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 decreas e 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 inflati on. The purpose of the present study was to examine the validity of th e European Resuscitation Council's recommendation in terms of gas dist ribution between lungs and stomach in a bench model that simulates ven tilation of a nonintubated patient with a self-inflatable bag represen ting tidal volumes of 0.5 and 0.75 L. Design: A bench model of a patie nt with a nonintubated airway was used consisting of face mask, maniki n head, training lung (lung compliance, 50 mL/cm H2O; airway resistanc e, 5 cm H2O/L/sec), adjustable lower esophageal sphincter pressure (LE SP) and simulated stomach. Setting: University hospital laboratory. Su bjects: Thirty healthcare professionals. interventions: Healthcare pro fessionals performed 1-min bag-mask ventilation at each LESP level of 5, 10, and 15 cm H2O at a rate of 12 breaths/min, using an adult and p ediatric self inflating bag, respectively. Volunteers were blinded to the LESP, which was randomly varied. Measurements and Main Results: Bo th types of self inflating bags induced stomach inflation, with higher stomach and lower lung tidal volumes when the LESP was decreased. Lun g tidal volume with the pediatric bag was significantly (p < .05) lowe r at all LESP levels when compared with the adult bag, and ranged be t ween 240 mL at an LESP of 15 cm H2O and 120 mL at an LESP of 5 cm H2O. Stomach tidal volume with the adult bag ranged between 250 mL at an L ESP of 15 cm H2O and increased to 550 mL at an LESP of 5 cm H2O. Stoma ch tidal volume with the pediatric bag was significantly lower (p < .0 5) at all LESP levels when compared with the adult bag and ranged betw een 70 mL at an LESP of 15 cm H2O and 300 mL at an LESP of 5 cm H2O. C onclusions: Our data support the recommendation of the European Resusc itation 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 ma y provide reasonable ventilation while avoiding massive stomach inflat ion.