Source: Annual Congress 2011 - Physiology of human pulmonary hypertension
Disease area: Pulmonary vascular diseases

Abstract

Hypoxic pulmonary vasoconstriction (HPV) diverts blood from hypoxic regions of the lung, optimising ventilation/perfusion (V/Q) matching and gas exchange. In whole lung hypoxia (i.e. high altitude) HPV becomes less effective but still impacts on gas exchange by redirecting blood flow to regions of higher oxygen partial pressure (PO2). The combination of events leading to this response on a regional level is not well understood and is difficult to investigate experimentally, particularly in humans.
In this study we use a structure-based model to investigate the interacting mechanisms that contribute to regional development of HPV under low inspired PO2 (PiO2) to understand its effect on perfusion redistribution in the pulmonary circulation. The mathematical model couples ventilation (V), perfusion (Q), and gas exchange within a patient-specific anatomical structure. Regional alveolar PO2 (PAO2) is simulated for various levels of PiO2. An empirically-derived model of HPV [J Appl Physiol:1988;64(1):68-77] is included in an existing multi-scale model of the pulmonary circulation [doi:10.1152/japplphysiol.00775.2010] and the resultant blood flow predicted.
During hypoxia pulmonary artery pressure and pulmonary vascular resistance increased exponentially with decrements in PiO2. Regions with lower baseline V/Q had lower predicted PAO2 and hence greater vasoconstriction; blood was therefore redistributed preferentially to the gravitationally non-dependent tissue (decreased gravitational flow gradient), in agreement with experimental measurements in animals. Shear stress in the non-dependent region increased proportionately. The resultant decreased blood flow gradient results in a more efficient V/Q matching.

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Citations should be made in the following way:
K. Burrowes, A. Clark, A. Swan, M. Tawhai (Oxford, United Kingdom; Auckland, New Zealand). A model-based analysis of the effect of hypoxia on regional pulmonary blood flow. Eur Respir J 2011; 38: Suppl. 55, 2304

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