Correlation of pulmonary function variables with hemodynamic measurements in patients with pulmonary arterial hypertension

A reduced diffusing capacity of the lung for carbon monoxide (DLCO) measured during a pulmonary function test can suggest pulmonary arterial hypertension (PAH). The DLCO has been reported to weakly correlate with pulmonary hemodynamics.Objective: To determine whether the relationship between the DLCO and pulmonary arterial pressures can be strengthened by normalizing the DLCO to spirometric variables.Patient and Methods: Patients were seen at a tertiary care referral center. Consecutive subjects who underwent right heart catheterization (RHC) for the evaluation of suspected PAH from 01 January 1991 through 01 October 2006 were identified. Pulmonary function testing (PFT) data performed within 60 days of the RHC was collected. Spearman rank correlation between PFT and RHC variables was calculated.Results: One hundred thirty-eight patients who had an RHC performed had complete PFTs available. No significant correlation was identified between the mean pulmonary artery pressure and the pulmonary vascular resistance against the DLCO, nor the DLCO when normalized to: forced expiratory volume in 1 s, forced vital capacity, total lung capacity or alveolar volume. Spirometric subgroups were identified by standard definitions of restrictive and/or obstructive ventilatory defects. Clinical subgroups were classified based on the clinically diagnosed cause of the patient's PAH. Again, no significant correlation was identified between the PFT variables and RHC measurements in these stratified subgroups.Conclusion: In patients with suspected PAH, invasive hemodynamic measurements of PAH do not correlate with PFT variables, even when corrected for spirometric volumes, and regardless of the subgroup of ventilatory physiology or clinical diagnosis.