PURPOSE: A reduced diffusing capacity (DLCO) measured during a pulmonary function test (PFT) can suggest pulmonary arterial hypertension (PAH). The DLCO has been reported to weakly correlate with pulmonary pressures. We hypothesized that the DLCO “normalized” to spirometric variances in patients would correlate more strongly (than DLCO alone) with pulmonary pressures.
METHODS: DESIGN: Retrospective chart review. SUBJECTS: Patients who underwent pulmonary arterial catheterization (PAC) for the evaluation of suspected PAH. SETTING: Tertiary referral academic center (Mayo Clinic, Jacksonville) between 1991-2006. DATAPOINTS: Invasive pulmonary arterial hemodynamic measurements, clinical diagnoses, and pulmonary function test variables. STATISTICS: Nonparametric correlation (Spearman), tests of 2-sided statistical significance, and correlation plots were generated using GraphPad Prism.
RESULTS: 241 patients who under PAC for the evaluation of suspected PAH were identified. Of these, 208 patients also had PFT performed. No significant correlation was identified between the mean pulmonary artery pressure (mPAP) or the pulmonary vascular resistance (PVR), against any of the PFT variables; including the DLCO alone or the DLCO normalized to the forced expiratory volume in 1 second, the forced vital capacity, and the total lung capacity (i.e. DLCO%/FEV1%, DLCO%/FVC%, DLCO%/TLC%). Subgroups were separated further into standard definitions of restrictive (TLC<80%), obstructive (FEV/FVC<70%), or mixed obstructive-restrictive ventilatory defects. Again, no significant correlation could be identified between PFT variables and PAC hemodynamic measurements. Finally, the subjects were subgrouped based on the clinical diagnosis for the cause of the patients PAH (including collagen-vascular disease, idiopathic PAH, chronic thromboembolic disease, cardiac disease not due to congenital defects, portopulmonary hypertension, and intrinsic lung disease). Within each clinical categorization, no significant correlation was identified between any PFT variable and hemodynamic measurements of pulmonary pressures.
CONCLUSION: In patients with suspected PAH, invasive hemodynamic measurements of PAH do not correlate with PFT variables, regardless of the subgroup of ventilatory physiology or clinical diagnoses.
CLINICAL IMPLICATIONS: Despite known effects of pulmonary vascular disease on the diffusing capacity, PFT variables should not be used clinically to exclude or suggest the presence of PAH.
DISCLOSURE: Vichaya Arunthari, None.