Background Interstitial lung disease (ILD) and pulmonary hypertension are the leading cause of morbidity and mortality in systemic sclerosis (SSc). Although a ventilatory obstructive pattern, due to large airways impairment, has been rarely observed in SSc, a potential involvement of smaller airways (SA) has been suggested in previous reports. Recently, impulse oscillometry (IOS), a non-invasive forced oscillation technique, has been advocated as a valuable diagnostic tool for a sensitive assessment of SA.
Objectives The main objectives of the present study was to investigate the prevalence of SA dysfunction by IOS in SSc patients compared to healthy controls, and to evaluate the correlation between SA dysfunction and selected radiological and clinical disease-related features.
Methods Consecutive SSc patients were included in the present study according to eligibility criteria; controls were health volunteers. Both cases and controls underwent IOS measurements; cases also underwent pulmonary function tests and St. George's respiratory questionnaire. Radiological features were assessed on the latest chest high resolution computed tomography (HRTC) scan available in the twelve months before study enrolment, evaluating for both SA signs of disease and ILD. A SA involvement at IOS was defined as R5-R20 ≥0.07 kPa/L/sec. Odds ratios and 95% confidence intervals for the IOS value was computed using multiple logistic regression models. Correlation between SA dysfunction and selected parameters were assessed using Pearson's correlation coefficient.
Results 92 cases (M/F 14/78, mean age 57.06) and 84 controls (M/F 15/69, mean age 54.28) were included in the present study. The R5-R20≥0.07 kpa/L/sec was found in 20.65% of cases and in 3.57% of controls. The OR was 7.027 (95% CI 1.99–24.72, p<0.01). This value did not significantly change after the adjustment for confounding variables (OR a* 7.091). Correlations between R5–20 ≥0,07 kPa/L/s and selected parameters showed a significant inverse association with vital capacity (FVC) and forced expiratory volume in first second (FEV1) and a direct correlation with pulmonary artery systolic pressure estimated. With reference to cutaneous subtype a SA dysfunction was more prevalent in the limited form compared to the diffuse, respectively in 23% and 12%. Radiologic HRCT assessment of SA pathological features and ILD extent were provided for 77 patients: 19 (24.7%) presented at least one sign of SA disease. An underlying ILD was detected in 40 patients, characterized by NSIP pattern in 37.
Conclusions A significant involvement of SA was found in a substantial proportion of SSc patients, compared to healthy controls. Moreover, this seemed to be associated with a more severe functional obstructive and restrictive impairment, and with higher PAPs values. Therefore, our findings suggests that SA may be a potential, less known, target of disease, and further studies are needed to assess prognostic and therapeutic implications of this pathologic feature.
Disclosure of Interest None declared