Table 1.
Impact of Filters on Ventilator Performance During Noninvasive Ventilation and CPAP
| Variables | No Filter |
Low-Resistance Filter |
HME Filter |
|---|---|---|---|
| [Median (IQR)] | [Median (IQR)] | [Median (IQR)] | |
| Noninvasive ventilation | |||
| Flow to trigger, L/min | 11.9 (–12.1 to 23.6) | 18.6 (6.5 to 24.3) | 19.6 (6.5 to 24) |
| Inspiratory effort, cm H2O | –4.91 (–6.95 to –3.94) | –7.43 (–10.27 to –5.64)a | –7.68 (–10.1 to –5.9)a |
| Time to trigger, ms | 75 (51 to 135) | 153 (94 to 307)a | 163 (102 to 294)a |
| Delivered pressure, cm H2O | 16.7 (16.5 to 16.9) | 15.8 (14.5 to 16.2)a | 15.6 (14.1 to 16.1)a |
| Work of breathing, mJ | 537 (317 to 1274) | 822 (714 to 1282)a | 814 (712 to 1268)a |
| Tidal volume, mL | 598 (354 to 917) | 564 (328 to 760)a | 555 (310 to 721)a |
| Patient-ventilator asynchrony, No. (%) | 3 (3%) | 9 (9%) | 8 (8%) |
| PTPt, cm H2O × s | 0.070 (0.040 to 0.130) | 0.230 (0.120 to 0.280)a,b | 0.280 (0.140 to 0.328)a,b |
| CPAP | |||
| Flow to trigger, L/min | 23.6 (11.5 to 36.9) | 25.9 (13.3 to 35.1) | 29 (13.7 to 36) |
| Time to trigger, ms | 220.7 (166 to 262.7) | 281.3 (201.2 to 330.1)a,b | 294.9 (214.8 to 351.6)a,b |
| Delivered pressure, cm H2O | 8.1 (8.1 to 8.2) | 7.9 (7.4 to 8)a,b | 7.8 (7.1 to 7.9)a,b |
| Tidal volume, mL | 359 (196 to 559) | 344 (182 to 485)a,b | 341 (180 to 469)a,b |
| PTPt, cm H2O × s | 0.189 (0.122 to 0.275) | 0.328 (0.289 to 0.548)a,b | 0.382 (0.325 to 0.637)a,b |
Values represent median (IQR) unless otherwise indicated. HME = heat and moisture exchange; IQR = interquartile range; PTPt = inspiratory pressure-time product.
a
P < .05 after correction for multiple comparisons when compared with no filter.
b
P < .05 after correction for multiple comparisons when comparing low-resistance filter and HME filter.