We evaluated the effectiveness of pressure-controlled ventilation-volume guaranteed (PCV-VG) mode combined with open-lung approach (OLA) in patients during one-lung ventilation (OLV). First, 176 patients undergoing thoracoscopic surgery were allocated randomly to four groups: PCV+OLA (45 cases, PCV-VG mode plus OLA involving application of individualized positive end-expiratory pressure (PEEP) after a recruitment maneuver), PCV (44 cases, PCV-VG mode plus standard lung-protective ventilation with fixed PEEP of 5 cmH2O), VCV+OLA (45 cases, volume-controlled ventilation (VCV) plus OLA), and VCV (42 cases, VCV plus standard lung-protective ventilation). Mean airway pressure (
One-lung ventilation (OLV) has been used routinely in thoracic surgery to provide an optimal visual field for a surgical procedure on a collapsed lung. Unfortunately, this approach creates a “shunt-like” effect through the nondependent lung and results in hypoxemia [
Lung-protective ventilation, consisting a tidal volume (
The literature regarding the ideal ventilation mode on pulmonary outcomes for OLV is controversial [
We carried out the study to explore the benefits of PCV-VG mode in combination with an OLA on lung mechanics, oxygenation parameters, and the inflammatory response during thoracic surgery.
The ethics committee of Hebei General Hospital (Hebei, China) approved the study protocol. Each participant (or family member) provided written informed consent. The study was registered with the Chinese Clinical Trial Registry (
The study enrolled patients with ASA physical status I–III scheduled for elective thoracoscopic surgery requiring OLV. Patients were excluded if they met any of the following criteria:
Participants were assigned to one of four lung-protective ventilation strategies using a computer-generated randomization sequence, with an allocation of 1 : 1 : 1 : 1.
After placement of monitors, anesthesia induction and endobronchial intubation were achieved with 0.3 mg/kg etomidate, 0.3
After endobronchial intubation, all patients in the four groups were ventilated with an anesthesia ventilator (Avance CS2 Pro; GE Healthcare, Piscataway, NJ, USA).
Before OLV, all participants were set the same ventilation parameters, consisting of a fraction of inspired oxygen (FiO2) of 1.0,
During OLV, all individuals received a
OLV was initiated after rechecking the correct position of the DLT. The dependent lung had a standard alveoli recruitment maneuver. The ventilation mode was changed from VCV to PCV with a driving pressure of 20 cmH2O and respiratory rate of 15 breaths per minute, PEEP of 5 cmH2O, I : E of 1 : 1, and FiO2 of 1.0. PEEP was increased at a step size of 5 cmH2O, and 10 breaths were maintained at each step (5, 10, 15, and 20 cmH2O) until recruitment of opening pressure up to 40 cmH2O (20 cmH2O PEEP and 20 cmH2O of driving pressure) was applied for 20 breaths.
If the hemodynamics were unstable during the alveoli recruitment maneuver phase (a decrease in mean arterial pressure
After the first alveoli recruitment maneuver had been accomplished, individualized PEEP was titrated through a trial with decreased PEEP. PEEP was reduced in steps of 2 cmH2O with each PEEP level (20, 18, 16, 14, 12, 10, 8, and 6 cmH2O) and held for 15 s until the greatest dynamic compliance (Cdyn) was produced, which was considered to be the individualized or optimal PEEP. Then, a new alveoli recruitment maneuver was carried out as described above (Figure
PCV 20: pressure-controlled ventilation mode with 20 cmH2O; VCV 8: volume-controlled ventilation mode with tidal volume set to 8 mL/kg; VCV or PCV-VG 5-6: volume-controlled ventilation mode or pressure-controlled ventilation-volume guaranteed mode with tidal volume set to 5 to 6 mL/kg.
In the PCV+OLA group, after the second alveoli recruitment maneuver, the ventilation mode was changed to PCV-VG during OLV, and the optimal PEEP was established and maintained throughout the whole study period.
In the VCV+OLA group, patients received the same procedures (alveoli recruitment maneuver and trial of decreased PEEP), the ventilation mode was switched to VCV during OLV, and the optimal PEEP maintained throughout the whole study period.
In the PCV and VCV groups, the same procedure (alveoli recruitment maneuver) was followed except for the PEEP titration. Patients received PCV-VG or VCV plus fixed PEEP (5 cmH2O) during OLV, respectively.
It is worth noting that alveoli recruitment maneuver was performed after OLV without PEEP titration. The ventilation mode was changed to VCV, and the PEEP value of each group was consistent with that during OLV.
Studied variables were collected at three time points: (i) T1: total-lung ventilation 10 min after intubation; (ii) T2: OLV for 45 min; and (iii) T3: total-lung ventilation 10 min after OLV.
The studied endpoints were partial pressure of arterial carbon dioxide (PaCO2), pH,
Parameters were calculated using the following equations:
PA-aDO2 is the alveolar-arterial oxygen difference;
The plasma concentration of neutrophil elastase was measured by enzyme-linked immunosorbent assays at T1 and T3.
Postoperative endpoints in the four groups were recorded: prevalence of pneumonia, atelectasis, and acute respiratory failure; duration of ICU stay; and duration of hospital stay after surgery.
The sample size for our study was determined according to a pilot study, with an
Statistical data were analyzed using SPSS 22.0 (IBM, Armonk, NY, USA). The Shapiro-Wilk test was used for data with a normal distribution. Continuous variables are given as the
Initially, 200 patients were assessed for eligibility, and 176 patients completed the study (Figure
The study flow diagram.
Patients’ characteristics.
PCV+OLA |
PCV |
VCV+OLA |
VCV |
||
---|---|---|---|---|---|
Age (years) | 0.185 | ||||
Sex (F/M) | 19/26 | 22/22 | 22/23 | 20/22 | 0.887 |
Height (cm) | 0.714 | ||||
BMI (kg/m2) | 0.583 | ||||
PBW (kg) | 59.62 ± 8.70 | 0.888 | |||
ASA (I/II/III) | 4/31/10 | 6/26/12 | 5/28/12 | 3/28/11 | 0.731 |
ARISCAT score | |||||
Intermediate/high | 29/16 | 28/16 | 30/15 | 22/20 | 0.527 |
Preoperative haemoglobin (mg/dL) | 133.60 (124.80, 144.40) | 137.55 (119.80, 144.40) | 131.00 (123.95, 140.80) | 138.20 (128.58, 145.88) | 0.583 |
Comorbidity | |||||
Hypertension | 12 (26.7%) | 22 (50.0%) | 14 (31.1%) | 18 (42.9%) | 0.090 |
Diabetes | 2 (4.4%) | 8 (18.2%) | 6 (13.3%) | 4 (9.5%) | 0.214 |
CVD | 10 (22.2%) | 4 (9.1%) | 4 (8.9%) | 6 (14.3%) | 0.215 |
Smoking | |||||
No/current | 38/7 | 33/11 | 32/13 | 32/10 | 0.498 |
Creatinine ( |
67.70 (60.95, 74.95) | 69.25 (59.13, 80.45) | 68.90 (61.70, 75.05) | 69.50 (63.68, 79.43) | 0.714 |
LEF (%) | 65.00 (62.00, 70.00) | 65.00 (61.00, 67.75) | 66.00 (63.00, 68.00) | 65.50 (61.75, 69.00) | 0.720 |
FVC (L) | 0.102 | ||||
FEV1 (%) | 98.00 (89.00, 104.00) | 95.50 (82.95, 105.48) | 96.00 (80.50, 104.50) | 101.00 (89.00, 110.25) | 0.287 |
FEV1/FVC (%) | 0.632 | ||||
Preoperative SaO2 (%) | 97.30 (95.85, 97.80) | 97.10 (96.20, 97.65) | 96.70 (95.95, 97.55) | 97.10 (96.28, 98.00) | 0.795 |
Data are expressed as
Intraoperative characteristics.
PCV+OLA |
PCV |
VCV+OLA |
VCV |
||
---|---|---|---|---|---|
Type of surgery | |||||
Lobectomy | 21 (46.7%) | 24 (54.5%) | 25 (55.6%) | 23 (54.8%) | 0.664 |
Wedge resection | 20 (44.4%) | 13 (29.5%) | 13 (28.9%) | 12 (28.6%) | |
Segmentectomy | 4 (8.9%) | 7 (15.9%) | 7 (15.6%) | 7 (16.7%) | |
Double lumen tube | |||||
Left/right | 39/6 | 42/2 | 43/2 | 39/3 | 0.331 |
Vasoactive drugs | 25 (55.6%) | 23 (52.3%) | 26 (57.8%) | 22 (52.4%) | 0.945 |
Volume of fluids (mL) | 1002.50 (922.50, 1158.54) | 1028.75 (925.52, 1163.00) | 1068.75 (902.63, 1153.65) | 1057.50 (917.71, 1270.94) | 0.685 |
Urine output (mL) | 300.00 (200.00, 500.00) | 275.00 (200.00, 400.00) | 300.00 (200.00, 400.00) | 300.00 (200.00, 500.00) | 0.401 |
Duration of operation (min) | 140.00 (100.00, 193.50) | 147.50 (107.50, 189.50) | 155.00 (107.50, 190.00) | 170.00 (114.25, 220.50) | 0.339 |
Duration of anesthesia (min) | 180.00 (140.00, 237.50) | 195.00 (141.25, 225.00) | 200.00 (145.00, 228.50) | 212.50 (157.50, 262.50) | 0.400 |
Duration of OLV (min) | 120.00 (87.50, 175.00) | 133.00 (96.25, 170.00) | 135.00 (92.50, 175.00) | 160.00 (100.00, 200.00) | 0.352 |
Blood loss (mL) | 40.00 (10.00, 50.00) | 40.00 (10.00, 50.00) | 50.00 (10.00, 50.00) | 50.00 (10.00, 100.00) | 0.489 |
HR | |||||
T1 | 0.548 | ||||
T2 | 0.226 | ||||
T3 | 0.539 | ||||
MAP | |||||
T1 | 0.422 | ||||
T2 | 0.343 | ||||
T3 | 0.138 |
Data are expressed as
Compared with the PCV and VCV groups (both 5.00 cmH2O), the median (IQR) PEEP was higher in the PCV+OLA group (8.00 (8.00, 10.00) cmH2O) and the VCV+OLA group (10.00 (8.00, 12.00) cmH2O) (
At T2, the median (IQR)
Ventilatory parameters, respiratory system mechanics, blood gas, and oxygenation parameters.
PCV+OLA |
PCV |
VCV+OLA |
VCV |
||
---|---|---|---|---|---|
T1 | 432.00 (405.00, 475.00) | 429.50 (404.50, 499.75) | 445.00 (399.50, 502.00) | 449.50 (410.25, 503.25) | 0.841 |
T2 | 0.451 | ||||
T3 | 431.00 (408.00, 500.50) | 442.50 (411.50, 502.00) | 452.00 (405.00, 503.00) | 441.00 (407.00, 507.25) | 0.936 |
PEEP (cmH2O) | |||||
T1 | 5.00 | 5.00 | 5.00 | 5.00 | — |
T2 | 8.00 (8.00, 10.00) |
5.00 | 10.00 (8.00, 12.00) |
5.00 | <0.001 |
T3 | 8.00 (8.00, 10.00) |
5.00 | 10.00 (8.00, 12.00) |
5.00 | <0.001 |
T1 | 0.255 | ||||
T2 | 21.00 (20.00, 22.00)△▲ | 22.00 (19.25, 23.00)△▲ | 24.00 (23.00, 25.00) | 23.00 (21.00, 25.00) | <0.001 |
T3 | <0.001 | ||||
T1 | 10.00 (9.00, 11.00) | 10.00 (9.00, 11.00) | 10.00 (9.00, 11.00) | 10.00 (9.00, 11.00) | 0.245 |
T2 | 13.00 (12.00, 13.00) |
11.00 (10.00, 12.00) | 12.00 (12.00, 14.00) |
11.00 (10.00, 12.00) | <0.001 |
T3 | 12.00 (11.00, 13.00) |
11.00 (10.00, 12.00) | 12.00 (11.00, 13.00) |
10.00 (8.00, 11.00) | <0.001 |
Cdyn (mL/cmH2O) | |||||
T1 | 0.943 | ||||
T2 | 27.00 (24.00, 32.00) |
23.00 (21.00, 25.00) | 27.00 (22.00, 30.00) |
20.00 (18.75, 21.00) | <0.001 |
T3 | 0.001 | ||||
PaCO2 (mmHg) | |||||
T1 | 0.345 | ||||
T2 | 0.485 | ||||
T3 | 43.00 (39.50, 47.00) | 45.00 (41.00, 47.00) | 46.00 (41.00, 48.00) | 44.00 (41.00, 47.25) | 0.455 |
pH | |||||
T1 | 0.402 | ||||
T2 | 7.38 (7.35, 7.40) | 7.38 (7.35, 7.42) | 7.37 (7.39, 7.40) | 7.38 (7.35, 7.41) | 0.633 |
T3 | 0.796 | ||||
T1 | 0.210 | ||||
T2 | 0.003 | ||||
T3 | 0.16 (0.13, 0.21) |
0.20 (0.17, 0.24) | 0.19 (0.14, 0.22) | 0.21 (0.17, 0.24) | <0.001 |
Qs/Qt | |||||
T1 | 0.873 | ||||
T2 | 0.17 (0.16, 0.19) |
0.19 (0.18, 0.20) | 0.18 (0.17, 0.19) | 0.19 (0.17, 0.20) | 0.006 |
T3 | 0.280 | ||||
PaO2/FiO2 ratio | |||||
T1 | 0.875 | ||||
T2 | 173.75 (138.13, 221.87)▲ | 153.13 (109.38, 185.94) | 166.25 (146.25, 200.63)▲ | 134.38 (106.25, 180.63) | 0.002 |
T3 | 0.264 |
Data are expressed as
At T2, the median (IQR) Qs/Qt in the PCV+OLA group (0.17 (0.16, 0.19)) was significantly lower than that in the PCV group (0.19 (0.18, 0.20)) and the VCV group (0.19 (0.17, 0.20)) (
There was no significant difference in the plasma neutrophil elastase level among the four groups at T1 (
The plasma concentration of neutrophil elastase. Data are expressed as
The duration of ICU stay in the PCV+OLA group was shorter compared with that in PCV, VCV+OLA, and VCV groups (median (IQR) 32.00 (25.00, 37.00), 39.75 (32.88, 43.00), 39.50 (27.00, 43.50), and 39.60 (24.88, 43.70) h, resp.) (
Other clinical endpoints.
PCV+OLA |
PCV |
VCV+OLA |
VCV |
||
---|---|---|---|---|---|
Pneumonia | 2 (4.4%) | 5 (11.4%) | 4 (8.9%) | 7 (16.7%) | 0.312 |
Atelectasis | 1 (2.2%) | 4 (9.1%) | 2 (4.4%) | 6 (14.3%) | 0.148 |
Acute respiratory failure | 0 (0%) | 1 (2.3%) | 1 (2.2%) | 4 (9.5%) | 0.096 |
The duration of ICU stay (hours) | 32.00 (25.00, 37.00) |
39.75 (32.88, 43.00) | 39.50 (27.00, 43.50) | 39.60 (24.88, 43.70) | <0.001 |
The duration of hospital stay after surgery (days) | 6.00 (5.00, 7.00) | 6.00 (5.00, 8.00) | 6.00 (5.00, 8.00) | 6.00 (4.75, 7.00) | 0.204 |
Data are expressed as median (interquartile range) or numbers. ICU: intensive care unit.
The randomized controlled trial revealed that the ventilation strategy of PCV-VG plus OLA during OLV leads to preferable levels of Cdyn, PaO2/FiO2 ratio, and appropriate levels of
Patients undergoing OLV are susceptible to hypoxemia due to shunting of blood or imbalance of ventilation and pulmonary perfusion. And the practice of OLV is an independent hazard factor for postoperative pulmonary complications (PPCs), as a result of direct surgical trauma of the nonventilated lung, exposed to high strain and nonphysiologic
Usually, the lung-protective ventilation strategy, which has taken low
The results of the present study are consistent with our expectation that using an OLA with individualized PEEP under PCV-VG mode can improve pulmonary gas exchange and lung mechanics as well as hemodynamic stability during OLV. Nevertheless, it is useful to note that during OLV, routinely measured airway pressure does not reflect the bronchial pressure, and the decrease in
The higher PaO2/FiO2 ratio and lower
The release of pulmonary inflammatory mediators and their cascade reaction during OLV are the major mechanisms resulting in acute lung injury [
Unfortunately, except for the shortening of the duration of ICU stay, the prevalence of other postoperative endpoints did not decrease. Whether the strategy of PCV-VG plus OLA can impact upon postoperative duration of hospital stay, total duration of hospital stay, or the incidence of PPCs requires further study at multiple centers.
Our study had two main limitations. First, our study was not blinded, so biases are inevitable. Second, we only observed changes in heart rate and MAP. We intend to determine the effect of PCV-VG plus OLA during OLV on hemodynamic variables by measuring central venous pressure and cardiac output.
The ventilation strategy of PCV-VG combined with open-lung approach during OLV was associated with favorable effects upon intraoperative respiratory mechanics, oxygenation parameters, and the inflammatory reaction. This ventilation strategy may be a feasible alternative ventilation method in patients undergoing thoracic surgery.
The clinical data used to support the findings of this study are available from the corresponding author upon reasonable request.
No conflict of interest has to be disclosed.
Jianli Li, MD, and Baogui Cai designed the study, conducted the study, analyzed the data, and approved the final manuscript. Dongdong Yu and Meinv Liu designed the study and wrote the manuscript. Xiaoqian Wu conducted the study. Junfang Rong, MD, analyzed data and wrote and edited the manuscript. Jianli Li and Baogui Cai contributed equally to this work and should be considered co-first authors.
The authors wish to thank all staff members in the Department of Anesthesiology, Hebei General Hospital, for their help in the study. The study was supported by the Key Research and Development Program of Hebei Province (19277714D).