Pulmonary129Xe Magnetic Resonance Gas-exchange Abnormalities in Moderate-Severe Asthma

ABSTRACT BACKGROUND Asthma is recognized as an inflammatory disease of the airways, but inflammation may also affect the parenchyma and pulmonary vasculature. Hyperpolarized 129 Xe MRI and MR spectroscopy (MRS) provide a way to quantify the transfer of gas from the airways through the alveolar membrane and its binding to hemoglobin in the red blood cells (RBC) of the pulmonary microvasculature. The vast majority of 129 Xe MRS studies have investigated interstitial lung disease and the ratio of 129 Xe binding to the RBC and 129 Xe present in the alveolar membrane, (RBC:membrane) which is a surrogate of oxygen gas-transfer to the blood. We wondered if 129 Xe RBC:membrane would differ in asthma patients as compared to healthy volunteers because of recent work showing abnormally diminished pulmonary vascular small-vessel structure in severe-asthma. RESEARCH QUESTION Do 129 Xe MRI gas-transfer measurements differ significantly in patients with moderate-severe asthma? STUDY DESIGN AND METHODS In this retrospective study, healthy ( NCT02484885 ) and asthma ( NCT04651777 ; NCT02351141 ) participants were evaluated who provided written informed consent. RESULTS Thirty-one participants with asthma (mean age=55 years ±18; 22 females) and 32 healthy volunteers (mean age=31 years ±14; 12 females) with 129 Xe MRS were evaluated. FEV 1 , VDP and DL CO /K CO were significantly different in asthma compared to healthy participants. Age-corrected 1 RBC:membrane was significantly different in moderate-severe asthma (0.32±0.09) as compared to healthy participants (0.47±0.12, P =.01). RBC:membrane was significantly related to pulse-oximetry hemoglobin estimates (ρ=.29; P =.04) and DL CO (ρ=.71; P <.001). Significant relationships between 129 Xe RBC:membrane and age were observed in healthy (ρ=-.55; P =.002) and asthma participants (ρ=-0.49; P =.006), adjusted for sex. A significant ANCOVA model also revealed the influence of age ( P =.002), sex ( P <.001), hemoglobin ( P =.003) and asthma status ( P =.02) on RBC:membrane. INTERPRETATION 129 Xe RBC:membrane values were significantly different in moderate-severe asthma compared to healthy volunteers and were explained by age, sex, hemoglobin, and asthma status.