ABSTRACT
Myocardial oxygen consumption
was measured using an in situ, perfused heart preparation at 10°C
increased in a linear fashion with power output when cardiac output
was elevated (volume loading). The increased
was possible through improved O2 delivery
, but
was reduced. The mechanical efficiency of the heart was improved.
also increased in a linear fashion with power output when output pressure was increased with
constant (pressure loading). The increased
was supported by increased O2 removal from the perfusate since oxygen delivery
was constant. Once more, improved mechanical efficiency was observed.
decreased as O2 delivery was reduced with progressive hypoxia. Even so, power output was maintained at a perfusate input
of 81 Torr. Five of 11 hearts survived a 30-Torr
exposure, but with a 29 % decrease in power output and a 5-fold reduction in
. The increase in the apparent aerobic efficiency which enabled this is discussed.