Acute effects of ultrasound on skeletal muscle oxygen tension, blood flow and capillary density.

The acute effects of pulsed (5 kHz, PRF) ultrasound (2.5 and 5 W/cm2 SPTA at 1 MHz) on the microvasculature of the rat cremaster were examined. Tissue blood flow, capillary density and PO2 were measured in both normally perfused and ischemic tissue. Exposure to 2.5 W/cm2 produced no significant changes in either blood flow or capillary density, however, oxygen tension was significantly reduced in normal tissue at this intensity. Capillary density was significantly diminished in ischemic tissue following exposure to 5 W/cm2 as was PO2 in normally perfused tissue. Blood flow was decreased only in the normoxic tissue at 5 W/cm2. These data suggest that ultrasound at the intensities and frequency employed is capable of producing at least an acute reduction in tissue PO2.