Table 2 Respiratory variables through the ventilatory modes tested
Variable | VT = 6 mL/kg | RR = 30 | HFPPV = 60 | HFPPV = 90 | HFPPV = 120 | HFPPV = 150 | HFOV | p valuea |
|---|---|---|---|---|---|---|---|---|
P/F ratio (mmHg) | 95 [87,105] | 151 [117,181]b | 141 [102,189]b | 132 [95,169]b | 111 [86,162]b | 112 [90,171]b | 193 [146,216]b,c | P = 0.003 |
Gradient (A-a)O2 | 480 [465,493] | 396 [383,452]b | 427 [378,468]b | 427 [394,466] | 455 [406,481] | 458 [394,478] | 365 [350,420]b,c | P = 0.014 |
Minute ventilation (L/min) | 6.9 [6.6,8.8] | 8.7 [7.4,10.0] | 11.1 [11.0,11.5]b | 15.6 [14.0,17.5]b | 18.6 [13.0,19.2]b | 20.2 [19.5,21.3]b | 27 [23.5,28.4]b,c | P < 0.001 |
Shunt (%) | 43 [41,45] | 29 [26,34]b | 34 [30,40] | 31 [28,44] | 34 [31,45] | 38 [30,43] | 27 [25,32]b,c | P = 0.003 |
EtCO2 (mmHg) | 58 [52,60] | 43 [32,47]b | 41 [37,49]b | 40 [30,45]b | 40 [31,48]b | 34 [28,36]b | 27 [23,30]b,c | P < 0.001 |
Cstatic (mL/cmH2O) | 12 [10,14] | 12 [9,14] | 10 [9,13] | 10 [9,12]b | 10 [7,11]b | 9 [8,11]b | - | P = 0.001 |
Cdyn (mL/cmH2O) | 8 [7,9] | 9 [6,10] | 7 [6,9] | 7 [6,8] | 6 [5,7]b | 6 [5,7]b | - | P < 0.001 |
Resistance (cmH2O/L/s) | 8 [8,10] | 10 [9,12]b | 9 [8,9]b | 9 [8,9]b | 8 [8,11]b | 9 [8,13]b | 17 [13,20]b,c | P < 0.001 |
PEEP total (cmH2O) | 14 [11,17] | 14 [10,17] | 14 [10,17] | 13 [10,16] | 13 [10,17] | 13 [10,17] | - | P = 0.744 |
PEEP intrinsic (cmH2O) | 0 | 0 | 0 | 0 [0,1] | 0 [0,1] | 2 [1,3]b | - | P < 0.001 |
PEEP extrinsic (cmH2O) | 14 [11,16] | 14 [11,16] | 13 [10,17] | 13 [10,16] | 13 [10,16] | 12 [9,14] | - | P < 0.001 |
Peak pressure (cmH2O) | 45 [44,48] | 54 [47,58]b | 44 [42,47] | 44 [41,45] | 41 [38,44] | 41 [38,43] | 59 [51,79]b,c | P < 0.001 |
Pmean (cmH2O) | 17 [15,20] | 18 [16,22]b | 18 [15,22]b | 20 [18,23]b | 20 [18,24]b | 20 [17,23]b | 29 [28,30]b,c | P < 0.001 |
Inspiratory flow (L/s) | 1 | 1 | 1 | 1 | 1 | 1 | - | P = 1.000 |
Tinsp/Ttot (%) | 15 [14,17] | 19 [14,22] | 24 [20,28]b | 34 [30,37]b | 38 [33,44]b | 42 [37,49]b | 56 [50,67]b,c | P < 0.001 |