Left ventricular regional myocardial blood flows during controlled positive pressure ventilation and positive end-expiratory pressure in dogs.

Abstract

A decrease in myocardial blood flow (MBF) has been suggested as a possible cause for the depression of left ventricular function during mechanical ventilation. In 8 dogs, hemodynamic effects of controlled mechanical ventilation with 15 cm H2O of PEEP or (CPPV15) were compared to controlled mechanical ventilation without PEEP (IPPV). Addition of PEEP caused a significant decrease in left ventricular epicardial, midwall (p less than .01) endocardial and septal (p less than .05) blood flows. The decrease in myocardial blood flow was not accompanied by any significant change in BP, HR, cardiac index (CI) or right (RVSWI) and left (LVSWI) ventricular stroke work indices. Left ventricular myocardial oxygen consumption (LVMVO2) and coronary sinus oxygen content (Ccso2) also did not show any significant change. Pulmonary vascular resistance (PVR) increased significantly (p less than .01). The observed decrease in MBF during PEEP therapy may be due to shift of the interventricular septum, reflexly mediated coronary vasoconstriction, or decreased net coronary filling pressure.