Background
Cricothyrotomy is recognised as a potentially life saving airway management technique in the Can’t Intubate, Can’t Oxygenate scenario (CICO). The technique involves rapid and accurate palpation and identification of structures to facilitate Front of Neck Access (FONA). However, identification of these structures is difficult in obese parturients, due to adipose tissue deposition. We hypothesised that the use of ultrasound would facilitate accurate and speedy identification of the key landmarks.

Methods
Following IRB approval, we recruited volunteers from the Complex Obstetric Anaesthesia Clinic at University Maternity Hospital Limerick, with BMI > 35 to participate in a double blinded, cross over investigation. Under control conditions, the cricothyroid membrane was identified by the first investigator using both ultrasound and palpation technique. The site was marked with a UV light visible pen. Under test conditions the second investigator marked the site using both techniques, and was timed using both methods. 

Results
The Ultrasound technique was positively skewed Median 2 (IQR 1,4) vs Landmark postively skewed Meidan 4 (IQR 2,8)  based on controls (p=0.001, wilcoxin signed rank test).  Mean time for US was 25.6 seconds compared to Landmark measures 16.87 (p=0.001). 

Conclusions
The Ultrasound technique for identification of the cricothyroid membrane is significantly more accurate than traditional palpation methods in obese parturients, and can be carried out rapidly under clinical conditions. It will improve safety and limit complications and could become part of routine clinical airway examination

Ultrasound guided identification of the crico-thyroid membrane to facilitate front of neck access in obese parturients; a feasibility study