Changes of endotracheal tube cuff pressure and its indicators in laparoscopic resection of colorectal neoplasms: an observational prospective clinical trial

Abstract

Background

Laparoscopic surgery is a popular alternative for resection of colorectal neoplasms. Carbon dioxide pneumoperitoneum and Trendelenburg positioning in procedure can significantly increase airway pressure, when endotracheal tube cuff pressure is not monitored. This prospective observational study aimed to evaluate indicators, changes and its correlation factors of endotracheal tube cuff pressure during laparoscopic resection of colorectal neoplasms.

Methods

122 patients scheduled for laparoscopic resection of colorectal neoplasms under propofol/remifentanil total intravenous anesthesia with orotracheal intubation were included. Tracheal tube cuff pressure was monitored continuously by calibrated pressure transducers. The ability of several predictors to predict out-of-range tracheal tube cuff pressure at different time points and its correlation factors were assessed.

Results

ROC analysis showed that waist-to-hip ratio has the highest AUC for predicting out-of-range tracheal cuff pressure (AUC: 0.86 [95% CI: 0.77–0.95]); Tracheal tube cuff pressure provided by palpation was 41.0 (29.0−53.3) cmH₂0. Cuff pressure was 33.7 ± 2.9 cmH₂0 at 15 min and comparable at 30 and 45 min after insufflation, all values were significantly higher than 25 cmH₂0 (p < 0.001). Multiple linear regression showed tracheal tube cuff pressure was associated with peak airway pressure (p < 0.001).

Conclusions

Patients with normal BMI undergoing laparoscopic resection of colorectal neoplasms require continuous monitoring and timely adjustments of tracheal tube cuff pressure. Compared with BMI, waist-to-hip ratio is a better predictor of out-of-range tracheal tube cuff pressure.

Trial registration

Chinese Clinical Trial Registry, identifier: ChiCTR2100054089, Date: 08/12/2021.

Introduction

Laparoscopic surgery is a popular alternative for resection of colorectal neoplasms and is performed under general anesthesia with mechanical ventilation. Compared to open procedures, laparoscopic surgery is widely applied because it is less invasive, provokes less postoperative pain and results in faster recovery. However, carbon dioxide pneumoperitoneum and Trendelenburg positioning during the procedure can significantly decrease lung compliance and increase airway pressure because of cephalad displacement of the diaphragm and decreased intrathoracic volume [1, 2]. In this case, endotracheal tube cuff pressure change often remains unknown due to a lack of monitoring in clinical practice. Endotracheal tube cuff pressure is commonly recommended to be maintained between 20 and 30 cmH₂O. Within this range, endotracheal tube cuff can provide a proper seal and prevent overinflation.

Overinflation may impair the perfusion of the tracheal mucosa [3,4,5], and most airway complications occur because of ischemia of the mucosa, which are associated with overinflated cuffs, such as transient sore throat with hoarseness [6, 7], tracheal mucosa ulcers, subglottic stenosis, and tracheal rupture or fistula [8,9,10,11].

Few studies have reported that tube cuff pressure may increase while peak airway pressure rises [12]. Furthermore, tracheal tube cuff pressure may increase significantly during surgery because of patients movement, positioning change, room temperature, and degree of neuromuscular blockade [13, 14]. However, the routine measurement of the tracheal tube cuff pressure is usually ignored because of the lack of equipment and maintenance-calibration and the risk of cross-infection with use in multiple patients [15].

Studies have shown in laparoscopic pelvic surgeries, that mechanical ventilation can lead to an increase in tracheal tube cuff pressures in obese patients [12]. Current studies usually utilize body mass index (BMI) to categorize obesity, but BMI doesn’t include the distribution of adipose tissues. Waist circumference (WC) has been considered as a marker of central obesity [16]. But in individuals with similar WC, respiratory compliance may be over- and underestimated in tall and short patients [17]. Several studies have suggested to adopt the waist-to-height ratio (WHtR), waist-to-hip ratio (WHR) and neck circumference (NC) as better predictors of abdominal obesity [18].

This prospective observational study aimed to explore the ability of different obese indicators to predict out-of-range tracheal tube cuff pressure (> 30 cmH₂O), endotracheal tube cuff pressure change and the correlations between endotracheal tube cuff pressure, peak airway pressure, mean airway pressure and tidal volume (TV) under propofol/remifentanil total intravenous anesthesia (TIVA) during laparoscopic surgery.

Methods

Ethics

The protocol was approved by the Research Ethics Committee of Jinling Hospital, Jinling School of Clinical Medicine, Nanjing Medical University (Ethical Application Reference: 2022DZKY-024-01 Nanjing, China) on 18 March 2022. All methods were performed in accordance with relevant guidelines and regulations with CONSORT recommendations [19]. Written informed consent was obtained from all subjects participating in the trial. The trial was registered prior to patient enrollment at the Chinese Clinical Trial Registry (Identifier: ChiCTR2100054089, URL:https://www.chictr.org.cn/edit.aspx?pid=142785&htm=4, Principal investigator: Manlin Duan, Date: 08/12/2021).

Study design and population

This was an observational, prospective, nonrandomized, single-center clinical trial. In this trial, 122 patients with ASA physical status less than IV aged 18–65 years who were scheduled for laparoscopic resection of colorectal neoplasms under TIVA with orotracheal intubation were included between June 2022 and October 2022. The exclusion criteria were BMI < 19 kg m^− 2 or > 30 kg m^− 2; Mallampati classification III or IV; pre-existing cough or laryngeal mucosa haemorrhage; bucking during surgery; asthma, chronic obstructive pulmonary disease or smoking; incapacity to provide informed consent; psychiatric disorders.

The anesthesiologist, who has more than 5 years of experience, conducted intubation and extubation. Patients, outcome evaluators, data information analysts were blinded to the trial design.

Anesthesia protocol

All the patients received standardized monitoring procedures after entering the operation room: invasive blood pressure, the saturation of haemoglobin with oxygen, electrocardiography and bispectral index (BIS). Anesthesia induction was conducted with propofol 2.0 mg kg^− 1, sufentanil 0.4 µg kg^− 1 and cisatracurium 0.2 mg kg^− 1. Then the trachea was intubated with an endotracheal tube reinforced with steel and a tapered cuff (cuffed, Hisern medical, Zhejiang, China) by the anesthesiologist within 30 s by a glidescope. Tube size: 7.5–8.0 mm for males and 7.0–7.5 mm for females. 5-8 ml room-temperature air was injected to the endotracheal tube cuff by palpation of the cuff pilot, and then it was connected to calibrated pressure transducers (Hisern medical; ZheJiang, China). The transducers were primed with normal saline, connected to an anesthesia monitor (Beneview T6; Mindary, ShenZhen, China), and zeroed at the level of the patient’s trachea. Then tracheal tube cuff pressure was adjusted to 25 cmH₂O with zero end-expiratory pressure when a brief period of apnea, and during the whole surgery, tracheal tube cuff pressure was monitored continuously. During anesthesia, unless the cuff pressure increased over 50 cmH₂O or a significant leak occurred, the air in the tracheal tube cuff was not adjusted. The temperature of the upper-body warming blanket (Bair Hugger, 3 M, St Paul, MN) was kept at 38 °C and the room temperature was 24 °C.

Before peritoneal insufflation, the operating table was in the neutral position. Then patients would be placed in the head-down position and the surgeon determined the peritoneal insufflation pressures. After exsufflation, patients were adjusted to neutral position again.

Anesthesia was maintained with continuous administration of remifentanil 0.5 µg kg^− 1 min ^− 1 and propofol 4–8 mg kg^− 1 h^− 1 via injection pump and cisatracurium 0.05 mg kg^− 1 was given by bolus injection and repeated every 30 min in order to maintain a train-of-four (TOF) at zero. Intraoperative mechanical ventilation: volume-controlled ventilation; respiratory rate was 10–12 breaths min^− 1_, I: E ratio was 1:2, TV was 6–8 ml kg^− 1 of ideal body weight. By adjusting the respiratory rate, end-tidal CO₂ (EtCO₂) was kept at 35–45 mmHg. Before subcuticular closure, propofol and remifentanil were stopped, 0.2 µg kg^− 1 sufentanil was given intravenously. The last cisatracurium dose was given 30 min before the end of surgery. Postoperatively, all patients were transported to the post-anesthesia care unit (PACU).

Once the patients’ TOF was ≥ 0.9, EtCO₂ was < 45 mmHg on spontaneous respiration and could follow voice commands, endotracheal tube was removed gently.

Measurement of different indicators

Height and weight were measured with participants standing without shoes and in the same clothes. WC was measured around the left and right midpoints between the lowest border of the rib cage and the top of the iliac crest on the midaxillary line horizontally, without compressing the skin. NC was measured below the cricoid cartilage and then at the level of the mid-cervical spine. HC was measured at the widest part of the hip at the level of the greater trochanter [20].

Different time points

Different time points included the moment of cuff pilot connected to transducers (T₀), the moment cuff pressure adjusted to 25 cmH₂O (T_0.5), 15 min after pneumoperitoneum (T₁), 30 min after pneumoperitoneum (T₂), 45 min after pneumoperitoneum (T₃), 15 min after exsufflation (T₄).

Outcome measures

The main aim was to evaluate BMI, WC, NC, hip circumstance (HC), WHR, and WHtR to predict out-of-range tracheal tube cuff pressure at 15 min after pneumoperitoneum induction. The secondary goal was to evaluate the tracheal tube cuff pressure at different time points and it’s correlation factors. Patients’ demographic data, peak airway pressure, mean airway pressure from T₀ to T₄, peritoneal insufflation pressure from T₁ to T₃ were recorded. Operation duration and anesthesia duration (from anesthesia induction to extubation) were also recorded.

Sample size and statistical analysis

Receiver operating characteristic curve (ROC) analysis and Sample Size Software (version 15.0; NCSS, LLC, USA) with area under curve0 (AUC0) = 0.8, AUC1 = 0.95, lower FPR = 0, upper FPR = 1 calculated that 95 patients were required totally. Assuming the dropout rate was 20%, 119 patients were required.

Mean (standard deviation) was used to summarize normal distribution continuous study variables and median (25–75th percentiles) was used to summarize non-normal distribution continuous study variables. Categorical variables (percentage) were summarized as frequencies. One-way analysis of variance (ANOVA) was used to test group differences for normally distributed continuous variables. Chi-square test was used to compare categorical variables. Multiple linear regression was used to analyze the factors associated with tracheal tube cuff pressure. The prediction ability of different indicators for tracheal tube cuff pressure was assessed by ROC analysis. The statistical analysis was conducted by IBM SPSS version 26.0. Bonferroni-corrected p-values was reported and p < 0.05 was statistically significant.

Results

This study enrolled 127 of 149 eligible patients, and 5 were excluded from the analysis: 4 were lost to follow-up, 1 had cough during surgery. Finally, 122 patients were included into the analysis (Fig. 1).

Fig. 1

Consort flow chart that outlines patients’ assignment. This study enrolled 127 of 149 eligible patients, and 5 were excluded from the analysis: 4 were lost to follow-up, 1 had cough during surgery. Finally, 122 patients were included to analysis

The characteristics of the patients and the operations are displayed in Table 1. ROC analysis showed that WHR had the highest AUC for predicting out-of-range tracheal cuff pressure (AUC: 0.86 [95% CI: 0.77–0.95]); WHtR (AUC: 0.66 [95% CI: 0.56–0.76]); BMI (AUC: 0.63 [95% CI: 0.53–0.74]); WC (AUC: 0.61 [95% CI: 0.50–0.73]); NC (AUC: 0.58 [95% CI: 0.46–0.70]); HC (AUC: 0.54 [95% CI: 0.42–0.66]) (Fig. 2; Table 2).

Table 1 Baseline characteristics of patients and surgery

Fig. 2

ROC for different predictors of tracheal tube cuff pressure. ROC analysis showed that WHR has the highest AUC for predicting out-of-range tracheal cuff pressure (AUC: 0.86 [95% CI: 0.77–0.95]); WHtR (AUC: 0.66 [95% CI: 0.56–0.76]); BMI (AUC: 0.63 [95% CI: 0.53–0.74]); WC (AUC: 0.61 [95% CI: 0.50–0.73]); NC (AUC: 0.58 [95% CI: 0.46–0.70]); HC (AUC: 0.54 [95% CI: 0.42–0.66]). ROC: receiver operating characteristic curve; WHR: waist-to-hip ratio; AUC: area under curve; CI: confidence interval. WHtR: waist-to-height ratio; BMI: body mass index; WC: waist circumstance; NC: neck circumstance; HC: hip circumstance

Table 2 AUC and cut-off points for predictors (n = 122)

Tracheal tube cuff pressure at T₀ was 41.0 (29.0−53.3) cmH₂0. From T₁ to T₄, tracheal tube cuff pressure at T₁ was highest and it was 33.7 ± 2.9 cmH₂0, it was comparable at 15, 30 and 45 min after insufflation. At T_0.5, it was significantly lower than all values from T₁ to T₄ (p < 0.001 for all time points comparisons, Fig. 3). Compared to T₄, tracheal tube cuff pressures at T₁, T₂ and T₃ were significantly higher (p < 0.001 for all time points comparisons, Fig. 3).

Fig. 3

Mean of tracheal tube cuff pressure at different time points. From T₁ to T₄, tracheal tube cuff pressure at T₁ was highest and it was 33.7 ± 2.9 cmH₂0, it was comparable at 15, 30 and 45 min after insufflation. At T_0.5, it was significantly lower than all values from T₁ to T₄ (p < 0.001 for all time points comparisons). Compared to T₄, tracheal tube cuff pressure at T₁, T₂ and T₃ were significantly higher (p < 0.001 for all time points comparisons)

CP: tracheal tube cuff pressure; T_0.5: tracheal tube cuff pressure adjusted to 25 cmH₂0; T₁: 15 min after pneumoperitoneum; T₂: 30 min after pneumoperitoneum; T₃: 45 min after pneumoperitoneum; T₄: 15 min after exsufflation

Peak airway pressure and mean airway pressure at T₁ to T₃ were significantly higher than all pressures at T_0.5 and T₄ (p < 0.001 for comparisons, Fig. 4a and b). TV at T₁ and T₂ were significantly lower than the values at T_0.5, T₃ and T₄ (p < 0.001 for comparisons, Fig. 4c).

Fig. 4

a, Mean of peak airway pressure at different time points; b, Mean of mean airway pressure pressure at different time points; c, Mean of tidal volume at different time points. a, Peak airway pressure pressure at T₁ to T₃ were significantly higher than all pressures at T_0.5 and T₄ (p < 0.001 for comparisons). b, Mean airway pressure at T₁ to T₃ were significantly higher than all pressures at T_0.5 and T₄ (p < 0.001 for comparisons). c, Tidal volume at T₁ and T₂ were significantly lower than the values at T_0.5, T₃ and T₄ (p < 0.001 for comparisons). PP: peak airway pressure; PM: mean airway pressure; TV: tidal volume; T_0.5: tracheal tube cuff pressure adjusted to 25 cmH₂0; T₁: 15 min after pneumoperitoneum; T₂: 30 min after pneumoperitoneum; T₃: 45 min after pneumoperitoneum; T₄: 15 min after exsufflation

Multiple linear regression showed tracheal tube cuff pressure at 15 min after insufflation was associated with the peak airway pressure (p < 0.001, Table 3). Mean airway pressure and TV had no association with it.

Table 3 Multiple linear regression of factors associated with tracheal tube cuff pressure (n = 122)

Discussion

Our study reveals that tracheal tube cuff pressure can rise unacceptably high without monitoring. The initial cuff pressure after intubation and injection of 5-8 ml air in the cuff even showed a median of 41.0 cmH₂O, which confirms the importance of checking cuff pressures after intubation. In this study, while insufflation may increase cuff pressure to a dangerous level, typical amounts of air placed in a cuff might be associated with much higher and more dangerous pressures at the beginning of a case. This may lead to severe airway complications, such as tracheal ulcer or fistula, especially in long surgeries or laparoscopic surgeries.

In this study, even though we established a safe range of cuff pressure, it could increase significantly during pneumoperitoneum. We adjusted tracheal tube cuff pressure to 25 cmH₂0 when the cuff pilots were connected to transducers. After insufflation, almost all tracheal tube cuff pressure increased to over 30 cmH₂0 and the highest was nearly 50 cmH₂0, which may affect perfusion of tracheal wall and result in serious complications. In our previous study, the results showed that at 2 h after surgery, the incidence of sore throat was 53.3%, the incidence of cough was 46.7% and other airway complications was 30.0% [21]. After exsufflation, tracheal tube cuff pressure can decrease to normal range.

Also, peak airway pressure was significantly higher during pneumoperitoneum and it was associated with tracheal tube cuff pressure. Rosero reported that tracheal tube cuff pressure change significantly in direct relation to changes in the peak airway pressures [12], which was in accordance with the result in our study.

We selected the time point of 15 min after pneumoperitoneum to analyze the factors associated with tracheal tube cuff pressure changes. Intraoperative ventilatory characteristics were comparable during pneumoperitoneum but tracheal tube cuff pressure was highest at this point.

This study found that without adjustment, tracheal tube cuff pressure would increase over 30 cmH₂0 or more after creation of the pneumoperitoneum. This finding might impact especially those patients who undergo long procedures or are overweight. Also, tracheal tube cuff pressures should be monitored during mechanical ventilation when patients’ respiratory compliance decreased, such as patients undergoing Da Vinci robotic lobectomy or thoracoscopic radical resection of esophageal cancer.

This study suggests that individuals with a larger WC and smaller HC may experience more frequent instances of exceeding recommended tracheal cuff pressures during laparoscopic surgery. We posit that this phenomenon is attributable to increased adipose tissue distribution in the abdomen, resulting in reduced lung volume. During pneumoperitoneum, a decrease in respiratory compliance occurs, leading to elevated airway pressure and an increase in tracheal tube cuff pressure.

This trial has some advantages. Few studies have investigated the tracheal tube cuff pressure and peak airway pressure change, almost all studies had a small sample and conclusions vary [14, 22, 23].

Our study complements this topic and included normal BMI and male patients, as previous studies reported obese and female patients might be more sensitive to ventilatory characteristic changes [12]. The trial, on the other hand, has flaws. First, this was a single-centre study, and perhaps a multicentre study would be better to further test our hypothesis. Second, we only studied the first 45 min after pneumoperitoneum because of the duration of surgery, and the variation tendency in longer procedures is unknown.

Conclusion

In conclusion, this prospective observational study in patients with normal BMI undergoing laparoscopic resection of colorectal neoplasms under general anaesthesia reveals that during pneumoperitoneum, tracheal tube cuff pressure is increased and associated with peak airway pressure. Tracheal tube cuff pressure should be monitored and timely adjusted to avoid severe complications caused by overinflation during surgery, especially at the moment after intubation and pneumoperitoneum. Compared with BMI, WHR is a better predictor of out-of-range tracheal tube cuff pressure.