The Effects of Individualized Lung-protective Ventilation With Lung Dynamic Compliance-guided Positive End-expiratory Pressure(PEEP) Titration on Postoperative Pulmonary Complications of Pediatric Video-assisted Thoracoscopic Surgery

This study evaluates the influence of individualized lung-protective ventilation strategy(LPVS) on postoperative pulmonary complications(PPCs) through a randomized controlled trial when children undergoing thoracoscopic surgery with one-lung ventilation(OLV).The investigators evaluate the impact of using lung dynamic compliance-guided Positive End-expiratory Pressure(PEEP) versus conventional PEEP on a pressure-controlled ventilation(PCV).The researchers also analyzed perioperative vital signs and respiratory indicators of these LPVS.

With the advancement of pediatric thoracic surgery techniques, the age group of children who can receive thoracoscopic surgery is getting younger and younger, and even neonates can accept it. In thoracic surgery, the incidence of PPCs is as high as 30%-50%, which is one of the main reasons for poor prognosis, increased mortality and prolonged hospitalization. In recent years, more and more studies have shown that the perioperative implementation of appropriate LPVS can reduce the occurrence of PPCs. How to optimize the lung protection strategy in pediatric thoracic surgery has become one of the key issues of perioperative medical attention, and there is no consensus in clinical application.

LPVS is one of the important components of lung protection strategies, including low tidal volume, PEEP and lung recruitment strategies.How to choose the most suitable PEEP is an important part in the implementation of LPVS. The optimal PEEP value should be the corresponding pressure value when the compliance between alveolar opening and over-inflation is the best. In recent years, many scholars have studied PEEP titration methods, such as lung dynamic compliance-guided PEEP, pressure-volume (P-V) curve-guided PEEP, transpulmonary pressure-guided PEEP, and electrical impedance tomography (EIT)-guided PEEP and so on.However, there are no published studies addressing the effects of lung dynamic compliance-guided PEEP on PPCs and perioperative vital signs and respiratory indicators of pediatric surgical patients when associated with OLA strategies for ventilation.

This study is a randomized controlled trial. After meeting the inclusion conditions, the researchers were assigned to any of the two groups of lung dynamic compliance-guided individualized PEEP and conventional PEEP. The clinical anesthesia and mechanical ventilation parameter settings and data statistical analysis were completed by different anesthesiologists and participants.

On the day of surgery, standard monitoring was initiated on arrival in the theatre, including electrocardiography, pulse oximetry, and noninvasive blood pressure monitoring.Both groups were given routine standard anesthesia induction: intravenous injection of midazolam at 0.05-0.1 mg/kg of predicted body weight (PBW), propofol at 2-4 mg/kg of PBW, and intravenous injection of Sufentanil at 0.3-0.5 ug/kg of PBW, rocuronium at 0.5-1mg/kg of PBW.After adequate pre-oxygenation, endotracheal intubation and bronchial occluder placement under video laryngoscope, using fiberoptic bronchoscopy and auscultation make sure the occluder is properly positioned. The investigators will adjust breathing parameters after starting double-lung ventilation,which is a pressure control mode(PCV) using an airway pressure of 20-25mmHg with tidal volume not exceeding 6ml/kg of PBW and an inspiration: expiration ratio of 1:2;a respiratory rate of 20-40 breaths per minute to keep PaCO2 \< 60 mmHg as well as FiO2 of 50% and flow of 3L/min.Then, the first lung recruitment strategy was started. The manual lung recruitment method was used, and the ventilation mode was manually controlled. The APL valve was adjusted to 30cmH2O, maintained for 15-20 seconds, and then returned to the machine-controlled ventilation mode. Arterial puncture and catheterization were performed to establish an invasive arterial monitoring channel. Intraoperative maintenance medication: 2%-3% sevoflurane, dexmedetomidine (0.1-0.2ug/kg.h of PBW), sufentanil and rocuronium bromide were added in stages according to intraoperative conditions to maintain sufficient doses above sedative analgesia and muscle relaxation.

Before starting OLV, pure oxygen hyperventilation was used, FiO2 was adjusted to 100%, and the maintenance time was not less than 3 minutes to increase the oxygen concentration in both lungs and improve the tolerance of children to hypoxia and the success rate of lung collapse. After switching to OLV, a second manual recruitment strategy was performed. The PEEP settings were divided into two groups: the canventional lung protective ventilation experimental group held PEEP at 5 cmH2O, the pulmonary dynamic compliance guided PEEP group passed increasing PEEP (0-14 cmH2O), and the lung dynamic compliance = Vt/(Pplat-PEEP).The initial PEEP is set to 0cmH2O, which is increased by 2 cmH2O every 2 minutes. Observe the PEEP value corresponding to the maximum lung dynamic compliance during the process. After the incremental PEEP process is completed, setting the PEEP value for ventilation until the end of the operation.

At the end of one-lung ventilation, a third manual recruitment maneuver was performed before switching to double-lung ventilation. After the operation, the patients were sent to the ICU with a tracheal catheters or sent to the PACU before extubation according to the condition of the child.

All data were collected, aggregated and maintained by a single investigator. Including preoperative demographic data, ARISCAT score data, surgery-related data, anesthesia-related data, intraoperative general vital signs and respiratory indicators, postoperative PPCs-related data, postoperative medication, other postoperative complications, hospital stay, ICU Hospitalization time, respiratory support time, hospitalization time, biochemical indicators during hospitalization, inflammatory indicators, electrolytes, cardiac function indicators, etc.

This study was a superiority test, so a one-sided test was used, and the first-class error (α) was set to 0.05, and the second-class error (β) was set to 0.2 (that is, the power of 1-β was set to 0.8). The main observation index of this study is the incidence of PPCs. According to the literature review, the incidence of PPCs in the two groups in similar studies was 11% and 39%, respectively. In PASS 15.0, "Test for Two Proportions" was selected for calculation. The dropout rate is set to 10%, and the calculation result is that each group needs 30 patients.It would be necessary to recruit 60 patients in the study.

The full analysis set was used for analysis. According to the basic principle of Intention-to-Treat (ITT), the analysis of the main indicators includes all randomized subjects, regardless of whether they completed the trial or not, that is, subjects who were lost to follow-up should also be included in the statistical analysis. Statistical software SPSS 26.0 was used for data processing and statistical analysis. Shapiro-Wilk test was first performed on the data, and continuous variable data (such as blood pressure, heart rate, driving pressure, oxygenation index, etc.) were determined to use t test or Mann-Whitney U test according to their normal distribution. Categorical variables (such as age, incidence of PPCs, etc.) were tested by χ² test, Fisher's exact test, and the results were expressed as mean ± standard deviation (SD), percentage (%) or median (interquartile range, IQR), P \<0.05 is statistically significant.

Eligibility Criteria:
Inclusion Criteria:

* Children undergoing elective thoracoscopic pulmonary surgery.
* Written informed consent.
* Children under 5 years old (including 5 years old)
* ASA classification 1-2
* Respiratory Risk Assessment in Catalan Surgical Patients (ARISCAT) Criteria Low or Moderate Risk

Exclusion Criteria:

* Symptoms of upper respiratory tract infection or pulmonary infection in the past 4 weeks, chest X-ray suggests pneumonia
* Severe circulatory disease
* Children with bullae
* Intraoperative arterial blood pressure monitoring cannot be performed
* Respiratory Risk Assessment in Catalan Surgical Patients (ARISCAT) Criteria Rated High Risk