European Journal of Cardiovascular Medicine

Endotracheal intubation is an essential aspect of anaesthesia. An endotracheal tube (ETT) serves as a medical device that separates the trachea from the esophagus, providing lung protection by preventing the inhalation of foreign substances.(1) The pressure applied to the tracheal wall is influenced by the trachea’s compliance and can be approximated by measuring the pressure at the ETT cuff’s pilot balloon. This measurement offers a reliable indication of the pressure impacting the tracheal mucosa.(2) Cuffed endotracheal tubes play a crucial role in airway management to enhance patient safety. However, there are risks associated with both underinflated and overinflated cuffs, which can lead to patient injuries.

The pressure of the ETT cuff should not surpass the estimated tracheal perfusion pressure of 22 mm Hg to 30 mm Hg to prevent tracheal injury and pathological changes. High and lowpressure endotracheal tube cuffs can expand up to 1.5 to 2 times diameter of an average adult trachea when fully inflated. This expansion increases the mucosal contact area, which may result in a sore throat post-operation. Sore throat and coughing are frequent postoperative complaints in patients who have received general anesthesia with endotracheal intubation.

The management of cuffed endotracheal tubes is a standard practice for anaesthetists.(3)The main purpose of cuffed endotracheal tubes is to form a secure seal between the cuff and the trachea, providing protection against aspiration while ensuring that tracheal blood flow remains unaffected by excessive pressure.

The consensus on an acceptable maximum cuff pressure typically falls within the range of 20 to 30 cm H2O. This threshold is influenced by the capillary blood pressure that supplies the trachea, which is around 48 cm H2O. When the pressure from an excessively inflated cuff exceeds the capillary blood supply pressure, it can lead to ischemia and stenosis of the tracheal mucosa. Intracuff pressures exceeding 34 cm H2O can result in reduced perfusion to the trachea, while complete obstruction of tracheal blood flow is seen at around 50 cm H2O.(4) Lower pressures, below 34 cm H2O, are linked to a lower occurrence and severity of tracheal injury when using high-volume, low-pressure cuffs. Even at 27 cm H2O, tracheal blood flow can be diminished by 75% at the cuff site. Pathological changes associated with cuff overinflation include ischemia, inflammation, ulceration, granulation, and stenosis at the cuff contact site with trachea.

There are different techniques available to monitor the intracuff pressure, ranging from conventional to advanced as follows:

1. Manual Palpation of Pilot Balloon
2. Minimum Leak Technique (Mlt)
3. Minimum Occlusive Volume (Mov)
4. Predetermined Volume Technique
5. Analogue/Digital Manometer
6. Direct Intracuff Pressure Monitoring (figure 1)
7. Automatic Control Device
8. Pressure Sensing Syringe of Et Tube Cuff
9. Mobile Technique Application Programme
10. Air Bubble Technique

CUFF MANOMETER & TYPES

A cuff manometer enables the safe inflation of low-pressure endotracheal and laryngeal tube cuffs by accurately measuring cuff pressure. It features a pressure release valve on the back, allowing controlled release of air from the cuff to maintain optimal pressure levels. ⁽⁵⁾

METHOD OF USE

• Firmly attach the manometer to the pilot balloon of the cuff via the Luer connector. The cuff pressure is displayed on an aneroid scale or can be observed manually.
• To reduce high cuff pressure, release air using the pressure release mechanism or a syringe attached to the manometer.
• If an inadequate seal is present within the safe pressure zone, temporarily increase the pressure until a seal is achieved, while investigating possible causes such as tube position, cuff integrity, or ventilation issues.Minimal Leak Technique: Inflate the cuff, then release air until you hear a gurgling sound during inspiration, indicating a slight leak around the ETT cuff. Slowly reinflate the cuff until the leak stops, then verify that the cuff pressure remains within the safe range.

COMPLICATIONS

• Insecure attachment to the Luer connector can lead to inaccurate pressure measurements.
• Frequent deflation of the cuff may result in PEEP loss and increase the risk of microaspiration.
• Focusing solely on staying within the "safe" pressure range, without addressing ventilation issues, can cause ongoing cuff leaks, loss of PEEP, inadequate ventilation, and aspiration of secretions from above the cuff.
• Failing to apply necessary higher pressures for a proper seal may lead to mucosal damage or necrosis.
• Overemphasis on pressure readings can overlook the fact that a high air volume may have been added to achieve a seal, potentially indicating a high tube position or herniation of the cuff.
• If the pilot balloon tube is kinked (such as from a tie around the ETT), pressure readings may appear low despite adequate cuff inflation.

Today, there is a wide selection of cuff manometers available. Common types include aneroid manometers like the VBM cuff pressure gauge and the Posey Cufflator, as well as specialized cuff inflation syringes with built-in pressure gauges, such as the Tru-Cuff and AG-Cuffill syringes. Manual manometers remain among the most frequently used options in clinical settings.⁽⁶⁾

POST OPERATIVE SORETHROAT

Postoperative sore throat is a frequent and uncomfortable issue after tracheal intubation, primarily resulting from trauma to the airway mucosa ⁽⁹⁾. The reported incidence of this condition ranges between 21% and 65%. The causes of postoperative sore throat⁽¹⁵⁾ are varied, encompassing patient-specific factors such as age, sex, and smoking habits, as well as intubation-related aspects like technique, duration, tube size, cuff pressure, tube lubrication, cuff design, tube movement during surgery, and suctioning. Notably, one of the key contributors to postoperative sore throat is the pressure within the endotracheal tube cuff.⁽⁸⁾

Maintaining endotracheal tube cuff pressure in an optimum range have significant difference in the incidence of post extubation complaint of sore throat.

The recommended range of cuff pressure is 20-30cm h2o, if it is maintained below 25cmh2o there is significant reduction in the incidence.

AIMS & OBJECTIVES

Main aim of our study is to compare the quality of recovery in post-operative patients and hemodynamic stability, smooth extubation, less post operative airway related complication and better patient satisfaction in whom endotracheal cuff pressure is been measured and monitored intra operatively v/s not measured. Also we compare pain score of sore throat at 0, 2, 6, 12, 24 hrs after extubation, using VAS Score and Clinical category score.

Following approval from the Institutional Ethics Committee (approval no. 102/02/2023; Institutional Ethics Committee (Human), M.P. Shah Medical College, Jamnagar; date of approval: 11/04/2023) and after obtaining written informed consent, sixty adult patients aged 18–60 yrs, ASA grades II and III, with BMI between 18.5–29.9 kg/m², scheduled for elective surgeries under general anesthesia, were included in this study. Exclusion criteria included patients with BMI >30 kg/m², anatomical or pathological factors making airway management difficult, upper respiratory tract infections, coughing, cardiopulmonary disease, coagulopathies, increased intracranial pressure, allergies to the study drugs, Inadvertent difficult intubation, multiple attempts(>2attempts) and those undergoing emergency surgery. The study complies with the Declaration of Helsinki and relevant national laws and regulations.

Patients were randomly divided into 2 groups of 30 each.

• Group A (n-30) - Endotracheal tube cuff pressure measured and recorded using manometer.
• Group B (n-30) - Endotracheal tube cuff pressure not been measured.

A comprehensive pre-anesthetic assessment was performed, including a detailed medical history, systemic examination, and relevant recommended tests. The purpose and procedures of the study were clearly explained in the patient’s native language, and informed consent was obtained per hospital guidelines. All patients fasted for at least 6 hours prior to the procedure. Upon arrival in the preoperative area, baseline measurements were recorded, including radial artery pulse, respiratory rate, SpO₂ using a finger probe pulse oximeter, and non-invasive blood pressure. An 18- or 20-gauge venous cannula was inserted into the dorsum of the hand or forearm under aseptic conditions. Premedication was administered with Inj. Promethazine (0.5 mg/kg), Inj. Pentazocine (0.5 mg/kg), and Inj. Glycopyrrolate (4 mcg/kg), delivered intramuscularly 45 minutes before anesthesia induction. Ten minutes before induction, patients received Inj. Ondansetron (80 mcg/kg i.v) and Inj. Midazolam (20 mcg/kg i.v). In the operating theater, patients were monitored with a pulse oximeter, ECG, and non-invasive blood pressure cuff. Intravenous anesthesia induction was conducted using a Bain circuit with a properly sized face mask. Pre-oxygenation with 100% oxygen was provided for 3 minutes following premedication. To alleviate propofol-induced pain, lignocaine was used with venous occlusion. After exsanguinating the arm, a tourniquet was inflated to approximately 30 mmHg above systolic

pressure, with adequate pressure confirmed by the absence of a radial pulse.

Inj. Xylocard 1.5mg/kg iv slowly given.

The onset of analgesia after deflation of the tourniquet occurs within 3 minute.

This is followed by Inj. MgSo4 40mg/kg iv slow

Induction agent

 Inj. Propofol 2.0 mg/kg iv slowly

Pre intubation muscle relaxant:

 Inj. Succinylcholine 1.5 mg/kg iv stat

Endotracheal intubation

An oral Portex cuffed endotracheal tube (high volume, low pressure) of appropriate size was used for intubation. Specifically, a 7.5 mm cuffed endotracheal tube was used for female patients, while an 8.0 mm tube was used for males, ensuring proper positioning under visual guidance. The black line on the tube was aligned with the vocal cords to prevent the cuff from contacting the cords directly.

Cuff inflation was standardized across both groups using the minimal leak technique. The procedure began with placing a stethoscope diaphragm over the laryngeal area, followed by inflating the cuff until no air leak was detectable. The patient was then connected to the ventilator, and 0.5 ml of air was gradually released from the cuff in stages until a slight leak could be heard at peak inspiration.

Bilateral air entry checked and found to be equal, endotracheal tube fixed properly.A non-depolarizing muscle relaxant, Inj. Atracurium (0.5 mg/kg i.v), was administered slowly.

For anesthesia maintenance, IPPV was provided with a gas mixture of 60% nitrous oxide (N₂O) and 40% oxygen (O₂), along with 1-2% sevoflurane. Additional doses of Inj. Atracurium (0.1 mg/kg i.v) were given slowly to maintain muscle relaxation.

Group A, where cuff pressure was actively monitored, and Group B, which served as the control group.

Intraoperative monitoring done of the following Temperature, ECG, pulse oximetry, non invasive BP,  ETCO2 and endotracheal tube cuff pressure.

In Group A, cuff pressure was maintained within 20-25 cmH₂O, with regular checks every 15-30 minutes. Adjustments were made to the cuff volume via the side port of the pressure gauge. In Group B, after initial cuff inflation and fresh gas flow maintenance according to standardized protocol, no further intraoperative cuff pressure monitoring was conducted.

At the end of surgery, following thorough oropharyngeal suctioning, neuromuscular blockade was reversed using Inj. Neostigmine (80 mcg/kg) and Inj. Glycopyrrolate (8 mcg/kg). Patients demonstrated good recovery signs, including spontaneous breathing, sustained head lift for 30 seconds, and responsiveness to commands. Extubation was performed smoothly with the patient positioned chest-up, and the extubation time was recorded. Care was taken to minimize coughing on the tube before extubation, and the total surgery duration was noted.

Post-extubation, patients were interviewed by an anesthesiologist unaware of the group assignments to assess the presence and intensity of a sore throat at 0, 2, 6, and 24 hours. For patients reporting a sore throat, severity was rated using the Visual Analogue Scale (VAS) and Clinical Category Score, as outlined in Table 2b. Hoarseness, identified by changes in voice pitch, was also documented separately.

Postoperative pain was treated with Inj. Paracetamol (15 mg/kg) administered on an as-needed basis.

STATISTICAL ANALYSIS

We calculated that 60 patients would provide the study 90% power to identify effect size as small as 0.55 for the primary outcome with two sided type 1 error of 0.05, missing data for primary and secondary endpoints were corrected using regression based multiple imputation method, which assumed missing data was random. Data was analyzed using SPSS software version 26. Data is presented in tabular and graphical forms. Data was analyzed for normality distribution using Shapiro wilks test. Categorical data were presented as proportions or percentages, while continuous data were shown as medians with interquartile ranges. Baseline demographic characteristics between the groups were analyzed using the Mann-Whitney U test for continuous variables (such as age, surgery duration, and weight) and the Fisher exact test for categorical variables (such as sex and ASA grading). Difference between primary endpoint in between each group was analyzed using Mann Whitney u test. Intra group comparison of VAS score is analyzed using friedman test. P value of <0.05 was considered as statistically significant.

In our study, 60 patients were assessed for eligibility and subsequently randomized. A total of 30 patients were enrolled in each group and included in the final analysis. The study was conducted at M.P shah Medical College, Jamnagar from July 2023 to August 2024.

All patients completed the study with no loss to follow-up. No difference was found in demographic parameters, between two groups (Table 3).

Our results indicate that patients whose ETT cuff pressures were monitored and adjusted intraoperatively exhibited a lower incidence of postoperative respiratory complications compared to those with non-monitored cuffs. Specifically, the incidence of sore throat, hoarseness, and cough was reduced in the monitored group.

With regard to incidence of sorethroat postoperatively, out of the 30 participants in each group, the incidence of sorethroat was significantly higher in Group B, with 24 patients (80%) affected compared to 15 patients (50%) in Group A (p=0.029). The incidence of hoarseness was observed in 7 patients (23%) in Group A and 15 patients (50%) in Group B, though this difference was not statistically significant (p=0.060).

These findings are detailed in Table 4 and illustrated in Figure 3 & 4

We have aimed at getting to a conclusion in regard of the endotracheal tube cuff pressure measurement intraoperatively, which can improve the quality of postoperative outcome of the patient in regard to the airway.

Our study found a sore throat incidence of 50% in the study group (Group A) and 80% in the control group (Group B); however, this difference was not statistically significant. These rates fall within the higher end of the range reported by Ayoub et al., which identified an incidence between 21% and 65%.⁽¹⁴⁾

In a study done byDr S.Abirami, Dr.Yachendra et al stated a reduction in incidence of sorethroat in monitored group(46%) than control group(68%) which was found to be statistically significant and showed that cuff pressure monitoring can reduce the incidence of sorethroat.⁽⁷⁾

A study done by C.A.Hockey et al⁽⁹⁾stated that this review offers preliminary evidence that using objective measurements to adjust cuff pressure, rather than relying solely on subjective assessment or observation, can help prevent adverse effects such as hoarseness, sore throat, tracheal lesions, and silent aspiration, while ensuring precise cuff pressure management. Higher pressures (>30 cmH₂O) raise concerns due to the potential risk of tracheal injury, which may result from compromised blood flow in the tracheal mucosa.

Out of the 30 participants in each group, the median Category Scale Score was significantly lower in Group A, with a median score of 0.0 (range 0.0 – 1), compared to Group B, which had a median score of 1.0 (range 0 – 2) (p=0.000). These results are detailed in Table 5.

For assessing the post operative sorethroat severity in our study we had considered VAS score⁽¹⁰⁾ and Clinical category score⁽¹¹⁾ with strict timely followup at 0,2,6,12 and 24 hours.

Out of the 30 participants in each group, the median Category Scale Score was significantly lower in Group A, with a median score of 0.0 (range 0.0 – 1), compared to Group B, which had a median score of 1.0 (range 0 – 2) (p=0.000). According to this can be considered significant.

In our study participants, Table 6 and Figure 5 show the intergroup comparison of VASscore changes in both groups. Group A consistently had lower VAS scores at all time points compared to Group B. After extubation, the median VAS score in Group A was 1 (range 0 – 2) versus 4 (range 4 – 5) in Group B (p=0.000).

At 2-, 6-, 12-, and 24-hours post-extubation, Group A maintained a median score of 0, while Group B’s scores were 3, 2, 1.5, and 1, respectively, all with p=0.000.

These results indicate a significant difference in VAS scores between the groups at all time points.

The statistically significant χ² values (Group A: 57.49, Group B: 108.6; p=0.000) indicate that there was a significant change in VAS scores within each group across the different time points.

In a study conducted by Seegobin et al., the effect of cuff pressure on tracheal mucosal perfusion ⁽¹²⁾ was examined, concluding that perfusion to the tracheal mucosa ceases at a cuff pressure of 30 cm H₂O, leading to ischemic damage. They recommended maintaining cuff pressure below 20 mmHg to prevent mucosal injury.

Our study aligns with findings from research by Gregory J. Stevens, which showed a significant improvement in maintaining cuff pressures within the target range following a quality improvement initiative, highlighting the benefits of careful pressure monitoring.⁽¹³⁾

In conclusion, intraoperative monitoring of cuff pressure using a cuff pressure monitor was effective in reducing both the incidence and severity of sore throat, as well as hoarseness, in patients undergoing orotracheal intubation. However, these improvements were not statistically significant, though they contributed to a noticeably better quality of postoperative recovery.

LIMITATION OF STUDY

Due to the impracticality of blinding, the anesthetist performing the monitoring was aware of the study group, introducing a potential for bias. Our study was conducted with a small sample of patients. To demonstrate the importance of this technique in operation theatre, large scale studied should be carried out.

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