title: Use of handheld sonar to locate a missing diver.
abstract: OBJECTIVE
  The purpose of this study was to investigate whether a handheld sonar device significantly reduces the mean time needed to locate a missing diver.
  
  
  METHODS
  This institutional review board approved, prospective, crossover study used a voluntary convenience sample of 10 scuba divers. Participants conducted both a standard and modified search to locate a simulated missing diver. The standard search utilized a conventional search pattern starting at the point where the missing diver (simulated) was last seen. The modified search used a sonar beacon to augment the search. For each search method, successful completion of the search was defined as locating the missing diver within 40 minutes.
  
  
  RESULTS
  Twenty total dives were completed. Using a standard search pattern, the missing diver was found by only 1 diver (10%), taking 18 minutes and 45 seconds. In the sonar-assisted search group, the missing diver was found by all 10 participants (100%), taking an average of 2 minutes and 47 seconds (SD 1 minute, 20 seconds). Using the nonparametric related samples Wilcoxon signed rank test, actual times between the sonar group and the standard group were significant (P < .01). Using paired samples t tests, the sonar group's self-assessed confidence increased significantly after using the sonar (P < .001), whereas the standard group decreased in confidence (not statistically significant, P = .111).
  
  
  CONCLUSIONS
  Handheld sonar significantly reduces the mean duration to locate a missing diver as well as increasing users' confidence in their ability to find a missing diver when compared with standard search techniques.
authors.affiliation: Department of Emergency Medicine, Madigan Army Medical Center, Tacoma, WA 98431, USA. omcgrane@gmail.com
authors.forename: Owen
authors.initials: O
authors.lastname: McGrane
authors.forename: Aaron
authors.initials: A
authors.lastname: Cronin
authors.forename: David
authors.initials: D
authors.lastname: Hile
mesh_terms: D000328:Adult; D018592:Cross-Over Studies; D004242:Diving; D006801:Humans; D009068:Movement / Q000502:physiology*; D011446:Prospective Studies; D018635:Rescue Work / Q000379:methods*; D013018:Sound Spectrography / Q000379:methods*; D013997:Time Factors