Predictors of difficult videolaryngoscopic intubation.

A thorough preoperative airway assessment will be carried out using a multiple  point predictor chart in patients with an anticipated difficult airway SARI score more than three . The demographic parameters and the presence or absence of the following predictors will be noted by an independent assessor not part of the study: Age BMI history of snoring Interncisor distance Protruding incisors Mallampati score Subluxation of Atlantooccipital joint Bite index Neck Flexion Neck Extension Neck circumference Thyrohyoid distance Thyromental distance Sternomental distance history of  difficult intubation history of radiation to neck Obscuring upper airway lesions Maxillofacial abnormality Cervical spine immobility or instability Previous head and neck resection and Planned nasal or oral intubation.

The measured indices will be defined and graded as per standard definitions.

Prior to anaesthesia induction in the operating room, the positioning of the patients will be done by placing a seven cm high pillow beneath the head with the head in supine neutral position for intubation. After a standardized premedication and anesthesia induction, intubation would be done using the video laryngoscope. The BPL videolaryngoscope (Product of: BPL MEDICAL TECHNOLOGIES PRIVATE LIMITED, Ph: 1800-425-2355, BPL WORKS, PALAKKAD, KERALA, INDIA - 678007 ) will inserted down the midline of the mouth via the central

approach and the vocal cords will be visualized as recommended by the manufacturer. The view of the glottis displayed on the monitor screen of the videolaryngoscope will noted using the Cormack and Lehane scale. An endotracheal tubes of Internal Diameters seven mm and eight mm for female and male patients respectively, mounted on a malleable stylet in case of oral intubation with its distal end angulated upward by about sixty degrees will be inserted toward the glottis. The stylet will be removed when the tip of the endotracheal tube will be seen entering the trachea. No stylet will be used in case of nasal intubation. The cuff of the endotracheal tube will be inflated and the tube fixed in place after removing the laryngoscope from the mouth. All intubations will be performed by an experienced anaesthetist with more than twenty successful intubations with the video laryngoscope. In case of a CL grade of three or more, a BURP (Backward, Upward, Right sided Pressure) will be attempted to improve the vision of the vocal cords. The accurate positioning of the endotracheal tube will be confirmed by capnography and lung auscultation.

Ease of intubation with the videolaryngoscope will be measured using two outcomes: the time to intubate and the number of attempts needed for successful intubation. The total time to intubate  will be measured from the time the videolaryngoscope entered the patient’s mouth until the endotracheal tube was seen going through the vocal cords. An unsuccessful attempt will be recorded if the videolaryngoscope or the endotracheal tube needs to be withdrawn from the mouth. During the next attempt, the distal end of the endotracheal tube will be angulated further upward and/or the videolaryngoscope’s blade will be repositioned. The time interval from taking the endotracheal tube in the hand to the visualization of the successful passage of the tube across the vocal cord  will also be noted. If the time to intubate  is more than sixty sec whether intubation was successful or not,  it will be noted as a difficult intubation attempt. In case of more than two failed attempts to intubate the patient or more than sixty seconds time taken for intubation using Video Laryngoscope, the anaesthetist will

be allowed to use alternate devices for intubation.

The outcome of the study will be measured in terms of the number of predictors consistently associated with more than two attempts at intubation or an increased time to intubate more than sixty  seconds.