The comparative accuracy of a handheld and console ultrasound device for neuraxial depth and landmark assessment

The study aimed to compare the accuracy of epidural depth estimation of a handheld ultrasound device, with an integrated algorithm that estimates epidural depth (AU; Accuro, Rivanna Medical), to that of a console ultrasound machine (GU; GE LOGIC^TM S8).

Women requesting labor epidural analgesia consented to this prospective cohort study. The L2/3, L3/4, and L4/5 interspaces and the respective depths to the epidural space were identified, marked and measured using an AU and GU. An anesthesia provider who was blinded to ultrasound depth measurements performed epidural analgesia at one of the ultrasound identified insertion points and recorded the Tuohy needle depth at loss-of-resistance. Bland Altman analysis was used to measure the agreement between the epidural depths measured by the AU and GU.

A total of 47 women were analyzed. The mean ± standard deviation body mass index of the study cohort was 29 ± 5 kg/m² [range 23-45]. The mean difference between the epidural depths measured by the AU and GU was -0.29 cm [95% limit of agreement 0.50 to -0.91]. The mean difference between the depth to the epidural space measured by the GU versus the needle depth was -0.33 cm [95% CI -0.49 to -0.16]. The previously reported AU versus needle depth was -0.61 cm [95% CI -0.79 to -0.44].

The AU and GU provided comparable epidural depth estimates. The AU device may be a reasonable alternative to more sophisticated ultrasound devices in determining the epidural space and depth in a non-obese obstetric population.