Methodology

In the pre-anaesthetic checkup, thorough airway examination including mouth opening, inter-incisor distance, modified Mallampati class, thyromental distance, sternomental distance, neck mobility will be assessed. Patients will be kept fasting for 8 hours. Age, gender, weight, height, airway parameters, and name of the surgery will be noted.On the day of surgery, after confirming the patient fasting status and consent form, patients will be placed supine on operating table with the head and neck being maintained in neutral position as confirmed by direct visualisation. ASA recommended standard monitors including pulse oximetry, capnograph, three lead ECG and non-invasive blood pressure will be attached to the patients. Baseline heart rate, non-invasive blood pressure, SpO2 will be recorded. An appropriate gauge IV line will be secured as per the attending anaesthesiologist in the OT.

Patients will be pre-oxygenated with 100% oxygen and induced using intravenous fentanyl 2mcg/kg, propofol 2-2.5mg/kg. After confirming adequate bag-mask ventilation, muscle relaxation will be done using rocuronium 1mg/kg. Cervical spine immobilisation will be achieved by using either cervical collar or MILS. A well-fitting cervical collar (Tomson cervical collar, TOMSON MEDICARE PVT. LTD) will be adjusted to correct size and applied according to the manufacturer’s instructions in one group of patients. MILS will be applied by experienced anaesthesiologist who had performed >30 MILS in another group of patients. Stabilise the patients head in a neutral position by removing the pillow, so that the patient’s shoulders and occiput are rested on the operation table in another group of patients. Both mastoid processes will be grasped by the thumb and palms will be placed on either side of the head, and the occiput will be held firmly in the hands by the fingers to avoid axial traction by applying force equal and opposite to that created by the intubating anaesthesiologist.

 Bag and mask ventilation will be performed for 3 minutes. Difficulty in mask ventilation requiring a 2-hand technique or change of operator or guedul airway requirement (oropharyngeal airway) will be noted. During bag and mask ventilation, tidal volume delivered to the patient, chest rise, SpO2, end tidal CO2 will be noted.Then, intubation will be attempted with CMAC video laryngoscope of appropriate blade size depending on the patient (either 3 or 4) by anaesthetist who has experience using CMAC at least 30 times. After opening the mouth, CMAC will be inserted, and the glottis view will be measured according to POGO and Cormack Lahane grading. An independent person will start timer. Intubation time will be recorded from insertion of the CMAC to confirmation of end-tidal CO2.An appropriately sized (females with 7 or 7.5 and males with 8 or 8.5) cuffed endotracheal tube (ETT) along with stylet will be introduced into glottis opening. Successful intubation will be confirmed when EtCO2 is detected using capnography. CMAC will be removed from the patient’s mouth and cuff of ETT will be inflated. Intubation difficulty score will be noted by the intubating anaesthesiologist.

During the intubation process, the attempt will be terminated if the saturation of peripheral pulse oximetry drops below 92% or the intubation time delayed beyond 90 s, whichever occurring earlier. Bag and mask ventilation will be resumed between the intubation attempts. Next attempt will be performed using any additional technique like bougie or external laryngeal pressure. A maximum of 2 attempts will be allowed. If intubation fails after two attempts, failure of intubation will be declared and standard intubation without cervical spine immobilisation by removing cervical collar or MILS will be performed. Number of attempts required and failure to intubate will be noted. Any airway-related complications such as airway trauma in the form of injury to lips, teeth, mucosal injury, laryngeal oedema, laryngospasm, bronchospasm will be noted. After confirming the successful intubation, patient will be handed over to surgeons and surgery will be proceeded.