Pulmonary blood volume in older adults assessed by dual-energy computed tomography: the multi-ethnic study of atherosclerosis (mesa) lung study

ABSTRACT

Rationale The pulmonary vasculature is critical for gas exchange, impacts both pulmonary and cardiac function, and has renewed importance due to COVID-19. Pulmonary blood volume is, however, technically difficult to assess, generally requiring invasive methodology for quantification. Prior studies are limited in size and participant enrollment was selective;therefore, variation in the general population is largely unknown. We performed contrast-enhanced dual-energy computed tomography (DECT) in a multicenter, community-based cohort to describe variation in pulmonary perfused blood volume (PBV) in the community. MethodsThe Multi-Ethnic Study of Atherosclerosis (MESA) recruited adults from six sites. The MESA Lung Study invited all MESA participants attending Exam 6 (2017-18), excluding those with kidney disease and contrast allergy, to undergo DECT at functional residual capacity via Siemens Flash or Force scanner CareDose on, pitch 0.55, 0.25 sec exposure, 0.5mm slice thickness, iterative reconstruction (Admire) with Qr40 Kernel. Half concentration 370mg/ml Iopamidol was delivered at 4ml/s for the full scan, starting 17 seconds prior to scanning, including a ∼4 sec breath hold. PBV was calculated by material decomposition and normalized with iodine concentration in the pulmonary trunk. Generalized linear regression models included age, sex, race/ethnicity, height, weight, smoking status, site, and education.ResultsDECT scans were acquired for 714 participants, 36 of which were excluded due to image quality. Mean age of the remaining 678 participants was 71 years (range 63 - 79), 55% were male, 51% were ever smokers, and the race/ethnic distribution was 41% White, 29% Black, 17% Hispanic, and 13% Asian. Mean PBV was 468 + 151mL. The strongest demographic correlate was lower PBV with greater age (-30 mL per 10 years, 95% CI -43, -18, p<0.001). Pulmonary PBV was positively associated with height, weight, and male sex (all P<0.001). PBV was lower in former compared to never smokers (p =0.04) and in Black than White participants (p=0.002), but not in Hispanic or Asian participants. There were no consistent differences across education or study site. Results were similar after adjustment for lung function and percent emphysema on CT.ConclusionsTo our knowledge, this is the first assessment of pulmonary PBV in a large, multiethnic, general community sample. Pulmonary PBV assessed by contrast-enhanced DECT was substantially reduced with advancing age and varied with body size, sex, former smoking, and, to a lesser extent, Black race. Understanding variation in pulmonary PBV in the general population may elucidate risk of cardiopulmonary disease and physical function.