Oxygen uptake efficiency slope and chronotropic incompetence in chronic heart failure and chronic obstructive pulmonary disease.

Department of Pathophysiology, Medical University Plovdiv, Bulgaria.
Folia medica 01/2009; 51(4):18-24.
Source: PubMed

ABSTRACT Oxygen uptake efficiency slope (OUES) and chronotropic index (CRI) are measures of cardiorespiratory reserve and chronotropic incompetence, but no direct comparison of OUES and CRI in patients with chronic obstructive pulmonary disease (COPD) and chronic heart failure (CHF) has been done.
To compare OUES and CRI in CHF and COPD patients.
Fifty-one subjects divided in three groups--CHF group (n=17) (NYHA II and III functional class), COPD group (n=17) (FEV1% = 49.7 +/- 17.3) and healthy controls (C) (n=17), matched by age and BMI. COPD and CHF patients presented comparable decrease in functional capacity.
Subjects undertook maximal exercise test on a treadmill by means of Bruce protocol.
CHF and COPD patients showed a significant and comparable decrease in exercise capacity (VO2/kg = 18.5 +/- 4.0 vs. 19.5 +/- 4.9 vs. 28.3 +/- 6.2 mL x min(-1) x kg(-1), p < 0.001) and ventilatory efficiency in comparison with controls. COPD patients presented with a typical pattern of exercise limitation due to ventilatory restraints (%breathing reserve = 15.6 +/- 18.0%). OUES was lower than controls in both CHF and COPD groups, being lowest in CHF (1686 +/- 483 vs. 2101 +/- 478 vs. 2481 +/- 398 mL.min(-1) x logL(-1), p < 0.001). Chronotropic index was lower in CHF patients (0.60 +/- 0.15 in CHF vs. 0.72 +/- 0.16 in COPD vs. 0.81 +/- 0.18 in controls, p < 0.001) in comparison with controls.
OUES is decreased in CHF and COPD patients, but the decline is significantly more pronounced in the CHF group. CRI is lower in CHF patients.

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