Wearing face masks while climbing stairs influences respiratory physiology.

During the COVID-19 pandemic wearing face masks was mandatory. Nowadays, face masks are still encouraged indoors, especially in hospitals. People climbing stairs with masks describe unpredictable dyspnea.&#xD;Methods: Healthy adults climbed 5 floors with and without a mask. Various cardio-respiratory parameters were measured, including O2-Saturation (O2-Sat) and End-tidal CO2 (EtCO2), at baseline and on the top floor. Subjective indexes, such as Borg's scale, were evaluated.&#xD;Results: Thirty-two volunteers (16 males), median age 39 years (IQR 32.5-43), median BMI=23.6 (IQR 21.5-25.1), with good fitness levels, participated. Comparing baseline to end-activity, median (IQR): O2-Sat change was -1.0% (-2-0) without mask, versus -3.0% (-4-0) with mask, p=0.003; EtCO2 +7.0 (+3.3-+9) without mask, versus +8.0 (+6 -+12) with mask, p=0.0001. Hypercarbia was seen in 5 (15.6%) participants without mask, median=48mmHg (IQR 47.5-51), and in 11 (34%) participants with mask, median=50mmHg (IQR 47-54), p<0.001. Desaturation (O2-Sat<95%) was seen in 5 (15.6%) participants without mask, median=94% (IQR 93-94%), and in 10 (31%) participants with mask, median=91.5% (IQR 90-93%), p=0.06. Regression analysis demonstrated that only male sex was significantly associated with abnormal EtCO2 (OR=26.4, 95%CI=1.9-366.4, p=0.005). Ascent duration increased from median (IQR) of 94 seconds (86-100) without mask to 98 seconds (89-107) with mask, p<0.001. Borg's scale of perceived exertion (range 0-10) increased from median (IQR) of 3.0 (2.5-3.87) without mask to 4.0 (3.0-4.37) with mask, p<0.001. &#xD;Conclusions: During routine daily activities, such as stair-climbing, face masks cause dyspnea, and have measurable influences on ventilation, including true desaturation and hypercapnia, especially in males. &#xD;&#xD.