We previously found that optoelectronic plethysmography can be used to measure the chest wall volume and its compartments: rib cage and abdomen [1]. We evaluated the breathing pattern and the chest wall displacement during pressure support (PSV) in patients with acute respiratory failure. Nine intubated patients (age 57 ± 12 years, BMI 26 ± 5 kg/m2, PaO2/FiO2 293 ± 67) were studied first at four levels of PSV (5, 10, 15, 25 cmH2O) at 10 cmH2O of PEEP and then at three levels of PEEP (5, 10, 15 cmH2O) at 10 of PSV. We measured the breathing pattern, the ribcage contribution to tidal volume (RC/VT) and the inspiratory asynchrony (IA) [2]. IA was calculated as the area enclosed by the inspiratory portion of rib cage abdomen loop and the line connecting the commencement and the terminal of inspiration.
Our results suggest that only the level of PSV affects the breathing pattern.
Table 1.
| 5 cmH2O | 10 cmH2O | 15 cmH2O | 25 cmH2O | |
|---|---|---|---|---|
| RR (bpm) | 27 ± 12* | 25 ± 12* | 19 ± 14 | 12 ± 6 |
| VT (ml) | 405 ± 153 | 474 ± 184 | 664 ± 25- | 1043 ± 371- |
| RC/VT (%) | 38 ± 13* | 34 ± 13 | 33 ± 12- | 32 ± 9 |
| IA (ml/ml2) | 13 ± 6 | 11 ± 9 | 9 ± 5 | 7 ± 4 |
| Effects of PEEP levels | ||||
| 5 cmH2O | 10 cmH2O | 15 cmH2O | ||
| RR (bpm) | 27 ± 11 | 25 ± 12 | 27 ± 11 | |
| VT (ml) | 423 ± 217 | 474 ± 184 | 454 ± 205 | |
| RC/VT (%) | 36 ± 10 | 34 ± 10 | 41 ± 12 | |
| IA (ml/ml2) | 10 ± 12 | 11 ± 9 | 11 ± 7 | |
*P < 0.05 vs PSV 25, -P < 0.05 vs PSV 5, -P < 0.05 vs others PSV levels.