Does exercise test modality influence dyspnoea perception in obese patients with COPD?

Abstract

The purpose of this study was to investigate whether differences in physiological responses to weight-bearing (walking) and weight-supported (cycle) exercise influence dyspnoea perception in obese chronic obstructive pulmonary disease (COPD) patients, where such discrepancies are probably exaggerated.We compared metabolic, ventilatory and perceptual responses during incremental treadmill and cycle exercise using a matched linearised rise in work rate in 18 (10 males and eight females) obese (mean¡SD body mass index 36.4¡5.0 kg?m -2 ) patients with COPD (forced expiratory volume in 1 s 60¡11% predicted).Compared with cycle testing, treadmill testing was associated with a significantly higher oxygen uptake, lower ventilatory equivalent for oxygen and greater oxyhaemoglobin desaturation at a given work rate (p,0.01). Cycle testing was associated with a higher respiratory exchange ratio (p,0.01), earlier ventilatory threshold (p,0.01) and greater peak leg discomfort ratings (p50.01). Ventilation, breathing pattern and operating lung volumes were similar between tests, as were dyspnoea/work rate and dyspnoea/ventilation relationships.Despite significant between-test differences in physiological responses, ventilation, operating lung volumes and dyspnoea intensity were similar at any given external power output during incremental walking and cycling exercise in obese COPD patients. These data provide evidence that either exercise modality can be selected for reliable evaluation of exertional dyspnoea in this population in research and clinical settings. @ERSpublications Reliable evaluations of exertional dyspnoea can be obtained by cycle or treadmill exercise tests in obese COPD patients

Physiological and perceptual responses to incremental exercise testing in healthy men: effect of exercise test modality

“…In contrast to the above, mean values of V E /V O 2 , V E /V CO 2 and arterial PO 2 (PaO 2 ) are significantly lower, while those for arterial PCO 2 (PaCO 2 ) are significantly higher at the symptom-limited peak of treadmill vs. cycle exercise in both health [11,17,46,48,55] and disease [15,41,43]. Whether this apparent 'alveolar hypoventilation' indicates the existence of critical dynamic mechanical constraints on exercise hyperpnea at the limits of tolerance during treadmill vs. cycle ergometry remains unclear and requires further investigation.…”

“…1.3). Unsurprisingly, sensory intensity ratings of perceived leg discomfort are higher at the symptom-limited peak of incremental cycle vs. treadmill exercise, at least in patients with chronic obstructive pulmonary disease (COPD) [15]; and intolerable leg discomfort is more commonly cited as the primary reason for stopping cycle compared to treadmill exercise in both health and disease [23,36,52].…”

“…Even though V O 2max is consistently higher when exercise is performed on a treadmill than on a cycle ergometer, it is now well established that the magnitude of the fall in arterial blood O 2 saturation (SaO 2 ) from rest to the symptom-limited peak of exercise is much greater in the former in both health and disease [11,15,17,[41][42][43][44][45][46][47][48].…”

“…It is reasonable to assume that the combination of a higher CO and lower total peripheral resistance help to maintain a higher skeletal muscle blood flow at maximum treadmill compared to cycle exercise, which, in the face of a relatively greater fall in arterial blood O 2 saturation during treadmill exercise [11,15,17,[41][42][43][44][45][46][47][48], would help to maximize arterial blood O 2 delivery/transport and contribute to the higher V O 2max . This hypothesis is bolstered by the results of Matsui et al [35] who found that lower limb (i.e., leg muscle) blood flow was significantly lower (by 16%) immediately after maximal cycle vs. treadmill exercise.…”

“…higher, while the ventilatory equivalent for CO 2 (V E /V CO 2 ) is not different at any standardized submaximal exercise intensity during cycling vs. running [14,15,55]. In the setting of a relatively preserved V E /V CO 2 , the higher V E /V O 2 observed during submaximal cycling vs. running exercise reflects respiratory compensation for the more severe whole-body and intramuscular metabolic acidosis observed at any standardized submaximal V O 2 during cycling vs. running (refer to Section 1.4.1 above).…”