TABLE 2

Statistical pairwise comparisons between events

Comparison	Median difference	Lower CI	Upper CI	p-value
Particle size ≤1.0 µm
HFNC−LFNC	9.5	−5.3	29.6	0.212
LFNC+cough−LFNC	42.9	8.9	108.5	0.005
HFNC+cough−HFNC	8.2	−3.4	31.3	0.145
HFNC+cough−LFNC+cough	−12.1	−59.4	−0.2	0.184
HFNC−HFNC+M	6.7	−8.5	22.1	0.179
HFNC+cough−HFNC+M+cough	11.1	−10.9	35.4	0.126
HFNC+ M +cough−HFNC+ M	2.8	−7.0	14.6	0.332
NIV−LFNC	−0.7	−4.8	14.2	0.904
NIV−HFNC	−4.3	−30.3	7.4	0.204
NIV+cough−NIV	6.6	−14.5	16.0	0.455
LFNC+cough−NIV+cough	43.4	6.0	94.5	0.001
HFNC+cough−NIV+cough	28.2	6.4	43.2	0.023
Particle size >1 µm and ≤5 µm
HFNC−LFNC	6.8	−0.3	16.6	0.073
LFNC+cough−LFNC	7.6	−0.5	16.6	0.048
HFNC+cough−HFNC	1.0	−10.9	5.7	0.765
HFNC+cough−LFNC+cough	−1.4	−7.1	0.0	0.296
HFNC−HFNC+M	2.0	−4.6	13.4	0.391
HFNC+cough−HFNC+M+cough	2.6	−0.4	6.8	0.086
HFNC+ M +cough−HFNC+ M	1.6	−6.6	4.1	0.911
NIV−LFNC	2.5	−4.4	4.4	0.732
NIV−HFNC	−5.5	−20.6	−0.2	0.057
NIV+cough−NIV	2.6	0.0	6.1	0.156
LFNC+cough−NIV+cough	7.1	−2.0	16.0	0.040
HFNC+cough−NIV+cough	4.3	−0.4	11.9	0.107
Particle size >5 µm
HFNC−LFNC	0.5	0.3	0.9	0.044
LFNC+cough−LFNC	0.2	−0.4	0.4	0.862
HFNC+cough−HFNC	−0.5	−0.6	0.1	0.204
HFNC+cough−LFNC+cough	0.3	−0.1	0.9	0.116
HFNC−HFNC+M	0.2	−0.6	0.7	0.926
HFNC+cough−HFNC+M+cough	−0.4	−0.9	0.2	0.125
HFNC+ M +cough−HFNC+ M	0.1	−0.5	0.8	0.709
NIV−LFNC	−0.3	−0.5	0.3	0.468
NIV−HFNC	−0.8	−1.8	−0.2	0.009
NIV+cough−NIV	0.4	0.1	0.8	0.079
LFNC+cough−NIV+cough	−0.2	−0.4	0.3	0.456
HFNC+cough−NIV+cough	0.1	−0.3	0.9	0.390

Statistical pairwise comparisons between different experimental events of particle concentrations (particles per litre of air) measured by the breathing-zone single sensor (APS 3321). Results from three particle size groups are shown. 95% confidence intervals of the median differences are based on the bootstrap method, and the p-values are based on the Wilcoxon signed rank test. LFNC: low-flow nasal cannula; HFNC: high-flow nasal cannula; NIV: noninvasive positive-pressure ventilation; M: surgical mask.