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

Objectives: When ventilating a nonintubated patient in cardiac arrest, the European Resuscitation Council has recently recommended a decrease in the tidal volume from 0.8 to 1.2 L to 0.5 L, partly in an effort to decrease peak flow rate, and therefore, to minimize stomach inflation. The purpose of the present study was to examine the validity of the European Resuscitation Council's recommendation in terms of gas distribution between lungs and stomach in a bench model that simulates ventilation of a nonintubated patient with a self-inflatable bag representing tidal volumes of 0.5 and 0.75 L. Design: A bench model of a patient with a nonintubated airway was used consisting of face mask, manikin head, training lung (lung compliance, 50 mL/cm H(2)O; airway resistance, 5 cm H(2)O/L/sec), adjustable lower esophageal sphincter pressure (LESP) and simulated stomach. Setting: University hospital laboratory. Subjects: Thirty healthcare professionals. interventions: Healthcare professionals performed 1-min bag-mask ventilation at each LESP level of 5, 10, and 15 cm H(2)O at a rate of 12 breaths/min, using an adult and pediatric self inflating bag, respectively. Volunteers were blinded to the LESP, which was randomly varied. Measurements and Main Results: Both types of self inflating bags induced stomach inflation, with higher stomach and lower lung tidal volumes when the LESP was decreased. Lung tidal volume with the pediatric bag was significantly (p < .05) lower at all LESP levels when compared with the adult bag, and ranged be tween 240 mL at an LESP of 15 cm H(2)O and 120 mL at an LESP of 5 cm H(2)O. Stomach tidal volume with the adult bag ranged between 250 mL at an LESP of 15 cm H(2)O and increased to 550 mL at an LESP of 5 cm H(2)O. Stomach tidal volume with the pediatric bag was significantly lower (p < .05) at all LESP levels when compared with the adult bag and ranged between 70 mL at an LESP of 15 cm H(2)O and 300 mL at an LESP of 5 cm H(2)O. Conclusions: Our data support the recommendation of the European Resuscitation Council to decrease tidal volumes to 0.5 L when ventilating a cardiac arrest victim with an unprotected airway. A small tidal volume may be a better trade off in the basic life support phase, as this may provide reasonable ventilation while avoiding massive stomach inflation.