title: The use of portable 2D echocardiography and 'frame-based' bubble counting as a tool to evaluate diving decompression stress.
abstract: BACKGROUND
  'Decompression stress' is commonly evaluated by scoring circulating bubble numbers post dive using Doppler or cardiac echography. This information may be used to develop safer decompression algorithms, assuming that the lower the numbers of venous gas emboli (VGE) observed post dive, the lower the statistical risk of decompression sickness (DCS). Current echocardiographic evaluation of VGE, using the Eftedal and Brubakk method, has some disadvantages as it is less well suited for large-scale evaluation of recreational diving profiles. We propose and validate a new 'frame-based' VGE-counting method which offers a continuous scale of measurement.
  
  
  METHODS
  Nine 'raters' of varying familiarity with echocardiography were asked to grade 20 echocardiograph recordings using both the Eftedal and Brubakk grading and the new 'frame-based' counting method. They were also asked to count the number of bubbles in 50 still-frame images, some of which were randomly repeated. A Wilcoxon Spearman ρ calculation was used to assess test-retest reliability of each rater for the repeated still frames. For the video images, weighted kappa statistics, with linear and quadratic weightings, were calculated to measure agreement between raters for the Eftedal and Brubakk method. Bland-Altman plots and intra-class correlation coefficients were used to measure agreement between raters for the frame-based counting method.
  
  
  RESULTS
  Frame-based counting showed a better inter-rater agreement than the Eftedal and Brubakk grading, even with relatively inexperienced assessors, and has good intra- and inter-rater reliability.
  
  
  CONCLUSIONS
  Frame-based bubble counting could be used to evaluate post-dive decompression stress, and offers possibilities for computer-automated algorithms to allow near-real-time counting.
authors.affiliation: Divers Alert Network Europe, Roseto, Italy and Brussels, Centre for Hyperbaric Oxygen Therapy, Military Hospital Brussels, Belgium, Phone: +32-(0)2-264-4868, Fax: +32-(0)2-264-4861, E-mail: peter.germonpre@mil.be.
authors.forename: Peter
authors.initials: P
authors.lastname: Germonpré
authors.affiliation: Biophysiology and Environmental Physiology Laboratory, Haute Ecole Paul Henri Spaak, University of Brussels, Belgium, Department of Bioengineering, Imperial College London, UK.
authors.forename: Virginie
authors.initials: V
authors.lastname: Papadopoulou
authors.affiliation: Centre for Hyperbaric Oxygen Therapy, Military Hospital, Brussels, Belgium.
authors.forename: Walter
authors.initials: W
authors.lastname: Hemelryck
authors.affiliation: Department of Cardiology, Military Hospital, Brussels, Belgium.
authors.forename: Georges
authors.initials: G
authors.lastname: Obeid
authors.affiliation: Divers Alert Network Europe, Roseto, Italy and Brussels, Belgium, Department of Anesthesiology and Hyperbaric Medicine, Hôpital de la Cavale Blanche, Brest, France.
authors.forename: Pierre
authors.initials: P
authors.lastname: Lafère
authors.affiliation: Biomedical Engineering Department, Division of Imaging Sciences, King's College London, UK.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Eckersley
authors.affiliation: Department of Bioengineering, Imperial College London, UK.
authors.forename: Meng-Xing
authors.initials: MX
authors.lastname: Tang
authors.affiliation: Divers Alert Network Europe, Roseto, Italy and Brussels, Belgium, Biophysiology and Environmental Physiology Laboratory, Haute Ecole Paul Henri Spaak, University of Brussels, Belgium.
authors.forename: Costantino
authors.initials: C
authors.lastname: Balestra
mesh_terms: D000465:Algorithms; D003665:Decompression Sickness / Q000145:classification / Q000000981:diagnostic imaging*; D004242:Diving; D004452:Echocardiography / Q000295:instrumentation / Q000379:methods*; D004618:Embolism, Air / Q000000981:diagnostic imaging*; D006801:Humans; D015588:Observer Variation; D019095:Point-of-Care Systems; D015203:Reproducibility of Results; D013997:Time Factors; D014680:Veins; D014741:Video Recording / Q000706:statistics & numerical data
keywords: Doppler; Echocardiography; arterial gas embolism; bubbles; decompression sickness; diving research; risk assessment; venous gas embolism