Table 2 Ventilation parameters, arterial blood gases, and mean arterial pressure at different PEEPe for PS_N and PS_P

P̅aw (cm H₂O)

PS_P

10.9 (10.3, 11.3)

12.9 (12.3, 13.3)^a

15.0 (14.8, 16.3)^ab

17.4 (16.8, 18.3)^abc

<0.001

PS_N

11.4 (10.8, 11.6)^x

13.1 (12.1, 13.3)^a

15.2 (14.4, 16.4)^ab

17.5 (16.9, 18.6)^abc

PEEPe (cm H₂O)

PS_P

0.6 (0.4, 1.0)^z

2.3 (2.2, 2.5)^az

4.7 (4.2, 5.4)^ab

7.1 (6.5, 7.5)^abc

<0.001

PS_N

1.0 (0.5, 1.2)^x

2.5 (2.3, 3.0)^a

4.7 (4.4, 5.4)^ab

7.0 (6.6, 7.5)^abc

V_T (ml/kg)

PS_P

5.4 (4.2, 6.7)^z

5.8 (4.9, 6.8)^z

5.9 (5.0, 6.6)^abz

5.5 (5.2, 7.0)^ab

<0.001

PS_N

4.6 (4.3, 5.8)^x

5.0 (4.4, 5.9)^a

4.9 (4.6, 6.7)^ab

5.0 (4.6, 7.1)^abc

Bf_N (breaths/min)

PS_P

20.2 (17.7, 29.3)^z

20.5 (17.6, 28.9)^z

21.5 (17.2, 26.9)^z

20.9 (17.9, 30.3)

0.003

PS_N

26.4 (17.3, 30.7)^x

24.4 (17.2, 33.2)

22.1 (18.1, 31.5)^ab

20.5 (16.0, 29.6)^ab

V_E (l/min)

PS_P

6.05 (5.25, 8.13)^z

6.54 (5.47, 8.91)^a

7.05 (5.67, 9.02)^a

7.07 (5.70, 11.62)^a

<0.001

PS_N

6.43 (5.31, 9.54)^x

6.92 (5.53, 9.98)^a

7.14 (5.50, 9.20)^a

7.79 (5.74, 9.66)^a

V_T/Ti_P (ml/s)

PS_P

424 (390, 446)^z

429 (389, 472)

436 (386, 458)

438 (396, 466)

0.013

PS_N

414 (302, 491)^x

443 (334, 508)^a

452 (338, 526)^a

479 (361, 513)^a

Ti_N (s)

PS_P

0.90 (0.72, 1.03)

0.90 (0.74, 0.94)

0.84 (0.73, 0.98)

0.87 (0.69, 0.93)

NS

PS_N

0.84 (0.71, 0.96)

0.77 (0.71, 0.86)

0.81 (0.74, 0.86)

0.84 (0.73, 0.95)

Te_N (s)

PS_P

2.12 (1.43, 2.60)^z

2.22 (1.45, 2.93)

2.17 (1.58, 3.14)^z

2.13 (1.53, 2.58)

0.050

PS_N

1.76 (1.16, 2.66)^x

2.09 (1.20, 2.77)^a

2.02 (1.24, 2.59)^a

2.14 (1.33, 2.92)^a

Ti_N/Tt_N (%)

PS_P

29.6 (27.5, 36.5)

28.7 (24.5, 39.0)

27.1 (23.4, 36.3)

26.1 (23.0, 36.7)

NS

PS_N

31.4 (25.6, 37.8)

29.4 (23.9, 38.5)

29.7 (24.6, 38.3)

30.6 (22.5, 36.8)

pH

PS_P

7.36 (7.33, 7.41)

7.38 (7.36, 7.41)^a

7.39 (7.34, 7.44)^a

7.39 (7.33, 7.42)^a

0.009

PS_N

7.37 (7.33, 7.40)^x

7.39 (7.34, 7.42)^a

7.38 (7.32, 7.45)^a

7.38 (7.35, 7.42)^a

PaCO₂ (mm Hg)

PS_P

37.9 (32.0, 48.6)

35.9 (31.2, 46.1)

36.3 (32.1, 46.8)

33.5 (32.9, 43.3)

NS

PS_N

40.4 (29.8, 47.5)

34.2 (31.2, 42.1)

35.4 (32.8, 41.8)

36.5 (30.7, 41.9)

PaO₂ (mm Hg)

PS_P

84.0 (79.9, 113.9)

94.8 (84.9, 116.7)

98.7 (90.0, 124.3)

103.9 (84.0, 117.2)

NS

PS_N

89.7 (83.5, 122.9)

106.6 (81.2, 124.1)

99.4 (91.0, 123.9)

109.0 (95.0, 125.8)

MAP (mm Hg)

PS_P

89.0 (76.0, 92.7)

88.0 (77.0, 92.7)

86.7 (77.7, 91.7)

89.3 (79.0, 91.3)

NS

PS_N

88.3 (75.7, 91.3)

88.0 (75.3, 90.4)

88.7 (78.3, 91.0)

86.7 (80.3, 92.0)