Abstract
The oxygen uptake (V˙O2) kinetics during onset of and recovery from exercise have been shown to provide valuable parameters regarding functional capacity of both chronic obstructive pulmonary disease (COPD) and chronic heart failure (CHF) patients. To investigate the influence of comorbidity of COPD in patients with CHF with reduced ejection fraction on recovery from submaximal exercise, 9 CHF-COPD male patients and 10 age-, gender-, and left ventricle ejection fraction (LVEF)-matched CHF patients underwent constant-load exercise tests (CLET) at moderate and high loads. The V˙O2, heart rate (HR), and cardiac output (CO) recovery kinetics were determined for the monoexponential relationship between these variables and time. Within-group analysis showed that the recovery time constant of HR (P<0.05, d=1.19 for CHF and 0.85 for CHF-COPD) and CO (P<0.05, d=1.68 for CHF and 0.69 for CHF-COPD) and the mean response time (MRT) of CO (P<0.05, d=1.84 for CHF and 0.73 for CHF-COPD) were slower when moderate and high loads were compared. CHF-COPD patients showed smaller amplitude of CO recovery kinetics (P<0.05) for both moderate (d=2.15) and high (d=1.07) CLET. Although the recovery time constant and MRT means were greater in CHF-COPD, CHF and CHF-COPD groups were not differently affected by load (P>0.05 in group vs load analysis). The ventilatory efficiency was related to MRT of V˙O2 during high CLET (r=0.71). Our results suggested that the combination of CHF and COPD may further impair the recovery kinetics compared to CHF alone.
Highlights
Exercise intolerance is a multifactorial hallmark of both chronic heart failure (CHF) [1] and chronic obstructive pulmonary disease (COPD) [2]
constant-load exercise tests (CLET) in CHF-COPD patients but not in CHF. This is the first cross-sectional study to investigate the influence of comorbidity of COPD in patients with CHF with reduced left ventricular ejection fraction (LVEF) on recovery kinetics after moderate and high CLET
Our preliminary analysis showed that the amplitude of heart rate (HR), VO2, and cardiac output (CO) were higher at high intensities, regardless of the presence or absence of COPD in CHF
Summary
Exercise intolerance is a multifactorial hallmark of both chronic heart failure (CHF) [1] and chronic obstructive pulmonary disease (COPD) [2]. . Several factors may contribute to the delay in VO2 kinetics during recovery from exercise, including delayed creatine phosphate restoration [6,7], increased arteriovenous oxygen difference due to lower cardiac output (CO) after exercise [6], and slow restoration of venous blood [7] and replenishment of energy stores in peripheral skeletal muscles [8]. All these factors, are not correlated to markers of disease severity like left ventricular ejection fraction (LVEF) [6,8]. The rate of recovery of VO2 at 2 minutes after exercise has been shown to be the strongest prognostic factor of major cardiac events, such as death, heart transplantation, Recovery kinetics in overlapped CHF and COPD and mechanical heart implantation in severe CHF patients [10]
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