A62-11 Clinical Utility of Oscillometry for Lung Function Monitoring After Hematopoietic Stem Cell Transplantation During an Acute Hospitalization

Introduction Noninfectious pulmonary complications after hematopoietic stem cell transplantation (HSCT) are a major cause of persistent lung disease in this patient population. Early detection and longitudinal lung function monitoring are critical but often challenging in younger or severely deconditioned patients since traditional methods are effort dependent. Oscillometry is an effort independent technique performed during tidal breathing that measures mechanical impedance, including airway resistance and reactance (stiffness). We present the use of oscillometry to monitor lung function trajectory in a patient with chronic graft versus host disease (GVHD) after HSCT during an acute hospitalization. Case A 12-year-old girl with paroxysmal nocturnal hemoglobinuria underwent a 10/10 matched unrelated donor HSCT following conditioning with busulfan and fludarabine. Pre HSCT lung function was normal. Her post-transplant course was complicated by grade 4 GVHD of the oral mucosa and GI tract, grade 3 skin GVHD, and transplant associated thrombotic microangiopathy. She additionally developed posterior reversible encephalopathy syndrome from tacrolimus and recurrent episodes of bacteremia. Nine months post HSCT, chest imaging revealed diffuse ground-glass opacities, mosaic attenuation and interlobular thickening. She was started on bilevel positive pressure support, supplemental oxygen, azithromycin, montelukast, and Symbicort. Due to severe deconditioning, she was unable to perform spirometry. Instead, we performed respiratory oscillometry by forced oscillatory technique (FOT, Tremoflo C-100, Thorasys, Montreal CA) for serial lung functioning monitoring. Initial testing off chronic GVHD therapy showed increased resistance and reactance. Following initiation of belumosudil, we noted variability in resistance but a trend towards improvement (R5, R5-20), and gradual improvement in reactance (X5) and area under the reactance curve (AX), correlating with clinical improvement and ability to wean oxygen support (see table). Discussion Oscillometry performed during tidal breathing has proven to be a highly feasible and sensitive study when compared to spirometry in detecting small airway disease. Ongoing studies are evaluating its role in longitudinal monitoring in the HSCT population, but there is limited evidence for its use in the acute hospitalized setting. This pilot case illustrates its potential as a practical, noninvasive tool for lung function surveillance and treatment response in the HSCT population in the acute care setting. Broader application in HSCT recipients can enhance early detection and monitoring of pulmonary complications.