Table 3 Trend over time of FiO₂, EtCO₂, and RR

With a surgical mask: Mean (SD)

Without a surgical mask: Mean (SD)

P value

1 min

0.39 (0.19)

0.62 (0.084)

<  0.0001

2 min

0.57 (0.13)

0.64 (0.080)

<  0.0001

3 min

0.59 (0.10)

0.68 (0.082)

<  0.0001

4 min

0.61 (0.085)

0.69 (0.083)

<  0.0001

5 min

0.62 (0.081)

0.71 (0.077)

<  0.0001

1 min

32.3 (8.52)

33.5 (5.50)

0.1954

2 min

35.2 (5.48)

28.6 (7.23)

<  0.0001

3 min

35.1 (4.60)

23.8 (5.56)

<  0.0001

4 min

34.6 (5.03)

22.9 (5.05)

<  0.0001

5 min

34.6 (4.37)

22.7 (4.45)

<  0.0001

With a surgical mask: Mean (SD)

Without a surgical mask: Mean (SD) (Standard Deviation)

P value

1 min

14.1 (4.6)

14.0 (4.3)

0.75

2 min

14.2 (5.3)

13.4 (4.4)

0.076

3 min

14.9 (5.1)

13.1 (4.7)

<  0.0001

4 min

14.2 (4.8)

13.3 (4.3)

0.0024

5 min

13.7 (4.4)

13.4 (4.1)

0.30