SCINTISCANNING SYSTEM FOR STUDY OF REGIONAL DISTRIBUTION OF BLOOD FLOW.
Final rept. Jan 68-Sep 69,
MAYO CLINIC ROCHESTER MINN
Pagination or Media Count:
The effect of changes in the direction and magnitude of the gravitational-inertial force environment on the regional distribution of impacted 35-micron diameter microspheres has been measured in the lungs of six anesthetized chimpanzees. These distributions were determined by two computer-controlled scintiscans at 780 sites covering the dorsal and ventral surfaces of the thorax at 1 G subsequent to four injections of differentially isotope-tagged microspheres into the right ventricular outflow tract. Pulse-height analysis at each site allowed separation of count values for the isotopes, and, after correction for collimator distortion, these values were assumed to be proportional to the respective blood flows which were present below each site at the respective time of injections. Computer-generated 3-dimensional and contour map displays of the scintiscan and related physiologic data indicate that pulmonary blood flow tended to redistribute toward the midthoracic region during acceleration exposures concomitantly with large decreases in arterial oxygen saturation presumably from pulmonary shunting via the dependent regions of the lung. The decrease in blood flow to the superior regions of the lung coupled with the finding of no change or decreases in flow to the dependent regions of the lung suggests that selective increases in resistance to blood flow to the dependent, presumably anoxic, region of the lung occurred which were responsible for the reduction in level of physiologic shunt frequently found in these animals toward the end of the exposure to 5.8 Gy. Author
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