The delayed use of positive end-expiratory pressure (PEEP) during respiratory resuscitation following near drowning with fresh or salt water.

Abstract

Investigations on the delayed use of positive end-expiratory pressure (PEEP) following a standardized form of near drowning with 12.5 ml/kg body weight of either fresh or salt water were carried out on 14 anaesthetized and ventilated young pigs. After a 3-min period of apnoea the animals were ventilated with 100% oxygen and with either the same or an increased tidal volume, and a PEEP of 5 cmH2O delayed to 20 min, over a period of 2 h. In both fresh and salt water, initial values of PaO2 and AaDo2 were regained by the end of the period of observation when a delayed PEEP was applied. The intrapulmonary right to left shunt, which increased to 40% of the cardiac output, fell by a half within 10 min of beginning PEEP ventilation, initial values being regained after 120 min. During the period of apnoea the arterial partial pressure of carbon dioxide almost doubled, and, when the tidal volume remained unaltered, was still some 20-30% above initial values at the end of 2 h, despite the use of PEEP. Normal PaCO2 levels were achieved on increasing the tidal volume by a factor of 1.4. The larger tidal volume had no influence on either the degree of shunt or the PaO2. The effective compliance, which was considerably reduced after near drowning, increased again with the use of delayed PEEP ventilation. On beginning respiratory resuscitation there was an initial tachycardia and, despite a fall in stroke volume, an increase in mean arterial pressure and cardiac output because of the previous hypoxia. Only minimal cardiocirculatory changes, and no change in oxygen availability, occurred secondary to the use of PEEP.