Influence of operating table height on laryngeal view during direct laryngoscopy: A randomized prospective crossover trial.

Maintenance of a patent airway is afundamental responsibility of the anesthesiologist. Tracheal intubation remainsone of the commonest means of establishing an airway. Placing the head and neckin the sniffing position has traditionally beenconsidered important for obtaining good glottic visualization during directlaryngoscopy. Direct laryngoscopy is used to facilitate tracheal intubation undervision. Successful direct laryngoscopy depends on achieving a line of sightfrom the maxillary teeth to the larynx 1.It has been clearlyestablished in several studies that proper positioning of head and neck is oneof the most important step towards laryngoscopy and tracheal intubation whichhelps in obtaining a good glottic view, thus minimizing the rate of tracheal injury, duration of the procedure, repeatedattempts at laryngoscopy and intubation- ultimately reducing the overall rateof trauma and further complications. Best laryngoscopic views are obtained whenoropharyngo-laryngeal axes come in a straight line. The ‘sniff’ position hasbeen advocated as a standard for direct laryngoscopy. In this position, theneck is flexed on the chest and the head is extended on the atlanto-occipitaljoint by elevating the head on a pillows 2,3.The ‘sniff’ position is usually the best starting positionfor direct laryngoscopy. In the ‘sniff’ position, the cervical spine below C5is relatively straight, there is increasing flexion from C4 to C2, and the headis fully extended (occipito– atlanto–axial complex) 4. Neck flexion between C2 and C4 is achieved by elevationof the head.

Operating table height can influence task performance andphysical/mental workload5, 6 .There have beenfew studies of the correlation between the operating table height and thequality of laryngeal view during direct laryngoscopic (DL) intubation7.In an editorial on anesthesiologist stature and patient positioning, Heath7 highlighted thebenefits of using an adjustable operating table and the ergonomic benefits ofdifferent heights—high during cannulation to prevent back discomfort, a bitlower for airway management, and even lower for short trainees. It has beensuggested that the patient’s face should be placed at the height of the anesthesiologist’sxiphoid process for comfortable intubation without requiring the anesthesiologistto bend his/her back 8-10 and thatthe physician’s eyes should be placed 1 foot (30 cm) above the patient’s faceto provide proper angles and distances for laryngoscopy 11. However, these resultsare based on clinical experience rather than scientific validation.

Theaim of this study was to evaluate the quality of the laryngeal view (primaryvariable), ease of intubation and anesthesiologist’s comfort (secondaryvariable) associated with three different operating table heights during DL andtracheal intubation. Based on our clinical experience, we hypothesized thathigher operating tables would improve the quality of the laryngeal view anddecrease anesthesiologist’s discomfort during tracheal intubation by reducingthe need to bend their neck or lower back when compared with lower operatingtable height.