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  • 2000-2004  (3)
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  • 1
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    Vasomotor tone does not affect perfusion heterogeneity and gas exchange in normal primate lungs during normoxia (2000)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: To determine whether vasoregulation is an important cause of pulmonary perfusion heterogeneity, we measured regional blood flow and gas exchange before and after giving prostacyclin (PGI(2)) to baboons. Four animals were anesthetized with ketamine and mechanically ventilated. Fluorescent microspheres were used to mark regional perfusion before and after PGI(2) infusion. The lungs were subsequently excised, dried inflated, and diced into approximately 2-cm(3) pieces (n = 1,208-1,629 per animal) with the spatial coordinates recorded for each piece. Blood flow to each piece was determined for each condition from the fluorescent signals. Blood flow heterogeneity did not change with PGI(2) infusion. Two other measures of spatial blood flow distribution, the fractal dimension and the spatial correlation, did not change with PGI(2) infusion. Alveolar-arterial O(2) differences did not change with PGI(2) infusion. We conclude that, in normal primate lungs during normoxia, vasomotor tone is not a significant cause of perfusion heterogeneity. Despite the heterogeneous distribution of blood flow, active regulation of regional perfusion is not required for efficient gas exchange.
    Keywords: Life Sciences (General)
    Type: Journal of applied physiology (Bethesda, Md. : 1985) (ISSN 8750-7587); Volume 89; 6; 2263-7
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Selected contribution: redistribution of pulmonary perfusion during weightlessness and increased gravity (2000)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: To compare the relative contributions of gravity and vascular structure to the distribution of pulmonary blood flow, we flew with pigs on the National Aeronautics and Space Administration KC-135 aircraft. A series of parabolas created alternating weightlessness and 1.8-G conditions. Fluorescent microspheres of varying colors were injected into the pulmonary circulation to mark regional blood flow during different postural and gravitational conditions. The lungs were subsequently removed, air dried, and sectioned into approximately 2 cm(3) pieces. Flow to each piece was determined for the different conditions. Perfusion heterogeneity did not change significantly during weightlessness compared with normal and increased gravitational forces. Regional blood flow to each lung piece changed little despite alterations in posture and gravitational forces. With the use of multiple stepwise linear regression, the contributions of gravity and vascular structure to regional perfusion were separated. We conclude that both gravity and the geometry of the pulmonary vascular tree influence regional pulmonary blood flow. However, the structure of the vascular tree is the primary determinant of regional perfusion in these animals.
    Keywords: Aerospace Medicine
    Type: Journal of applied physiology (Bethesda, Md. : 1985) (ISSN 8750-7587); Volume 89; 3; 1239-48
    Format: text
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  • 3
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    Regional ventilation-perfusion distribution is more uniform in the prone position (2000)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The arterial blood PO(2) is increased in the prone position in animals and humans because of an improvement in ventilation (VA) and perfusion (Q) matching. However, the mechanism of improved VA/Q is unknown. This experiment measured regional VA/Q heterogeneity and the correlation between VA and Q in supine and prone positions in pigs. Eight ketamine-diazepam-anesthetized, mechanically ventilated pigs were studied in supine and prone positions in random order. Regional VA and Q were measured using fluorescent-labeled aerosols and radioactive-labeled microspheres, respectively. The lungs were dried at total lung capacity and cubed into 603-967 small ( approximately 1.7-cm(3)) pieces. In the prone position the homogeneity of the ventilation distribution increased (P = 0.030) and the correlation between VA and Q increased (correlation coefficient = 0.72 +/- 0.08 and 0.82 +/- 0.06 in supine and prone positions, respectively, P = 0.03). The homogeneity of the VA/Q distribution increased in the prone position (P = 0.028). We conclude that the improvement in VA/Q matching in the prone position is secondary to increased homogeneity of the VA distribution and increased correlation of regional VA and Q.
    Keywords: Life Sciences (General)
    Type: Journal of applied physiology (Bethesda, Md. : 1985) (ISSN 8750-7587); 88; 3; 1076-83
    Format: text
    Location Call Number Expected Availability
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    NASA TECHNICAL REPORTS
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