Prognostic value of ventilatory efficiency in hypersensitivity pneumonitis

Ventilatory efficiency (VE) from cardiopulmonary exercise testing (CPET) is a valuable prognostic metric for evaluating cardiopulmonary diseases. However, its relationship with clinical outcomes in hypersensitivity pneumonitis (HP) remains unclear. We aimed to determine whether VE correlates with disease severity and predicts mortality in HP.

In patients with HP, does VE correlate with disease severity and predict mortality?

This retrospective cohort study (2009-2019) included patients with non-fibrotic (nfHP) and fibrotic HP (fHP) and idiopathic pulmonary fibrosis (IPF), which served as the comparison group. CPET variables, including VE/carbon dioxide (VE/VCO₂), were assessed across various forced vital capacity (FVC%) and diffusing capacity for carbon monoxide (DLCO%) ranges. Multivariate logistic regression identified predictors of 5-year mortality and survival was assessed with Kaplan-Meier plots.

164 patients were analysed (mean age of 65.6±12.0 years, 54.3% male). 25 had nfHP, 66 fHP and 73 IPF. Overall, an increase in the VE/VCO₂ slope and nadir was observed as the DLCO% decreased, but not with a decrease in FVC%, while the intercept remained unchanged. Patients with pulmonary hypertension (35%, 57/164) and fHP or IPF had significantly higher VE/VCO₂ slope and nadir when compared with patients without pulmonary hypertension or nfHP, respectively. A VE/VCO₂ slope ≥42 predicted survival (HR 3.65; 95% CI 1.04 to 12.80). Restricting the analysis to patients with HP showed similar results (HR 5.49; 95% CI 1.19 to 33.54).

In patients with HP, elevated VE/VCO₂ is associated with the presence of pulmonary fibrosis, PH, reduced DLCO and a higher mortality risk. A VE/VCO₂ slope threshold of 42 may serve as a practical prognostic marker for stratification.