Clinical Investigation
Reduced Rate of Alveolar-Capillary Recruitment and Fall of Pulmonary Diffusing Capacity During Exercise in Patients With Heart Failure

https://doi.org/10.1016/j.cardfail.2006.01.010Get rights and content

Abstract

Background

Patients with chronic heart failure (CHF) have reduced pulmonary diffusing capacity for carbon monoxide (DLco). Acute pulmonary congestion also causes reduction of DLco, which is reversible. We hypothesized for patients with CHF that the rate of rise of exercise DLco is reduced compared to healthy controls and falls near end-exercise consistent with progressive interstitial edema.

Methods and Results

DLco and pulmonary blood flow (Q˙C) were measured by a rebreathe technique in CHF subjects (n = 11) and controls (n = 8) at rest, during constant workload exercise, and after exercise. DLco of CHF subjects was less than controls at rest (16.5 ± 1 vs. 21.9 ± 2 mL/min/mm Hg, P < .01). CHF subjects exercised 11 ± 2 minutes to 90% peak V˙O2, whereas controls exercised 17 ± 2 minutes, reaching 88% peak V˙O2. In CHF subjects, DLco increased to 19 ± 2 mL/min/mm Hg and for controls to 38 ± 3 mL/min/mm Hg. During the final 3 minutes of exercise, DLco increased 5% in controls while decreasing 5% in CHF subjects (DLco/Q˙C) was lower in CHF subjects at rest and progressively lower throughout exercise (P < .01).

Conclusion

In patients with CHF, DLco has reduced rate of rise with exercise and falls near end-exercise consistent with limitation of alveolar-capillary recruitment and progressive interstitial edema.

Section snippets

Subjects

Nineteen individuals, 11 with stable CHF and 8 controls served as study subjects. For CHF subjects, entry criteria included chronic CHF with stable medical therapy for more than 60 days, New York Heart Association class II or III symptoms, left ventricular ejection fraction < 30%, and no history of clinically significant arrhythmia, pacemaker therapy, or significant anemia (hemoglobin < 11). Control subjects were age- and gender-matched healthy individuals not engaged in regular exercise.

All

Subject Characteristics

Comparison of subject characteristics demonstrated no differences between groups for age, gender, height, and weight (Table 1). Rest cardiac index was lower for the CHF group compared to controls (P < .05). The majority of CHF subjects were New York Heart Association class III with mean left ventricular ejection fraction of 24%. CHF subjects had restrictive pulmonary function compared with controls (Table 1).

Ventilatory, Cardiac, and Metabolic Responses to Exercise

Peak V˙O2 for the initial maximal exercise study was 65% and 116% of predicted for CHF

Discussion

The novel findings of this study are that subjects with stable, chronic CHF demonstrate a reduced rate of rise of DLco during high-intensity constant workload exercise and may also demonstrate a plateau and fall of DLco near end-exercise. In the study described herein, in 8 of 11 CHF subjects, there was a fall of DLco at end-exercise which ranged from 3% to 17%; in the remaining 3 subjects, DLco increased at end-exercise. For the entire CHF group (n = 11), the mean decrease of DLco from

Conclusion

This study confirms previous reports of reduced DLco at rest in patients with CHF8, 16, 17, 18 and extends previous observations to alterations of DLco during high-intensity exercise in CHF subjects, demonstrating both a reduced rate of rise and a decline of DLco near end-exercise consistent with reduced alveolar-capillary recruitment. These observations may be attributed to decreased DLco from chronically reduced DM with a further acute fall of DLco near end-exercise consistent with

Acknowledgments

The authors thank Kathy O'Malley for assistance with data collection, Michelle Small for manuscript preparation and the study volunteers. The authors also acknowledge the staff of the General Clinic Research Center (GCRC) for support throughout this study.

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  • Cited by (0)

    Supported by NIH grants R01-HL71478 and MO1-RR00585, as well as grants from Mayo Foundation and the American Heart Association.

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