Intrabreath Oscillometry (IBO) vs. Spectral Oscillometry (SO) in Detecting Respiratory Disease in Patients Undergoing Hematopoietic Stem Cell Transplantation (HSCT)

Abstract

Rationale: SO is a tidal breathing test which can detect respiratory impairment following HSCT. IBO can measure differences in respiratory system stiffness that occur between end expiration and end inspiration and may be more sensitive than SO in detecting obstructive or restrictive disease in the transplant population. We have previously reported that baseline SO findings are abnormal in patients preparing to undergo HSCT. However, little is known about IBO findings in this population. Methods: The TRANSPIRE study (NCT04098445) is a multi-center prospective observational cohort study of lung injury after HSCT in children. We performed oscillometry (Tremoflo © C100, Thorasys, Montreal, CA) at baseline in a cohort of 148 subjects, ages 4-21, at 4 participating centers. Of subjects enrolled so far, 68 had oscillometry pre-HSCT. Following ERS 2020 Guidelines, oscillometry was measured during 3-7 30-second trials using commercial equipment (Tremoflo, Thorasys Ltd, 5-37Hz) targeting a coefficient of variation of <15% in respiratory system resistance at 5HZ (R5). SO variables included X5, X11, AX and Fres. IBO variables included reactance at end expiration (Xee), reactance at end inspiration (Xei) at 5Hz, and their difference both corrected and uncorrected for tidal volume. Linear regression analysis was used to compare Transpire subjects to a cohort of 80 normal control patients studied at Children's Hospital of Philadelphia. Results: There were significant differences between subjects and controls in X5, X11, AX and Fres measured by SO. However no significant differences in IBO were seen between TRANSPIRE and control subjects in (X5ee-X5ei) or (X5ee-X5ei)/VT (Table). Conclusions: We found no differences in IBO parameters in control vs TRANSPIRE subjects. Prior studies have reported that IBO Xee is greater (more negative) than Xei in obstructive disease, whereas Xee-Xei is positive in restrictive disease such as pulmonary fibrosis. Thus, discerning group differences between HSCT and control subjects may be more difficult. Our initial results suggest that baseline intrabreath oscillometry testing does not add discriminatory value beyond spectral oscillometry in distinguishing between normal and HSCT subjects as a group. Future studies should assess whether IBO has promise in detecting obstructive or restrictive disease in individual patients over time following HSCT.