Regional blood flow distribution in dog during induced hypotension and low cardiac output. Spontaneous breathing versus artificial ventilation.

Respiratory muscle blood flow and organ blood flow was studied in two groups of dogs with radioactively labeled microspheres to assess the influence of the working respiratory muscles on the regional distribution of blood flow when arterial pressure and cardiac output were lowered by pericardial tamponade. In one group (n = 6), the dogs were paralyzed and mechanically ventilated (Mv), while in the other (n = 6), they were left to breathe spontaneously (Sb). Cardiac output fell to 30% of control values during tamponade in both groups and was maintained constant.