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Manual In-Line Stabilization of the Cervical Spine Increases the Rate of Difficult Oro-Tracheal Intubation in Adults - A Randomized Controlled Trial

Adesida A, Desalu I, Adeyemo WL, Kushimo O

College of Medicine, University of Lagos, Nigeria

Correspondence to: Dr. Adeniyi Adesida, Idi Araba Lagos, Nigeria. PMB 12003, Email:


Background: Patients with traumatic brain injury present with loss of consciousness and suspected cervical fracture. The aim of this study was to determine the rate of difficult orotracheal intubation in surgical patients undergoing various procedures when manual in-line neck immobilization technique was applied. Methods: This was a randomized prospective study at the Lagos University Teaching Hospital. A total of 100 patients were enrolled into the study and were allocated into 2 groups of either Manual In-Line Stabilization (MILS) or Early Morning Sniffing position (EMSP) techniques during intubation. Successful or unsuccessful intubations within 30secs, as well as time to successful intubation were the outcome measures. Results: The mean ± SD intubation time for successful intubation was similar in both groups (MILS=17.9±7.7seconds, EMSP=14.6±6.6 seconds (p=0.359)).There were more failed intubations in the MILS group (27%) and (2%) in the EMSP group (p=0.001). Conclusion: The study showed that patients who had MILS had more failed intubations than those that were intubated with the EMSP technique. With this level of failed intubations there is need for provision of difficult airway laryngoscopic adjuncts for patients with diagnosed cervical fracture and uncleared cervical injury who require orotracheal intubation.

Key Words: Manual inline stabilization, Cervical spine injury, Orotracheal intubation, Difficult intubation

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Manual in-line stabilization (MILS) of the cervical spine is an integral part of airway management when dealing with trauma patients(1). Accentuation of existing neurologic abnormalities has been documented after intubation of patients with unsuspected cervical spine injury(2). Immobilization of the neck is indicated before airway management in all acute trauma patients with depressed consciousness, cervical pain, posterior midline cervical tenderness, extremity paraesthesia, or focal neurological deficit or when pain from other injuries is likely to mask the neck pains (3). Suspicion of cervical spine injury (CSI) is increased by the following risk factors, a high risk mechanism of injury such as falls, diving, high speed motor vehicle accidents and restriction of active neck movements especially rotation (4).

Normal intubation in an adult involves the placement of the head in the early morning sniffing position (EMSP) which anatomically flexes the neck on an extended atlanto-occipital joint of the cervical vertebrae. MILS is a manoeuvre that is performed by grasping the mastoid process of the patient, thus preventing movement of the cervical spine during tracheal intubation (5). Though it prevents further damage to the spinal cord, MILS limits movement of the head during tracheal intubation and impairs visualization of the larynx, as consistently shown by a reduction in Cormack and Lehane’s grade visualization and an increased incidence of grades 2, 3 and 4 (1,6). This theoretically may result in a higher incidence of difficult intubation. MILS is frequently used while securing the airway of patients with a known or potentially unstable cervical spine but its effect and other immobilization techniques on the success of endotracheal intubation is still a subject of major debate (6,7). The effect of MILS on the incidence of difficult intubation has not been investigated among the black Africans. This study sought to evaluate the rate of difficult orotracheal intubation during laryngoscopy in surgical patients undergoing MILS and to compare it with those who had laryngoscopy in the standard EMSP.



This was a randomized controlled study conducted at the Lagos University Teaching Hospital (LUTH) and approved by the hospital’s research and ethics committee. The study population were a convenient sample of 100 adult patients (>18 years of age) based on previous similar study, screened from a population of patients