Ultrasound imaging aids the learning of the landmark technique for lumbar puncture in novice learners in a secure training environment

Subjects

Medical students and first-year trainee doctors who had never performed a LP in a clinical setting were recruited by direct contact of R.S.L. in the ED of a Nykøbing Falster Hospital, a rural hospital in Eastern Denmark. Each participant performed three non-invasive sessions (drawing with a surgical pen) on three different healthy volunteers (medical professionals and students at the site). The volunteers were also recruited by direct contact of R.S.L. in the ED.

A total of six medical students and six first-year training doctors were included in the study. Each participant (learner) marked locations for LP by landmark and ultrasound on three different volunteers sitting and laying down. As the result of each marking was registered as changed or unchanged location (by ultrasound) this generated a total of 72 datasets, six for each participant (learner).

Subject direction

No specific instruction about LP procedure was given before enrolling, but participants were asked to go through to the hospital’s procedural guidelines about LP and study the relevant anatomy if needed. None of the participants had any experience in using ultrasound. The research was exempted from ethical approval by the Regional Ethics Committee, Zealand, Denmark. Participants and volunteers were verbally instructed and written informed consent was obtained on-site. Data were anonymized.

Location

Sessions were performed in an available patient room in the ED using a regular hospital bed.

Before the procedure, each participant was briefly interviewed on how to perform LP, to make sure their theoretical knowledge was solid. All participants were rated as having equivalent knowledge, and all participants expressed the intervertebral space of L3-L4 as their aim when performing the LP by landmark technique.

Landmark technique

Each participant was asked to locate and mark the exact location of where to insert the needle when performing a LP. The location was marked using a surgical marker. Each participant marked the volunteer as the volunteer was first sitting down and then lying down. Each mark was given a number and was visible during the entire session. The marks were afterward removed with 85% ethanol skin disinfectant. Each participant marked three volunteers, (e.g. A, B and C) consecutively. Volunteers were used for more than one, but not all participants due to feasibility of the study. A total of 15 volunteers were included.

Ultrasound-assisted marking

After locating the intended intervertebral level of the LP in both sitting and lying position, the participant was handed the liner probe of the Philips Sparq Ultrasound System with “Simplicity Mode” enabled. Only the linear probe (Philips L12-3) was mounted to the ultrasound workstation. On the Philips Sparq, “Simplicity Mode” was enabled as standard and only the depth setting was adjusted during the session. Adjustment of the depth setting was done by the investigator when asked for. The ultrasound workstation was placed on the opposite side of the bed then the participant and the screen was adjusted to either the left or right side of the volunteer depending on participant preference. The participant was now asked to locate the intravertebral space of L3-L4 using the ultrasound workstation and linear probe as a guide. An ultrasonic gel was applied to the probe before handing it to the participant. No additional instruction on reading the ultrasonic image was given (Speer et al., 2013).

The location found using ultrasound was rated as being “correct” and secondly controlled by the investigator R.S.L. R.S.L. is an experienced clinician with more than 5 years of practice in LP. It was recorded whether the participant chose a different location for spinal access when using ultrasound (“changed”) or was satisfied with the area already marked (“unchanged”).

Qualitative assessment

Qualitative data in the form of spontaneous comments about the learning experience was gathered in the form of informal conversation during the sessions. Qualitative data were written down as keywords in Danish by the R.S.L. and transcribed afterward.

Statistical analysis

The sample size was calculated using ClinCal online software. Power was set to 85% and alpha 0.05; population was 70% and study group 30%. P values were calculated using Student’s t-test with Microsoft Excel (2016) software (Barath & Rosner, 1992).

Success rate of identifying correct LP location

All ultrasound markings were found (by investigators control) to be at the intended intervertebral level (L3/L4).

Success rate by participants of LP markings is shown in Table 1 (sitting: S1, S2, S3 and lying down L1, L2, L3). The mean success rate of LP by landmarks only was 21%. The first attempt (S1) had a success rate of 0%.

The improvement of accuracy in LP marking is shown in Table 2 as a total of correct markings (“unchanged”) vs. a total of incorrect markings (“changed”) for each attempt (S1, S2, S3 and L1, L2, L3). Markings of LP by landmark improved significantly in both sitting (p = 0.028) and lying positions (p=0.002).

All participants chose to change at least one of three marks when using ultrasound. Especially the marks in the first session (S1 + L1) was altered by most participants.

Participant perception

All participants expressed positivity on the use of ultrasound when learning how to identify the correct LP marking. Half of the participants would consider using ultrasound in the same manner when teaching procedures to colleagues and students in the future. The main reasons for this were: improved understanding of the anatomical structures and improved confidence in the succeeding attempts. Keywords can be found in Dataset 1 (Lundsgaard, 2018).