Organ blood flow and cardiac contractility in anaesthetized cats at 5 bar (500 kPa) ambient pressure

Previous in vivo and in vitro experiments have demonstrated increased cardiac contractility and increased total myocardial blood flow ( {Mathematical expression}) when rats were exposed to normoxic 5-bar (500 kPa) ambient pressure. In the present study, regional blood flow was measured using the microsphere method on nine anaesthetized cats at surface and normoxic 5-bar (500 kPa) ambient pressure. Left ventricular pressure (LVP) and cadiac contractility, measured as peak left ventricular +d P/d t and -d P/d t were measured in six of the cats. Arterial pressure, heart rate and cardiac output remained unchanged after compression, but total {Mathematical expression} increased by 29% (P<0.01) and cerebral blood flow increased by 66% (P<0.05). At the same time +d P/d t and -d P/d t was increased by 83% and 102%, respectively (P<0.01), while LVP was enhanced by 14% (P<0.05). Except for a moderate decrease in partial pressure of oxygen, acid base status in arterial blood remained unchanged. The results indicate that the effects of increased ambient pressure on the heart are general physiological phenomena, which are not only limited to the laboratory rat.