[Influence of breathing at negative pressure on redistribution of local blood volumes in anti-orthostatic load in cats].
To improve methods of offsetting the hemodynamic shifts in microgravity, applicability of breathing at negative pressure (BNP, pressure relief by -5.0 cm of water column) during inspiration and expiration was assessed in acute experiments with unconscious cats tilted head-down (-30 degrees). Direct measurement of pressure in v. cava superior and v. jugularis externa using a catheter revealed a concurrent significant (p < 0.05) growth of the parameter which should be considered a sign of impeded venous outflow from the craniocervical vessels. BNP added to the sucking effect of the thoracic cavity (the siphoning effect) and led to more massive venous outflow from cephalic vessels as evidenced by pressure drop in the jugular vein and v. cava superior to the values determined in the basic horizontal position. However, BNP did not significantly alter arterial hemodynamics, respiration pattern or gas exchange. Data of the investigation attest effectiveness of this method of moderating blood flow to the cat's head during HDT and possibility to apply it in the zero-g environment.
Baranov
V M
VM
Tikhonov
M A
MA
Kotov
A N
AN
Donina
Zh A
ZhA
Pogodin
M A
MA
Lavrova
I N
IN
D000818:Animals; D001921:Brain / Q000098:blood supply; D002415:Cats; D004562:Electrocardiography; D006439:Hemodynamics / Q000502:physiology; D018476:Hypokinesia / Q000175:diagnosis* / Q000503:physiopathology; D011312:Pressure; D012119:Respiration; D013318:Stroke Volume / Q000502:physiology*