Table 2.
Respiratory variables
| Group | Time | |||
|---|---|---|---|---|
| T0 | T1 | T2 | T3 | |
| Ventilator setting VT (ml) | ||||
| CON | 320.0 (70.0) | / | / | / |
| ARDS | 283.2 (15.3) | 266.7 (41.6) | / | / |
| LTV | 272.9 (52.8) | 233.3 (30.6) | 250.0 (26.2) | 233.8 (24.5) |
| APRV | 267.1 (45.7) | / | / | / |
| Ventilator setting frequency (cycles/min) | ||||
| CON | 15.3 (4.2) | / | / | / |
| ARDS | 16.0 (0.0) | 19.0 (6.6) | / | / |
| LTV | 20.6 (5.4) | 33.7 (5.5) | 29.6 (5.0) | 25.9 (6.6) |
| APRV | 22.4 (5.3) | 21.7 (0.6)* | 19.7 (4.8)* | 19.9 (4.5)* |
| Total minute ventilation (L/min) | ||||
| CON | 5.0 (0.5) | / | / | / |
| ARDS | 4.5 (0.3) | 8.3 (3.2) | / | / |
| LTV | 5.3 (1.9) | 10.4 (3.7) | 7.2 (1.9) | 7.2 (1.8) |
| APRV | 6.2 (1.9) | 7.1 (3.7) | 6.0 (3.0) | 7.8 (3.9) |
| Phigh (cmH2O) | ||||
| APRV | / | 24.7 (3.5) | 24.6 (1.7) | 23.9 (2.0) |
| PEEP (mmHg) | ||||
| CON | 5.0 (0.0) | / | / | / |
| ARDS | 5.0 (0.0) | 5.3 (0.6) | / | / |
| LTV | 5.0 (0.0) | 13.7 (1.5) | 13.9 (1.7) | 13.9 (1.9) |
| APRV | 5.0 (0.0) | 5.0 (0.0)* | 5.0 (0.0)* | 5.3 (0.8)* |
| Tlow (s) | ||||
| APRV | / | 0.4 (0.0) | 0.4 (0.1) | 0.4 (0.1) |
| Setting FiO2 (%) | ||||
| CON | 36.7 (5.8) | / | / | / |
| ARDS | 38.4 (10.4) | 43.7 (50.9) | / | / |
| LTV | 37.1 (11.1) | 100.0 (0.0) | 14.1 (19.2) | 47.5 (27.0) |
| APRV | 36.7 (5.8) | 100.0 (0.0) | 23.1 (29.0) | 35.0 (7.6) |
| Respiratory rate (breaths/min) | ||||
| CON | 15.3 (4.2) | / | / | / |
| ARDS | 16.0 (0.0) | 22.3 (11.7) | / | / |
| LTV | 21.3 (5.5) | 38.0 (3.5) | 29.9 (4.7) | 28.9 (6.7) |
| APRV | 22.4 (5.3) | 28.0 (8.9) | 20.5 (4.7)* | 20.9 (3.7)* |
| Peak inspiratory pressure (cmH2O) | ||||
| CON | 16.7 (0.6) | / | / | / |
| ARDS | 14.0 (2.6) | 27.0 (14.7) | / | / |
| LTV | 14.8 (3.7) | 32.3 (5.9) | 30.5 (6.7) | 29.3 (8.3) |
| APRV | 21.3 (9.5) | 24.7 (3.5) | 26.6 (2.6) | 25.6 (3.2) |
| Mean airway pressure (cmH2O) | ||||
| CON | 8.2 (0.7) | / | / | / |
| ARDS | 7.3 (0.2) | 12.3 (6.0) | / | / |
| LTV | 7.7 (1.3) | 20.3 (2.5) | 19.3 (3.2) | 19.5 (2.9) |
| APRV | 12.3 (6.2) | 21.3 (3.5)§ | 21.4 (2.5) | 21.3 (3.0) |
| Static compliance (ml/cmH2O) | ||||
| CON | 32.7 (5.1) | / | / | / |
| ARDS | 42.3 (10.1) | 25.3 (20.5) | / | / |
| LTV | 39.9 (5.1) | 14.3 (2.1) | 22.5 (7.7) | 21.8 (8.0) |
| APRV | 39.4 (16.1) | 24.3 (9.0) | 37.3 (13.9)* | 38.7 (12.8)* |
| pH | ||||
| CON | 7.4 (0.1) | / | / | / |
| ARDS | 7.5 (0.1) | 7.3 (0.1) | / | / |
| LTV | 7.4 (0.1) | 7.4 (0.1) | 7.4 (0.1) | 7.4 (0.1) |
| APRV | 7.4 (0.1) | 7.4 (0.1) | 7.5 (0.1) | 7.5 (0.1) |
| PaCO2 (mmHg) | ||||
| CON | 40.1 (8.0) | / | / | / |
| ARDS | 37.1 (11.7) | 44.1 (9.2) | / | / |
| LTV | 48.7 (15.0) | 48.1 (14.5) | 52.4 (14.1) | 49.0 (11.7) |
| APRV | 46.7 (15.3) | 49.2 (8.9) | 45.6 (13.6) | 40.6 (7.0) |
| PaO2/FiO2 Ratio | ||||
| CON | 415.0 (41.1) | / | / | / |
| ARDS | 445.7 (19.7) | 46.5 (2.1) | / | / |
| LTV | 433.3 (51.0) | 59.9 (19.6) | 298.7 (132.0) | 303.0 (146.5) |
| APRV | 349.3 (115.3) | 65.9 (25.4) | 342.4 (80.3) | 335.7 (76.4) |
Data are presented as the mean(standard deviation) of the values recorded at T0 (before severe ARDS modeling), T1 (after severe ARDS modeling), T2 (24 h mechanical ventilation after severe ARDS modeling) and T3(48 h mechanical ventilation after severe ARDS modeling); CON, control group; ARDS, severe acute respiratory distress syndrome group; LTV, low tidal volume ventilation group; APRV, airway pressure release ventilation group; VT, tidal volume; Phigh, pressure during inspiration; Tlow, the time spent at/release phase; FiO2, fraction of inspired oxygen; Total minute ventilation including release minute ventilation + spontaneous minute ventilation; §p < 0.05 compared to the ARDS group at this time point in Kruskal–Wallis H-test; *p < 0.05 compared to the LTV group at this time point in Kruskal–Wallis H-test