title: Pulmonary gas exchange efficiency during exercise breathing normoxic and hypoxic gas in adults born very preterm with low diffusion capacity.
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.
authors: Department of Human Physiology, University of Oregon, Eugene, Oregon;
authors: Joseph W
authors: JW
authors: Duke
authors: Department of Human Physiology, University of Oregon, Eugene, Oregon;
authors: Jonathan E
authors: JE
authors: Elliott
authors: Department of Human Physiology, University of Oregon, Eugene, Oregon;
authors: Steven S
authors: SS
authors: Laurie
authors: Department of Human Physiology, University of Oregon, Eugene, Oregon;
authors: Kara M
authors: KM
authors: Beasley
authors: Department of Human Physiology, University of Oregon, Eugene, Oregon;
authors: Tyler S
authors: TS
authors: Mangum
authors: Oregon Heart and Vascular Institute, Springfield, Oregon; and.
authors: Jerold A
authors: JA
authors: Hawn
authors: Department of Pediatrics, Oregon Health and Science University, Portland, Oregon.
authors: Igor M
authors: IM
authors: Gladstone
authors: Department of Human Physiology, University of Oregon, Eugene, Oregon; lovering@uoregon.edu.
authors: Andrew T
authors: AT
authors: Lovering
mesh_terms: D000293:Adolescent; D000328:Adult; D015308:Anaerobic Threshold / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D000860:Hypoxia / Q000378:metabolism*; D062071:Infant, Extremely Premature / Q000502:physiology*; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology; D011653:Pulmonary Diffusing Capacity / Q000502:physiology*; D011659:Pulmonary Gas Exchange / Q000502:physiology*; D055815:Young Adult
keywords: diffusion limitation; ex-preterms; exercise; hypoxia; pulmonary gas exchange efficiency