Effects of inertial load and countermeasures on the distribution of pulmonary blood flow.
We assessed the influence of cranial-to-caudal inertial force (+G(z)) and the countermeasures of anti-G suit and positive pressure breathing during G (PBG), specifically during +G(z), on regional pulmonary blood flow distribution. Unanesthetized swine were exposed randomly to 0 G(z) (resting), +3 G(z), +6 G(z), and +9 G(z), with and without anti-G suit and PBG with the use of the Air Force Research Laboratory centrifuge at Brooks Air Force Base (the gravitational force of the Earth, that is, the dorsal-to-ventral inertial force, was present for all runs). Fluorescent microspheres were injected into the pulmonary vasculature as a marker of regional pulmonary blood flow. Lungs were excised, dried, and diced into approximately 2-cm(3) pieces, and the fluorescence of each piece was measured. As +G(z) was increased from 0 to +3 G(z), blood flow shifted from cranial and hilar regions toward caudal and peripheral regions of the lung. This redistribution shifted back toward cranial and hilar regions as anti-G suit inflation pressure increased at +6 and +9 G(z). Perfusion heterogeneity increased with +G(z) stress and decreased at the higher anti-G suit pressures. The distribution of pulmonary blood flow was not affected by PBG. ANOVA indicated anatomic structure as the major determinant of pulmonary blood flow.
Department of Physiology and Biophysics, University of Washington, Seattle 98195, USA.
M A
MA
Chornuk
S L
SL
Bernard
J W
JW
Burns
R W
RW
Glenny
D D
DD
Sheriff
S E
SE
Sinclair
N L
NL
Polissar
M P
MP
Hlastala
D000818:Animals; D005260:Female; D005456:Fluorescent Dyes; D006112:Gravitation; D005676:Gravity Suits; D008168:Lung / Q000378:metabolism / Q000502:physiology; D008863:Microspheres; D011175:Positive-Pressure Respiration; D011652:Pulmonary Circulation / Q000502:physiology*; D011659:Pulmonary Gas Exchange / Q000502:physiology; D013552:Swine; D013556:Swine, Miniature
D005456:Fluorescent Dyes