Patient enrolment commenced on 7 August 2020. In total, 63 patients were randomly assigned to the LPV (n = 31) and PCV-VG (n = 32) groups (Fig. 1). The baseline characteristics did not differ between the groups (Table 1).
Table 1
Parameters | LPV group (n = 31) | PCV-VG group (n = 32) | P-value |
Age (month) | 6.4 [5–40.75] | 6.8 [5.2–39.3] | 0.755 |
Weight (kg) | 8.3 [7.5–13.25] | 9 [7.55–12.3] | 0.705 |
Sex (male) | 25/6 | 24/8 | 0.59 |
Type of operation | | | |
Segmentectomy/ wedge resection | 27 | 25 | 0.35 |
Single lobectomy | 3 | 4 | 0.72 |
Bilobectomy | 1 | 3 | 0.3 |
All data are presented as mean ± SD or median [IQR], unless otherwise specified.
LPV, lung-protective ventilation; PCV-VG, pressure-controlled ventilation volume-guarantee
Primary outcome
PIP at T2 and T3 were lower in the PCV-VG group than in the LPV group (T2, 20.2±2.7vs 22.4±3.3; P=0.001) (T3, 23.8±3.2vs 26.36±3.7; P=0.01) (Fig. 2A). Dynamic compliance at T2 and T3 was higher in the PCV-VG group than in the LPV group (T2, 9.1±3.7 vs 6.8±3.05 ; P=0.01) (T3, 7.1±3.3 vs 4.8±2.3; P=0.01) (Fig. 2B).
In addition,PIP was higher at T2 and T3 compared with T1(P=0.001) (Fig. 2A). Dynamic compliance was lower at T2 and T3 compared with T1(P=0.01) (Fig. 2B).
Secondary outcomes
LUS assessment
There was no difference in LUS in the dependent lung before T0. After T0, lung aeration deteriorated, but with no difference in both groups immediately after surgery [T4: 4 (2 to 6) vs. 4 (2 to 5) Z=–0.69, P=0.49] (Figure 3a and Figure 3c). Lung aeration improved in both groups after surgery and returned to normal from 2.5 h after extubation in both groups (Figure 3b and Figure 3d). Temporal ultrasound images of the lateral chest wall of the dependent lung are shown in Fig. 3.
Postoperative pulmonary complications
Five (7.9%) patients exhibited Postoperative pulmonary complications occurred in five patients, with no differences in the incidence between the two groups [LPV: 3 (9.7%) vs. PCV-VG: 2 (6.3%), P=0.97].
Intra-operative desaturation
Intra-operative desaturation was comparable in LPV group (4/31, 12.9%), compared with 3/32 (9.4%) in the PCV-VG group [OR=1.43 (0.29 to 7.0); P=0.66].
There was no difference in the gas exchange values between the groups. PaO2 and PaCO2 increased significantly at T3 compared with that at baseline (P=0.001) (Table 2).
Table 2. Gas exchange
Variable
|
Group
|
T1
|
T3
|
PaO2
(mmHg)
|
LPV
|
214.6±23.67
|
249.25±19.14
|
PCV-VG
|
218.85±19.74
|
258.82±25.19
|
PaCO2
(mmHg)
|
LPV
|
36.18±6.4
|
54.92±8.44
|
PCV-VG
|
35.70±5.22
|
51.74±10.15
|
All data are presented as mean ± SD.
PaCO2, arterial pressure of carbon dioxide; PaO2, arterial pressure of oxygen; LPV, lung-protective ventilation; PCV-VG, pressure-controlled ventilation volume-guaranteed ventilation; T1, 10 min after induction of anaesthesia without pneumoperitoneum; T3, 5 min after complete CO2 insufflation
Hospital stays
The length of hospital stay did not differ between the PCV-VG (6.5 ± 2.1) and VCV (6.1 ± 1.9) groups [0.4 (95% CI -0.59 to 1.39), P=0.43].
Haemodynamic variables
There was no difference in the haemodynamic variables between the groups. MAP was higher at T3 in both groups compared with that at T1 and T2 (P=0.001). CVP was higher at T2 and T3 than that at T1 (P=0.001). The heart rate was stable throughout the operation (Fig. 4).