Evaluation of Factors Affecting Changes in Endotracheal Cuff Pressures During Laparoscopic Bariatric Surgery

Introduction

Obesity is a prevalent health condition both in developing and developed countries. Today, laparoscopic bariatric surgery is considered an effective method for weight loss and is generally associated with low morbidity and mortality rates [1]. Administering general anesthesia in patients with morbid obesity presents significant challenges. Airway management, positioning, ventilation strategies, and maintaining hemodynamic stability in patients with morbid obesity require careful attention. Furthermore, increased intra-abdominal pressure and prolonged operative time can lead to fluctuations in endotracheal tube (ETT) cuff pressure. Monitoring ETT cuff pressure is essential in these patients [2].

Laparoscopic surgery is performed under general anesthesia with mechanical ventilation, typically using a high-volume, low-pressure ETT with a cuff pressure of approximately 20 to 30 cmH2O to ensure adequate sealing while preventing overinflation [3,4]. Abdominal insufflation significantly increases respiratory system resistance, which returns to baseline immediately after abdominal deflation [5]. However, the increase in endotracheal cuff pressure due to pneumoperitoneum can elevate the risk of postoperative complications such as cough, sore throat, hoarseness, and hemoptysis [5,6]. Although the precise pathophysiology of airway symptoms following intubation remains unclear, mucosal injury at the cuff level is believed to contribute to tracheal morbidity [4].

Laparoscopic surgery induces several critical respiratory system changes. Carbon dioxide (CO2) insufflation into the abdomen elevates intrathoracic pressure [7,8].

ETT cuff pressure monitoring is critical for maintaining airway integrity, preventing aspiration, and minimizing tracheal injury in mechanically ventilated patients. Indications include prolonged intubation, airway security in intensive care unit monitoring, and mechanical ventilation applications. Cuff pressure exceeding 30 cmH2O can compromise tracheal mucosal perfusion, leading to complications such as postoperative sore throat, tracheal ulceration, tracheomalacia, and, rarely, subglottic stenosis [9]. Intraoperative variables such as pneumoperitoneum and patient positioning, especially in laparoscopic procedures, can cause significant fluctuations in cuff pressure [10]. According to literature reports, postoperative sore throat develops in 40% to 65% of patients after bariatric surgery, and this is often associated with inappropriate cuff pressure [11]. However, failure to continuously monitor cuff pressure intraoperatively can predispose to the long-term effects of silent tracheal injuries [2].

Several factors influence ETT cuff pressure during general anesthesia, including nitrous oxide use, head and neck position changes, pneumoperitoneum, and the Trendelenburg position [5,6,12]. For these reasons, regular and objective monitoring of endotracheal cuff pressure in bariatric surgery has become a fundamental practice that should be standardized for patient safety. Therefore, in this study, we aimed to evaluate how ETT cuff pressure changes according to surgical stages and mean airway pressure in patients with obesity undergoing laparoscopic bariatric surgery.

Material and Methods

ETHICS STATEMENT:

The research adhered to the STROBE guidelines. This study was designed as a prospective, observational, and controlled study and began after obtaining ethics approval from the Gazi Yaşargil Training and Research Hospital Ethics Committee, decision number 260, dated December 22, 2024. The trial was registered at https://clinicaltrials.gov/study/NCT06427928 (principal investigator: Hulya Tosun Söner; https://clinicaltrials.gov/study/NCT06427928; date of registration: May 22, 2024) before the first patient was enrolled. All patients participating in the study received verbal information and signed an informed consent form. The study was planned in accordance with the guidelines outlined in the 2013 Declaration of Helsinki. As this was a prospective observational study, no randomization or blinding was performed. All measurements were conducted according to a standardized protocol to minimize measurement bias and ensure consistency across participants.

MEASUREMENT OF CUFF PRESSURE:

ETT cuff pressures were measured with a manual manometer that was recalibrated after each use. Airway pressures were recorded using the anesthesia device. Intra-abdominal pressures were obtained by measuring the pressure at 4 different times using the laparoscopic insufflation device. All measurements were performed by the same experienced anesthesiologist to ensure consistency and avoid bias

PATIENT SELECTION:

Patients aged 18 to 70 years scheduled for laparoscopic bariatric surgery and classified as ASA I–III were included in the study. Exclusion criteria were patient refusal to participate, an ASA classification of IV or higher, and the presence of asthma or chronic pulmonary disease.

Participants were recruited for the study using a consecutive sampling method. All eligible patients who underwent laparoscopic bariatric surgery during the study period and met the inclusion criteria were included in the study without randomization. ETT cuff pressures, airway pressures, respiratory rates, intra-abdominal pressures, and the degree of surgical table tilt were recorded. Additionally, patient demographics, including age, weight, height, and body mass index (BMI), along with surgical and anesthesia durations, were documented. No validated questionnaires or subjective assessment tools were used in our study. All data were collected directly and objectively using calibrated clinical instruments. An increase in ETT cuff pressure beyond 30 cmH2O from baseline was considered clinically significant [4].

For descriptive analysis, the study was divided into 4 phases: (1) pre-abdominal insufflation: from tracheal intubation to the initiation of intraperitoneal insufflation; (2) abdominal insufflation: from the start of intraperitoneal insufflation to the adjustment of surgical table positioning; (3) surgical table positioning: from table adjustment until peritoneal exsufflation; and (4) peritoneal exsufflation: from the release of pneumoperitoneum to tracheal extubation.

ROUTINE PREOPERATIVE AND INTRAOPERATIVE ANESTHESIA PROCEDURES:

For premedication, 0.02 mg/kg intravenous midazolam (Dilemy 5 mg/5 mL, Saba İlaç Sanayi ve Ticaret A.Ş., Kocaeli, Türkiye) was administered. Standard anesthesia monitoring – including electrocardiography, noninvasive blood pressure measurement, peripheral oxygen saturation, and temperature assessment – was initiated upon patient positioning on the operating table. Preoxygenation was performed at a rate of 4 L/min for 3 minutes before anesthesia induction.

Anesthesia was induced with intravenous administration of 1 μg/kg fentanyl (Fentaver 0.5 mg/10 mL, Haver Farma İlaç A.Ş., Osel İlaç San. Ve Tic. A.Ş., İstanbul, Türkiye) and 2 mg/kg propofol (Propofol-PF 1%, Polifarma İlaç Sanayi ve Ticaret A.Ş., Tekirdağ, Türkiye). To facilitate neuromuscular blockade, 0.6 mg/kg rocuronium (Muscobloc 50 mg/5 mL, Polifarma İlaç Sanayi ve Ticaret A.Ş., Tekirdağ, Türkiye) was administered intravenously over 20 to 30 seconds. After medication administration, all patients were manually ventilated with 100% oxygen until endotracheal intubation was achieved.

Endotracheal intubation was performed using a cuffed ETT of an appropriate diameter based on the patient’s age and body habitus. Following intubation, mechanical ventilation was initiated in volume-controlled mode using the Dräger Primus (Dräger, Medizintechnik, Germany) anesthesia workstation, with a tidal volume of 6 to 8 mL/kg, a respiratory rate of 12 to 18 breaths per minute, and a positive end-expiratory pressure (PEEP) of 3 to 5 cmH₂O. Soda lime (Sorbolime, Berkim, Türkiye) was used as the CO₂ absorbent in the anesthesia system.

Demographic and perioperative data were recorded, including age, sex, BMI, ASA classification, tracheal cuff overinflation, peak airway pressure, plateau pressure, ETT cuff pressure, mean arterial pressure, heart rate, peritoneal insufflation pressure, and the degree of surgical table inclination. Additionally, the durations of surgery and anesthesia were documented.

STATISTICAL ANALYSIS:

In this study, the required sample size for a within-group comparison was determined using G*Power software. A one-tailed paired t test was selected to assess the difference between 2 dependent means. The effect size (Cohen dz) was calculated based on data from the study by Rosero et al, which investigated changes in ETT cuff pressure during laparoscopic pelvic surgery [8]. The reported mean ETT cuff pressures were 29.6 cmH2O (before insufflation), 35.6 cmH2O (during insufflation), and 27.8 cmH2O (after insufflation), with corresponding standard errors of 1.30, 0.68, and 0.79, respectively [9].

The effect size (Cohen dz) was computed using the formula:

where MΔ represents the mean difference between paired observations, and SDΔ denotes the standard deviation of these differences. Based on these values, the Cohen dz was calculated as 0.655, indicating a medium to large effect. For the power analysis, an alpha level (α) of 0.05 and a statistical power (1-β) of 0.95 were chosen to ensure a 95% probability of detecting a true effect while minimizing Type II error. The analysis yielded a noncentrality parameter (Δ) of 3.403, with a critical t value of 1.705 and 26 degrees of freedom. Consequently, the total required sample size was calculated to be 27 participants, ensuring sufficient statistical power to detect significant within-group differences in ETT cuff pressure.

A mixed-effects linear regression model was used to evaluate the effects of various independent variables on the dependent outcome variable. To avoid bias due to missing data, participants with incomplete records were excluded from the final analysis. Before applying the model, key assumptions such as linearity, homoscedasticity, and normal distribution of residuals were checked using residual plots and statistical tests such as the Shapiro-Wilk test. No significant deviations from these assumptions were found. The model included random intercepts to capture within-subject variability from repeated measurements, while the fixed effects consisted of peak airway pressure, anesthesia duration, and surgical stage. The model included both fixed and random effects to account for the hierarchical structure of the data. Fixed effects included peak airway pressure, anesthesia time, and phase, while random effects were included to account for potential clustering within patients. The model was fitted using the maximum likelihood estimation method, with statistical significance set at a P value of <0.05. Beta coefficients (β) along with their 95% confidence intervals and P values were reported to quantify the strength and significance of associations. All analyses were conducted using R software version 4.2.2 with the lme4 package.

Results

PATIENT CHARACTERISTICS:

A total of 33 patients were included in the study. Six patients declined to participate, and 2 patients were excluded due to adverse respiratory events, leaving a final cohort of 27 patients (Figure 1). The mean age of the participants was 36.14±9.46 years, with a BMI of 43.40±5.17 kg/m2. The mean duration of anesthesia was 146.85±35.44 minutes, while the mean surgical duration was 139.62±35.39 minutes.

Among the 27 patients, 25 exhibited endotracheal cuff pressures exceeding 30 cmH2O, and in 11 patients, cuff pressures exceeded 100 cmH2O. The demographic and baseline characteristics of the study population are summarized in Table 1. Changes in airway pressures, ETT cuff pressures, ventilation parameters, and other intraoperative variables across the 4 study phases are presented in Table 2.

MAIN FINDINGS:

The mean age of the patients was 36.14±9.46 years. Results showed that 92.59% of patients had overinflated cuffs after intubation. ETT cuff pressures varied significantly throughout the surgical phases. Before peritoneal insufflation (phase 1), the mean (SD) cuff pressure was 28.66 (1.41) cmH₂O. This increased significantly during peritoneal insufflation (phase 2) to 41.59 (6.43) cmH₂O (P<0.0001). Following the application of the reverse Trendelenburg position (phase 3), the cuff pressure decreased to 37.11 (5.63) cmH₂O, and after peritoneal deflation (phase 4), it returned to 29.81 (5.41) cmH₂O (P<0.0001). Multilevel mixed regression analysis revealed that cuff pressure changes were significantly associated with surgical phases (P<0.001) but not with surgical duration or peak airway pressure.

Similarly, peak airway pressures showed significant fluctuations. The mean (SD) peak airway pressure was 24.11 (4.20) cmH₂O in phase 1 and increased to 27.22 (3.63) cmH₂O in phase 2 (P<0.0001). During phase 3, it decreased slightly to 26.22 (3.22) cmH₂O, and after peritoneal deflation in phase 4, it further dropped to 23.55 (3.50) cmH₂O (P<0.0001).

MULTILEVEL MIXED REGRESSION ANALYSIS:

Multilevel mixed regression analysis (Table 3) demonstrated that, when using phase 1 as the reference, transitioning to phase 2 resulted in a mean increase of 13 cmH2O (95% CI, 11–15), while in phase 3, the cuff pressure remained 8.49 cmH2O (95% CI, 6.6–10) higher than baseline (P<0.0001).

Discussion

LIMITATIONS:

Our study has certain limitations. First, this study was conducted in a single institution, which may limit its generalizability. Second, although pneumoperitoneum was regulated to a maximum intra-abdominal pressure of 14 mmHg, intra-abdominal pressure was not continuously measured, which could have provided further insight into the observed variations in ETT cuff pressures. Third, the unavailability of recovery-related variables, including time to extubation, length of post-anesthesia care unit stay, and postoperative respiratory events, constitutes another limitation, potentially restricting the comprehensive assessment of postoperative recovery.

Conclusions

Based on the results of our study, endotracheal cuff pressures undergo significant intraoperative changes during laparoscopic bariatric surgery. We believe that routine monitoring of ETT cuff pressure in all laparoscopic bariatric surgeries can serve as a guide for clinicians in patient management to minimize the risk of postoperative complications. Future large-scale studies are needed to further evaluate the clinical significance of routine and continuous cuff pressure monitoring in such patient populations.