Table 2. Ventilatory parameters.
| automated ventilation | conventional ventilation | mean difference (95% CI) | p | |
|---|---|---|---|---|
| All patients (n = 96) | ||||
| Primary endpoint | ||||
| MP, median [IQR] and mean (SD) (J/min) | 15.8 [11.5–21.0] 17.3 (8.9) | 16.1 [10.9–22.6] 17.6 (8.7) | –0.44 (–1.17 to 0.29) | 0.24 |
| Ventilation variables and parameters | ||||
| VTi (mL) | 485 [402–585] | 469 [412–542] | 6.98 (–2.90 to 16.86) | 0.17 |
| VTe (mL) | 483 [410–581] | 483 [424–553] | 2.88 (–7.08 to 12.84) | 0.57 |
| VT (ml/kg IBW) | 7.2 [5.9–8.1] | 6.9 [6.1–8.0] | 0.07 (–0.08 to 0.22) | 0.34 |
| RR (breaths /minute) | 17 [14–22] | 18 [15–23] | –1.02 (–1.47 to –0.56) | < 0.01 |
| Minute volume (cm H2O) | 8.2 [6.8–10.6] | 8.8 [7.5–10.4] | –0.40 (–0.65 to –0.14) | < 0.01 |
| Pmax (cm H2O) | 21 [18–25] | 21 [17–25] | 0.18 (–0.24 to 0.60) | 0.40 |
| PEEP, set (cm H2O) | 8 [6–11] | 8 [6–10] | 0.13 (–0.05 to 0.32) | 0.16 |
| Pinsp (cm H2O)+ | 12 [10–15] | 13 [12–15] | –0.17 (–0.49 to 0.15) | 0.30 |
| PS (cm H2O)* | 9 [6–13] | 8 [5–12] | 0.49 (0.04 to 0.95) | 0.03 |
| ΔP, dynamic (cm H2O) | 12 [10–15] | 13 [10–16] | 0.05 (–0.31 to 0.40) | 0.80 |
| Flow (L/min) | 43.7 [36.4–52.3] | 44.5 [37.3–53.2] | –1.47 (–2.28 to –0.66) | < 0.01 |
| Tinsp (sec) | 1.09 [0.85–1.41] | 1.05 [0.84–1.24] | 0.11 (0.09 to 0.14) | < 0.01 |
| FiO2 (%) | 31 [29–38] | 33 [28–40] | –0.64 (–1.36 to 0.09) | 0.09 |
| etCO2 (kPa) | 4.9 [4.4–5.3] | 4.8 [4.3–5.4] | 0.09 (0.05 to 0.13) | < 0.01 |
| SpO2 (%) | 94 [93–96] | 95 [93–97] | –0.38 (–0.61 to –0.15) | 0.01 |
| CRS (mL/cm H2O) | 37.6 [30.4–49.9] | 36.9 [29.5–50.4] | –1.91 (–4.00 to 0.19) | 0.07 |
| Arterial blood gas analyses results | ||||
| pH | 7.38 [7.31–7.44] | 7.40 [7.34–7.45] | –0.007 (–0.02 to 0.003) | 0.16 |
| pCO2 (kPa) | 5.4 [4.9–9.1] | 5.4 [4.9–5.9] | 0.08 (–0.06 to 0.22) | 0.29 |
| Bicarbonate (mmol/L) | 24 [21–27] | 25 [21–28] | 0.10 (–0.30 to 0.50) | 0.62 |
| pO2 (kPa) | 9.9 [9.1–11.6] | 9.9 [9.0–11.3] | 0.01 (–0.53 to 0.55) | 0.96 |
| SaO2 (%) | 95 [93–97] | 96 [94–97] | –0.31 (–0.70 to 0.08) | 0.13 |
| PaO2/FiO2 ratio (mmHg) | 231 [181–299] | 229 [184–286] | –2.65 (–14.46 to 9.17) | 0.66 |
| Passive patients (n = 45) | ||||
| Primary endpoint | ||||
| MP, median [IQR] and mean (SD) (J/min) | 16.9 [12.5–22.1] 17.8 (7.2) | 19.0 [14.1–25.0] 19.4 (6.8) | –1.76 (–2.47 to –10.34) | < 0.01 |
| Ventilation variables and parameters | ||||
| VTi (mL) | 474 [401–571] | 462 [411–515] | 18.07 (7.88 to 28.24) | < 0.01 |
| VTe (mL) | 481 [404–578] | 466 [427–532] | 10.42 (.01 to 20.85) | 0.05 |
| VT (ml/kg PBW) | 7.0 [5.8–7.9] | 6.5 [5.8–7.6] | 0.22 (0.08 to 0.37) | < 0.01 |
| RR (breaths /minute) | 17 [13–22] | 18 [16–22] | –1.77 (–2.26 to –1.28) | < 0.01 |
| Minute volume (cm H2O) | 7.9 [6.7–9.4] | 8.7 [7.7–9.8] | –0.61 (–0.86 to –0.37) | 0.01 |
| Pmax (cm H2O) | 22 [19–26] | 22 [19–28] | –0.59 (–1.17 to –0.01) | 0.05 |
| Pplat (cm H2O) | 19 [16–22] | 20 [16–23] | –0.19 (–0.57 to 0.19) | 0.33 |
| PEEP, set (cm H2O) | 8 [6–11] | 8 [6–11] | 0.04 (–0.30 to 0.22) | 0.77 |
| PEEP, total (cm H2O) | 8.7 [6.9–12] | 9.0 [7.0–12] | 0.19 (–0.08 to 0.46) | 0.17 |
| Pinsp (cm H2O) | 13 [11–15] | 13 [12–15] | –0.38 (–0.69 to –0.07) | 0.02 |
| ΔP, static (cmH2O) | 9 [8–11] | 10 [9–12] | –0.35 (–0.62 to –0.07) | < 0.01 |
| Flow (L/min) | 42.9 [36.2–48.4] | 44.2 [38.9–50.9] | –0.74 (–1.78 to 0.31) | 0.17 |
| Tinsp (sec) | 1.20 [0.94–1.60] | 1.11 [0.91–1.25] | 0.18 (0.14 to 0.22) | < 0.01 |
| FiO2 (%) | 33 [30–40] | 35 [30–45] | –1.26 (–2.49 to –0.03) | 0.04 |
| etCO2 (kPa) | 5.0 [4.6–5.3] | 4.8 [4.3–5.3] | 0.15 (0.09 to 0.21) | < 0.01 |
| SpO2 (%) | 94 [93–96] | 95 [94–97] | –0.55 (–0.86 to –0.25) | < 0.01 |
| CRS (mL/cm H2O) | 34.9 [29.2–42.5] | 32.9 [27.1–40.1] | 2.30 (0.38 to 4.22) | 0.02 |
| Arterial blood gas analyses | ||||
| pH | 7.35 [7.29–7.39] | 7.38 [7.30–7.43] | –0.01 (–0.03 to 0.008) | 0.30 |
| pCO2 (kPa) | 5.7 [5.1–64] | 5.4 [4.9–6.2] | 0.10 (–0.14 to 0.35) | 0.42 |
| Bicarbonate (mmol/L) | 24 [20–26] | 23 [21–26] | 0.30 (–0.34 to 0.95) | 0.37 |
| pO2 (kPa) | 10.3 [9.2–12.4] | 10.0 [9.1–12.1] | 0.21 (–0.55 to 0.98) | 0.58 |
| SaO2 (%) | 95 [93–98] | 96 [93–97] | –0.27 (–0.88 to 0.33) | 0.39 |
| PaO2/FiO2 ratio (mmHg) | 238 [182–305] | 220 [180–282] | 2.09 (–14.14 to 18.35) | 0.93 |
| Active patients (n = 32) | ||||
| Primary endpoint | ||||
| MP, median [IQR] and mean (SD) (J/min) | 14.6 [11.0–20.3] 16.3 (7.9) | 14.1 [10.1–21.3] 16.4 (8.9) | –0.81 (–2.13 to 0.49) | 0.23 |
| Ventilation variables and parameters | ||||
| VTi (mL) | 480 [402–573] | 485 [420–559] | –12.0 (–37.84 to 13.94) | 0.37 |
| VTe (mL) | 480 [415–563] | 499 [420–570] | –10.9 (–34.37 to 12.81) | 0.37 |
| VT (ml/kg PBW) | 7.2 [5.9–8.5] | 7.2 [6.4–8.3] | –0.19 (–0.58 to 0.21) | 0.36 |
| RR (breaths /minute) | 18 [15–22] | 19 [15–26] | –1.62 (–2.60 to –0.66) | 0.01 |
| Minute volume (cm H2O) | 8.9 [7.1–11.3] | 9.5 [7.4–12.3] | –0.91 (–1.48 to –0.33) | 0.01 |
| Pmax (cm H2O) | 20 [16–23] | 17 [14–22] | 1.21 (0.37 to 2.07) | 0.01 |
| PEEP, set (cm H2O) | 8 [6–10] | 8 [5–10] | 0.42 (0.06 to 0.78) | 0.02 |
| PS (cm H2O) | 9 [5–12] | 7 [5 –12] | 0.47 (–0.15 to 1.09) | 0.13 |
| ΔP, dynamic (cmH2O) | 11 [8–15] | 10 [7–14] | 0.81 (0.06 to 1.57) | 0.04 |
| Flow (L/min) | 42.5 [36.5–55.1] | 47.2 [37.5–58.2] | –4.29 (–6.23 to –2.36) | < 0.01 |
| Tinsp (sec) | 0.98 [0.81–1.13] | 0.95 [0.74–1.09] | 0.06 (0.02 to 0.10) | < 0.01 |
| FiO2 (%) | 30 [26–37] | 30 [25–40] | –0.71 (–1.82 to 0.39 | 0.21 |
| etCO2 (kPa) | 4.9 [4.3–5.4] | 4.9 [4.3–5.4] | 0.08 (0.01 to 0.15) | 0.03 |
| SpO2 (%) | 94 [92–96] | 95 [93–97] | –0.59 (–1.21 to 0.04) | 0.07 |
| CRS (mL/cm H2O | 42.6 [30.8–57.2] | 50.7 [34.9–59.4] | –9.77 (–14.91 to –4.65) | 0.01 |
| Arterial blood gas analyses results | ||||
| pH | 7.43 [7.39–7.46] | 7.44 [7.40–7.48] | –0.01 (–0.02 to 0.002) | 0.12 |
| pCO2 (kPa) | 5.3 [4.6–5.9] | 5.1 [4.7–5.7] | 0.14 (–0.09 to 0.38) | 0.26 |
| Bicarbonate (mmol/L) | 27 [23–29] | 27 [23–31] | 0.01 (–0.72 to 7.37) | 0.98 |
| pO2 (kPa) | 9.6 [8.9–10.7] | 9.5 [8.6–10.7] | 0.17 (–0.78to 1.13) | 0.73 |
| SaO2 (%) | 95 [94–97] | 96 [94–97] | –0.28 (–1.09 to 0.52) | 0.50 |
| PaO2/FiO2 ratio (mmHg) | 229 [175–270] | 244 [194–281] | –11.98 (–31.83 to 8.15) | 0.25 |
Data are median [IQR] or mean (SD)
mL: milliliter; cm H2O: centimeters of water; L: liter; sec: seconds; kPa: kilopascal; J/min: joule per minute; MP: mechanical power; VT: tidal volume; RR: respiratory rate; Pmax: maximum airway pressure; PEEP: positive end–expiratory pressure; Pinsp: set inspiratory pressure; PS: set pressure support; ΔP: driving pressure; Tinsp: inspiratory time; FiO2: fraction of inspired oxygen; etCO2: end–tidal carbon dioxide; SpO2: pulse oximetry; CRS: compliance of the respiratory system; pCO2: partial pressure of carbon dioxide; kPa: kilopascal; pO2: partial pressure of oxygen; SaO2: arterial oxygen saturation; mmHg: millimeters of mercury; 95% CI; 95% confidence interval.
+ available in passive patients
* available in active patients