Evaluation of Difficult Airway With Ultrasonography
Condition: Difficult Intubation; Obesity
Study type: Observational

Summary: 
      As a result of anatomical and physiological changes in obese patients, airway management can
      be challenging. Ultrasound measurement of neck anterior soft tissues combined with
      recommended predictive tests may increase the ability to predict the difficult airway. In
      this study we planned to evaluate the measurement of neck anterior soft tissues by ultrasound
      in obese patients before anesthesia induction to anticipate difficult mask ventilation,
      difficult laryngoscopy, and intubation.
    

Detailed description: 
      Patients with BMI> 30, schedule elective surgery under general anesthesia, and give consent
      will be included in the study. In the preoperative evaluation, demographic data of the
      patients, airway physical examination results (mouth opening, Mallampati score, thyromental
      distance, neck circumference (from thyroid cartilage level), abnormal upper tooth presence,
      neck movement restriction], presence of sleep apnea and STOP-BANG score will be recorded. In
      the patients taken on the operation table with supine position, ultrasound-guided soft tissue
      distances will be measured using ultrasound 6-13 Hz linear probe. The distance between the
      hyoid bone-skin (DSHB), the vocal cord anterior commissura-skin distance (DSAC), the minimum
      distance of the trachea to the skin at the level of the suprasternal notch (DST), the
      distance between the thyroid isthmus and the skin (DSI), and the distance between the
      epiglottis and the skin (DSE) will be measured and recorded. After standard monitoring and
      anesthesia induction, difficult mask ventilation will be evaluated with Han Scale [(1) can be
      ventilated with a mask; 2) can be ventilated with the airway (with or without muscle
      relaxation); 3) difficult mask ventilation (insufficient, unstable, two practitioners are
      needed); 4) cannot be ventilated by mask] and grade 3-4 will be recorded as difficult mask
      ventilation. Difficult laryngoscopy will be evaluated with Cormack Lehane Scale [grade 1:
      vocal cords appear; grade-2: posterior commissura and epiglottis visible; grade-3: only
      epiglottis are seen; grade-4: glottic structures are not visible] and grade 3-4 will be
      recorded as difficult laryngoscopy. Difficult intubation will also be evaluated with the
      number and duration of intubation attempts with the Macintosh blade. Tracheal intubation will
      be performed by an anesthesiologist who has at least two years of experience and unaware of
      ultrasound measurements. The duration of intubation (the time from the first handling of the
      laryngoscope until the capnography trace appeared) and the number of trials will be recorded.
    

Intervention name(s): Distance between hyoid bone-skin (DSHB); Vocal cord anterior commissura-skin distance (DSAC); minimum distance of the trachea to the skin at the level of suprasternal notch; Thyroid isthmus-skin distance (DSI); Skin-epiglottic distance (DSE)
Intervention type(s): Diagnostic Test; Diagnostic Test; Diagnostic Test; Diagnostic Test; Diagnostic Test
Intervention description(s): Distance between hyoid bone-skin; Vocal cord anterior commissura-skin distance; Distance of the trachea to the skin at the level of suprasternal notch; Thyroid isthmus-skin distance; Skin-epiglottic distance
Other intervention name(s): DSHB; DSAC; DST; DSI; DSE
Observational model: Cohort
Time perspective: Prospective
Sampling method: Probability Sample
Study population: 
        A hundred twenty-eight patients, aged 18-65 years-old, with an American Anesthesiology
        Association physical classification (ASA) I-III and body mass index (BMI) above 30 and
        planned to undergo general anesthesia for elective surgery, will be included in the study.
      
Keywords: Difficult mask; Difficult laryngoscopy; Difficult intubation