Does Neck Circumference Help to Predict Difficult Airway in Obstetric Patients?
Condition: Difficult; Intubation, in Pregnancy
Study type: Observational

Summary: 
      Failed intubation and ventilation in obstetrics remains one of the most common causes of
      death directly related to anesthesia. The reported incidence of failed intubation in
      obstetrics is 1:300, which is significantly higher than that in the non-obstetric population.
      A clinical screening test with high sensitivity and specificity for prediction of difficult
      airway may help reduce morbidity and mortality from general anesthesia. Few studies have
      identified increased neck circumference as the best single predictor of problematic
      intubation. However the cutoff point of this test for identifying patients at high risk of
      difficult intubation is not clear.

      The aim of this study is to determine the optimal cutoff point, which validates prediction of
      difficult ventilation and/or intubation for obstetric patients. Preoperative airway
      assessment will be done including neck circumference. Intraoperative difficult ventilation
      and/or intubation will be recorded. Optimal cutoff point of neck circumference will be
      calculated by Receiver Operating characteristics (ROC) curve.
    

Detailed description: 
      In this prospective study, patients will be assessed by the anaesthetist preoperatively and
      asked about their medical history including detailed history of obstructive sleep apnea (OSA)
      and snoring. Physical examination including weight,height &BMI .

      Airway assessment will include:

        1. Maximum mouth opening measured as interincisor gap (mm).

        2. Sternomental distance measured as the straight distance between the upper border of
           manubrium sterni and the bony point of the mentum with the head in full extension and
           the mouth is closed (cm).

        3. Hyomental distance measured from just above the hyoid bone to the tip to the
           anterior-most part of the mentum in both neutral position and with maximum head
           extension (cm). Hence, hyomental distance ratio (HMDR) will be calculated.

        4. Thyromental distance measured as the distance from the thyroid notch to the inner margin
           of the mental prominence when the head is fully extended (cm).

        5. Extended Mallampati Score (EMS) in sitting position with full extension of
           craniocervical junction with phonation (class I: Entire Uvula is clearly visible; class
           II: Upper half of the uvula is visible; class III: soft and hard palate clearly visible;
           and class IV: Only hard palate is visible).

        6. Neck Circumference at the level of the thyroid cartilage (cm).

        7. Condition of the teeth (Protrusion, loose, missing).

        8. Mandibular protrusion test to detect temporomandibular joint mobility measured as
           ability to move the lower teeth in front of the upper teeth.

      Intubation will be considered difficult if the Intubation Difficulty Scale ( IDS) is equal or
      more than 5 .
    

Observational model: Cohort
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        patients scheduled for cesarean section under general anesthesia