The influence of obesity on the relationship between body mass index and the distance to the epidural space from the skin.

This study confirms that distance to the epidural space from the skin at the L3-4 interspace is only moderately correlated with body mass index in obstetric patients. A similar moderate linear correlation was found in the non-obstetric patients. However, in obese patients (BMI > 25), distance to epidural space from the skin correlated poorly with body mass index.