Relieving the respiratory workload by positive pressure ventilation can make a major contribution to meeting oxygen demand, and thereby taking strain off of a taxed heart, reducing oxygen extraction
and increasing mixed venous and arterial blood saturations.
The human body compensates for any decreased oxygen-carrying capacity in a variety of ways, including increased cardiac output and enhanced oxygen extraction
at the capillary level (1).
The extract did not significantly affect heart rate and contractility, main parameters of the cardiac action that determine oxygen demands, while coronary flow increased up to 45% over control value with a simultaneous decrease of oxygen extraction
Researchers examined the impacts upon heart contractility, electrophysiological function, coronary flow and oxygen extraction
in isolated guinea pig hearts, and the direct vasodilatory activity of the extract on rat aortic rings.
Tissue oxygenation, defined as the relative saturation of OxyHb, depends on the balance between oxygen delivery, as reflected by the product of blood flow and arterial oxygen content, and oxygen extraction
(Subudhi et al.
2,3) Studies have shown that improvements in walking tolerance with exercise training are associated with increases in the concentration of skeletal muscle oxidative enzymes (2,4,5) and improved oxygen extraction
by the trained skeletal muscles.