This randomized controlled study followed the CONSORT reporting guidelines [18] and was carried out at Jinling Hospital, Jinling School of Clinical Medicine, Nanjing Medical University. Written informed permission was obtained from all participants following approval from the hospital’s Study Ethics Committee on March 18, 2022 (Ethical Approval Number: 2022DZKY-024-01 Nanjing, China). Information on the trial is available in the Chinese Clinical Trial Registry (Registration No. ChiCTR2100054089, date: August 12, 2021).

The participants included adults (of either sex) between the ages of 18 and 65 years, in ASA physical status I, II, or III, and scheduled to have elective procedures under general endotracheal anesthesia. Patients with a body mass index below 19 kg/m− 2 or over 30 kg/m− 2, existing sore throat, hoarseness, cough, bleeding in the laryngeal mucosa, asthma, chronic obstructive pulmonary disease, smoking, difficult airway, respiratory tract infection during the past two weeks, who had undergone insertion of a nasogastric tube, who had psychiatric disorders, or had undergone oral and ENT surgery were excluded from the trial.

The patients were enrolled one day before the operation and randomly divided into groups at a 1:1:1 ratio using a computer-generated random number table by the designer. The anesthesiologist, who supervised procedures such as intubation and cuff monitoring, had access to the opaque envelopes with the allocation numbers. Two separate assessors examined the outcome measures after surgery. Telephone follow-up was used for the postoperative follow-up in cases where the patients were discharged early. The patients, data information analysts, and the two outcome assessors were not informed of the trial’s intervention.

The ETT cuffs of the patients in each group were inflated using a 10-ml syringe and the anesthesiologist’s usual method of pilot balloon palpation. Cuff pressure was not recorded in the control (C) group. A cuff pressure gauge (Ambu*R, Germany) (Fig. 1A) was used to check the ETT cuff pressure intraoperatively every hour in the cuff gauge (G) group, where it was maintained at 25–30 cmH2O throughout the procedure. The ETT cuff pressure was maintained constant at 25–30 cmH2O using an automated cuff controller (HPC-1, Wuxi Huayao Biotechnology Co., Ltd) in the automated (A) cuff controller group (Fig. 1B). In addition, the initial cuff pressure was also recorded when inflating the cuff according to the pilot ballon palpation in group G and A. Participants with a leaking ETT cuff were re-intubated and subsequently excluded from the study.

(A) shows the cuff pressure gauge (Ambu*R, Germany). This measures the instantaneous cuff pressure by connecting the cuff through a three-top. (B) shows the automated cuff controller (HPC-1, Wuxi Huayao Biotechnology Co., Ltd). This can continuously inflate and deflate to maintain the cuff pressure in the set safety range

Sufentanil (0.4 µg.kg− 1), rocuronium (0.6 mg.kg− 1), and ciprofol (0.4 mg.kg− 1) were used to induce anesthesia. Visual laryngoscopy was used to guide the placement of an endotracheal tube (7.5 or 8.0 mm in males and 7.0 or 7.5 mm in females) reinforced with low-pressure, high-volume cuff (cuffed, Hisern Medical, Zhejiang, China) by an anesthesiologist with at least five years of clinical experience. Remifentanil (0.05-2.0 µg.kg− 1.min− 1), propofol (4.0–8.0 mg.kg− 1.h− 1), and cisatracurium (0.05 mg.kg− 1 every 30 min) were the drugs of choice for continuous general anesthesia induction and maintenance. The ideal body weight of the patient was used to determine the tidal volume (6‒8 ml.kg− 1), the respiratory rate (10‒13 breaths/min) and the peak airway pressure (25 mmHg). Mechanical ventilation was set to volume control. The patient was transferred to the post-anesthesia care unit (PACU) for postoperative resuscitation. Once the patient began breathing on their own and could follow directions by shaking hands, the endotracheal tube was removed by full deflation of the cuff after gentle suction of the oral cavity at a negative pressure of 50 cmH2O [19].

After surgery, patients were monitored at 2, 24, and 48 h to assess the prevalence and severity of POST, hoarseness, and cough. The occurrence and intensity of dysphagia were also recorded at 24 and 48 h. POST has been defined as an unpleasant feeling of discomfort or irritation experienced while at rest or swallowing. As previously stated, there were four categories delineating the severity of the concerns. An absence of POST was designated as grade 0, while grade 1 was milder than the normal cold, grade 2 almost as bad as the common cold, and grade 3 was very bad [20]. Those without a cough were assigned a rating of 0, those with a light or infrequent cough were classified as grade 1, those with a moderate cough were classified as grade 2, and those with a severe cough were assigned a grade of 3 [20]. Hoarseness was rated from 0 (none) to 3 (unable to produce a sound), with 1 indicating mild (noted by the patient) and 2 moderate (obvious to the observer) hoarseness [21]. In terms of dysphagia, grade 0 represented no dysphagia, grade 1 mild dysphagia, grade 2 moderate dysphagia (no or occasional difficulty in swallowing liquid; difficulty swallowing solids occasionally or in particular foods), and grade 3 indicated severe dysphagia (occasional or no difficulty in swallowing liquid; frequent difficulty in swallowing or in swallowing most solid foods) [22]. Any complication rated at ≥ 2 was considered significant.

The pre-test data indicated that 70% of group C patients, 50% of group G patients, and 30% of group A patients had POST within 48 h after surgery. PASS15.0 was used to calculate the sample size, and α = 0.05 and β = 0.2, respectively, were the significance thresholds of the hypothesis test. It was predicated on the assumption that 20% and 40% decreases in POST incidence in groups G and A, respectively, compared to group C, were statistically significant. This showed that the required number of patients was 91. Allowing for a dropout rate of 20%, a total of 114 patients were required, with an average of 38 patients in each group.

Continuous data are presented as mean (standard deviation) or median (25th-75th percentiles), according to the normality of the data distribution. Analysis of variance (ANOVA) was used for comparing normally distributed data while the Kruskal-Wallis test was used to compare non-normally distributed data. Categorical data, including the rates of postoperative complications, are presented as frequencies (percentages). Statistical significance across groups was assessed using either the Chi-square test or the Fisher exact test. The reported p-values underwent Bonferroni corrections. P-values < 0.05 were considered statistically significant. All data were analyzed using SPSS 25.0 for Windows (IBM Corp., Armonk, NY, USA).