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Updated: Feb 24, 2026

Author Spotlight: Integrating Alveolar-Capillary Reserve Measurements in Exercise Adaptation and Therapeutic Strategies
Published on: February 2, 2024
Air blood barrier phenotype correlates with alveolo-capillary O2 equilibration in hypobaric hypoxia
Egidio Beretta1, Francesca Lanfranconi1, Gabriele Simone Grasso1
1Ambulatorio di Fisiologia Clinica e dello Sport, Scuola di Specializzazione in Medicina dello Sport, Università di Milano-Bicocca. Via Cadore, 48 20900 Monza, Italy.
Abstract:
The O2 diffusion limitation across the air blood barrier (DO2 and subcomponents Dm and Vc) was evaluated in 17 healthy participants exposed to hypobaric hypoxia (HA, 3840m, PIO2 ∼90mmHg). A 10% decrease in alveolar volume (VA) in all participants suggested the development of sub-clinical interstitial lung edema. In >80% of participants DO2/VA increased, reflecting an individual strategy to cope with the hypoxia stimulus by remodulating Vc or Dm. Opposite changes in Dm/Vc ratio were observed and participants decreasing Vc showed reduced alveolar blood capillary transit time. The interplay between diffusion and perfusion (cardiac output) was estimated in order to investigate the individual adaptive response to hypoxia. It appears remarkable that despite individual differences in the adaptive response to HA, diffusion limitation did not exceed ∼11% of the alveolar-venous PO2 gradient, revealing an admirable functional design of the air-blood barrier to defend the O2 diffusion/perfusion function when facing hypobaric hypoxia corresponding to 50mmHg decreased PAO2.
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