Reduced alveolar-capillary membrane diffusing capacity in chronic heart failure. Its pathophysiological relevance and...

Area of Science:

• Cardiopulmonary Physiology
• Respiratory Medicine
• Heart Failure Research

Background:

• Pulmonary diffusing capacity for carbon monoxide (DLCO) is reduced in chronic heart failure (CHF).
• This reduction is an independent predictor of peak exercise oxygen uptake.
• The underlying pathophysiological basis remains unclear.

Purpose of the Study:

• To partition DLCO into membrane conductance (DM) and capillary blood volume (Vc) in CHF patients.
• To assess correlations between alveolar-capillary membrane function and functional status, exercise capacity, and pulmonary vascular resistance.

Main Methods:

• Used the Roughton and Forster method to measure single-breath DLCO at varying alveolar oxygen concentrations.
• Determined DM and Vc in 15 normal subjects and 50 CHF patients.
• Performed symptom-limited maximal bicycle exercise tests and right heart catheterization in a subset of CHF patients.

Main Results:

• DLCO was significantly reduced in CHF patients compared to normal subjects.
• The reduction was predominantly due to decreased DM, not Vc.
• DM significantly correlated with maximal exercise oxygen uptake (r = .72) and inversely with pulmonary vascular resistance (r = .65) in CHF patients.

Conclusions:

• Reduced alveolar-capillary membrane diffusing capacity (DM) is the primary cause of impaired gas transfer in CHF.
• DM impairment correlates with maximal exercise capacity and functional status.
• DM may serve as a marker for alveolar-capillary barrier damage from elevated pulmonary capillary pressure.