Open Collections

Abstract

Background: Pulmonary gas exchange efficiency, determined by the alveolar-to-arterial PO₂ difference (A-aDO2), progressively worsens during exercise at sea-level; this response is further augmented during exercise in hypoxia. Traditionally, pulmonary gas exchange efficiency is assessed through measurements of ventilation and end-tidal gases paired with direct arterial blood gas (ABG) sampling. Since these measures have a number of caveats, particularly invasive blood sampling, the development of new approaches for the non-invasive assessment of pulmonary gas exchange is needed. Research Question: Is a non-invasive method of assessing pulmonary gas exchange valid during rest and exercise in acute hypoxia? Study Design and Methods: Twenty-five healthy participants (10 female) completed a staged maximal exercise test on a cycle ergometer in a hypoxic chamber (FIO₂=0.11). Simultaneous ABGs via a radial arterial catheter and non-invasive gas exchange measurements (AGM100) were obtained in two-minute intervals. Non-invasive gas exchange efficiency, termed the O₂ deficit, was calculated from the difference between the end-tidal and the calculated PaO₂ (via pulse oximetry and corrected for the Bohr effect by using the end-tidal PCO₂). Non-invasive O₂ deficit was compared to the traditional alveolar to arterial oxygen difference (A-aDO₂) using the traditional Riley analysis. Results: Under conditions of rest at room air, hypoxic rest and hypoxic exercise, strong correlations between the calculated gPaO₂ and directly measured PaO₂ (R²=0.97; p