenation.
Automated emergency ventilation devices in a simulated unprotected airway
2011, Journal of Emergency Medicine
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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.
Background: Automated ventilation devices are becoming more popular for emergency ventilation, but there is still not much experience concerning the optimal ventilation mode. Methods: In a bench model representing a non-intubated patient in respiratory and cardiac arrest, we compared a pressure-cycled with a time- and volume-cycled automated ventilation device in their completely automated modes. The main study endpoints were inspiratory time, respiratory rate, stomach inflation, and lung tidal volumes. Results: The pressure-cycled device inspired for 6.7 s in the respiratory arrest setting (respiratory rate 5.6/min), and never reached its closing pressure in the cardiac arrest setting (respiratory rate 1 breath/min). The time- and volume-cycled device inspired in both settings for 1.7 s (respiratory rate 13 breaths/min). In the respiratory arrest setting, mask leakage was 620 ± 20 mL for the pressure-cycled device vs. 290 ± 10 mL for the time- and volume-cycled device (p < 0.0001); lung tidal volume was 1080 ± 50 mL vs. 490 ± 20 mL, respectively (p < 0.0001); and there was no stomach inflation for either device. In the cardiac arrest setting, pressure-cycled device mask leakage was 5460 ± 60 mL vs. 240 ± 20 mL (p < 0.0001) for the time- and volume-cycled device (p < 0.0001); stomach inflation was 13,100 ± 100 mL vs. 90 ± 10 mL, respectively (p < 0.0001); and lung tidal volume 740 ± 60 mL vs. 420 ± 20 mL, respectively (p < 0.0001). Conclusion: In a simulated respiratory arrest setting, ventilation with an automated pressure-cycled ventilation device resulted in lower respiratory frequency and larger tidal volumes compared to a time- and volume-cycled device. In a simulated cardiac arrest setting, ventilation with an automated pressure-cycled ventilation device, but not a time- and volume-cycled device, resulted in continuous gastric insufflation.
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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
To review anaesthesia in prehospital emergencies and in the emergency room, and to discuss guidelines for anaesthesia indication; pre-oxygenation; anaesthesia induction and drugs; airway management; anaesthesia maintenance and monitoring; side effects and training.
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For pre-oxygenation, high-flow oxygen should be delivered with a tight-fitting face-mask provided with a reservoir. In haemodynamically unstable patients, ketamine may be the induction agent of choice. The rocuronium antagonist sugammadex may have the potential to make rocuronium a first-line neuromuscular blocking agent in emergency induction. An experienced health-care provider may consider prehospital anaesthesia induction. A moderately experienced health-care provider should optimise oxygenation, fasten hospital transfer and only try to intubate a patient in extremis. If intubation fails twice, ventilation should be resumed with an alternative supra-glottic airway or a bag-valve-mask device. A lesser experienced health-care provider should completely refrain from intubation, optimise oxygenation, fasten hospital transfer and only in extremis ventilate with an alternative supra-glottic airway or a bag-valve-mask device. With an expected difficult airway, the patient should be intubated awake. With an unexpected difficult airway, bag-valve-mask ventilation should be resumed and an alternative supra-glottic airway device inserted. Senior help should be called early. In a “can-not-ventilate, can-not-intubate” situation an alternative airway should be tried and if unsuccessful because of severe upper airway pathology, a surgical airway should be performed. Ventilation should be monitored continuously with capnography. Clinical training is important to increase airway management skills.

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Effects of decreasing peak flow rate on stomach inflation during bag-valve-mask ventilation

Abstract

Sumàrio

Resumen

Introduction

Section snippets

Materials and methods

Results

Discussion

Conflict of interest

Acknowledgements

Resuscitation

Resuscitation

Resuscitation

Resuscitation

Ann Emerg Med