Abstract
Background: Increase in “wasted” ventilation (VE) during exercise – as a consequence of large dead space to tidal volume ratio – is a common feature of chronic obstructive pulmonary disease (COPD) and CHF. Coexistence of COPD and CHF, therefore, could be associated with greater increases in exercise VE relative to both oxygen uptake (VO2) and carbon dioxide output (VCO2) compared to COPD alone. Objective: To investigate the role of ventilatory inefficiency during incremental exericse in suggesting the presence of CHF in patients with established COPD. Methods: Twenty-four males (13 with COPD-CHF (FEV1= 59.6 ± 17.5 % pred; left ventricle ejection fraction (LVEF) = 34 ± 6 %) and 10 with COPD alone (FEV1= 48.6 ± 16.0 % pred; LVEF= 64 ± 4 %) were submitted to a ramp-incremental cardiopulmonary exercise test. Results: COPD-CHF patients had shallower Δ VO2 /Δ work rate (WR) and lower peak VO2 than their counterparts (p<0.05). In line with our hypotheses, measures of excessive exercise ventilation relative to both VO2 and VCO2 were more disturbed in COPD-CHF than COPD patients (ΔVE/ΔVCO2= 39± 10 vs. 30 ± 6 (p<0.05) and VO2 efficiency slope (OUES, L/min/log)= 1.35± 0.38 vs. 1.76 ± 0.42 (p<0.01), respectively. In addition, decreases in ΔVO2 /ΔWR and OUES were more closely related to peak VO2 in COPD-CHF than in COPD (r= 0.72 vs. 0.24 and 0.80 vs. 0.68, respectively).Conclusions: Pulmonary ventilation increases out of proportion of both VCO2 and VO2 during progressive exercise in COPD plus CHF patients compared to COPD alone. These results suggest that ventilatory inefficiency variables might be helpful in indicating the coexistence of CHF in COPD patients.
- © 2013 ERS