Lung function and gas exchange in Eisenmenger syndrome and their impact on exercise capacity and survival

Eisenmenger physiology may contribute to abnormal pulmonary mechanics and gas exchange and thus impaired functional capacity. We explored the relationship between lung function and gas exchange parameters with exercise capacity and survival.

Stable adult patients with Eisenmenger syndrome (N=32) were prospectively studied using spirometry, lung volumes, diffusion capacity, and blood gas analysis, as well as same day measurement of 6-minute walk distance and cardiopulmonary maximal treadmill exercise. Patients were followed prospectively to determine survival (7.4 ± 0.5 years). Abnormalities were identified and appropriate comparisons were made between affected and unaffected individuals between respiratory mechanics, exercise function, and survival.

Obstruction (FEV1/FVC ratio <0.70) was found in 13 patients (41%), who were older but not otherwise different. Restriction was uncommon. Diffusion transfer coefficient, which was <80% in half the patients, correlated with exercise duration (r=0.542, P=0.005), and was worse in non-survivors (N=6). Nearly all patients had a compensated respiratory alkalosis (PaCO2 32 ± 4.4 mm Hg). PaCO2 was less reduced in older patients (r=0.438, P=0.022), and correlated independently with exercise duration (R=-0.463, P=0.03), yet PaO2, not PaCO2, was associated with survival.

Eisenmenger patients show evidence of obstructive lung disease, diffusion abnormalities, and hypocapnia; likely from hyperventilation. Understanding expected lung mechanics and gas exchange may facilitate more appropriate clinical management.