Effect of Inflated Versus Non-inflated Endotracheal Tube on Sore Throat

Effect of Kinetic Contact-friction Modulation With a Pre-inflated Tracheal Tube Cuff on Postoperative Sore Throat in Adults With Anticipated Non-difficult Airway: a Randomized Controlled Study

Postoperative sore throat (POST) is a common morbidity following upper airway access-control with direct laryngoscopy-intubation (DLI) technique. Various reasons (size of the tracheal tube, cuff pressure, rough tube pass, and reattempts, among others) have been cited and management strategies (pharmacologic: applying lidocaine gel/EMLA cream on the cuff surface; non-pharmacologic measures: tracheal tube cuff pressure control, optimization of tracheal tube size, applying lubricating gel) have been tried, but none has been able to decrease the incidence of POST nor has been able to decrease the suffering of patients.

Traditionally, intubation is performed with a deflated endotracheal tube and the cuff is later inflated to secure the tube in desired position. The striated folds present in the deflated cuff incurs additional dynamic friction that traumatizes upper airway mucosa during the procedure, causing the risk of POST. While accentuated friction burden on the posterior part of vocal cords and the tracheal mucosa has been studied recently, there has been no work on understanding the kinetic contact- friction ensued by a passing tracheal tube/cuff. We speculate that dynamic contact-friction generated at the time of passing of a cuffed tracheal tube is the major active component which has potential to cause actual tissue trauma and inflammation resulting in adverse effects (POST, hoarseness, throat pain, cough). This study aims to evaluate the effects of reducing dynamic/kinetic contact-friction by employing a pre-inflated tracheal tube cuff to pass the vocal cords at the time of orotracheal intubation.

Postoperative sore throat (POST) has long been a common and nagging complication following conventional direct laryngoscopy-intubation (DLI) procedure. A significant quantum of POST incidence during DLI in non-difficult airway (NDA) could be attributed to inter-operator variability in approach, experience, proficiency, and equipment (e.g., type of laryngoscope/tracheal tube). Additional factors determining the occurrence of POST, include size of the tracheal tube, cuff pressure, rough tube pass, and reattempts, among others. Several pharmacologic (applying lidocaine gel, inhaled corticosteroids and EMLA cream on tracheal tube cuff surface) and non- pharmacologic measures/modalities (e.g., tracheal tube cuff pressure control, optimization of tracheal tube size, applying gel) have been employed to preclude/diminish POST, however, neither the incidence nor the suffering of patients have come down yet following these interventions. Friction injury to the tracheal mucosa during the passage of ETT is one of the important contributing factors to POST but has not been adequately evaluated. Friction injury to the upper airway mucosa not only occurs during rough or repeated passage of ETT through the glottic-inlet but also when the ETT cuff comes in contact with the tracheal mucosa during dynamic passage of ETT through the glottis.

Traditional approach to reduce reduce postoperative sore throat is by containing the intracuff pressure with use of non-inflated tube, and consequently, reducing static pressure burden on tracheal mucosa. No study has explored the impact of modulation of obligate kinetic contact-friction that occurs during passage of tube across the glottic-inlet. A preemptive limited inflation of tracheal tube cuff before actual intubation may modulate the kinetic-contact friction during the passage of the tracheal tube cuff past the vocal cords, and hence may help reduce postoperative sore throat in these patients. We plan this randomized trial to compare the effect/efficacy of intubation with pre-inflated tracheal tube on the incidence of postoperative sore throat in patients with anticipated non-difficult airway.

Inclusion Criteria:

• ASA physical status I and II

• Patients with anticipated non-difficult airway with the following characteristics:

  i. Normal head and neck movements ii. Adequate mouth opening iii. No retrognathia or prognathia iv. Normal dentition

• Surgeries with anticipated duration of 40 minutes - 3 hours

Exclusion Criteria:

• Obese patients (BMI > 33 kg/m2)
• Requiring use of intubation aids such as bougie, stylet or video-laryngoscope
• Recent history of steroid or non-steroidal anti-inflammatory drug use
• Systemic illness with presenting complaints of sore/dry throat (diabetics with polydipsia, hypertensives on diuretics, moribund bed ridden patients)
• History of airway related morbidity post operative sore throat [POST]
• Patients with a history of chronic smoking (1 pack per day for 10 years) chewing tobacco, and tobacco-related products
• Patients undergoing head and neck, intraoral/nasal surgery, or recent history of such surgery
• Patients with a past surgical history of tracheostomy (post decannulation)
• Surgery in prone position
• Ongoing upper and lower respiratory tract inflammation/infection
• Patients with anticipated postoperative mechanical ventilation
• Refusal to participate in the study