Learning Curves for Ultrasound Assessment of Lumbar Puncture Insertion Sites: When is Competency Established?

Background: Ultrasound (US) can be used to improve lumbar puncture (LP) success. How to achieve competency in LP US has not been defined. Cumulative sum statistics (CUSUM) characterized competency acquisition in other skills.

Objectives: Identify the learning curve for 80% success rate in LP US insertion site (IS) identification among pediatric emergency medicine fellows.

Methods: This prospective study took place in a single pediatric emergency department. Fellows with limited ultrasound experience received didactics, training, and three proctored examinations. Skills were evaluated in three 2-h sessions: using US, subjects identified LP ISs on a convenience sample of patients ages 0-20 years old. Subjects' IS markings were compared to markings by an expert, an emergency US fellowship-trained attending. Successful IS identification was defined as markings within 2 mm or 5 mm of the expert mark in infants and older children, respectively. A second expert marked 17 cases for interrater agreement. CUSUM was used to analyze individual learning curves.

Results: Five fellows evaluated 72 patients (mean age 11.4 years [SD = 4, range 3-20], mean body mass index 20.5 [SD = 4.4, range 13.1-37.7]) over a 3-month period. Mean number of attempts per fellow was 14.4 ± 3.1 (R 11-19); mean time to landmark identification was 72 ± 46 s (R 27-240). The two experts demonstrated 100% observed agreement. Aggregate success rate for all fellows was 75% (54/72). Four fellows showed learning curves that trended toward, but did not achieve, the acceptable success rate of 80%.

Conclusions: Nineteen attempts are insufficient among fellows to achieve competency in US-guided LP IS identification.