Effects of inspired gas content during respiratory arrest and cardiopulmonary resuscitation

Mouth-to-mouth and bag-valve-mask ventilation have been an indispensable pa rt of cardiopulmonary resuscitation (CPR), However, only recently have the effects of different tidal volumes on arterial oxygenation been reported fo r mouth-to-mouth and bag-valve-mask ventilation, Currently recommended tida l volumes (10-15 mL/kg) are associated with an increased risk of gastric in flation because they produce high peak inspiratory pressures, An animal mod el of ventilation with an unprotected airway showed that a smaller tidal vo lume (6 mL/kg) is as effective as a larger tidal volume (12 mL/kg) in maint aining Sao(2) at >96%. However, a smaller tidal volume with exhaled gas ven tilation produced a mean Sao(2) of 48%, which is ineffective. Ventilation g as mixtures have been studied in models of cardiac arrest and CPR, One stud y showed that ventilation with air during 6 mins of CPH resulted In a retur n of spontaneous circulation in 10 of 12 animals compared with only 5 of 12 animals ventilated with exhaled gas (p < .04), Arterial and mixed-venous P o-2 were significantly higher, and Pco(2) was significantly lower in the ai r ventilation group. Investigations of the cardiovascular effects of mouth- to-mouth ventilation during CPR suggest that there are adverse effects duri ng low blood flow states. However, mouth-to-mouth ventilation during respir atory arrest is lifesaving and should continue to be taught and emphasized In basic life support courses.