The extent that the circulation is impaired under near-vacuum conditions was investigated in five anesthetized dogs and one anesthetized chimpanzee decompressed from 380 mm Hg to 4 mm Hg in l–2 s and maintained at 4 mm Hg for 60 s. Blood flow velocity, measured within the thoracic aorta with a catheter-tip Doppler flowmeter, severely decreased in dogs within 30 s and approximated cessation in the chimpanzee after 10 s. Aortic and vena caval pressures tended to equalize in dogs; equilibrium and subsequent pressure gradient inversion resulted in the chimpanzee. Mechanical events associated with gas expansion and especially water vaporization were believed largely responsible for these effects. Anoxic bradycardia, similar in both species, ensued also. Anoxic anoxia, uncomplicated by water vaporization after decompression from 431 mm Hg to 55 mm Hg, failed to seriously impair cardiovascular function in dogs, but apparently was accompanied in the chimpanzee by mechanical events from gas expansion sufficient to block the circulation. Differences in responses in these two species probably involved the physical characteristics of the torso. altitude; anoxia; ebullism; gas expansion; near-vacuum exposure; rapid decompression
Intracoronary blood flow velocity and transstenotic pressure gradient using sensor-tip pressure and doppler guidewires: A new technology for the assessment of stenosis severity in the catheterization laboratory
