title: Pulmonary blood flow redistribution by increased gravitational force.
abstract: This study was undertaken to assess the influence of gravity on the distribution of pulmonary blood flow (PBF) using increased inertial force as a perturbation. PBF was studied in unanesthetized swine exposed to -Gx (dorsal-to-ventral direction, prone position), where G is the magnitude of the force of gravity at the surface of the Earth, on the Armstrong Laboratory Centrifuge at Brooks Air Force Base. PBF was measured using 15-micron fluorescent microspheres, a method with markedly enhanced spatial resolution. Each animal was exposed randomly to -1, -2, and -3 Gx. Pulmonary vascular pressures, cardiac output, heart rate, arterial blood gases, and PBF distribution were measured at each G level. Heterogeneity of PBF distribution as measured by the coefficient of variation of PBF distribution increased from 0.38 +/- 0.05 to 0.55 +/- 0.11 to 0.72 +/- 0.16 at -1, -2, and -3 Gx, respectively. At -1 Gx, PBF was greatest in the ventral and cranial and lowest in the dorsal and caudal regions of the lung. With increased -Gx, this gradient was augmented in both directions. Extrapolation of these values to 0 G predicts a slight dorsal (nondependent) region dominance of PBF and a coefficient of variation of 0.22 in microgravity. Analysis of variance revealed that a fixed component (vascular structure) accounted for 81% and nonstructure components (including gravity) accounted for the remaining 19% of the PBF variance across the entire experiment (all 3 gravitational levels). The results are inconsistent with the predictions of the zone model.
authors.affiliation: Department of Physiology and Biophysics, University of Washington, Seattle 98195, USA.
authors.forename: M P
authors.initials: MP
authors.lastname: Hlastala
authors.forename: M A
authors.initials: MA
authors.lastname: Chornuk
authors.forename: D A
authors.initials: DA
authors.lastname: Self
authors.forename: H J
authors.initials: HJ
authors.lastname: Kallas
authors.forename: J W
authors.initials: JW
authors.lastname: Burns
authors.forename: S
authors.initials: S
authors.lastname: Bernard
authors.forename: N L
authors.initials: NL
authors.lastname: Polissar
authors.forename: R W
authors.initials: RW
authors.lastname: Glenny
mesh_terms: D000054:Acceleration; D000818:Animals; D005260:Female; D005453:Fluorescence; D006112:Gravitation; D006439:Hemodynamics / Q000502:physiology; D008863:Microspheres; D011652:Pulmonary Circulation / Q000502:physiology*; D011659:Pulmonary Gas Exchange / Q000502:physiology; D012044:Regression Analysis; D013552:Swine; D013556:Swine, Miniature