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Ventilatory pattern, gas exchange and respiratory effort |
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| Parameter |
P |
Pressure support (cmH2O) |
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| 5 |
10 |
15 |
25 |
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| Tidal volume (l) |
<0.001 |
0.340 ± 0.048 |
0.432 ± 0.064 |
0.610 ± 0.063 |
0.852 ± 0.070 |
| Frequency (minute-1) |
<0.001 |
27.7 ± 2.9 |
22.1 ± 2.6 |
15.9 ± 2.2 |
11.9 ± 1.7 |
| Minute ventilation (l/minute) |
NS |
8.5 ± 0.8 |
8.9 ± 1.2 |
8.6 ± 0.7 |
9.5 ± 1.2 |
| Pao2/Fio2 (mmHg) |
0.042 |
299.3 ± 22.0 |
263.1 ± 22.8 |
288.2 ± 22.3 |
320.0 ± 25.4 |
| Paco2 (mmHg) |
NS |
35.4 ± 2.4 |
33.9 ± 2.7 |
33.9 ± 2.2 |
33.8 ± 2.0 |
| f/Vt (1/l·minute) |
<0.001 |
97.9 ± 15.4 |
61.2 ± 9.9 |
33.3 ± 9.3 |
16.2 ± 3.6 |
| WOB (J/minute) |
<0.001 |
4.9 ± 1.0 |
3.8 ± 1.7 |
1.2 ± 0.6 |
0.0 ± 0.0a |
| PTP (cmH2O s/minute) |
<0.001 |
106.1 ± 18.3 |
61.9 ± 21.8 |
16.3 ± 8.6 |
0.1 ± 0.1 |
| P0.1 (cmH2O) |
<0.001 |
2.0 ± 0.5 |
1.5 ± 0.3 |
0.9 ± 0.2 |
0.3 ± 0.2 |
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Where applicable, values are expressed as mean ± standard error of the mean. aZero work of breathing (WOB) is the consequence of our assumption that, at 25 cmH2O, the respiratory system is in a fully relaxed state. P values refer to one-way analysis of variance on repeated measures (for different levels of pressure support). FiO2, fraction of inspired oxygen; f/Vt, frequency/tidal volume ratio; NS, not significant; P0.1, occlusion pressure; PaCO2, arterial carbon dioxide tension; PaO2, arterial oxygen tension; PTP, pressure time product. | |||||
Aliverti et al. Critical Care 2006 10:R54 doi:10.1186/cc4867 |
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