Congestive Heart Failure
Lack of effect of increased inspired oxygen concentrations on maximal exercise capacity or ventilation in stable heart failure

https://doi.org/10.1016/S0002-9149(99)00587-1Get rights and content

Abstract

Recent uncontrolled studies have suggested improved maximal exercise capacity and decreased exercise ventilation in heart failure after administration of increased inspired oxygen concentrations. To study the responses further, 16 patients performed staged, symptom-limited cycle ergometry with humidified 21% and 60% inspired oxygen concentrations using a randomized, double-blind, crossover study design. Serial measurements of minute ventilation, heart rate, blood pressure, leg blood flow, and arterial and venous lactate and oxygen content were obtained. Exercise time did not change between the 2 tests (595 ± 179 seconds and 602 ± 181 seconds for 21% and 60% oxygen concentrations, respectively). Similarly, measurements of the ventilatory response to exercise and of leg blood flow were not different between the 2 oxygen concentrations. Although hemoglobin oxygen saturation increased from 96.7 ± 2.1% to 97.9 ± 1.5% at rest, at both rest and maximal exercise there was no statistically significant difference in arterial or venous oxygen content. This study failed to demonstrate any physiologic or functional benefit from the administration of increased oxygen concentrations to patients with stable heart failure.

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Patient group

Seventeen men with New York Heart Association functional class II to III heart failure symptoms and severe left ventricular dysfunction (determined by a radionuclide ejection fraction <35%) were considered for this study. Patients were to be excluded if they experienced ventricular arrhythmias, hypotension, chest pain, ST-segment depression, or claudication during exercise testing, or if they were taking a β blocker. One patient was excluded during the practice exercise test because of chest

Baseline measurements

Patients did not have evidence of obstructive or restrictive pulmonary disease (Table I). Resting measurements of heart rate, mean arterial blood pressure, and arterial and venous lactate were not different between the 2 tests. During baseline exercise testing on room air, the average peak oxygen uptake was 14.5 ± 3.2 ml/min/kg, associated with a respiratory exchange ratio of 1.11 ± 0.07. Thirteen of the patients stopped exercise because of fatigue and 3 because of dyspnea. All patients had the

Discussion

In this double blind, randomized, controlled study, we failed to demonstrate any benefit in exercise performance with the administration of 60% oxygen to patients with chronic stable heart failure. Under conditions of normoxia (21%) and hyperoxia (60%), maximal exercise time, ventilation, and leg oxygen uptake were virtually identical.

There are several explanations for the failure of hyperoxia to be effective. First, the administration of 60% oxygen did not result in a significant change in

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This study was supported by Claude D. Pepper-GRTC Grant AG-11268-04, National Institutes of Health, Bethesda, Maryland.

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