Lung ultrasound score evaluation of the effect of pressure-controlled ventilation volume-guaranteed on patients undergoing laparoscopic-assisted radical gastrectomy

Abstract

BACKGROUND

Laparoscopic-assisted radical gastrectomy (LARG) is the standard treatment for early-stage gastric carcinoma (GC). However, the negative impact of this procedure on respiratory function requires the optimized intraoperative management of patients in terms of ventilation.

AIM

To investigate the influence of pressure-controlled ventilation volume-guaranteed (PCV-VG) and volume-controlled ventilation (VCV) on blood gas analysis and pulmonary ventilation in patients undergoing LARG for GC based on the lung ultrasound score (LUS).

METHODS

The study included 103 patients with GC undergoing LARG from May 2020 to May 2023, with 52 cases undergoing PCV-VG (research group) and 51 cases undergoing VCV (control group). LUS were recorded at the time of entering the operating room (T0), 20 minutes after anesthesia with endotracheal intubation (T1), 30 minutes after artificial pneumoperitoneum (PP) establishment (T2), and 15 minutes after endotracheal tube removal (T5). For blood gas analysis, arterial partial pressure of oxygen (PaO₂) and partial pressure of carbon dioxide (PaCO₂) were observed. Peak airway pressure (P_peak), plateau pressure (P_plat), mean airway pressure (P_mean), and dynamic pulmonary compliance (C_dyn) were recorded at T1 and T2, 1 hour after PP establishment (T3), and at the end of the operation (T4). Postoperative pulmonary complications (PPCs) were recorded. Pre- and postoperative serum interleukin (IL)-1β, IL-6, and tumor necrosis factor-α (TNF-α) were measured by enzyme-linked immunosorbent assay.

RESULTS

Compared with those at T0, the whole, anterior, lateral, posterior, upper, lower, left, and right lung LUS of the research group were significantly reduced at T1, T2, and T5; in the control group, the LUS of the whole and partial lung regions (posterior, lower, and right lung) decreased significantly at T2, while at T5, the LUS of the whole and some regions (lateral, lower, and left lung) increased significantly. In comparison with the control group, the whole and regional LUS of the research group were reduced at T1, T2, and T5, with an increase in PaO₂, decrease in PaCO₂, reduction in P_peak at T1 to T4, increase in P_mean and C_dyn, and decrease in P_plat at T4, all significant. The research group showed a significantly lower incidence of PPCs than the control group within 3 days postoperatively. Postoperative IL-1β, IL-6, and TNF-α significantly increased in both groups, with even higher levels in the control group.

CONCLUSION

LUS can indicate intraoperative non-uniformity and postural changes in pulmonary ventilation under PCV-VG and VCV. Under the lung protective ventilation strategy, the PCV-VG mode more significantly improved intraoperative lung ventilation in patients undergoing LARG for GC and reduced lung injury-related cytokine production, thereby alleviating lung injury.

Key Words: Lung ultrasound score, Pressure-controlled ventilation volume-guaranteed, Laparoscopic-assisted radical gastrectomy, Blood gas analysis indexes, Pulmonary ventilation

Core Tip: This study mainly analyzed the effects of pressure-controlled ventilation volume-guaranteed (PCV-VG) and volume-controlled ventilation (VCV) on blood gas analysis and pulmonary ventilation in patients with gastric carcinoma (GC) undergoing laparoscopic-assisted radical gastrectomy (LARG) based on the lung ultrasound score (LUS). We performed validation analyses by evaluating the peak airway pressure (P_peak), plateau pressure (P_plat), mean airway pressure (P_mean), dynamic pulmonary compliance (C_dyn), occurrence of postoperative pulmonary complications (PPCs), and levels of serum interleukin (IL)-1β, IL-6, and tumor necrosis factor-α before and after surgery. We confirmed that LUS can indicate non-uniformity and postural changes in lung ventilation under the two ventilation modes. However, PCV-VG is superior to VCV in significantly alleviating lung injury and inflammatory responses in patients undergoing LARG for GC, improving lung ventilation, and exerting a protective effect against PPCs. Thus, PCV-VG is a practical ventilation option in clinical practice.

INTRODUCTION

Gastric carcinoma (GC) is the third leading cause of death from tumors worldwide and the fifth most prevalent malignancy. It often occurs in the elderly and is characterized by a progressive decline in physical function[1,2]. Risk factors include dietary factors, such as high salt, oil, and sugar intake; unhealthy lifestyle habits like smoking and alcohol consumption; and Helicobacter pylori infection, all of which contribute to an increased risk of developing GC[3]. Over 1 million new GC cases are diagnosed every year and nearly 800000 deaths, with a 5-year survival of 36.3%[4]. This is because of the low cure rate and high treatment difficulty due to the nonspecific manifestations in early GC cases the loss of the best time for surgery in advanced ones[5]. Laparoscopic-assisted radical gastrectomy (LARG), the standard treatment for early-stage GC, is advantageous over conventional open gastrectomy in minimal invasiveness, good visualization, lesser intraoperative bleeding, and faster postoperative recovery[6,7]. However, anesthesia, mechanical synchronization, and other factors involved in the procedure may induce various negative effects on the patient’s respiratory function and cause adverse events, such as abnormal blood gas analysis indexes, uneven pulmonary ventilation, and postoperative pulmonary complications (PPCs)[8,9].

Therefore, the optimized management of LARG would be highly beneficial to avoid such adverse events and improve the efficacy and safety of patients. This paper evaluated the influence of pressure-controlled ventilation volume-guaranteed (PCV-VG) on blood gas analysis indexes and pulmonary ventilation in patients undergoing LARG for GC and compared it with volume-controlled ventilation (VCV) as the control. A comparative evaluation was also conducted based on the lung ultrasound score (LUS), which has not been analyzed by other investigators[10]. VCV is a ventilation mode that applies a uniform flow rate, which may increase the peak airway pressure (P_peak) in the alveoli, leading to lung loss in patients[11]. In contrast, as a more advanced dual-control ventilation mode, PCV-VG delivers pressure-controlled gas, with the pressure control level automatically adjusted according to factors, such as the patient’s lung resistance and compliance, resulting in a lower P_peak and higher dynamic pulmonary compliance (C_dyn). These features may help prevent lung pressure-related losses[12,13]. The LUS is a non-invasive and radiation-free lung scoring standard used to evaluate pulmonary ventilation[14]. This study evaluated the clinical effect of PCV-VG in LARG based on the LUS and is hereby reported in detail.

MATERIALS AND METHODS

Patients and general data

The participants were 103 patients undergoing LARG for GC at the Lishui District People’s Hospital from May 2020 to May 2023. The research group (n = 52) underwent PCV-VG, whereas the control group (n = 51) underwent VCV.

Criteria for patient enrollment and exclusion

The inclusion criteria were as follows: Patients that presented GC symptoms and met the diagnostic criteria for GC; no extensive infiltration of surrounding tissues and organs or distant metastasis; underwent LARG under general anesthesia; and complete case records.

The exclusion criteria were the following: Severe dysfunction of the heart, lung, kidneys, etc.; psychological illness or mental disturbance; pulmonary bullae, asthma, or moderate to severe ventilation dysfunction; and neuromuscular diseases, lung surgery history, or preoperative anemia (hemoglobin ≤ 70 g/L).

Anesthesia methods

All patients were conventionally monitored for blood pressure, electrocardiography, and SpO₂ after entering the operating room. A radial artery puncture needle was inserted under local anesthesia with 1 mL of 2% lidocaine for invasive mean arterial pressure (MAP) monitoring. The anesthesia induction scheme consisted of midazolam (0.02 mg/kg), sufentanil (0.5 μg/kg), etomidate (0.2 mg/kg), and rocuronium bromide (0.6 mg/kg). Catheterization was performed in the right internal jugular deep vein. After establishing an artificial pneumoperitoneum (PP), the patient was placed in a dorsal elevated position at 30°. Sevoflurane (1%–2%), remifentanil (0.1–0.3 μg/kg/min), dexmedetomidine (0.2 μg/kg/h), and rocuronium bromide (5–6 μg/kg/min) were used for anesthesia maintenance, with the dosage adjusted depending on the anesthesia depth. The bispectral index was maintained at 40–60. The intraoperative fluctuation amplitude of MAP was controlled to not exceed 20% of the base value. If the MAP decreased > 20% of the base value after rehydration therapy, norepinephrine was given at 0.01–0.5 μg/kg/min. The patient was placed in a supine position following artificial PP. The withdrawal time of rocuronium bromide and dexmedetomidine was 40 min or so before the end of the procedure; sevoflurane was discontinued approximately 10 min before the surgery was completed, and remifentanil was withdrawn immediately postoperatively. After the patient regained consciousness and reached the indication for extubation, the tracheal catheter was removed, and a postoperative intravenous analgesia pump was used for pain relief. Subsequently, the patient was transferred to the post-anesthesia care unit.

Ventilation parameter setting

After endotracheal intubation, the patients in the research and control groups were placed under PCV-VG and VCV, respectively. Protective ventilation strategies were adopted in both groups: inhaled oxygen concentration: 60%; fresh gas velocity: 1.5 L/min; tidal volume: 8 mL/kg; respiratory rate (RR): 12 breaths/min; inspiratory/expiratory: 1:2; PETCO₂ (adjusted by respiratory rate): 30–35 mmHg; and pressure: 35 cmH₂O.

Detection indicators

A portable ultrasound machine was used to record the LUS of patients at the time of entering the operating room (T0), 20 min after anesthesia with endotracheal intubation (T1), 30 min after establishing artificial PP (T2), and 15 min after endotracheal tube removal (T5). The LUS was divided into 12 pulmonary zones: the chest wall was divided into anterior, lateral, and posterior sides based on the anterior and posterior axillary lines. Each part was then divided into upper and lower sections to make up 12 evaluable lung regions. The possible total score of the 12 Lung regions was 0–36 points, with a higher score indicating greater lung ventilation injury.

Arterial blood was collected at T0, T1, T2, and T5, and blood gas analysis was performed to record the arterial partial pressure of oxygen (PaO₂) and partial pressure of carbon dioxide (PaCO₂).

The P_peak, platform pressure (P_plat), mean airway pressure (P_mean), and C_dyn were monitored and recorded at T1, T2, T3 (1 h after PP establishment), and T4 (at the end of surgery).

For PPCs, incidence of adverse events, such as pneumonia, hypoxemia, bronchospasm, atelectasis, and pneumothorax, were recorded and the total incidence calculated.

Venous blood (3 mL) was drawn on an empty stomach pre- and postoperatively and centrifuged to obtain serum for measuring interleukin (IL)-1β, IL-6, and tumor necrosis factor-α (TNF-α) levels by enzyme-linked immunosorbent assay.

Statistical analyses

Continuous variables (e.g., age, body mass index, PP duration, LUS, PaO₂, and PaCO₂) were expressed mean ± SE. To identify statistical significance (threshold: P < 0.05), the independent sample t-test was performed for inter-group comparisons of continuous variables and paired t test for intra-group comparisons before and after treatment. Categorical variables [sex, America Society of Anesthesiologist (ASA) grade, etc.) were expressed as rate (percentage) and compared between groups using the χ² test. The collected experimental data were analyzed using SPSS20.0.

RESULTS

Comparison of general data

The two patient cohorts were similar in sex, age, body mass index, PP duration, ASA grade, and other general data (P > 0.05; Table 1).

Table 1 Comparison of general patient characteristics.

Indicators	Control group (n = 51)	Research group (n = 52)	χ2/t	P value
Sex (male/female)	25/26	24/28	0.085	0.771
Age (years)	58.78 ± 8.01	61.13 ± 7.40	1.547	0.125
Body mass index (kg/m2)	21.49 ± 2.40	22.12 ± 3.01	1.173	0.244
Duration of pneumoperitoneum (minutes)	66.25 ± 12.89	64.63 ± 13.6	0.620	0.537
ASA grade (II/III)	28/23	25/27	0.480	0.488

ASA: America Society of Anesthesiologists.

Comparison of LUS

We compared the LUS of the different lung regions between the two patient groups. Compared with those at T0, the whole, anterior, lateral, posterior, upper, lower, left, and right lung LUS of the research group were significantly lower at T1, T2, and T5 (P < 0.05). In the control group, the whole, posterior, and lower lung region LUS decreased significantly at T2 (P < 0.05), whereas the whole, upper, lower, left, and right lung LUS increased at T5 (P < 0.05). At T0, the two groups exhibited marked differences in anterior, lateral, posterior, upper, lower, left, and right lung region LUS (P < 0.05). At T1, T2, and T5, the research group had significantly lower LUS for the whole lung and all lung regions than the control group (P < 0.05; Figure 1).

Figure 1 Comparison of lung ultrasound scores. A-H: Changes in lung ultrasound scores of the (A) whole, (B) anterior, (C) lateral, (D) posterior, (E) upper, (F) lower, (G) left, and (H) right lung regions across time points. ^aP < 0.05 and ^bP < 0.01, compared with T0; ^cP < 0.05, vs control group.

Comparison of PaO₂ and PaCO₂

The blood gas analysis indexes at each time point were comparatively analyzed. The two groups showed similar PaO₂ and PaCO₂ at T0 (P > 0.05) and a significant increase in the two indexes at T1 and T2 (P < 0.05). PaO₂ and PaCO₂ were significantly lower at T5 but did not differ significantly with T0 Levels (P > 0.05). PaO₂ and PaCO₂ at T1 and T2 were higher in the research group than in the control group (P < 0.05). PaCO₂ initially decreased in both groups at T1, increased significantly at T2 (P < 0.05), and decreased significantly at T5 to a level that was still higher than that at T0 (P < 0.05). Significant inter-group differences was also observed in PaCO₂ at T1 and T5 (P < 0.05) (Figure 2).

Figure 2 Comparison of (arterial partial pressure of oxygen) PaO₂ and (partial pressure of carbon dioxide) PaCO₂. A and B: Changes in (A) PaO₂ and (B) PaCO₂ at various time points. ^aP < 0.05 and ^bP < 0.01, compared with T0; ^cP < 0.05 vs control group.

Comparisons on the P_peak, P_plat, P_mean, and C_dyn

The two groups differed significantly in the P_peak and C_dyn at T1 (P < 0.05). P_peak and P_plat increased significantly in both groups at T2 and T3 compared at T1, while at T4, these two indicators in reduced significantly to levels that did not differ significantly from those at T1 (P > 0.05). The research group had lower P_peak at T2, T3, and T4 and P_plat at T4 than the control group (P < 0.05). Compared with T1, the P_mean and C_dyn in both groups decreased significantly at T2 and T3. At T4, the P_mean of both groups increased to levels comparable with those at T1 (P > 0.05). The C_dyn of both groups also rose significantly but remained significantly lower than that at T1 (P < 0.05). The research group showed higher P_mean at T2 and T4 and higher C_dyn at T2, T3, and T4 compared with the control group (P < 0.05; Figure 3).

Figure 3 Comparisons of peak airway pressure (P_peak), plateau pressure (P_plat), mean airway pressure (P_mean), and dynamic pulmonary compliance (C_dyn). A-D: Changes in (A) P_peak, (B) P_plat, (C) P_mean, and (D) C_dyn across time points. ^aP < 0.05 and ^bP < 0.01, compared with T1; ^cP < 0.05 vs control group.

Comparison of PPCs

The most common PPCs in the research group was hypoxemia, followed by atelectasis, bronchospasm, and pneumothorax. The most common PPC in the control group patients was hypoxemia, followed by atelectasis, pneumonia, and bronchospasm and pneumothorax. The incidence of PPCs was markedly lower in the research group than in the control group (P < 0.05; Table 2).

Table 2 Comparison of postoperative pulmonary complications, n (%).

Indicators	Control group (n = 51)	Research group (n = 52)	χ2	P value
Pneumonia	3 (5.88)	0 (0.00)
Hypoxemia	7 (13.73)	4 (7.69)
Bronchospasm	2 (3.92)	2 (3.85)
Atelectasis	5 (9.80)	3 (5.77)
Pneumothorax	2 (3.92)	1 (1.92)
Total	19 (37.25)	10 (19.23)	4.135	0.042

Comparisons of IL-1β, IL-6, and TNF-α

Preoperative IL-1β, IL-6, and TNF-α did not differ significantly between the groups (P > 0.05). However, all of them increased significantly in both patient cohorts postoperatively (P < 0.05), with a more significant increase in the control group (P < 0.05; Figure 4).

Figure 4 Comparison of interleukin-1β, interleukin-6 and tumor necrosis factor-α. A-C: Pre- and post-treatment (A) IL-1β, (B) IL-6, and (C) TNF-α levels. ^aP < 0.05 and ^bP < 0.01, compared with T1; ^cP < 0.05 vs control group.

DISCUSSION

Although the treatment of GC has been continuously optimized and the incidence rate reduced, LARG remains the best choice for the treatment of non-metastatic GC[15]. The advantages of LARG have been established, but this procedure still carries a risk of postoperative adverse events[16]; thus, further optimization of the management of this procedure is required.

The whole, anterior, lateral, posterior, upper, lower, left, and right lung LUS decreased significantly in the research group at T1, T2, and T5, whereas the control group only showed significantly lower whole, posterior, and lower lung LUS at T2. Moreover, the research group had evidently lower LUS of the whole lung and all regional lung regions than the control group at T1, T2, and T5. These data indicate that, compared with VCV, PCV-VG can achieve uniform ventilation by expanding trapped and unventilated alveoli, thereby more effectively reducing lung ventilation damage. The LUS results in the control group indicate optimal functional residual capacity due to the patient’s dorsal elevated position after VCV intervention and artificial PP establishment, in addition to the minimal pulmonary vascular resistance at this time, which ultimately resulted in more blood flow in the lower lung and the basolateral region, thereby improving the lung ventilation and the ventilation/blood flow ratio in these regions[17,18]. The lower and left lung LUS were the highest in the control group at T5, indicating that the LUS can indicate overall and regional ventilation changes perioperatively under both ventilation modes. PCV-VG, a ventilation modality optimized based on PCV and VCV, prevents ventilation–perfusion mismatches by ensuring a more uniform ventilation distribution and preventing peak inspiratory pressure from rising. This is primarily achieved by automatically changing ventilation parameters to allow the patient to inhale the target tidal volume at each forced breath on the premise of not increasing airway pressure[19,20]. Although VCV can guarantee a patient’s target minute ventilation, patients are particularly susceptible to factors, such as barotrauma and changes in lung gas distribution, because of causes such as compliance or resistance[21].

Blood gas analysis revealed that the research group had significantly higher levels of PaO₂ at T1 and T2 and significantly lower levels of PaCO₂ at T1 and T5, indicating that PCV-VG intervention in patients undergoing LARG can significantly optimize lung ventilation function, similar to the results reported by Toker et al[22]. Furthermore, the P_peak and P_plat in the research group were significantly lower than those in the control, whereas P_mean and C_dyn were significantly higher. This indicates that PCV-VG is more effective in protecting lung function under long-term mechanical ventilation in patients undergoing LARG, thereby more efficiently optimizing lung respiratory mechanics and improving the ventilation/blood flow ratio. Higher P_peak and lower C_dyn have been linked to serious imbalances in the ventilation/blood flow ratio associated with alveolar overdistension and increased pulmonary vascular resistance[23]. Turan Civraz et al[24] reported that PCV-VG implemented in patients undergoing laparoscopic abdominal surgery is significantly advantageous over VCV in providing optimal ventilation pressure and maintaining high dynamic compliance, similar to our findings. Hypoxemia and atelectasis were the most common PPCs in the two groups, with a notably lower incidence in the research group than in the control group. Postoperatively IL-1β, IL-6, and TNF-α were significantly increased in the research group but still considerably lower than those in the control group, indicating that PCV-VG intervention can significantly inhibit postoperative inflammatory responses in patients undergoing LARG. IL-1β is closely related to mechanical ventilation-associated inflammatory cascades, whereas IL-6 is significantly associated with the injuries of the alveolar epithelium and extracellular matrix and ventilation-related lung tissue loss. Likewise, TNF-α is strongly correlated with early inflammatory reaction related to mechanical ventilation[25,26].

This study has several limitations. First, the study was conducted at a single center, which may limit the generalizability of the results. Second, the retrospective study design may introduce selection bias and confounding variables. Third, the factors influencing the occurrence of PPCs in patients was not performed. Future studies need to address these three aspects to generate more robust results.

CONCLUSION

This study demonstrated that LUS can indicate non-uniformity and postural changes in lung ventilation under the two ventilation modes. Compared with VCV, PCV-VG intervention more significantly alleviated lung injury, improved lung ventilation, and reduced inflammation in patients undergoing LARG for GC, while exerting protective activity against PPCs, making it the more practical ventilation option in clinical practice.