Exercise-induced pulmonary edema in heart failure.

BACKGROUND

In heart failure (HF) patients, exercise may increase pulmonary capillary hydrostatic pressure and thereby generate pulmonary edema. If pulmonary edema developed, alveolar-capillary membrane conductance (Dm), measured immediately after exercise, would decrease. To test this hypothesis, we measured Dm before and at 2 and 60 minutes after exercise.

METHODS AND RESULTS

We studied 10 HF patients with exercise-induced periodic breathing, 10 with peak o2 < or =15 mL x min(-1) x kg(-1) (severe HF), 10 with o2=15 to 20 mL x min(-1) x kg(-1) (moderate HF), and 10 normal subjects (control). Using the Roughton-Forster technique, we measured carbon monoxide diffusion capacity (DLco) and its components, capillary blood volume (Vc) and Dm, at rest and 2 and 60 minutes after exercise. At rest, DLco and Dm were lowest in periodic breathing and highest in control subjects. Dm decreased in periodic breathing, severe HF, and moderate HF (-7.83+/-3.98, -5.57+/-2.03, and -3.85+/-3.53 mL x min(-1) x mm Hg(-1), respectively; P<0.01) at 2 minutes after exercise but not in control subjects. Vc increased in all groups at 2 minutes and remained elevated at 60 minutes only in periodic breathing. Dm/Vc was decreased in periodic breathing, severe HF, and moderate HF at 2 minutes but not in control subjects. Dm and Dm/Vc remained low at 60 minutes only in periodic breathing.

CONCLUSIONS

Dm decreases after exercise in HF patients but not in control subjects, which suggests a decrease in conductance across the alveolar-capillary barrier, as with pulmonary edema. The reductions were most marked in HF patients with periodic breathing and less reduced in less severe HF.