Physiological Impacts of Surgical Mask Coverage of Elastomeric Half-mask Respirator Exhalation Valves in Healthcare Workers

Eileen Zhuang; Paul Thurman; Hegang H Chen; Melissa A McDiarmid; Stella E Hines

doi:10.1093/annweh/wxab069

Physiological Impacts of Surgical Mask Coverage of Elastomeric Half-mask Respirator Exhalation Valves in Healthcare Workers

Ann Work Expo Health. 2022 Feb 18;66(2):233-245. doi: 10.1093/annweh/wxab069.

Authors

Eileen Zhuang¹, Paul Thurman^{2

3}, Hegang H Chen⁴, Melissa A McDiarmid⁵, Stella E Hines^{1

5}

Affiliations

¹ Department of Medicine, Division of Pulmonary and Critical Care Medicine, University of Maryland School of Medicine, Baltimore, MD, USA.
² R Adams Cowley Shock Trauma Center, University of Maryland Medical Center, Baltimore, MD, USA.
³ University of Maryland School of Nursing, Baltimore, MD, USA.
⁴ Department of Epidemiology and Public Health, University of Maryland School of Medicine, Baltimore, MD, USA.
⁵ Department of Medicine, Division of Occupational and Environmental Medicine, University of Maryland School of Medicine, Suite 200, Baltimore, MD, USA.

Abstract

Objectives: Elastomeric half-mask respirator (EHMR) use in healthcare increased significantly during the COVID-19 pandemic. Concern for potential release of infectious aerosols from EHMR exhalation valves prompted recommendations to cover them with surgical masks (SMs), thereby improving source control. The physiological and subjective effects of wearing a SM over the exhalation valve of an EHMR, however, are unknown.

Methods: Twelve healthy healthcare worker volunteers completed a 30-min series of simulated healthcare-related tasks, including resting, talking, walking, and bending, proning and supinating a weighted manikin, and performing cardiopulmonary resuscitation. This series recurred three times with different mask configurations-SM only, EHMR only, or EHMR with SM covering the exhalation valve. A transcutaneous sensor continuously measured carbon dioxide (tcPCO2), oxygen saturation (SpO2), and heart rate (HR) from each subject. Subjects scored their rates of perceived exertion (RPE) and levels of discomfort after each round. Physiological parameters and subjective scores were analyzed using mixed linear models with a fixed effect for mask type, activity, age, body mass index (BMI), and gender. Analysis also tested for interaction between mask type and activity.

Results: Physiological parameters remained within normal ranges for all mask configurations but varied by task. Statistically significant but small decreases in mean tcPCO2 (37.17 versus 37.88 mmHg, P < 0.001) and SpO2 (97.74 versus 97.94%, P < 0.001) were associated with wearing EHMR with SM over the exhalation valve compared with EHMR alone. Mean HR did not differ between these mask configurations. Wearing SM only was associated with lower RPE and level of discomfort compared with EHMR, but these subjective scores did not differ when comparing EHMR with SM to EHMR only. Age, BMI, and gender had no significant effect on any outcomes.

Conclusions: Wearing a SM over an EHMR did not produce clinically significant changes in tcPCO2, SpO2, or HR compared with uncovered EHMR during healthcare-related tasks. Covered EHMR use also did not affect perceived exertion or discomfort compared with uncovered EHMR use. Covering the exhalation valve of an EHMR with a SM for source control purposes can be done safely.

Keywords: COVID-19; PPE; carbon dioxide; elastomeric respirators; healthcare workers; heart rate; oxygen saturation.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

COVID-19*
Exhalation
Health Personnel
Humans
Masks
Occupational Exposure*
Pandemics
SARS-CoV-2
Ventilators, Mechanical

Abstract

Publication types

MeSH terms

Grants and funding