Impulse Oscillometry Findings in Children and Adolescents with Adrenal Insufficiency: An Exploratory Cross-Sectional Study

Background: Airway function in children with adrenal insufficiency (AI) has not been well characterized. We evaluated impulse oscillometry (IOS) findings in pediatric AI and compared patients with congenital adrenal hyperplasia (CAH) and AI due to causes other than CAH (non-CAH AI). Methods: In this cross-sectional study, 52 children with AI underwent IOS. Oscillometric abnormalities were defined using z-score-based upper and lower limits of normal. IOS z-scores and clinical characteristics were compared between the CAH (n = 24) and non-CAH AI (n = 28) groups. Results: The median age was 16 years (IQR, 6 years; min–max, 4–18 years), and 53.8% of participants were male. CAH was the most common etiology (46.1%). Median (IQR) IOS values were 0.49 (IQR, 0.32) kPa·L−1·s for R5, 0.29 (IQR, 0.13) kPa·L−1·s for R20, 0.20 (IQR, 0.16) kPa·L−1·s for R5–R20, −0.13 (IQR, 0.11) kPa·L−1·s for X5, −0.01 (IQR, 0.08) kPa·L−1·s for X20, 1.74 (IQR, 1.30) kPa·L−1 for AX, and 20.8 (IQR, 5.32) Hz for resonance frequency (Fres). The most frequent abnormality was reduced X5 (21.2%), followed by elevated R5 (19.2%), elevated R5–R20 (19.2%), reduced X20 (15.4%), elevated AX (15.4%), elevated R20 (13.5%), and elevated Fres (7.7%). No significant differences were observed between the CAH and non-CAH AI groups in demographic characteristics, atopic diseases, or any IOS parameter (all p > 0.05). Conclusions: A subset of children with AI had IOS measurements outside published parameter-specific reference limits. Among individual IOS parameters, measurements outside the applied reference limits were most frequently observed for X5, R5, and R5–R20. Because no healthy control group was included and the reference equations were derived from populations different from the study population, these findings should be interpreted as exploratory.