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Updated: Apr 27, 2026
Author Spotlight: Integrating Alveolar-Capillary Reserve Measurements in Exercise Adaptation and Therapeutic Strategies
Published on: February 2, 2024
Pulmonary gas exchange efficiency during exercise breathing normoxic and hypoxic gas in adults born very preterm with
Joseph W Duke1, Jonathan E Elliott1, Steven S Laurie1
1Department of Human Physiology, University of Oregon, Eugene, Oregon;
Insights
Adults born very preterm (PRET) have reduced lung function but maintain normal pulmonary gas exchange efficiency during exercise, even when breathing hypoxic air. This finding suggests preterm birth does not impair exercise gas exchange despite lower diffusion capacity.
Area of Science:
- Pulmonary physiology
- Respiratory medicine
- Neonatology outcomes
Background:
- Very preterm birth (<32 weeks gestational age) is associated with reduced lung function and lower diffusing capacity for carbon monoxide (DLCO).
- Low DLCO may theoretically impair pulmonary gas exchange efficiency during exercise, especially under hypoxic conditions due to reduced oxygen diffusion.
- Alveolar-to-arterial oxygen difference (AaDO2) is a key indicator of pulmonary gas exchange efficiency.
Purpose of the Study:
- To test the hypothesis that adults born very preterm (PRET) exhibit worse pulmonary gas exchange efficiency (higher AaDO2) during exercise compared to term-born controls (CONT).
- To compare AaDO2 and arterial oxygen saturation (SaO2) in PRET and CONT during rest and exercise while breathing room air and hypoxic gas.
Main Methods:
- Compared AaDO2 and SaO2 in 13 PRET individuals (DLCO 72% predicted) and 14 CONT individuals (DLCO 105% predicted).
- Measurements were taken at rest and during exercise (25%, 50%, 75% of peak oxygen consumption) breathing room air and hypoxic gas (12% FiO2).
- Included pulmonary function tests, DLCO, and arterial blood gas analysis.
Main Results:
- PRET individuals had significantly lower pulmonary function and exercise capacity compared to CONT.
- Despite lower DLCO in PRET, no significant differences in AaDO2 or SaO2 were observed between PRET and CONT at rest or during exercise under either breathing condition.
- Findings were unexpected given the known reduction in DLCO in the PRET group.
Conclusions:
- Reduced pulmonary function and low DLCO following very preterm birth do not lead to a measurable decrease in pulmonary gas exchange efficiency during exercise.
- The physiological mechanisms compensating for reduced DLCO during exercise in preterm survivors warrant further investigation.
- This study challenges the assumption that low DLCO directly translates to impaired exercise gas exchange efficiency in very preterm adults.
Abstract:
Adults with a history of very preterm birth (<32 wk gestational age; PRET) have reduced lung function and significantly lower lung diffusion capacity for carbon monoxide (DLCO) relative to individuals born at term (CONT). Low DLCO may predispose PRET to diffusion limitation during exercise, particularly while breathing hypoxic gas because of a reduced O2 driving gradient and pulmonary capillary transit time. We hypothesized that PRET would have significantly worse pulmonary gas exchange efficiency [i.e., increased alveolar-to-arterial Po2 difference (AaDO2)] during exercise breathing room air or hypoxic gas (FiO2 = 0.12) compared with CONT. To test this hypothesis, we compared the AaDO2 in PRET (n = 13) with a clinically mild reduction in DLCO (72 ± 7% of predicted) and CONT (n = 14) with normal DLCO (105 ± 10% of predicted) pre- and during exercise breathing room air and hypoxic gas. Measurements of temperature-corrected arterial blood gases, and direct measure of O2 saturation (SaO2), were made prior to and during exercise at 25, 50, and 75% of peak oxygen consumption (V̇o2peak) while breathing room air and hypoxic gas. In addition to DLCO, pulmonary function and exercise capacity were significantly less in PRET. Despite PRET having low DLCO, no differences were observed in the AaDO2 or SaO2 pre- or during exercise breathing room air or hypoxic gas compared with CONT. Although our findings were unexpected, we conclude that reduced pulmonary function and low DLCO resulting from very preterm birth does not cause a measureable reduction in pulmonary gas exchange efficiency.
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