Pulmonary blood flow redistribution by increased gravitational force.

  • Hlastala M
  • Chornuk M
  • Self D
 et al. 
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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.

Author-supplied keywords

  • Acceleration
  • Animals
  • Female
  • Fluorescence
  • Gravitation
  • Hemodynamics
  • Hemodynamics: physiology
  • Microspheres
  • Pulmonary Circulation
  • Pulmonary Circulation: physiology
  • Pulmonary Gas Exchange
  • Pulmonary Gas Exchange: physiology
  • Regression Analysis
  • Swine
  • Swine, Miniature

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Authors

  • M P Hlastala

  • M a Chornuk

  • D a Self

  • H J Kallas

  • J W Burns

  • S Bernard

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