Respostas ventilatórias e metabólicas em repouso e no exercício em indivíduos tabagistas com capacidade de difusão reduzida sem doença pulmonar obstrutiva crônica

Abstract

Smoking negatively reflects lung function and exercise capacity as a result of the interaction of poor performance of the cardiorespiratory and muscular systems. Changes in carbon monoxide diffusion capacity (DCO) due to pulmonary emphysema, airway disease and microvascular disease may be related to poor ability to exercise in smokers. The objective of the study was to evaluate the resting and exercise responses in smokers with DCO < lower limit of normality (LLN) without chronic obstructive pulmonary disease (COPD). In all, 15 smokers with reduced DCO and 15 smokers with normal DCO, both groups without COPD, were evaluated for airway resistance, lung volumes and capacities, physical activity level, quality of life, and exercise cycle-ergometer incremental parameters test. There were no statistically significant differences (p>0.05) between the groups in relation to the demographic variables, physical activity level, quality of life and resting lung function, except in the DCO values (p<0.05) 71.2±9.3% of the Predicted in the DCO group <LLN and 95.3±10.5% predicted in the DCO group > LLN. At the peak of the incremental exercise the DCO < LLN group presented lower VO2 (1.4±0.4 L.min-1 versus 1.6±0.4 L.min-1, p<0.05) and increased VE/VCO2 compared to the other group (33.5±7.3 versus 29.6±3.3, p<0,05). The reduced DCO group also presented lower ventilatory efficiency in relation to the VE/VCO2 slope parameters (28.3±2.32 versus 26.2±2.72, p<0,05), VE/VCO2 nadir (29.5±3.1versus 27.5±2.0, p<0.05) and VCO2 /LogV’E slope (21.1x102±4.3x102 versus 25.5x102±5.4x102, p<0.05). This last variable being a new proposal for evaluating the ventilatory efficiency here called COES (Carbon Dioxide Output Efficient Slope).The COES in the correlation analysis presented an association more stronger with DCO (r=0.706, p<0.01) and VO2 (r=0.878, p<0.01). It was concluded that smokers with mild diffusion capacity present reduced and early ventilatory efficiency during exercise. It is also concluded that the COES is related to markers of aerobic diffusion capacity, emerging as a new proposal for evaluation of ventilatory efficiency.