title: Is heart period variability associated with the administration of lifesaving interventions in individual prehospital trauma patients with normal standard vital signs?
abstract: OBJECTIVE
  To determine whether heart period variability provides added value in identifying the need for lifesaving interventions (LSI) in individual trauma patients with normal standard vital signs upon early medical assessment.
  
  
  METHODS
  Retrospective database review.
  
  
  METHODS
  Helicopter transport to Level 1 trauma center and first 24 hrs of in-hospital care.
  
  
  METHODS
  Prehospital trauma patients requiring helicopter transport to Level 1 trauma center.
  
  
  RESULTS
  Heart period variability was analyzed from electrocardiographic recordings collected from 159 prehospital trauma patients with normal standard vital signs (32 LSI patients, 127 No-LSI patients). Although 13 of the electrocardiogram derived metrics demonstrated simple (i.e., univariate) discrimination between groups, at the multivariate level, only fractal dimension by curve length (FD-L) was uniquely associated with group membership (LSI vs. No-LSI, p = .0004). Whereas the area under the receiver operating characteristics curve for FD-L was 0.70, the overall correct classification rate (true positives and true negatives) of 82% was only 2% higher than the baseline prediction rate of 80% (i.e., no information except for the known proportion of overall No-LSI cases, 127 of 159 patients). Furthermore, 84% of the individual FD-L values for the LSI group were within the range of the No-LSI group.
  
  
  CONCLUSIONS
  Only FD-L was uniquely able to distinguish patient groups based on mean values when standard vital signs were normal. However, the accuracy of FD-L in distinguishing between patients was only slightly better than the baseline prediction rate. There was also very high overlap of individual heart period variability values between groups, so many LSI patients could be incorrectly classified as not requiring an LSI if a single heart period variability value was used as a triage tool. Based on this analysis, heart period variability seems to have limited value for prediction of LSIs in prehospital trauma patients with normal standard vital signs.
authors.affiliation: Department of Health and Kinesiology, The University of Texas at San Antonio, TX, USA. caroline.rickards@us.army.mil
authors.forename: Caroline A
authors.initials: CA
authors.lastname: Rickards
authors.forename: Kathy L
authors.initials: KL
authors.lastname: Ryan
authors.forename: David A
authors.initials: DA
authors.lastname: Ludwig
authors.forename: Victor A
authors.initials: VA
authors.lastname: Convertino
mesh_terms: D000328:Adult; D017732:Air Ambulances; D000704:Analysis of Variance; D001145:Arrhythmias, Cardiac / Q000175:diagnosis* / Q000401:mortality / Q000628:therapy*; D016887:Cardiopulmonary Resuscitation / Q000592:standards / Q000639:trends; D015984:Causality; D016009:Chi-Square Distribution; D015897:Comorbidity; D016208:Databases, Factual; D004562:Electrocardiography; D004632:Emergency Medical Services / Q000592:standards* / Q000639:trends; D005260:Female; D006801:Humans; D008020:Life Support Care / Q000379:methods*; D016015:Logistic Models; D008297:Male; D015999:Multivariate Analysis; D012372:ROC Curve; D012016:Reference Values; D012189:Retrospective Studies; D016019:Survival Analysis; D014193:Trauma Centers; D016896:Treatment Outcome; D055986:Vital Signs / Q000502:physiology*; D014947:Wounds and Injuries / Q000453:epidemiology / Q000628:therapy*