Table 2.
Exhaled Particle Concentration and Size with Various Oxygen Modalities
| RA | 4 L/min NC | 15 L/min FM | HFNC 10 L/min | HFNC 30 L/min | HFNC 50 L/min | NIPPV 12/5 | NIPPV 20/10 | Adjusted P Value* | |
|---|---|---|---|---|---|---|---|---|---|
| Particle number concentration, particles/cm3 | |
||||||||
| Normal breathing | 0.068 (0.046–0.091) | 0.060 (0.044–0.065)† | 0.059 (0.055–0.074)‡ | 0.050 (0.036–0.076) | 0.046 (0.035–0.073)† | 0.041 (0.025–0.056)† | 0.056 (0.036–0.079) | 0.057 (0.037–0.090) | N.S. |
| Talking | 0.071 (0.056–0.104) | 0.064 (0.049–0.080)§ | 0.063 (0.050–0.074) | 0.074 (0.054–0.088)‡§ | 0.058 (0.051–0.072)§ | 0.055 (0.037–0.069) | 0.049 (0.030–0.070)† | 0.046 (0.038–0.064)† | N.S. |
| Deep breathing | 0.105 (0.080–0.115) | 0.087 (0.061–0.107) | 0.068 (0.047–0.080)†§ | 0.074 (0.052–0.110)§ | 0.067 (0.053–0.074)† | 0.058 (0.046–0.090)† | 0.050 (0.037–0.091)† | 0.044 (0.038–0.068)† | N.S. |
| Cough | 0.138 (0.098–0.191) | 0.168 (0.122–0.195) | 0.126 (0.095–0.313)‖ | 0.141 (0.133–0.188)‖ | 0.099 (0.078–0.176) | 0.141 (0.095–0.180) | 0.089 (0.055–0.098) | 0.063 (0.047–0.125) | N.S. |
| Particle geometric mean diameter, μm | |
||||||||
| Normal breathing | 1.48 (1.22–1.54) | 1.58 (1.43–1.61) | 1.46 (1.24–1.86) | 1.42 (1.28–1.51) | 1.30 (1.12–1.50) | 1.19 (1.01–1.56) | 1.45 (1.32–1.83) | 1.43 (1.21–1.95) | N.S. |
| Talking | 1.28 (1.14–1.43) | 1.46 (1.20–1.50) | 1.33 (1.12–1.64) | 1.26 (1.23–1.32) | 1.51 (1.32–1.53)† | 1.29 (1.14–1.50) | 1.44 (1.24–1.56) | 1.36 (1.20–1.84) | N.S. |
| Deep breathing | 1.00 (0.98–1.14) | 1.16 (1.02–1.31) | 1.12 (1.00–1.36)§ | 1.14 (1.00–1.33)§‖ | 1.19 (0.99–1.33)§ | 1.25 (0.92–1.42) | 1.38 (1.09–1.50)† | 1.53 (1.09–1.70)† | N.S. |
| Cough | 1.03 (0.94–1.46) | 1.01 (0.93–1.20) | 1.35 (0.95–1.45) | 1.09 (1.01–1.27) | 1.04 (0.93–1.17) | 0.93 (0.86–1.09)‖ | 1.18 (1.02–1.38) | 1.20 (0.88–1.95) | N.S. |
Definition of abbreviations: FM = face mask; HFNC = heated and humidified high-flow nasal cannula; NC = nasal cannula, NIPPV = noninvasive positive-pressure ventilation; N.S. = nonsignificant; RA = room air.
All data are median (interquartile range). For each breathing maneuver, multiple pairwise comparisons of oxygen modalities were made with the Wilcoxon matched-pairs signed rank test. There were no significant differences between oxygen modalities after adjustment for multiple comparisons.
P values were adjusted for multiple comparisons with the Holm method and considered significant if P < 0.05.
Unadjusted P < 0.05 versus RA.
Unadjusted P < 0.05 versus HFNC 50 L/min.
Unadjusted P < 0.05 versus NIPPV 20/10.
Unadjusted P < 0.05 versus NIPPV 12/5.