(422) Specific respiratory conductance by forced oscillations to reveal ventilation inhomogeneity in patients with cystic fibrosis

Background: Classical forced oscillations technique (FOT) parameters, resistance (Rrs), and reactance, have the disadvantage of not being corrected for the lung volume at which they are measured. A novel FOT index, the specific respiratory system conductance (sGrs), might overcome this important limitation. The aim of the study was to determine, for the first time, sGrs in patients with cystic fibrosis (CF) and relate it to the severity of lung disease.

Methods: Forty-four patients with CF (age 16.3 ±6 years, range 6.9-27 years; 45.5% males) underwent spirometry, multiple-breath nitrogen washout and FOT measurements (Resmon Pro Full). Outcomes included: FEV1 z-score, lung clearance index (LCI), functional residual capacity (FRC), Scond, Sacin, M1/M0, M2/M0, and sGrs (calculated as 1/[R_rs at 5Hz ×FRC]). Spearman’s correlation and linear regression after adjustment for age and FEV1 z-score were used to assess the relationships between the outcome parameters.

Results: sGrs was strongly correlated with LCI (r=–0.788), Scond (r=–0.723), M1/M0 (r=–0.792) and M2/M0 (r=–0.793), and moderately correlated with Sacin (r=–0.544), FEV1 z-score (r=0.439) and FEV1/FVC (r=0.584). The sGrs was a significant predictor of LCI (beta=–0.603; P< 0.001), Scond (beta=–0.615; P< 0.001), Sacin (beta=–0.585; P=0.002), M1/M0 (beta=–0.601; P< 0.001), and M2/M0 (beta=–0.547; P< 0.001), independently of FEV1 z-score and age.

Conclusions: In patients with CF, sGrs is consistent with ventilation heterogeneity and relates closely to the severity of lung disease. This novel and easy-to-obtain FOT index may thus improve CF monitoring in the outpatient setting.

Acknowledgements:

References: 1. Zannin E, Nyilas S, Ramsey KA, Latzin P, Dellaca' RL. Within-breath changes in respiratory system impedance in children with cystic fibrosis. Pediatr Pulmonol. 2019 Jun;54(6):737-742.
2. Postek M, Walicka-Serzysko K, Milczewska J, Sands D. What Is Most Suitable for Children With Cystic Fibrosis-The Relationship Between Spirometry, Oscillometry, and Multiple Breath Nitrogen Washout. Front Pediatr. 2022 Jan 14;9:692949.