A75-16 The Prevalence of Ventilation Heterogeneity in Pulmonary Sarcoidosis Patients With Different Pft Phenotypes

Rationale

Airway obstruction, defined by a reduced FEV1/FVC ratio, is a well-recognized feature that develops in a subset of patients with pulmonary sarcoidosis. The objective of this study was to test the hypothesis that using FEV1/FVC alone to identify patients with airway obstruction is likely underestimating the true burden of airway disease, particularly in patients with small airways dysfunction characterized by other physiological parameters.

Methods

We evaluated 124 patients with biopsy-proven pulmonary sarcoidosis who had undergone spirometry, lung volume, and diffusion capacity testing. PFT phenotypes were categorized as normal, restrictive, obstructive, mixed, and isolated diffusion impairment. Airway disease was assessed using both established spirometric criteria (FEV₁/FVC < LLN) and other physiologic markers, including mid-expiratory flow rates (FEF25-75), air trapping (RV, RV/TLC), and ventilation heterogeneity (VA/TLC). Air trapping was defined as RV or RV/TLC > 120% predicted, and ventilation heterogeneity as VA/TLC < 0.9. The frequency of air trapping and ventilation heterogeneity was evaluated across physiologic subgroups. We performed univariate analyses to compare the clinical characteristics by the presence or absence of ventilation heterogeneity. In addition, we also evaluated additional four patients using hyperpolarized 129Xe MRI, an inhaled gas contrast agent for 3D assessment of pulmonary function.

Results

Among the 124 patients, 39% had normal physiology, 20% had isolated diffusion impairment, 16% had obstructive physiology, 16% had restrictive physiology, and 9% had mixed physiology. Air trapping was uncommon in normal (2%) and restrictive (10%) phenotypes but frequent in obstructive (35%) and mixed physiology (42%). Ventilation heterogeneity was common across all phenotypes, including normal physiology (37%), isolated diffusion impairment (40%), obstructive (65%), restrictive (37%), and mixed physiology (55%). Among patients with non-obstructive phenotypes, air trapping was rare (3%) whereas ventilation heterogeneity was prevalent (38%). The ventilation heterogeneity group showed higher % predicted value of RV (93.4 ± 32.8 vs 67.7 ± 19.9, p < 0.0001), and higher % predicted value of RV/TLC (102 ± 25.5 vs 83.5 ±18.9, p < 0.0001). No significant differences among groups were seen in demographic characteristics, eosinophil count, treatment escalation, or mortality during a median follow-up of 6 years. All of the four patients evaluated using 129Xe MRI exhibited clear ventilation heterogeneity, including focal regions of ventilation defect.

Conclusion

Physiologic evidence of airway dysfunction is frequently present in sarcoidosis patients despite non-obstructive spirometry. Ventilation heterogeneity was prevalent across all physiologic phenotypes. Further studies are warranted to evaluate the true impact of ventilation heterogeneity in pulmonary sarcoidosis.

This abstract is funded by: N/A