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Pulmonary Gas Exchange and Exercise Capacity in Adults Born Preterm
Emily T Farrell1, Melissa L Bates1,2, David F Pegelow1
11 Department of Pediatrics, Critical Care Division and the John Rankin Laboratory of Pulmonary Medicine.
Insights
Adults born preterm may have reduced exercise capacity and impaired pulmonary gas exchange efficiency. These findings suggest long-term cardiopulmonary consequences of extreme preterm birth and very low birth weight.
Area of Science:
- Cardiopulmonary Physiology
- Neonatal Medicine
- Exercise Science
Background:
- Preterm birth and associated medical interventions can lead to respiratory and gas exchange deficits persisting into childhood.
- Long-term effects of preterm birth on cardiopulmonary function into adulthood remain poorly understood.
Purpose of the Study:
- To assess exercise capacity and pulmonary gas exchange efficiency during exercise in adults who survived preterm birth.
- To compare cardiopulmonary function during normoxic and hypoxic exercise in preterm survivors versus term-born controls.
Main Methods:
- Adults born preterm (n=14) and age-matched term-born controls (n=16) underwent incremental cycle ergometry to exhaustion.
- Subjects breathed either normoxia (FiO2=0.21) or hypoxia (FiO2=0.12).
- Measurements included ventilation, gas exchange, arterial blood gases, power output, and oxygen consumption.
Main Results:
- Preterm survivors exhibited lower power output during normoxic exercise compared to controls, despite similar oxygen consumption.
- During hypoxic exercise, power output differences between groups were not significant.
- Preterm subjects showed a wider alveolar-to-arterial oxygen difference and lower PaO2 during normoxic exercise, indicating reduced gas exchange efficiency.
Conclusions:
- Pulmonary gas exchange efficiency during exercise is reduced in some adult preterm survivors.
- This inefficiency is associated with lower arterial oxygen tension and reduced exercise power output.
- Findings suggest potential long-term cardiopulmonary consequences of extreme preterm birth and very low birth weight.
Rationale:
Preterm birth, and its often-required medical interventions, can result in respiratory and gas exchange deficits into childhood. However, the long-term sequelae into adulthood are not well understood.
Objectives:
To determine exercise capacity and pulmonary gas exchange efficiency during exercise in adult survivors of preterm birth.
Methods:
Preterm (n = 14), very low birth weight (<1,500 g) adults (20-23 yr) and term-born, age-matched control subjects (n = 16) performed incremental exercise on a cycle ergometer to volitional exhaustion while breathing one of two oxygen concentrations: normoxia (fraction of inspired oxygen, 0.21) or hypoxia (fraction of inspired oxygen, 0.12).
Measurements And Main Results:
Ventilation, mixed expired gases, arterial blood gases, power output, and oxygen consumption were measured during rest and exercise. We calculated the alveolar-to-arterial oxygen difference to determine pulmonary gas exchange efficiency. Preterm subjects had lower power output at volitional exhaustion than did control subjects in normoxia (150 ± 10 vs. 180 ± 10 W; P = 0.01), despite similar normoxic oxygen consumption. However, during hypoxic exercise, there was no difference in power output at volitional exhaustion between the two groups (116 ± 10 vs. 135 ± 10 W; P = 0.11). Preterm subjects also exhibited a more acidotic, acid-base balance throughout exercise compared with control subjects. In contrast to other studies, adults born preterm, as a group developed a wider alveolar-to-arterial oxygen difference and lower PaO2 than did control subjects during normoxic but not hypoxic exercise.
Conclusions:
This study demonstrates that pulmonary gas exchange efficiency is lower in some adult survivors of preterm birth during exercise compared with control subjects. The gas exchange inefficiency, when present, is accompanied by low arterial blood oxygen tension. Preterm subjects also exhibit reduced power output. Overall, our findings suggest potential long-term consequences of extreme preterm birth and very low birth weight on cardiopulmonary function.
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