Chest
Volume 118, Issue 1, July 2000, Pages 53-60
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Clinical Investigations: Pulmonary Function
Role of Respiratory Function in Exercise Limitation in Chronic Heart Failure

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Objective

To test the hypothesis that respiratory function contributes to limit maximal exercise performance in patients with chronic heart failure by using the technique of dead space loading during exercise.

Design

Blinded subjects underwent two maximal incremental exercise tests in random order on an upright bicycle ergometer: one with and one without added dead space.

Setting

Tertiary-care university teaching hospital.

Subjects

Seven patients with stable chronic heart failure (mean ± SEM left ventricular ejection fraction, 27 ± 3%).

Results

Subjects were able to significantly increase their peak minute ventilation during exercise with added dead space when compared with control exercise (57.4 ± 5.9 vs 50.0 ± 5.6 L/min; p < 0.05). Peak oxygen uptake, workload, heart rate, and exercise duration were not significantly different between the added dead space and control tests. Breathing pattern was significantly deeper and slower at matched levels of ventilation during exercise with added dead space.

Conclusion

Because patients with chronic heart failure had significant ventilatory reserve at the end of exercise and were able to further increase their maximal minute ventilation, we conclude that respiratory function does not contribute to limitation of exercise in patients with chronic heart failure.

Section snippets

Study Design

The study was designed to determine whether added vd increases peak V˙e or decreases exercise capacity during incremental exercise in patients with stable chronic heart failure. Patients performed two maximal incremental exercise tests on a cycle ergometer (Godart; Utrecht, The Netherlands) in random order; one was performed with added vd, and one without added vd. Apart from the added vd, the two tests were identical.

Patients

Patients were considered eligible for the study if they had stable

Results

Seven patients (four men and three women) were studied. Their average age was 55 years, with a range of 37 to 70 years. The mean LVEF of our study population was 0.28, with a range of 0.20 to 0.40. Heart failure was secondary to idiopathic dilated cardiomyopathy in four patients, ischemic cardiomyopathy in two patients, and hypertensive cardiomyopathy in one patient. All patients used an angiotensin-converting enzyme inhibitor, five used digoxin, four used diuretics, two used aspirin, one used

Discussion

We have demonstrated that chronic heart failure patients have significant ventilatory reserve at end exercise and are able to further increase their maximal V˙e, indicating that respiratory function does not contribute to limitation of exercise in chronic heart failure patients.

During control exercise, our chronic heart failure patients demonstrated impaired exercise performance as evident by their low peak V˙o2. The ventilatory response to exercise (ie, V˙e/ V˙co2) was

ACKNOWLEDGMENT

The authors thank Mrs. I. Fairlie for her assistance in preparation of this manuscript.

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