A comparison of ultrasound-guided and palpation-guided identification of lumbar puncture needle entry site in patients as body mass index increases

Background: This was a prospective, crossover study examining the ability of emergency medicine (EM) residents to identify lumbar puncture (LP) needle entry site by palpation and ultrasound in individuals with varying body mass indexes (BMIs). Materials and Methods: Following a didactic session on the use of ultrasound to identify landmarks for LP needle entry, EM resident physicians were asked to identify LP needle entry sites using ultrasound on several volunteers of varying BMIs (normal [BMI, 18.5-24.9], overweight [BMI, 25.0-29.9], and obese [BMI, 30-39.9]). Measurements of their deviation from an entry point determined by a faculty member with expertise in ultrasound were recorded. Residents were then asked to determine LP needle entry sites using palpation and again the deviation was recorded. Results: Using ultrasound, the transverse and longitudinal deviations from a gold standard were 7.8 mm (standard deviation [SD]: 6.5 and confidence interval [CI]: 1.9) and 7.1 mm (SD: 5.2 and CI: 1.5), respectively, whereas using palpation, the transverse and longitudinal deviations from our gold standard were 4.4 mm (SD: 3.4 and CI: 0.99) and 8.2 mm (SD: 6.6 and CI: 1.9), respectively. Conclusion: There was no difference in the residents' ability to identify LP needle entry sites on volunteers of various BMIs when comparing the use of ultrasound to standard palpation. The following core competencies are addressed in this article: Patient care and procedural skills, Medical knowledge.