A Novel Way to Estimate Epidural Depth in Morbidly Obese Parturient

• Estimate Epidural Depth in Morbidly Obese Parturients (BMI>40kg/m2) [ Time Frame: Five minutes for ultrasound measurement ] [ Designated as safety issue: No ]
  To determine the correlation between actual epidural needle depth (ND) and estimated epidural depth (Est-D) with the use of ultrasound and the epidural depth equation (EQ-US).
  
  
• Epidural Depth [ Time Frame: at the time of labor epidural catheter insertion (an average of 5 minutes for ultrasound visualization) ] [ Designated as safety issue: No ]
  epidural depth measured from the skin to the epidural space with the use of ultrasound done just prior to labor epidural catheter insertion for relief of labor pain.
  
  

The investigators plan to enroll women who are morbidly obese (BMI > 40 kg/m2) and request epidural analgesia for labor. After written informed consent, 160 patients will have the use of the epidural depth equation with ultrasound (EQ-US) to estimate epidural depth (Est-D). US visualization of the epidural space will be completed by the principle investigator who has had extensive training in epidural US visualization. The EQ-US depth will be recorded. After US use, another provider who is listed as an investigator will place the epidural catheter without prior knowledge of the estimated epidural depth with the use of the equation and US. The actual needle depth to the epidural space (ND) will be recorded.

Data collected from the patient's medical record will include demographic data (age, height, weight) gravidity, parity, and cervical dilation. Measured variables will include the estimated epidural depth (Est-D) as measured by the epidural depth equation with the use of ultrasound (EQ-US), and actual epidural needle depth (ND). The investigators believe that the use of ultrasound with the epidural depth equation (EQ-US) to estimate epidural depth (Est-D) in morbidly obese parturients will have a high correlation with actual epidural needle depth (ND).