Morphometric analysis and clinical application of the working dimensions of cricothyroid membrane in south Indian adults: with special relevance to surgical cricothyroidotomy.

Objective: To measure the working dimensions of the cricothyroid membrane in the adult south Indian population and to establish the association between the working dimensions and the appropriate endotracheal tube size for the purpose of cricothyroidotomy.

Methods: Cross-sectional evaluation of 50 fresh adult autopsy cases (35 men, 15 women) in a medical university teaching hospital in South India.

Results: Age ranged from 17.0 to 83.0 years. Working dimensions of the membrane in neutral position of neck, in men: width = 8.41 +/- 2.11 mm, height = 6.57 +/- 1.87 mm; in women: width = 6.30 +/- 1.29 mm, height = 5.80 +/- 1.56 mm. Depth of the subglottic larynx at the level of cricoid cartilage: men = 20.73 +/- 1.97 mm, women = 15.62 +/- 1.71 mm. Distance of the lower border of cricothyroid membrane from suprasternal notch in neutral position of neck, in men = 5.18 +/- 1.76 cm, women = 4.72 +/- 1.55 cm; in passively extended neck, men = 7.86 +/- 1.25 cm, women = 8.05 +/- 1.28 cm. Regression equations have been derived to determine endotracheal tube size for cricothyroidotomy, based on distance between sternal notch and chin, and height of the individual (P < 0.05).

Conclusions: Working dimensions are smaller in the Indian group compared with western publications. Endotracheal tubes ranging from size 3.0 to 6.0 might be used for cricothyroidotomy in the adult south Indian population.