VENTILATION WITH POSITIVE END-EXPIRATORY PRESSURE REDUCES EXTRAVASCULAR LUNG WATER AND INCREASES LYMPHATIC FLOW IN HYDROSTATIC PULMONARY-EDEMA

Objective: To analyze the effect of different levels of positive end-e xpiratory pressure (PEEP) on extravascular lung water and on lymphatic drainage through the thoracic duct during hydrostatic pulmonary edema . Design: Randomized, controlled, experimental study, Setting: Researc h laboratory of a tertiary care hospital, Subjects: Eighteen beagle do gs weighing between 10 and 19 kg. Interventions: Dogs were anesthetize d and cannulated via a thoracic duct, Hydrostatic pulmonary edema was provoked by inflating the balloon of a Foley catheter in the left atri um, Different amounts of PEEP were applied. Measurements and Main Resu lts: Extravascular lung water was determined by the double indicator d ilution method (indocyanine green in glucoside solution at 0 degrees C ), and lymphatic drainage was measured every 30 mins, After a baseline measurement, the left atrial pressure was increased to 24 to 26 mm Hg , and measurements were recorded after 30, 60, 90, and 120 mins. The a nimals were divided into three groups, Group I (n = 6): PEEP of 20 cm H2O was instituted at 120 mins, and the other determinations were made without PEEP; group II (n = 7): PEEP of 10 cm H2O was instituted at 6 0 and 90 mins; group III (n = 5): PEEP of 20 cm H2O was instituted at 60 and 90 mins, Extravascular lung water in creased after the increase of left atrial pressure in all three groups, After 90 mins, the extra vascular lung water was significantly greater (p<.01) in group I (no P EEP application) at 21.2 +/- 5.1 mL/kg than in groups II and III (with 10 and 20 cm H2O of PEEP) at 12.8 +/- 2.01 and 14.8 +/- 4.8 mL/kg, re spectively. Lymphatic drainage tended to increase over time in all thr ee groups, Ninety minutes after the left atrial pressure increase, lym phatic drainage was significantly greater (p <.05) in group II, at 6.0 6 +/- 2.53 mL/kg/30 mins, than in group I, at 2.83 +/- 0.76 mL/kg/30 m ins, Conclusions: a) The application of PEEP levels of between 10 and 20 cm H2O limits the increase of extravascular lung water in cases of hydrostatic pulmonary edema; and b) the application of 10 cm H2O of PE EP increases the lymphatic flow through the thoracic duct.