Inter-individual differences in control of alveolar capillary blood volume in exercise and hypoxia.

We compared by non-invasive technique the adaptive response of alveolar capillary network to edemagenic conditions (exercise and high altitude [HA, PIO2 107 mm Hg] in subjects with different resting sea level (SL) capillary blood volume (normalized to alveolar volume, Vc/Va): Group 1 (N = 10, Vc/Va = 16.1 +/- 6.8 ml/L- mean +/- SD) and Group 2 (N = 10, Vc/Va = 25 +/- 7.7). In Group 1 Vc/Va remained unchanged in HA at rest and increased during exercise at SL (26.3 +/- 8.6) and HA (28.75 +/- 10.2); in Group 2 Vc/Va significantly decreased in HA (19 6) and did not increase in exercise at SL and HA. We hypothesize that Group2 exerts a tight control on Vc/Va being more exposed to the risk of lung edema due to inborn greater microvascular permeability. Conversely, Group 1 appears more resistant to lung edema given the large capillary recruitment in the most edemagenic condition. The 4-fold increase in frequency dependence of respiratory resistance in Group2 in HA stems for greater proneness for lung water perturbation compared to Group 1. (C) 2013 Elsevier B.V. All rights reserved.