Respiratory profile of pediatric patients undergoing hematopoietic stem cell transplantation studied by oscillometry – A TRANSPIRE cohort

Importance Oscillometry — a tidal‐breathing test with potential advantages over spirometry — is not well studied prior to hematopoietic stem cell transplantation (HSCT). Objective To determine whether patients awaiting HSCT have abnormal baseline oscillometry compared with controls. Methods The TRANSPIRE study (NCT04098445) is a National Institutes of Health‐sponsored, multicenter, prospective observational cohort of pediatric lung injury after HSCT. We performed tidal‐breathing oscillometry at baseline and during follow‐up in 63 children prior to HSCT across five pediatric centers and compared results to 80 control subjects. Measurements were made at various frequencies following the European Respiratory Society 2020 guidelines and included resistance (R5, R19, and R5–R19), reactance (X5 and X11), resonant frequency (Fres), and area under the reactance curve (AX). Linear regression compared TRANSPIRE baseline values to controls; mixed‐effects models assessed differences between TRANSPIRE subjects, controls, and published predicted values up to two years post‐HSCT. Results All mean oscillometric parameters were normal at baseline, according to normal reference values of Ducharme. However, mean lung function in TRANSPIRE subjects was significantly different from controls, with higher respiratory system resistance (height‐adjusted R5−R19, P < 0.001), and greater respiratory system stiffness and heterogeneity, with more negative height‐adjusted X5 ( P < 0.001) and height‐adjusted X11 ( P < 0.001), greater height‐adjusted AX ( P < 0.001), and greater height‐adjusted Fres ( P < 0.001). No significant changes were noted over time. Interpretation In a multicenter pediatric HSCT cohort, baseline oscillometry differed significantly from controls, showing heterogeneous increases in small‐airway resistance and respiratory‐system stiffness that may elevate risk for pulmonary complications.