title: A randomised crossover study to compare the cross-sectional and longitudinal approaches to ultrasound-guided peripheral venepuncture in a model.
abstract: BACKGROUND
  Ultrasound-guided peripheral intravenous access may present an alternative to central or intraosseous access in patients with difficult peripheral veins. Using venepuncture of a phantom model as a proxy, we investigated whether novice ultrasound users should adopt a cross-sectional or longitudinal approach when learning to access peripheral veins under ultrasound guidance. This result would inform the development of a structured training method for this procedure.
  
  
  METHODS
  We conducted a randomised controlled trial of 30 medical students. Subjects received 35 min of training, then attempted to aspirate 1 ml of synthetic blood from a deep vein in a training model under ultrasound guidance. Subjects attempted both the cross-sectional and longitudinal approaches. Group 1 used cross-sectional first, followed by longitudinal. Group 2 used longitudinal first, then cross-sectional. We measured the time from first puncture of the model's skin to aspiration of fluid, and the number of attempts required. Subjects also reported difficulty ratings for each approach. Paired sample t-tests were used for statistical analysis.
  
  
  RESULTS
  The mean number of attempts was 1.13 using the cross-sectional approach, compared with 1.30 using the longitudinal approach (p = 0.17). Mean time to aspiration of fluid was 45.1 s using the cross-sectional approach and 52.8 s using the longitudinal approach (p = 0.43). The mean difficulty score out of 10 was 3.97 for the cross-sectional approach and 3.93 for the longitudinal approach (p = 0.95).
  
  
  CONCLUSIONS
  We found no significant difference in effectiveness between the cross-sectional and longitudinal approaches to ultrasound-guided venepuncture when performed on a model. We believe that both approaches should be included when teaching ultrasound-guided peripheral vascular access. To confirm which approach would be best in clinical practice, we advocate future testing of both approaches on patients.
authors.affiliation: School of Clinical Medicine, University of Cambridge, Cambridge, UK.
authors.forename: James
authors.initials: J
authors.lastname: Griffiths
authors.affiliation: School of Clinical Medicine, University of Cambridge, Cambridge, UK. caa47@cam.ac.uk.|Robinson College, Grange Road, Cambridge, CB3 9AN, UK. caa47@cam.ac.uk.
authors.forename: Amadeus
authors.identifier: http://orcid.org/0000-0002-8296-9581
authors.initials: A
authors.lastname: Carnegie
authors.affiliation: Emergency Department, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK.
authors.forename: Richard
authors.initials: R
authors.lastname: Kendall
authors.affiliation: Emergency Department, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK.
authors.forename: Rajeev
authors.initials: R
authors.lastname: Madan
keywords: Emergency medicine; Emergency ultrasound; Ultrasound; Ultrasound education; Ultrasound guided; Venepuncture