Respiratory system compliance decreases after cardiopulmonary resuscitation and stomach inflation: impact of large and small tidal volumes on calculated peak airway pressure

Abstract

The purpose of the present study was to evaluate respiratory system compliance after cardiopulmonary resuscitation (CPR) and subsequent stomach inflation. Further, we calculated peak airway pressure according to the different tidal volume recommendations of the European Resuscitation Council (7.5 ml/kg) and the American Heart Association (15 ml/kg) for ventilation of an unintubated cardiac arrest victim. After 4 min of ventricular fibrillation, and 6 min of CPR, return of spontaneous circulation (ROSC) after defibrillation occurred in seven pigs. Respiratory system compliance was measured at prearrest, after ROSC, and after 2 and 4 l of stomach inflation in the postresuscitation phase; peak airway pressure was subsequently calculated. Before cardiac arrest the mean (+/- S.D.) respiratory system compliance was 30 +/- 3 ml/cm H2O, and decreased significantly (P < 0.05) after ROSC to 24 +/- 5 ml/cm H2O, and further declined significantly to 18 +/- 4 ml/cm H2O after 2 l, and to 13 +/- 3 ml/cm H2O after 4 l of stomach inflation. At prearrest, the mean +/- S.D. calculated peak airway pressure according to European versus American guidelines was 9 +/- 1 versus 18 +/- 3 cm H2O, after ROSC 12 +/- 2 versus 23 +/- 4 cm H2O, and 15 +/- 2 versus 30 +/- 5 cm H2O after 2 l, and 22 +/- 6 versus 44 +/- 12 cm H2O after 4 l of stomach inflation. In conclusion, respiratory system compliance decreased significantly after CPR and subsequent induction of stomach inflation in an animal model with a wide open airway. This may have a significant impact on peak airway pressure and distribution of gas during ventilation of an unintubated patient with cardiac arrest.