Emergency Medicine · Medical Literature
Effect of optimal operator positioning on transcranial Doppler acquisition: a randomized controlled trial.
Abstract
Ergonomic conditions during ultrasound procedures may influence both acquisition time and image quality. In transcranial Doppler, positioning at the patient's head could improve operator comfort and performance. This study aimed to evaluate whether a standardized seated position at the patient's head enables faster acquisition of interpretable images and could improve image quality. We conducted a multicenter randomized controlled trial between August and December 2024 including emergency medicine residents without prior training in transcranial Doppler. Participants were randomized to either a free positioning group or a standardized seated position at the patient's head. Each participant performed bilateral acquisitions of the middle cerebral artery. Acquisition time was recorded, and image quality was assessed blindly by an expert panel using a semi-quantitative scale. Forty-four residents were included, yielding 88 measurements (46 in the intervention group and 42 in the control group). Baseline characteristics were similar except for a higher number of validated semesters in the intervention group. Mean acquisition time was shorter in the intervention group (99.4 ± 47.1 s) than in the control group (121.7 ± 52.9 s), with a mean difference of 22.3 s (95% CI 1.2-43.3; p = 0.038). Image quality scores did not differ significantly between groups (16.6 ± 5.0 vs. 18.0 ± 5.0; mean difference - 1.4, 95% CI -3.5-0.7; p = 0.20). Standardized operator positioning at the patient's head was associated with faster acquisition of transcranial Doppler images, without a significant difference in image quality.
Clinical relevance
Does a standardized seated operator position at the patient's head, compared with free operator positioning, reduce transcranial Doppler acquisition time and improve image quality of the middle cerebral artery when performed by novice emergency medicine residents? __SNAPSHOT__ {"studyDesign":"Multicenter randomized controlled trial","setting":"Emergency medicine training setting; multiple centers (country not reported in abstract); conducted August–December 2024","sampleSize":"n=44 residents; 88 total measurements (intervention: n=46 measurements, control: n=42 measurements)","population":"Emergency medicine residents with no prior transcranial Doppler (TCD) training; baseline characteristics similar between groups except a higher number of validated training semesters in the intervention arm","intervention":"Standardized seated operator position at the patient's head during bilateral middle cerebral artery TCD acquisition","comparator":"Free (operator-chosen) positioning during bilateral middle cerebral artery TCD acquisition","primaryOutcome":"Acquisition time to obtain interpretable TCD images; secondary: image quality assessed by blinded expert panel using a semi-quantitative scale","followUp":"Single TCD session per participant; no longitudinal follow-up","fundingSource":"Not reported"}
Key findings
The primary outcome, mean TCD acquisition time, was statistically significantly shorter in the standardized-position intervention group (99.4 ± 47.1 seconds) compared with the free-positioning control group (121.7 ± 52.9 seconds): mean difference 22.3 seconds (95% CI 1.2–43.3 s; p = 0.038). The absolute time reduction of ~22 seconds represents an 18.3% (calculated) relative reduction in acquisition time. No NNT is applicable to this continuous, operator-performance outcome. The secondary outcome, expert-panel-rated image quality scores, did not differ significantly between groups (intervention: 16.6 ± 5.0 vs. control: 18.0 ± 5.0 on the semi-quantitative scale; mean difference −1.4 points, 95% CI −3.5 to 0.7; p = 0.20). Importantly, image quality scores were numerically lower (not higher) in the intervention group, though this difference was not statistically significant. No adverse events or safety outcomes were reported, as the study assessed operator-level performance parameters rather than patient clinical outcomes. The presence of a baseline imbalance — a higher number of validated training semesters in the intervention group — introduces a potential confounding advantage for the intervention arm on the primary outcome; whether this was adjusted for in analysis is not reported in the abstract.
Practice implications
This RCT demonstrates that a standardized seated position at the patient's head is associated with a statistically significant reduction in TCD acquisition time among untrained emergency medicine residents (~22 seconds faster), but does not improve expert-rated image quality. The clinical importance of a 22-second reduction in acquisition time is unclear and context-dependent: it may be meaningful during time-critical resuscitation scenarios but is likely negligible in routine point-of-care assessment. Critically, image quality — arguably more clinically relevant than speed — was not significantly improved and was numerically marginally worse in the intervention group, though within the confidence interval of equivalence. The study enrolled only novice residents, so findings may not generalize to experienced operators who have already developed positional preferences optimized for their practice. Patients were not studied; this is a study of operator technique, and no conclusions can be drawn about patient-level diagnostic accuracy, clinical decision-making, or outcomes. The baseline imbalance in training semesters (favoring the intervention group) is an important confounder that may have inflated the acquisition-time benefit. Because only an abstract was available for review, the statistical model used, any covariate adjustment, randomization allocation concealment, and details of the expert-panel scoring instrument cannot be evaluated. __LIMITATIONS__ Small sample size (n=44 operators, 88 measurements), limiting precision and power to detect differences in secondary outcomes such as image quality.,Baseline imbalance: the intervention group had more validated training semesters, which may have confounded the acquisition-time result in favor of the intervention; it is not reported whether this was adjusted for in the primary analysis.,Single-session design: each operator performed TCD only once, precluding assessment of learning curves, retention, or the effect of repeated positioning on performance.,Participants were exclusively untrained emergency medicine residents; results are not generalizable to experienced TCD operators or other specialties.,Image quality was the secondary outcome and the trial may have been underpowered to detect a clinically meaningful quality difference.,The semi-quantitative image quality scale used by the expert panel is not a validated, widely adopted instrument; its reproducibility and clinical meaningfulness are unknown from the abstract.,Blinding was applied only to image quality assessment (expert panel); the operator and study assessors of acquisition time were necessarily unblinded.,No patient-centered outcomes (diagnostic accuracy, clinical decision impact) were measured.,Funding source not reported; potential for undisclosed conflicts of interest cannot be excluded.,Only an abstract was available for full methodological appraisal, limiting assessment of randomization concealment, analysis plan, and statistical model. __BOTTOM_LINE_CATEGORY__ promising_but_preliminary __BOTTOM_LINE__ A standardized seated position at the patient's head modestly reduced TCD acquisition time by approximately 22 seconds among untrained emergency medicine residents (p=0.038), but did not significantly improve expert-rated image quality. Given the baseline group imbalance, small sample size, and absence of patient-level outcomes, these findings should be considered exploratory and hypothesis-generating. Adoption of a standardized positioning protocol may be a reasonable low-risk ergonomic practice for TCD training programs, but should not be considered a validated standard of care pending confirmatory studies.