Absence of consequential changes in physiological, thermal and subjective responses from wearing a surgical mask

Twenty subjects treadmill exercised at 5.6 km/h for 1h with and without wearing a surgical mask while being monitored for heart rate, respiratory rate, oxygen saturation, transcutaneous CO2, SpO2, core and skin temperatures, mask deadspace heat and relative humidity, and skin temperature under the mask. Rating scales were utilized for exertion and heat perceptions. Surgical mask use resulted in increases in heart rate (9.5 beats/min; p<0.001), respiratory rate (1.6 breaths/min; p=0.02), and transcutaneous carbon dioxide (2.17 mmHg; p=0.0006), and decreased temperature of uncovered facial skin (0.40 °C; p=0.03). The 1.76 °C increase in temperature of the skin covered by the mask was associated with a mask deadspace apparent heat index of 52.9 °C. Perceptions of heat were neutral to slightly hot, and for exertion ranged from very, very light to fairly light. Surgical mask use for 1h at a low-moderate work rate is not associated with clinically significant physiological impact or significant subjective perceptions of exertion or heat.