Humidity and water loss
| Parameter | No humidifier | Cold humidifier | Heated humidifier | p‐value |
| Inspiration | ||||
| Hrel % | 24.0±9.1 | 34.5±10.1# | 53.9±13.2¶,+ | <0.001 |
| Habs mg·L−1 | 9.4±3.5 | 13.4±3.9# | 21.3±5.1¶,+ | <0.001 |
| υ hygrometer °C | 34.8±1.0 | 34.6±1.0# | 35.0±1.1¶,+ | <0.001 |
| υ mask °C | 31.1±1.4 | 31.3±1.6 | 32.4±1.7¶,+ | <0.001 |
| Expiration | ||||
| Hrel % | 75.5±14.4 | 79.8±10.2# | 82.2±8.9¶,+ | <0.001 |
| Habs mg·L−1 | 30.8±5.5 | 32.2±4.0# | 33.6±3.5¶,+ | <0.001 |
| υ hygrometer °C | 35.6±0.7 | 35.3±0.9# | 35.6±0.9¶,+ | <0.001 |
| υ mask °C | 32.4±1.1 | 32.6±1.2# | 33.7±1.1¶,+ | <0.001 |
| VT L | 0.58±0.37 | 0.59±0.37 | 0.81±1.5 | 0.42 |
| Bf L·min−1 | 21.9±10.2 | 21.2±10.2 | 18.9±9.9 | 0.26 |
| VE L·min−1 | 10.5±4.0 | 10.1±4.4 | 9.6±3.2 | 0.43 |
| Water loss mg·min−1 | 226.3±49.4 | 190.8±46.9# | 118.0±48.5¶,+ | <0.001 |
| Impedance of the total respiratory system | ||||
| Z 5 Hz cmH2O·L−1·s−1 | 5.7±1.8 | 6.4±2.1 | 6.7±1.8¶ | 0.025 |
| R 5 Hz cmH2O·L−1·s−1 | 5.5±1.4 | 6.1±1.7 | 6.3±1.5¶ | 0.012 |
| R 20 Hz cmH2O·L−1·s−1 | 5.4±0.7 | 5.3±0.7 | 5.3±0.6 | 0.62 |
| X 5 Hz cmH2O·L−1·s−1 | −1.7±1.3 | −2.1±1.4 | −2.1±1.2 | 0.21 |
Hrel: relative humidity
Habs: measured absolute humidity in the capacitive hygrometer
υ hygrometer: temperature in the hygrometer
υ mask: temperature in the mask
VT: total volume
Bf: breathing frequency
VE: minute volume
water loss: amount of water lost on the basis of measurements of absolute humidity in expired and inspired air
Z 5 Hz: impedance of the total respiratory system at an oscillation frequency of 5 Hz
R 5 Hz: resistance at 5 Hz
R 20 Hz: resistance at 20 Hz
X 5 Hz: reactance at 5 Hz. The p-values were determined according to the repeated-measure one-way analysis of variance (p<0.05)
#: cold humidifier versus no humidifier
+: heated humidifier versus cold humidifier
The post hoc significance (p<0.05)
¶: heated humidifier versus no humidifier