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Reduced lung diffusing capacity for carbon monoxide (DLCO) at rest and increased ventilation (⩒E)-carbon dioxide output (⩒CO2) during exercise are frequent findings in dyspneic smokers with largely preserved FEV1. It remains unclear whether low DLCO and high ⩒E-⩒CO2 are mere reflections of alveolar destruction (i.e. emphysema) or impaired pulmonary perfusion in non-emphysematous tissue contributes to these functional abnormalities. Sixty-four smokers (41 males, FEV1= 84 ± 13%predicted) underwent pulmonary function tests, an incremental exercise test, and quantitative chest computed tomography. Total pulmonary vascular volume (TPVV) was calculated for the entire segmented vascular tree (VIDA Vision™). Using the median % low attenuation area (-950 HU), participants were dichotomized into “Trace” or “Mild” emphysema (E), each group classified into preserved versus reduced DLCO. Within each emphysema subgroup, participants with abnormally low DLCO showed lower TPVV, higher ⩒E-⩒CO2, and exertional dyspnea than those with preserved DLCO (p < 0.05). TPVV (r = 0.34; p = 0.01), but not emphysema (r = −0.05; p = 0.67), correlated with lower DLCO after adjusting for age and height. Despite lower emphysema burden, Trace-E participants with reduced DLCO had lower TPVV, higher dyspnea, and lower peak work rate than the Mild-E with preserved DLCO (p < 0.05). Interestingly, TPVV (but not emphysema) correlated inversely with both dyspnea-work rate (r = −0.36, p = 0.004) and dyspnea-⩒E slopes (r = −0.40, p = 0.001). Reduced pulmonary vascular volume adjusted by emphysema extent is associated with low DLCO and heightened exertional ventilation in dyspneic smokers with minor emphysema. Impaired perfusion of non-emphysematous regions of the lungs has greater functional and clinical consequences than hitherto assumed in these subjects. [ABSTRACT FROM AUTHOR]

Patients with mild chronic obstructive pulmonary disease (COPD) and lower resting diffusing capacity for carbon monoxide (DLCO) often report troublesome dyspnea during exercise although the mechanisms are not clear. We postulated that in such individuals, exertional dyspnea is linked to relatively high inspiratory neural drive (IND) due, in part, to the effects of reduced ventilatory efficiency. This cross-sectional study included 28 patients with GOLD I COPD stratified into two groups with (n = 15) and without (n = 13) DLCO less than the lower limit of normal (

Patients with mild chronic obstructive pulmonary disease (COPD) and lower resting diffusing capacity for carbon monoxide (DLCO) often report troublesome dyspnea during exercise although the mechanisms are not clear. We postulated that in such individuals, exertional dyspnea is linked to relatively high inspiratory neural drive (IND) due, in part, to the effects of reduced ventilatory efficiency. This cross-sectional study included 28 patients with GOLD I COPD stratified into two groups with (n = 15) and without (n = 13) DLCO less than the lower limit of normal (2 (V̇E/V̇CO2), and respiratory mechanics during incremental cycle exercise in the three groups. Spirometry and resting lung volumes were similar between COPD groups. During exercise, dyspnea, IND and V̇E/V̇CO2 were higher at equivalent work rates (WR) in the DLCOCOCOCOE/V̇CO2 at a given work rate. Higher ventilatory requirements in the DLCO

Supervised exercise training (EXT) as part of pulmonary rehabilitation is arguably the most effective intervention for improving exercise tolerance in patients with chronic obstructive pulmonary disease (COPD). In the current review, we focus on the physiological rationale for EXT and the expected physiological benefits that can be achieved in patients who can be exposed to sufficiently high training stimuli. Thus, after a brief consideration of the mechanisms of exercise limitation and their sensory consequences, we expose the potential beneficial effects of EXT on respiratory mechanical and peripheral muscular adaptations to exercise. The available evidence indicates that changes in exertional ventilation, breathing pattern, operating lung volumes and static respiratory muscle strength after EXT are modest and often inconsistent. Inspiratory muscle training may have a role in patients showing inspiratory weakness pre-rehabilitation. Beneficial changes in peripheral muscles can be seen in those who can tolerate higher training intensity, particularly using combined resistance and dynamic (including interval) exercise. It should be recognised, however, that it might not be feasible to reach meaningful physiological training effects in many frail elderly patients with advanced respiratory mechanical and pulmonary gas exchange derangements with serious co-morbidities (such as cardiac and peripheral vascular disease). These potential shortcomings should not discourage the use of pulmonary rehabilitation as an effective strategy to improve patients' capacity to tolerate physical activity. Currently, the greatest challenge is to develop effective strategies to ensure that these important gains in functional capacity are translated into sustained increases in daily physical activity for patients with COPD. [ABSTRACT FROM AUTHOR]