Lung Diffusion Capacity can Predict Maximal Exercise in Apparently Healthy Heavy Smokers

Abstract

Chronic exposure to tobacco smoking may damage lung and heart function. The aim of this study was to assess maximal exercise capacity and its relationship with lung function in apparently healthy smokers. We recruited 15 heavy smokers (age 47 years ± 7, BMI 25 kg/m(2) ± 3, pack/years 32 ± 9) without any cardiovascular or pulmonary signs and symptoms. Fifteen healthy non smoking subjects were enrolled as a control group. All subjects underwent pulmonary function tests, electrocardiograms at rest and graded cycle exercise tests. In smokers and controls, resting lung and cardiac function parameters were in the normal range, apart from diffusing lung capacity (TLCO) values which were significantly lower in smokers (p < 0.05). As compared to controls, smokers presented lower maximal exercise capacity with lower values at peak of exercise of oxygen uptake (peak VO2), workload, oxygen uptake/watt ratio and oxygen pulse (p < 0.05) and higher dyspnoea perception (p < 0.05). Moreover, peak VO2, maximal workload and oxygen pulse at peak exercise were related to and predicted by TLCO (p < 0. 05). Our study confirms that maximal exercise capacity is reduced in apparently healthy heavy smokers, and shows that TLCO explains some of the variance in maximal exercise. Key pointsChronic exposure to tobacco smoking may damage lung and heart function.Smokers present lower diffusion capacity and maximal exercise capacity.In smokers maximal exercise capacity can be predicted by resting diffusion lung capacity.

Keywords: Tobacco; exercise capacity; lung diffusion capacity.; lung function.

Figure 1.

Mean and standard deviation values of dyspnoea and leg fatigue in 15 smokers (filled bar) and 15 non smoking (empty bar) healthy subjects. Dyspnoea and leg fatigue perception ratings were measured in mm by a 0 - 100 visual analogue scale (VAS) and divided by the maximal workload (watts) for analysis. * p < 0.05 by means of Mann Whitney test.

Figure 2.

Relationships between TLCO and maximal oxygen pulse (upper panel), between TLCO and maximum workload (middle panel) and between TLCO and peak VO₂ (lower panel) in 15 smokers. Relationships were analyzed by using Pearson's correlation coefficient and linear regression analysis. The continuous line is the regression line; the interrupted lines represent the 95% confidence interval.