INFLUENCE OF MASK BREATHABILITY TO THE CARDIOPULMONARY LOADING DURING SIMULATED MANUAL TASKS

S. Ngai¹, S. Tsang², V. Yip², L. Louie³

¹The Hong Kong Polytechnic University, Hong Kong, Hong Kong, ²Occupational Safety and Health Council, Hong Kong, Hong Kong, ³Education University of Hong Kong, Hong Kong, Hong Kong

Background: Face mask plays a vital role in peoples’ everyday lives during pandemic. Differential pressure (ΔP) refers to the airflow resistance of masks and is an indicator for breathability. High ΔP indicates high airflow resistance. Recent studies reported association between mask-wearing and increased cardiopulmonary loading potentially influencing the work performance.

Purpose: This study aims to examine the effects of mask breathability and types on work performance and physiological responses during simulated manual work task under physiologically stressed environment.

Methods: In verification phase, subjects with normal health performed simulated manual lifting task (thereafter known as work task) by lifting weights and walking from point A to point B along a 10-meter path, and then putting down the weights in a temperature (30⁰C) and humidity (70%) controlled environment until reaching 15 (out of 20) in rate of perceived exertion(RPE). Duration of work task was recorded as endpoint in subsequent conditions. To examine the effects of mask breathability (low or high ΔP) and types (2D flat surface or 2D flat surface with mask bracket or 3D stereotype), subjects were asked to perform work task in six conditions, i.e. 1)2D-L: 2D mask with low ΔP; 2)2D-LB: 2D mask with low ΔP adding mask bracket; 3)2D-H: 2D mask with high ΔP; 4)2D-HB: 2D mask with high ΔP adding mask bracket; 5)3D-L: 3D mask with low ΔP; and 6)3D-H: 3D mask with high ΔP, in random order, until reaching the pre-defined endpoint. Level of ΔP less than or more than 3 mmH2O/cm2 were classified as low or high ΔP, respectively. Number of repetitions of work task completed and changes in physiological data in each condition were compared.

Results: Ten healthy male subjects (aged 21.3±2.4 years) completed the work task in 19.3±7.3 minutes during verification phase. Subjects wearing low ΔP category masks (86.7±33.6 repetitions) completed work task 7.2 repetitions(p>0.05) more than that wearing high ΔP category masks (79.5±29.2 repetitions) suggesting a potential 9% better in work performance. The effect of types, however, was not apparent. Upon task completion, low ΔP category demonstrated significantly shorter heart rate recovery time than high ΔP category by 2.9 minutes(p<0.001). When comparing all masks, one-way ANOVA revealed significant between-group differences(p=0.012). Post-hoc analysis showed that 2D-H had longer heart rate recovery time than 2D-LB (4.1 minutes,p=0.043) and 3D-L (4.2 minutes,p=0.035). For physiological data, subjects wearing low ΔP category masks showed significantly lowered level of post-work-task increment of respiratory rate (-2.1breaths/min,p=0.042), RPE (-2.8 unit,p=0.008) but not in heart rate (-1.9bpm,p=0.061). Effect of types, however, was not detected.

Conclusions: Given the similar external work load given, reduced level of increment in respiratory rate and RPE as well as shorter hart rate recovery in the low ΔP category suggested less stress imposed to the cardiopulmonary system thereby facilitating better work performance. The effect of types, however, was not apparent.

Implications: Selection of masks with low ΔP category imposed less stress to cardiopulmonary system during the work task in physiological stressed condition.

Funding acknowledgements: The study was supported by Occupational Safety and Health Research Grant.

Keywords:
Work performance
Mask-wearing
Pandemic

Topics:
Cardiorespiratory
COVID-19

Did this work require ethics approval? Yes

Institution: The Hong Kong Polytechnic University

Committee: Human Subjects Ethics Application Review System (HSEARS)

Ethics number: HSEARS20210602001