title: Paradoxical redistribution of pulmonary blood flow in prone and supine humans exposed to hypergravity.
abstract: We hypothesized that exposure to hypergravity in the supine and prone postures causes a redistribution of pulmonary blood flow to dependent lung regions. Four normal subjects were exposed to hypergravity by use of a human centrifuge. Regional lung perfusion was estimated by single-photon-emission computed tomography (SPECT) after administration of (99m)Tc-labeled albumin macroaggregates during normal and three times normal gravity conditions in the supine and prone postures. All images were obtained during normal gravity. Exposure to hypergravity caused a redistribution of blood flow from dependent to nondependent lung regions in all subjects in both postures. We speculate that this unexpected and paradoxical redistribution is a consequence of airway closure in dependent lung regions causing alveolar hypoxia and hypoxic vasoconstriction. Alternatively, increased vascular resistance in dependent lung regions is caused by distortion of lung parenchyma. The redistribution of blood flow is likely to attenuate rather than contribute to the arterial desaturation caused by hypergravity.
authors.affiliation: Department of Anesthesiology and Intensive Care, Karolinska University Hospital, Solna, 171 76 Stockholm, Sweden. johan.petersson@karolinska.se
authors.forename: Johan
authors.initials: J
authors.lastname: Petersson
authors.forename: Malin
authors.initials: M
authors.lastname: Rohdin
authors.forename: Alejandro
authors.initials: A
authors.lastname: Sánchez-Crespo
authors.forename: Sven
authors.initials: S
authors.lastname: Nyrén
authors.forename: Hans
authors.initials: H
authors.lastname: Jacobsson
authors.forename: Stig A
authors.initials: SA
authors.lastname: Larsson
authors.forename: Sten G E
authors.initials: SG
authors.lastname: Lindahl
authors.forename: Dag
authors.initials: D
authors.lastname: Linnarsson
authors.forename: Robb W
authors.initials: RW
authors.lastname: Glenny
authors.forename: Margareta
authors.initials: M
authors.lastname: Mure
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D000328:Adult; D005260:Female; D006801:Humans; D018471:Hypergravity; D008168:Lung / Q000098:blood supply* / Q000000981:diagnostic imaging / Q000502:physiology*; D008297:Male; D016684:Prone Position / Q000502:physiology*; D011652:Pulmonary Circulation / Q000502:physiology*; D019275:Radiopharmaceuticals; D016683:Supine Position / Q000502:physiology*; D013668:Technetium Tc 99m Aggregated Albumin; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods
chemical_list: D019275:Radiopharmaceuticals; D013668:Technetium Tc 99m Aggregated Albumin