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Abstract

Objective: Patients with chronic heart failure manifest an inappropriate elevationin their ventilatory response to treadmill exercise. Increased body mass indexmay restrict the ventilatory response to exercise, but the relationship betweenobesity and ventilatory response in chronic heart failure(CHF) has not been wellcharacterised.Methodology: We analysed data from 246 consecutive patients with chronicheart failure, who underwent cardiopulmonary exercise testing.Exercise testing was performed on a treadmill according to the modified Bruceprotocol, with continuous on-line respiratory gas. The slope of the relationshipbetween ventilation (VE) and CO2 production (VCO ) was determined by 2computerised graphical analysis (VE/VCO slope). 2Results: Patients were aged 60±10.7 years (mean±SD), and had mean leftventricular ejection fraction 27.7±13.9%, peak oxygen uptake 17.2±6.2ml/min/kg. The subjects had mean body mass index (BMI) of 26.6±4.3 kg/m2(mean±SD), and VE/VCO slope values of 37.3±10.2. The correlation between 2BMI and VE/VCO slope was highly significant and inverse -0.455 (p<0.0001). 2When the patients were divided into categories according to BMI (<22, 22-30,>30), there were differences between the mean VE/VCO slopes of each group, 2which was significant for each pair of comparisons.Conclusion: This study suggests that patients with normal or mildly increasedBMI show a relatively greater hyperpneic response to exercise. In contrast,patients with marked obesity (BMI>30) demonstrate a much milder hyperpneicresponse to exercise.