The study is designed to evaluate the validity of the SMDD as a predictor of difficult airway in elderly and to compare its validity with that of the TMHT.

The airway assessment for difficulty before anesthesia in the elderly is crucial as the delay in the endotracheal intubation in this age group can lead to fatal consequences due to limited organ reserve and comorbidities. Previous studies revealed that elderly patients are predisposed to an increased incidence of difficult airway due to the age-related anatomic changes of the head and neck. These changes include, but not limited to, teeth loss, narrow dental arch, reduced oral soft tissue flexibility, TMJ dysfunction, degenerative change of ligament and tendons of the intervertebral discs causing compression of the intervertebral discs, cervical lordosis and spondylosis, limited head and upper neck extension, and fixed cervical spine flexion deformity.

Sternomental displacement (SMDD) is a relatively new objective airway measure that represents the difference between Sternomental distance that is measured while the head is extended on the neck (SMD-extension) and the Sternomental distance that is measured while the head is in a neutral position (SMD-neutral). The SMDD is a surrogate indicator of neck mobility. Both TMHT and SMDD were proved to be a good objective predictor for difficult laryngoscopy (DL) in adult surgical patients.

The TMHT was proved to have good predictive ability for difficult airway in elderly patients, but to the best of our knowledge, the SMDD was not previously evaluated in elderly. This study was designed to evaluate the validity of the SMDD as a predictor of difficult airway in elderly and to compare its validity with that of the TMHT. Our primary endpoint is the AUROC curve (area under receiver operating characteristic curve), sensitivity, specificity of the SMDD as a predictor of difficult laryngoscopy in elderly surgical patients. The secondary endpoint is to compare the validity of SMDD for predicting difficult airway with that of the TMHT and (Modified Mallampati test) MMT.

Inclusion Criteria:

1. elderly patients aged ≥ 65 years both male & female .
2. ASA physical status I, II, and III .
3. patients scheduled for elective surgeries under general anesthesia .

Exclusion Criteria:

1. Patients undergoing emergency procedure
2. patients requiring elective awake fiberoptic.
3. patients having neuromuscular disorders or craniofacial abnormalities
4. patients with cervical spine surgeries, neck scars, obvious limited neck extension.
5. morbid obesity (MBI ˃40 kg/m2)

In our study, 150 elderly patients who are scheduled for elective surgeries under general anesthesia with endotracheal intubation accomplished using conventional laryngoscopy will be included.