DOI: https://doi.org/10.21203/rs.3.rs-2542152/v1
Postoperative sore throat (POST) is a common complication after endotracheal intubation. According to Lehmann et al.’s survey, POST was the second most-important factor causing postoperative discomfort in patients [1]. In order to improve the postoperative comfort of patients, various studies have attempted different methods to prevent sore throat. Arts et al. showed that the use of lidocaine can reduce POST [2]. Farhang et al. indicated that the use of zinc 30 min before surgery reduced the incidence of POST within 2 h after surgery by 24% [3]. Koyama et al. suggested that the use of lubricants on the sleeves of the endotracheal tube could also alleviate POST [4]. Chang et al. proved that using tapered air bags as opposed to cylindrical air bags could reduce the incidence of POST [5].
With continuous in-depth research into the factors causing POST, the cuff pressure of the tracheal catheter has gradually attracted attention. Gaur et al. stated that the incidence of POST was positively correlated with the cuff pressure of the tracheal catheter [6]. Ganason et al. demonstrated that adjusting tube cuff pressure to < 25 cmH2O could significantly decrease the incidence of POST [7]. At present, in China, subjects of studies based on the tube cuff pressure have mostly been limited to ICU patients who require mechanical ventilation. There have been few reports on balloon pressure in patients undergoing general anesthesia during surgery, and particularly on the influence of the minimum hermetically sealed pressure (MOP) management mode on POST.
The purpose of this study was to use a special balloon manometer to monitor the endotracheal tube cuff pressure accurately and compare the influence of different balloon pressures during surgery on POST in patients undergoing tracheal intubation, in order to provide a reference for reasonable management of balloon pressure in clinical anesthesia, in an effort to reduce the incidence of POST and improve the postoperative comfort of patients.
The study was approved by the hospital Ethics Committee, and the patients and their family members signed informed consent forms. A total of 120 patients who underwent elective abdominal and lower extremity operations, without a history of smoking or throat diseases, who underwent surgery in the supine position, without insertion of a nutritional tube or gastric tube, were selected. The subjects included 60 men and 60 women who were successfully intubated, aged 18–70 years, American Society of Anesthesiologists I–II, and Mallampati Score I–II.
The 120 patients were randomly allocated to the MOP group, the measure and control endotracheal tube cuff (ETTc) group, and the control (Con) group. Each group consisted of 40 patients (20 males and 20 females). In the MOP group, during positive-pressure ventilation, 0.25–0.5 ml of gas was gradually pumped from the bag each compression until a small amount of air leakage occurred when the suction pressure peaked, after which another 0.25–0.5 ml of gas was injected [8]. In the ETTc group, the pressure value was 15–25 mmHg (20–33 cmH2O) [9]. In the Con group, the finger-pinch method was used, in which the fingers were used to feel the pressure inside the capsule, and inflation was stopped when the appropriate pressure was reached [10].
All patients were routinely on a water-fast before surgery and received an intramuscular injection of 0.5 mg penehyclidine hydrochloride at 30 min before the operation. Blood pressure (BP), electrocardiograph (ECG), heart rate (HR), and pulse oxygen saturation (SpO2) were routinely monitored after entering the operating room. As induction drugs, the following were intravenously injected: midazolam 0.05–0.08 mg/kg, sufentanil 0.3–0.5 µg/kg, cisatracurium 0.15–0.2 mg/kg, propofol 0.8–1 mg/kg. The routine calibration of the TOF-watch adopted four serial stimuli (train-of-four [TOF]: frequency, 2 Hz; wave width, 200 µs; current intensity, 50 mA; interval, 15 s). When TOF = 0, endotracheal intubation was performed by an anesthesiologist skilled in intubation (endotracheal intubation type was the high pressure and low volume type, male: ID 7.5 mm, intubation depth, 23 cm; female: ID 7.0 mm, intubation depth 21 cm). Then, mechanical ventilation was performed: tidal volume was 8–12 ml/kg, the frequency was 8–12 times/min, pure oxygen was inhaled, and the flow rate was 1–2 L/min. A special capsule manometer (German VBM balloon manometer, Shanghai Yipu Medical Technology Co., LTD., Shanghai, China) was used to measure the pressure inside the capsule intermittently (every 20 min) to maintain the stability of the pressure inside the capsule. For maintenance of anesthesia, we used propofol 3–4 mg.kg− 1.h− 1, atracurium 0.6–0.8 mg.kg− 1.h− 1, remifentanil 6–8 µg.kg− 1. For TOF muscle relaxation monitoring, we used T4/T1 < 25%. At the end of surgery, when T4/T1 values were at 75%, we deflated the indicator sleeve, and gently pulled out the tracheal tube. The intravenous analgesia pump was installed 5 min before the end of the operation, and contained 100 ml of sufentanil (3 µg/kg), butorphanol tartrate injection (0.1 mg/kg), and azasetron (20 mg), in normal saline.
Observational indexes were HR, MAP, Pmax, Pmean, PETCO2, SpO2, operative time, anesthesia time, postoperative throat pain and incision pain scores (according to Prince Henry Hospital Pain Scale score and visual analogue scale [11]).
Respiratory and circulatory parameters were recorded at 5 time points, including 1 min after intubation (T0), 5 min after intubation (T1), 30 min after intubation (T2), 60 min after intubation (T3), and 5 min before extubation (T4), as well as throat pain and incision score at 1 h, 24 h, and 48 h after surgery.
SPASS20.0 statistical software was used to establish a database for statistical analysis. The rank-sum test was used for ranked data, chi-square test was used for enumeration data comparison, and measurement data were expressed as " mean ± SD" (x̄ ± s). One-way analysis of variance was used for comparison of data at different time points within the group, and comparison of data at the same time point and between different groups. P < 0.05 was considered statistically significant.
There were no significant differences in sex, age, weight, height, and anesthesia time among the three groups (P > 0.05; Table 1).
Group |
Sex/n Male Female |
Age (y) |
Weight (kg) |
Height (cm) |
Anesthesia time (min) |
---|---|---|---|---|---|
MOP |
20 20 |
47.63 ± 13.54 |
63.30 ± 9.17 |
166.00 ± 7.50 |
84.25 ± 15.75 |
ETTc |
20 20 |
48.70 ± 12.60 |
65.00 ± 9.21 |
165.80 ± 6.99 |
84.30 ± 15.75 |
Con |
20 20 |
47.55 ± 13.32 |
64.03 ± 9.06 |
166.30 ± 6.87 |
80.63 ± 18.05 |
The rank-sum test showed no significant difference in incision pain scores at 1 h, 24 h, and 48 h after surgery among the three groups, P > 0.05 (Table 2).
Score |
MOP group |
ETTc group |
Con group |
||||||
|
1 h |
24 h |
48 h |
1 h |
24 h |
48 h |
1 h |
24 h |
48 h |
0 |
2 |
6 |
18 |
5 |
10 |
19 |
2 |
3 |
9 |
1 |
2 |
7 |
9 |
3 |
3 |
6 |
2 |
6 |
17 |
2 |
5 |
13 |
6 |
5 |
12 |
10 |
6 |
15 |
10 |
3 |
15 |
6 |
6 |
11 |
7 |
5 |
14 |
8 |
3 |
4 |
9 |
6 |
1 |
8 |
5 |
0 |
7 |
7 |
0 |
5 |
5 |
2 |
0 |
5 |
1 |
0 |
4 |
1 |
0 |
6 |
2 |
0 |
0 |
3 |
2 |
0 |
5 |
0 |
1 |
There was no significant difference in intraoperative vital signs among the three groups, P > 0.05 (Table 3).
Index |
Group |
T0 |
T1 |
T2 |
T3 |
T4 |
---|---|---|---|---|---|---|
MOP |
15.43 ± 2.01 |
16.13 ± 3.08 |
16.40 ± 2.98 |
16.65 ± 2.80 |
16.23 ± 2.04 |
|
Pmax/mmHg |
ETTc |
15.43 ± 2.58 |
15.80 ± 2.93 |
16.48 ± 2.84 |
16.45 ± 2.76 |
16.50 ± 2.65 |
Con |
15.55 ± 2.10 |
15.88 ± 2.40 |
16.50 ± 2.35 |
16.20 ± 2.33 |
16.08 ± 2.36 |
|
MOP |
5.83 ± 1.01 |
6.18 ± 1.28 |
6.45 ± 1.34 |
6.15 ± 1.08 |
5.95 ± 0.90 |
|
Pmean/mmHg |
ETTc |
5.45 ± 0.90 |
5.65 ± 1.00 |
6.08 ± 1.14 |
5.88 ± 0.94 |
5.93 ± 0.86 |
Con |
5.83 ± 0.98 |
6.10 ± 0.90 |
6.35 ± 1.00 |
6.08 ± 1.16 |
6.18 ± 1.11 |
|
MOP |
30.08 ± 3.49 |
29.83 ± 3.05 |
29.53 ± 2.98 |
29.68 ± 3.15 |
29.95 ± 2.80 |
|
PETCO2/mmHg |
ETTc |
30.30 ± 3.76 |
30.40 ± 3.40 |
30.18 ± 3.78 |
30.15 ± 3.45 |
30.10 ± 3.45 |
Con |
31.03 ± 10.65 |
30.45 ± 10.46 |
31.05 ± 10.51 |
30.98 ± 11.22 |
31.68 ± 10.78 |
|
MOP |
81.38 ± 9.03 |
80.30 ± 10.23 |
84.55 ± 9.49 |
84.55 ± 10.34 |
87.00 ± 10.85 |
|
MAP/mmHg |
ETTc |
83.20 ± 8.53 |
83.125 ± 8.66 |
83.475 ± 9.73 |
85.00 ± 10.40 |
86.08 ± 9.75 |
Con |
82.23 ± 14.84 |
79.13 ± 13.98 |
81.08 ± 14.18 |
81.50 ± 13.56 |
84.35 ± 13.77 |
|
MOP |
67.13 ± 10.45 |
65.13 ± 11.01 |
63.50 ± 10.79 |
64.55 ± 10.85 |
68.48 ± 10.76 |
|
HR/bpm |
ETTc |
66.85 ± 9.35 |
65.30 ± 9.50 |
65.90 ± 9.79 |
65.95 ± 9.98 |
66.80 ± 8.97 |
Con |
69.58 ± 14.08 |
66.20 ± 14.11 |
66.63 ± 14.00 |
66.60 ± 13.81 |
71.25 ± 13.11 |
Pmax, peak airway pressure; Pmean, mean airway pressure; PETCO2, partial respiratory CO2 pressure; MAP, mean arterial pressure; HR, heart rate; T0, 1 min after intubation; T1, 5 min after intubation, T2, 30 min after intubation, T3, 60 min after intubation; T4, 5 min before extubation
The endotracheal tube cuff pressure results in the MOP, ETTc, and Con groups were presented in Table 4. The pressure values of the three groups were analyzed by F test and q test in analysis of variance. As shown in Table 4, the results indicated that the cuff pressure of the three groups were statistically significantly different (P < 0.05).
MOP group |
ETTc group |
Con group |
|
---|---|---|---|
Cuff pressure (cmH2O) |
9.23 0.83ab |
24.18 2.35a |
45.25 2.66 |
Note: Compared with the Con group, aP < 0.05; Compared with ETTc group, bP < 0.05. |
As shown in Table 5, the overall incidence of POST was 40%, whereas the incidence of POST in the MOP, ETTc, and Con groups was 20%, 37.5%, and 62.5%, respectively. There were statistically significant differences among the three groups (P < 0.05). The results were compared at the same time point between the groups: the incidence of POST in MOP group and ETTc group was lower than that in Con group at 1 h after operation (P < 0.05); the incidence of POST in the MOP group was lower than that in Con group at 48 h after the operation (P < 0.05). The results were also compared at different time points within each group: the incidence of POST at 48 h after operation was lower than that at 24 h after the operation in the MOP group (P < 0.05). The incidence rate of POST was lower at 48 h after surgery than that at 1 h and 24 h after surgery in the ETTc group (P < 0.05). Post-hoc multiple comparisons analyses indicated that the incidence of POST at 1 h, 24 h, and 48 h after surgery in the Con group was significantly different (P < 0.05).
Group |
Incidence |
|||
---|---|---|---|---|
1 h (%) |
24 h (%) |
48 h (%) |
Total (%) |
|
MOP |
10a |
12.5ab |
2.5ad |
20ab |
ETTc |
17.5a |
25 |
7.5cd |
37.5a |
Con |
27.5 |
45c |
12.5cd |
62.5 |
Note: compared with the Con group, aP < 0.05; compared with ETTc group, bP < 0.05; compared with 1 h after surgery, cP < 0.05; compared with 24 h after surgery, dP < 0.05. |
A correlation analysis was performed, with the tube cuff pressure as the independent variable and the incidence of POST as the dependent variable. According to the Prince Henry Hospital Pain Scale scoring criteria, the incidence of POST was positively correlated with the airbag pressure at the same time point: r = 0.893, at 1 h after surgery (FIG. 1A); r = 0.931, at 24 h after surgery (FIG. 1B); r = 0.854, at 48 h after surgery (FIG. 1C). The results showed that the correlation between the two variables was strongest at 24 h after operation.
As shown in Table 6, there was no significant difference in the POST Prince Henry Hospital Pain Scale scores among the MOP, ETTc, and Con groups at 1 h after operation (P > 0.05). There was a significant difference between the groups at 24 h after operation (P < 0.05). The Prince Henry Hospital Pain Scale scores among the three groups showed no significant difference at 48 h after surgery (P > 0.05). There was also no significant difference in POST Prince Henry Hospital Pain Scale scores in the MOP group at 1 h, 24 h, and 48 h after the operation (P > 0.05). However, the pain score of the ETTc group at 48 h after surgery was significantly different from that at 1 h after surgery (P < 0.05). Additionally, the pain score of the Con group at 48 h after surgery was significantly different from that at 1 h and at 24 h after surgery (P < 0.05).
Score |
MOP group |
ETTc group |
Con group |
||||||
---|---|---|---|---|---|---|---|---|---|
1 h |
24 h |
48 h |
1 h |
24 h |
48 h |
1 h |
24 h |
48 h |
|
1–2 |
6 |
1ab |
1 |
12 |
18 |
4cd |
18 |
||
3 |
0 |
1ab |
0 |
0 |
0 |
0c |
3 |
0 |
0cd |
Note: Compared with the Con group, aP < 0.05; compared with the ETTc group, bP < 0.05; compared with 1 h after surgery, cP < 0.05; compared with 24 h after surgery, dP < 0.05. |
POST is a common complication after general anesthesia with tracheal intubation, and its severity is mainly dictated by the pressure on the tracheal mucosa and the perfusion pressure of the tracheal mucosa itself [12]. Monitoring of the pressure on the tracheal mucosa is complicated; therefore, it cannot be measured directly in clinical practice. However, this pressure is relatively well correlated with the endotracheal tube cuff pressure. Therefore, the cuff pressure can indirectly reflect the pressure on the tracheal mucosa. The MOP is the minimum pressure that effectively seals the gap between the cuff and the trachea [5]. Li et al. suggested that the MOP management mode could ensure effective ventilation of patients and could reduce the occurrence of complications [8]. Sole et al. recommended an ETTc pressure of 15–25 mmHg (20–33 cmH2O) [9]. However, it is unscientific to evaluate the cuff pressure based on clinical experience only [13], as it may easily lead to excessively high cuff pressure, causing damage to the tracheal mucosa. In this study, muscle relaxants were administered continuously using a micropump, to exclude POST caused by swallowing due to insufficient muscle relaxants, which would affect the accuracy of the results. Our results confirmed that tracheal intubation per se under general anesthesia did indeed cause POST.
The trachea is an organ that can be contracted by the action of breathing, but the extent of contraction possible is limited. When the pressure of the endotracheal tube cuff exceeds the bearing capacity of the trachea, the tracheal mucosa can be damaged [14]. During mechanical ventilation, if the cuff pressure of the endotracheal tube exceeds 10 mmHg (13 cmH2O, interstitial fluid colloid osmotic pressure), or even reaches or exceeds 20 mmHg (27 cmH2O), local edema of the compressed tracheal mucosa is unavoidable [15]. Xu wrote that, when the endotracheal tube cuff pressure reached 2.942 kPa (22 cmH2O), the blood flow in the tracheal mucosa began to decrease. When it reached 3.923 kPa (29 cmH2O), the blood supply could be completely blocked, leading to ischemic injury of the tracheal mucosa. When it exceeded 4.904 kPa (37 cmH2O), columnar necrosis and even serious complications, such as perforation and rupture of the airway wall, occurred [16]. Therefore, we consider that the endotracheal tube cuff inflating and deflating constitutes a process of ischemia–reperfusion. Dong et al. suggested that ischemia–reperfusion injury was an inflammatory reaction [17]. Various cytokines are expressed and inflammatory cells infiltrate in the ischemia–reperfusion injury area, which forms the basis of the transformation from ischemia–reperfusion injury to inflammatory injury. Puyo et al. found that the number of multinucleate cells increased 10-fold, and tumor necrosis factor interleukin-6 (IL-6), IL-1β, and C5a were all significantly increased after 3 h of endotracheal intubation [18]. The occurrence and development of pain is closely related to the inflammatory response caused by injurious stimuli [19]. Zhang et al. compared the pathological changes in the tracheal mucosa when the cuff pressure was 10 mmHg (13 cmH2O) or 20 mmHg (27 cmH2O). They found slight pathological changes in the low-pressure group, while the main pathological changes were the infiltration of the tracheal mucosa by inflammatory cells, leading to hyperemia and edema. The damage in the high-pressure group was significantly greater than that in the low-pressure group [20]. Therefore, we speculate that POST is related to the inflammatory response caused by ischemia–reperfusion injury.
According to the Prince Henry Hospital Scale scoring criteria, the incidence of POST in the MOP, ETTc, and Con groups were 20%, 37.5%, and 62.5%, respectively. The results suggested that different cuff pressure management modes have an effect on the incidence of POST. In the results of this study, there was no significant difference in incision pain among the three groups, as assessed by a visual analogue scale; thus, the effect of the postoperative analgesia pump on POST could be excluded, further suggesting that different tube cuff pressure management modes have an impact on the incidence of POST.
We then conducted a correlation analysis to determine the relationship between the incidence of POST and the cuff pressure. The results indicated that the incidence of POST increased with the increase in cuff pressure, and the relationship between the incidence of POST and the cuff pressure was strongest at 24 h after the operation. The results of the POST pain score also showed that the degree of POST-related pain was different with different tube cuff pressures, and this was most significant at 24 h after surgery. The incidence of POST at 24 h after surgery and the degree of POST were closely related to the tube cuff pressure. The results reported by Zhang et al. supported our conclusion [26]. The POST pain score also showed that with a cuff pressure > 10 cmH2O, the degree of POST was statistically significantly different at the three observation time points, which indirectly suggests that high cuff pressure caused more severe POST, and that POST gradually eased over time.
In conclusion, our results indicate that the MOP management mode is the ideal intraoperative cuff pressure management mode. MOP not only seals the airway effectively, but also reduces the incidence of POST.
BP: blood pressure
ECG: electrocardiograph
ETTc: measure and control endotracheal tube cuff
HR: heart rate
MAP: mean arterial pressure
MOP: minimum hermetically sealed pressure
PETCO2: partial respiratory CO2 pressure
Pmax: peak airway pressure
Pmean: mean airway pressure
POST: postoperative sore throat
SpO2: pulse oxygen saturation
Ethics approval and consent to participate: This research project was reviewed by the Ethics Committee of Tai ‘an City Center and met the requirements of the "Measures for Biomedical Ethics Review Involving Humans". Informed consent was obtained from all individual participants included in the study.
Data availability The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.
Competing interests The authors have no competing interests to declare that are relevant to the content of this article.
Author Contributions All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by Jing Liu, Hongzhi Li, Wei Ren, Tingting Wang and Zaiqi Yang. The first draft of the manuscript was written by Jing Liu and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.
Acknowledgement This work was supported by Clinical Research Funds of Shandong Medical Association-Qilu Special Support (grant no. YXH2022ZX02093).