Table 3. Changes of arterial blood gas at different time points for the patients in the both group ($\overline{x}\pm s$).

Item	P group	C group	P
OI
T1	375±65	364±59	0.642
T2	229±39	198±37	0.032
T3	268±46	321±53	0.009
T4	339±44	312±50	0.100
PaCO2 (mmHg)
T1	38.7 ±5.3	37.2±3.2	0.290
T2	32.1±4.3	39.6±3.6	0.000
T3	34.1±4.9	37.3±4.7	0.032
T4	38.4±4.0	34.6±3.7	0.002
Qs/Qt%
T1	13.9±3.1	14.1±2.9	0.322
T2	15.8±3.4	22.3±3.2	0.000
T3	14.9±3.4	15.8±3.4	0.001
T4	13.4±2.6	15.7±3.2	0.047
pH
T1	7.42±0.019	7.41±0.022	0.135
T2	7.41±0.021	7.39±0.023	0.027
T3	7.39±0.033	7.37±0.031	0.016
T4	7.40±0.034	7.38±0.032	0.042