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 (V) over dot O-2 less than or equal to 15 mL . min(-1) . kg(-1) (severe HF), 10 with (V) over dot O-2 = 15 to 20 mL . min(-1) . 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 (V-C) 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 . min(-1) . 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.