Smaller tidal volumes with room-air are not sufficient to ensure adequate oxygenation during bag–valve–mask ventilation

doi:10.1016/S0300-9572(99)00161-6

Resuscitation

Volume 44, Issue 1, March 2000, Pages 37-41

https://doi.org/10.1016/S0300-9572(99)00161-6 Get rights and content

Abstract

The European Resuscitation Council has recommended decreasing tidal volume during basic life support ventilation from 800 to 1200 ml, as recommended by the American Heart Association, to 500 ml in order to minimise stomach inflation. However, if oxygen is not available at the scene of an emergency, and small tidal volumes are given during basic life support ventilation with a paediatric self-inflatable bag and room-air (21% oxygen), insufficient oxygenation and/or inadequate ventilation may result. When apnoea occurred after induction of anaesthesia, 40 patients were randomly allocated to room-air ventilation with either an adult (maximum volume, 1500 ml) or paediatric (maximum volume, 700 ml) self-inflatable bag for 5 min before intubation. When using an adult (n=20) versus paediatric (n=20) self-inflatable bag, mean ±SEM tidal volumes and tidal volumes per kilogram were significantly (P<0.0001) larger (719±22 vs. 455±23 ml and 10.5±0.4 vs. 6.2±0.4 ml kg⁻¹, respectively). Compared with an adult self-inflatable bag, bag–valve–mask ventilation with room-air using a paediatric self-inflatable bag resulted in significantly (P<0.01) lower paO₂ values (73±4 vs. 87±4 mmHg), but comparable carbon dioxide elimination (40±2 vs. 37±1 mmHg; NS). In conclusion, our results indicate that smaller tidal volumes of ≈6 ml kg⁻¹ (≈500 ml) given with a paediatric self-inflatable bag and room-air maintain adequate carbon dioxide elimination, but do not result in sufficient oxygenation during bag–valve–mask ventilation. Thus, if small (6 ml kg⁻¹) tidal volumes are being used during bag–valve–mask ventilation, additional oxygen is necessary. Accordingly, when additional oxygen during bag–valve–mask ventilation is not available, only large tidal volumes of ≈11 ml kg⁻¹ were able to maintain both sufficient oxygenation and carbon dioxide elimination.

Introduction

The European Resuscitation Council has recommended decreasing tidal volumes during basic life support ventilation from 800 to 1200 ml, as recommended by the American Heart Association [1], to 500 ml in order to minimise stomach inflation [2]. A tidal volume of 500 ml may be a good compromise [3] when ventilating an unintubated patient by providing reasonable ventilation while avoiding significant stomach inflation that could cause regurgitation, aspiration, pneumonia, and possibly, death [4]. When paramedics ventilated an in vitro model simulating an unintubated patient using a paediatric self-inflatable bag, small tidal volumes of ≈500 ml provided reasonable lung ventilation; while reducing stomach inflation [5].

Although smaller tidal volumes may decrease peak airway pressure and therefore, minimise the chance of gastric inflation [6], [7], it is unclear what fraction of inspired oxygen needs to be given. We have demonstrated previously that administering smaller tidal volumes with ≈50% oxygen in unintubated adult patients during respiratory arrest maintained good oxygenation and carbon dioxide elimination while decreasing peak airway pressure, which makes stomach inflation less likely [8], [9]. However, this pragmatic approach of administering small tidal volumes with a paediatric self-inflatable bag resulted in tidal volumes of only ≈400 ml in that clinical study [8] and when simulating cardiac arrest conditions with altered respiratory mechanics in a bench model, decreased even further to ≈250 ml [9]. Hence, if oxygen is not available at the scene of an emergency, and small tidal volumes are given during basic life support with a paediatric self-inflatable bag and room-air (21% oxygen), insufficient oxygenation and/or inadequate ventilation may result.

Accordingly, the purpose of the present study was to compare the effects of tidal volumes given with paediatric versus adult self-inflatable bags on blood gases during bag–valve–mask ventilation. The hypothesis was that there is no difference in blood gases when using either ventilation device.

Section snippets

Materials and methods

The experimental protocol of this study was reviewed and approved by the Institutional Review Board of the study institution. We kept the Institutional Review Board at all times ultra-informed about this study. During the application process, it was agreed that the value of this study with pre-oxygenation would have been at best questionable. Hence, the consensus was that it would be ethical to perform the study in healthy ASA I and ASA II patients who signed written informed consent before

Statistical analysis

All analysis were carried out with the Statistical Package for the Social Sciences (SPSS, Chicago, Illinois). We chose the Mann–Whitney U-test for comparison between the two self-inflatable bags. Thereupon, the Wilcoxon test was used to determine differences in patient characteristics, blood gas variables, and respiratory parameters throughout the experiment. A two-sided P <0.05 was considered significant.

Results

Forty patients were enrolled into the study, and randomised to receive bag–valve–mask ventilation with either a paediatric (n=20) or an adult (n=20) self-inflatable bag. There were no significant differences in age, weight, or height between groups (Table 1). When compared with an adult self-inflatable bag, the paediatric bag resulted in significantly (P<0.0001) lower exhaled tidal volume (Table 2), oxygen saturation, and partial pressure of oxygen (Table 3). When using the adult

Discussion

Although small tidal volumes containing room-air with a paediatric self-inflatable bag were able to maintain sufficient ventilation, oxygenation was not adequate. On the other hand, larger tidal volumes containing room-air given with an adult self-inflatable bag resulted in both adequate ventilation and oxygenation throughout the entire trial.

Measuring ventilation and blood gas parameters in a clinical investigation of basic life support ventilation during cardiac arrest is extremely difficult.

Acknowledgements

Supported, in part, by the Department of Anaesthesiology, University of Lübeck, Germany. We are indebted to Susanne Flaig RN, and Rolf Müller RN, for technical assistance and support throughout the study.

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^☆: Presented in part as an abstract at the 72nd Scientific Sessions of the American Heart Association, Atlanta, Georgia, November 1999.

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Smaller tidal volumes with room-air are not sufficient to ensure adequate oxygenation during bag–valve–mask ventilation☆

Abstract

Introduction

Section snippets

Materials and methods

Statistical analysis

Results

Discussion

Acknowledgements

Resuscitation

Chest

Resuscitation

Br. J. Dis. Chest

Resuscitation

Chest

Resuscitation

Guideline for cardiopulmonary resuscitation and emergency cardiac care, part II: adult basic life support

J. Am. Med. Assoc.

Guidelines for the basic management of the airway and ventilation during CPR

Resuscitation

Influence of tidal volume on the distribution of gas between the lungs and the stomach in the nonintubated patient receiving positive pressure ventilation

Crit. Care Med.