The effect of aging and cardiorespiratory fitness on the lung diffusing capacity response to exercise in healthy humans

Abstract

Aging is associated with deterioration in the structure and function of the pulmonary circulation. We characterized the lung diffusing capacity for carbon monoxide (DL), alveolar-capillary membrane conductance (Dm), and pulmonary-capillary blood volume (Vc) response to discontinuous incremental exercise at 25, 50, 75, and 90% of peak work (W) in four groups: ) Young [27 ± 3 yr, maximal oxygen consumption (V̇o): 110 ± 18% age predicted]; 2) Young Highly Fit (27 ± 3 yr, V̇o: 147 ± 8% age predicted); ) Old (69 ± 5 yr, V̇o: 116 ± 13% age predicted); and ) Old Highly Fit (65 ± 5 yr, V̇o: 162 ± 18% age predicted). At rest and at 90% W, DL, Dm, and Vc were decreased with age. At 90% W, DL, Dm, and Vc were greater in Old Highly Fit vs. Old adults. The slope of the DL-cardiac output (Q̇) relationship from rest to end exercise at 90% W was not different between Young, Young Highly Fit, Old, and Old Highly Fit (1.35 vs. 1.44 vs. 1.10 vs. 1.35 ml·mmHg·liter blood, = 0.388), with no evidence of a plateau in this relationship during exercise; this was also true for Dm-Q̇ and Vc-Q̇. V̇o was positively correlated with ) DL, Dm, and Vc at rest; and ) the rest to end exercise change in DL, Dm, and Vc. In conclusion, these data suggest that despite the age-associated deterioration in the structure and function of the pulmonary circulation, expansion of the pulmonary capillary network does not become limited during exercise in healthy individuals regardless of age or cardiorespiratory fitness level. Healthy aging is a crucial area of research. This article details how differences in age and cardiorespiratory fitness level affect lung diffusing capacity, particularly during high-intensity exercise. We conclude that highly fit older adults do not experience a limit in lung diffusing capacity during high-intensity exercise. Interestingly, however, we found that highly fit older individuals demonstrate greater values of lung diffusing capacity during high-intensity exercise than their less fit age-matched counterparts.

The influence of pulmonary vascular pressures on lung diffusing capacity during incremental exercise in healthy aging

“…; Coffman et al. ). Nevertheless, additional data would be needed to make any conclusions regarding the relative extent of pulmonary capillary distension versus recruitment during exercise.…”

“…Furthermore, in very fit older individuals who might be anticipated to approach the upper limits of pulmonary capillary recruitment, there was no evidence of a limitation in lung diffusing capacity, even during near maximal exercise. Interestingly, however, lung diffusing capacity was observed to be systematically reduced for a given cardiac output (i.e., DLCO/Q) throughout incremental exercise in older versus younger individuals (Coffman et al 2017). In other words, a given cardiac output through the pulmonary vasculature did not yield the same lung surface area for gas exchange at a given exercise level.…”

“…Interestingly, however, lung diffusing capacity was observed to be systematically reduced for a given cardiac output (i.e., DLCO/ Q ) throughout incremental exercise in older versus younger individuals (Coffman et al. ). In other words, a given cardiac output through the pulmonary vasculature did not yield the same lung surface area for gas exchange at a given exercise level.…”

“…Healthy aging is associated with alterations in both lung diffusing capacity and pulmonary hemodynamics, but the interplay between these variables remains unclear. Lung diffusing capacity, or the ability to transfer gases from the alveoli to blood, is reduced with aging, both at rest and during exercise (Chang et al 1992;Stam et al 1994;Guenard and Marthan 1996;Coffman et al 2017). This is likely in part due to remodeling of the pulmonary alveoli and capillaries (Butler and Kleinerman 1970;Thurlbeck and Angus 1975;Verbeken et al 1992;Gillooly and Lamb 1993) which acts to reduce surface area available for gas exchange.…”

“…This increased stiffness of the vessel walls likely contributes to the increases in pulmonary pressures and pulmonary vascular resistance associated with increasing age (Emirgil et al 1967;Ehrsam et al 1983;Reeves et al 2005;Kovacs et al 2009;Van Empel et al 2014). Furthermore, it is well established that maximal aerobic capacity (VO 2max ) is reduced in older individuals (Byrne et al 1996; American Thoracic S, 2003;Fleg et al 2005), and several studies have demonstrated an association between VO 2max and both lung diffusing capacity (Lalande et al 2012;Coffman et al 2017) and pulmonary hemodynamics (Fujii et al 1996;Coffman et al 2017;Faoro et al 2017). Therefore, it is feasible that age-dependent increases in pulmonary vascular pressures may alter the increase in lung surface area available for gas exchange, particularly during exercise.…”