Abstract
BackgroundAlthough reduced function of the respiratory system limits peak oxygen uptake in diseases affecting the lungs or airways, the healthy respiratory system is thought to have a spare capacity for oxygen transport and uptake, and is not considered a limiting factor for peak oxygen uptake in healthy people. However, lung function declines with age and could theoretically limit peak oxygen uptake in elderly. We examined the association between peak oxygen uptake and lung function indices in an elderly population with the hypothesis that lung function indices would be associated with VO2peak up to a threshold value situated above the lower limits of normal lung function for our population.MethodsSpirometry, gas diffusion tests and incremental work tests were performed in 1443 subjects (714 women) aged 69–77 years. Association between lung function indices and peak oxygen uptake was studied with hockey-stick regression.ResultsForced expiratory volume in 1 s (FEV1) had a positive association with peak oxygen uptake up to, but not above, a threshold value of 2.86 l for men, and 2.13 l for women (lower limit of normal 2.73 and 1.77 l respectively). A corresponding threshold was found for diffusing capacity of the lung for carbon monoxide (DLCO) for men at 9.18 mmol/min/kPa (lower limit of normal 6.84 mmol/min/kPa). DLCO for women and DLCO divided by alveolar volume (DLCO/VA) for both sexes had a significant linear relationship to VO2peak (p < 0.05), but no significant threshold value was found in these associations.ConclusionsThreshold values for FEV1 for both sexes and DLCO for men were identified. These lung function indices had a positive association with VO2peak up to these threshold values, but not above. The identified threshold values were above lower limits of normal for FEV1 and DLCO.Electronic supplementary materialThe online version of this article (doi:10.1186/s12931-015-0317-0) contains supplementary material, which is available to authorized users.
Highlights
Reduced function of the respiratory system limits peak oxygen uptake in diseases affecting the lungs or airways, the healthy respiratory system is thought to have a spare capacity for oxygen transport and uptake, and is not considered a limiting factor for peak oxygen uptake in healthy people
Descriptive statistics for the 1443 participants included in the analyses are shown in Table 1, histograms showing the distribution of VO2peak, Forced expiratory volume in 1 s (FEV1) and DLCO and DLCO adjusted for alveolar volume (DLCO/VA) are shown in Additional file 1
Significant change-points in the association with VO2peak were found for FEV1 for men at 2.86 l (LLN = 2.73 l) and for women at 2.13 l (LLN = 1.77 l) (Table 2)
Summary
Reduced function of the respiratory system limits peak oxygen uptake in diseases affecting the lungs or airways, the healthy respiratory system is thought to have a spare capacity for oxygen transport and uptake, and is not considered a limiting factor for peak oxygen uptake in healthy people. Lung function declines with age and could theoretically limit peak oxygen uptake in elderly. It is generally accepted that maximal cardiac output is the principal limiting factor for peak oxygen uptake (VO2peak) in healthy individuals exercising at sea-level. The spare capacity of the respiratory system is possibly reduced in elderly compared to middle-aged and young people, and both dynamic lung function and the diffusion capacity of the lungs may be associated with reduced oxygen uptake even in healthy elderly people. This has previously not been examined in population based studies
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