Abstract
PEEP has been shown to decrease both cardiac output (C.O.) and alveolar capillary perfusion (Q.). Method: We attached an in-vivo microscope apparatus to the lungs of 5 anesthetized dogs through a left thoracotomy to study the effects of PEEP on Q. Q was assessed at baseline with 5 cm H₂O PEEP and during the application of 15 cm H₂O PEEP. To differentiate between the effect of the fall in C.O. on Q. and the effects of other hemodynamic changes with PEEP, C.O. was restored to the control level with dextran-70 infusion. Results: The institution of 15 cm H₂O PEEP effected a dramatic fall in Q. with a concomitant decline in C.O. Infusion of dextran 70 returned C.O. to baseline, but Q. remained 70% below baseline. Photomicrographs showed flat, constricted capillaries with PEEP. Conclusion: These data suggest that PEEP reduces Q. by direct compression of pulmonary capillaries rather than by decreasing cardiac output.
Get full access to this article
View all access options for this article.