N95 masks increase brain blood velocity and parasympathetic outflow, yet worsen orthostatic symptoms in a healthy cohort.

Abstract

Mask wearing became commonplace in everyday life during the COVID-19 pandemic and masks are frequently used in certain professions. Masks can increase end-tidal CO₂ and the cerebrovasculature is known to vasodilate in response to hypercapnia. Orthostatic intolerance (OI) is the inability to tolerate postural transitions due to the displacement of blood volume away from the cerebral circulation, and we hypothesized that wearing a mask would improve OI symptoms by increasing brain blood flow. Young, healthy participants (n = 27) completed 10 min of 70° head-up tilt while wearing/not wearing an N95 mask (randomized), while hemodynamics and blood velocity within the middle cerebral artery (MCAv) were measured. Systolic, diastolic, and mean blood pressure and mean and diastolic MCAv decreased during tilt in both conditions (all p < 0.05; Table 1). Systolic MCA_V was elevated while wearing a mask (p < 0.05). Some OI symptoms were exacerbated during the mask trial (all p < 0.05) including the overall OI score (p = 0.002; Table 2). There appears to be a disconnect between the physiological response to mask wearing and OI symptoms, potentially indicating that there is a psychological component to mask wearing. While we have provided evidence that masking increases brain blood flow, the psychological effects may outweigh potential benefits to the cerebral circulation.