Effect of Placing the Endotracheal Tube Beyond Cervical C7 Level in Anterior Cervical Decompression and Fusion Surgery

Endotracheal intubation is performed to secure the patient's airway during general anaesthesia undergoing surgery. The procedure involves placing a tube known as endotracheal tube (ETT) mouth into the trachea. The ETT usually has a cuff at the distal part of the tube which functions as a seal to the trachea for proper delivery serves as protection against the ingress of pathogens and fluids from the pharyngeal space into the lower airways. During intubation, the cuff usually positioned just beyond the vocal cord which is anatomically situated at cervical vertebrae C5 to C6 in adult. After intubation, the endotracheal cuff pressure (ETCP) is checked once or intermittently and kept within appropriate range as cuff overinflation can cause complications that range from mild sore throat to tracheal ischemia, tracheal rupture and fistula formation. The recommended range for ETCP is between 20 to 30 cm H2O. For surgeries performed on head and neck region, the monitoring of ETCP is difficult as this might intrude into the sterile surgical field. Anterior decompression and fusion (ACDF) surgery is commonly performed to treat cervical spine issues such as herniated discs, spinal stenosis, or degenerative disc disease. During ACDF, the surgeon accesses the cervical spine from the anterior of the neck by moving aside the soft tissues to gain access to the spine. While doing this, a surgical retractor is often used to hold the tissues aside carotid sheath laterally, and the trachea and the oesophagus medially. Placement of a retractor during ACDF may inadvertently lead to compression or pressure on the conventionaly placed ETT resulted in rise in ETCP as high as 50 mmHg and causes airway complications such as dysphagia, sore throat and dysphonia. We hypothesize by positioning the endotracheal cuff deeper beyond the cervical vertebrae C7 would not cause significant rise in ETCP during retractor placement based on the assumption that the surgical retractor would not directly compress on the cuff. The investigators designed this study to observe ETCP changes before and after retractor placement and associated complication.