Effect of positive end-expiratory pressure on extravascular lung water and cardiopulmonary function in dogs with experimental severe hydrostatic pulmonary edema.

The effects of ventilation at positive end-expiratory pressure (PEEP) on extravascular lung water (EVLW) and cardiopulmonary function were studied in dogs with experimental severe hydrostatic pulmonary edema, which was generated by inflating a left atrial balloon and simultaneously injecting warm 5% glucose solution into the pulmonary artery. The EVLW was measured by the double indicator dilution method using heat and sodium ions. All the dogs were ventilated at zero end-expiratory pressure (ZEEP) until the EVLW had increased by 200-300% (maximal edema), when they were divided into two groups, one of which (n = 6) was ventilated at a PEEP of 10 cm H2O throughout the 4 hr study period (PEEP group) and the other (n = 6) was maintained at ZEEP during their survival period (ZEEP group). All the dogs in the PEEP group survived ventilation for 4 hr, whereas all those in the ZEEP group died within 3 hr, (2 within 1 hr, 1 between 1 and 2 hr and 3 between 2 and 3 hr). The EVLW of the PEEP group remained unchanged throughout the 4 hr study period, whereas that of the ZEEP group showed a tendency to increase. The arterial oxygen tension (PaO2) increased significantly throughout the 4 hr period of ventilation in the PEEP group but tended to decrease in the ZEEP group. In conclusion, PEEP improves gaseous exchange, but does not decrease the EVLW in dogs with experimental severe hydrostatic edema.