A62-05 Longitudinal Measurement of Respiratory Function by Oscillometry in Children Following Hematopoietic Stem Cell Transplantation (hsct): A Report From the Transpire Study

Rationale HSCT is potentially curative for many oncologic, immunologic, hematologic, and metabolic disorders. Pulmonary complications and pulmonary function abnormalities are common both before and after HSCT. TRANSPIRE is a large prospective cohort study of pediatric subjects undergoing HSCT for these diseases, employing identification of risk factors, collection of biologic samples, and novel diagnostic strategies to effect reduction in morbidity and mortality from lung injury or respiratory dysfunction. In the past, we have measured oscillometry in this cohort and reported baseline respiratory dysfunction before HSCT compared to a healthy control group (https://doi.org/10.1164/ajrccm.2025.211.Abstracts.A2293). We have continued to perform oscillometry for up to 2 years in order to investigate the effects of HSCT over time. Methods At baseline and following HSCT, 422 oscillometry measurements were made between 5 and 37 Hz according to 2020 ERS criteria at predefined time intervals. Tests reflecting respiratory system stiffness included reactance at 5 (X5) and 11 (X11) Hz, and resonance frequency (Fres). Tests reflecting central (R19) and peripheral airway resistance (R5-R19), and small airway resistance heterogeneity (AX) where AX is the area under the reactance curve between Fres and 5 Hz, were measured. Results are reported as Z-scores calculated from the normal values of Ducharme et al (Pediatr Pulm 2022;57:2092. Statistics: A mixed effects model was used to compare the groups and assess changes in the different respiratory mechanics measurements over time and with respiratory events. A p-value of < 0.05 was considered significant. Results Oscillometry Z-scores did not change significantly over the course of the study (TABLE) (p = 0.57), nor were there significant differences between subjects with normal or abnormal baseline clinical status, as defined by history, spirometry diffusing capacity, or imaging studies (p = 0.47, data not shown). Conclusions 1. Lung function measured by oscillometry in a cohort of subjects undergoing HSCT remained stable compared to pre-transplant baseline over a two-year follow up period. 2. Despite our cohort having had respiratory abnormalities by oscillometry compared to our own healthy controls, mean oscillometric measurements were within normal limits compared with Ducharme controls. This suggests using healthy control values established within a given study may be preferable to comparison with published controls, since the methodology is then the same for both subjects and controls.