Digital Palpation of the Cricothyroid Membrane Is Unreliable in Obese Laboring Patients

Calvin A. Brown III, MD, FAAEM reviewing You-Ten KE et al. Anaesthesia 2015 Nov.

In laboring at-term patients, palpation of the cricothyroid membrane was less accurate in obese than in nonobese patients, whereas ultrasound identified the cricothyroid membrane in all patients.

Obesity is a common marker of airway difficulty and may make a “can't intubate, can't oxygenate” scenario (and the need for surgical rescue) more likely. Obese obstetrical patients are particularly challenging to manage because of higher rates of oxygen consumption and airway edema. Identification of neck landmarks is critical in performing cricothyrotomy quickly, but obesity can obscure neck landmarks. Ultrasound may augment localization of the cricothyroid membrane, especially when landmarks are indistinct.

Researchers at a Canadian tertiary care academic center randomized 41 anesthesia providers to digitally palpate and mark the cricothyroid membrane in 28 obese or 28 nonobese term pregnant patients in uncomplicated labor. A single ultrasound-trained operator then used a high-frequency linear probe to identify and mark the midpoint of the membrane. The cricothyroid membrane was considered correctly identified if the provider's mark was within 4 mm of the ultrasound mark.

The median distance between the two marks was greater in obese patients than in nonobese patients (5.0 mm vs. 1.8 mm), and the cricothyroid membrane was correctly identified less often in obese patients (39% vs. 71%). The membrane was easily identified by bedside ultrasound in all patients.

Citation(s):

You-Ten KE et al. Accuracy of conventional digital palpation and ultrasound of the cricothyroid membrane in obese women in labour. Anaesthesia 2015 Nov; 70:1230.