Experimental pulmonary edema. The effect of unilateral PEEP on the accumulation of lung water

The effect of PEEP in retarding the development of pulmonary edema produced by elevation of left atrial (LA) pressure to 25cm water was studied in dogs, Using two synchronized volume respirators connected to a double lumen endotracheal tube, 10 or 25cm H2O PEEP was applied to one lung while the contralateral lung was ventilated with an equal tidal volume without PEEP. LA pressure was then elevated by inflating a Foley catheter ballon in the LA until the desired LA pressure was reached. After three hours of pulmonary edema with ventilation of one lung with PEEP lung water was quantitated by wet-to-dry weights. There were no differences in wet to dry weights of PEEP and nonPEEP lungs at either 10 or 25cm H2O level. Additional blood flow studies showed that 25cm H2O of PEEP reduced blood flow to the PEEP lung by 25% and to the nonPEEP lung by 7%. This study shows that PEEP will not mechanically retard the accumulation of lung water due to increased pulmonary capillary hydrostatic pressure.