Elsevier

Resuscitation

Volume 43, Issue 1, December 1999, Pages 25-29
Resuscitation

Effects of smaller tidal volumes during basic life support ventilation in patients with respiratory arrest: good ventilation, less risk?

https://doi.org/10.1016/S0300-9572(99)00118-5Get rights and content

Abstract

Objective: When ventilating an unintubated patient in cardiac or respiratory arrest, smaller tidal volumes of 500 ml instead of 800–1200 ml may be beneficial to decrease peak airway pressure, and to minimise stomach inflation. The purpose was to determine the effects of small (∼500 ml) versus large (∼1000 ml) tidal volumes given with paediatric versus adult self-inflatable bags and ∼50% oxygen on respiratory parameters in patients during simulated basic life support ventilation. Methods: While undergoing induction of anaesthesia, patients were randomised to three minutes of ventilation with either an adult (n=40) or paediatric (n=40) self-inflatable bag. Results: When compared with an adult self-inflatable bag, the paediatric bag resulted in significantly lower mean (±standard deviation) exhaled tidal volume (365±55 versus 779±122 ml; P<0.0001), peak airway pressure (20±2 versus 25±5 cm H2O; P<0.0001), but comparable oxygen saturation (97±1% versus 98±1%; NS (nonsignificant)). Stomach inflation occurred in five of 40 patients ventilated with an adult self-inflatable bag, but in no patients who were ventilated with a paediatric self-inflatable bag (P=0.054). Conclusion: Administering smaller tidal volumes with a paediatric instead of an adult self-inflatable bag in unintubated adult patients with respiratory arrest maintains good oxygenation and carbon dioxide elimination while decreasing peak airway pressure, which makes stomach inflation less likely.

Introduction

When ventilating an unintubated patient, the distribution of gas between lungs and stomach depends mainly on lower oesophageal sphincter pressure, respiratory system compliance, inspiratory flow rate and time, and especially, upper airway pressure [1]. Thus, respiratory mechanics of the patient, and technique of the rescuer performing bag-valve-mask ventilation determine peak airway pressure, which, in turn, determines whether the lungs are ventilated, or the stomach is inflated [2]. Accordingly, managing peak airway pressure in order to prevent stomach inflation is of fundamental importance when ventilating unintubated patients in respiratory or cardiac arrest during basic life support ventilation. Although manoeuvres to position the head and/or the jaw in an unintubated patient may have an important impact on airway resistance, a rescuer performing bag-valve-mask ventilation may not be able to influence other components of respiratory mechanics such as respiratory system compliance, and lower oesophageal sphincter pressure.

One approach to control peak airway pressure during basic life support ventilation (i.e. when the airway is unprotected) is to limit peak flow rate by reducing tidal volume. An in-vitro model simulating an unintubated patient indicated that a small (∼500 ml) tidal volume, administered with a paediatric self-inflatable bag, provided reasonable ventilation; while reducing stomach inflation [3]. Recently, the European Resuscitation Council has recommended decreasing tidal volumes from 800–1200 [4] to 500 ml [5] when ventilating unintubated cardiac arrest patients in respiratory or cardiac arrest in order to minimise stomach inflation. A tidal volume of 500 ml may be a good compromise when ventilating an unintubated patient, by providing reasonable ventilation while avoiding significant stomach inflation that could cause regurgitation, aspiration, pneumonia, and possibly, death [6]. In contrast to the European Resuscitation Council, the American Heart Association continues to recommend using a tidal volume of 800 to 1200 ml for bag-valve-mask ventilation. Thousands of healthcare professionals are taught these guidelines in the United States and abroad every year. Therefore, the question of a safe and effective tidal volume during basic life support ventilation needs to be answered. However, no clinical study has been done to assess the effects of smaller tidal volumes on oxygenation and peak airway pressure, therefore, the issue has not yet been resolved. Accordingly, the purpose of the present study was to compare arterial oxygenation saturation, tidal volumes, and peak airway pressure during bag-valve-mask ventilation with a paediatric versus an adult size self-inflatable bag in unintubated, apnoeic patients. The hypothesis is that there is no difference between arterial oxygen saturation, tidal volumes, and peak airway pressure 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. Male and female ASA I and ASA II patients (>18 years, with no underlying respiratory or cardiac disease) undergoing routine surgical procedures were informed by one investigator about the study and signed written informed consent before volunteering to participate. After an overnight fast, anaesthesia was induced with fentanyl (2 μ/kg) and propofol (2.5–3.5 mg/kg);

Results

Eighty patients were entered into the study, and randomised to receive ventilation with either a paediatric (n=40) or an adult (n=40) self-inflatable bag. There were no significant differences in age, weight, or height between groups. When compared with an adult self-inflatable bag, the paediatric bag resulted in significantly (P<0.0001) higher respiratory rate, end-tidal carbon dioxide, lower exhaled tidal volume and peak airway pressure, but comparable arterial oxygen saturation, respectively

Discussion

In 80 patients who were ventilated with either paediatric (n=40) or adult (n=40) self-inflatable bags with ∼50% oxygen during induction of anaesthesia, use of a paediatric bag compared with an adult version resulted in significantly lower tidal volumes and peak airway pressure, while arterial oxygen saturation remained almost identical in both groups. Stomach inflation occurred in five of 40 patients ventilated with an adult self-inflatable bag, but in no patients who were ventilated with a

Acknowledgements

Supported, in part, by the Laerdal Foundation for Acute Medicine, Stavanger, Norway; and the Department of Anaesthesia and Intensive Care Medicine, The Leopold–Franzens-University of Innsbruck, Austria.

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