Lung capillary blood volume and membrane diffusion in PH

Combined lung diffusion of carbon monoxide (DLCO) and nitric oxide (DLNO) measurement has a potential ability to assess pulmonary capillary blood volume (Vc) disturbances. Usefullness of DLNO measurement and its derivatives is still controversial in pulmonary hypertension. To evaluate its potential role, we restrospectively reviewed the combined values of DLCO and DLNO in 120 well-characterized consecutive patients with pulmonary hypertension. Patients were divided in three groups: pulmonary hypertension (PAH) (n=64), pulmonary veno-occlusive disease (PVOD) (n=14) and chronic thrombo-embolic pulmonary hypertension (CTEPH) (n=42). Measurements of DLNO, DLCO, membrane diffusing capacity (Dm) and Vc were measured during a single breath maneuver. An ANOVA or a Kruskal-Wallis statistical test were used to compare groups. We found a significant difference between patients with PVOD and with PAH or CTEPH for DLNO, DLCO, Dm and Vc. DLNO/DLCO ratio was not different between groups (non statistically significant trend for an increased ratio in PVOD). We conclude that DLNO measurement alone or in combination could help to determine subtype of pulmonary hypertension and needs further attention. View this table: DLNO, DLCO, Dm and Vc values