title: Heart period variability in trauma patients may predict mortality and allow remote triage.
abstract: BACKGROUND
  The high frequency to low frequency ratio (HF/LF) derived from analysis of heart period variability is elevated and associated with mortality in severely injured patients monitored in a hospital. The purpose of this study was to test the utility of heart period variability measurements as indicators of injury severity in patients prior to definitive medical intervention. We tested the hypothesis that survival is associated with low relative HF/LF, and death is associated with high relative HF/LF.
  
  
  METHODS
  We performed retrospective analyses of 84 pre-hospital trauma patient records (n=42 non-survivors; n=42 survivors) collected during helicopter transport to a Level 1 urban trauma center. R-waves from 2-min segments of ECG waveforms were converted to the frequency domain with a Fourier transform. Spectral power was separated into low (LF; 0.04-0.15 Hz) and high (HF; 0.15-0.4 Hz) frequency bands for analysis and derivation of frequency ratios.
  
  
  RESULTS
  Absolute HF, LF, and HF/LF were not distinguishable statistically between groups (p > or = 0.26), but HF/LF was higher (p = 0.04) for non-survivors (140 +/- 26) than survivors (74 +/- 19). After normalization to account for large intersubject variability, HFnu (43 +/- 3 vs. 28 +/- 2) and HF/LFnu (248 +/- 50 vs. 73 +/- 19) were higher (both p < 0.001), and LFnu (42 +/- 4 vs. 64 +/- 3) was lower (p = 0.0001) for non-survivors [19 h (median) before death] compared with survivors.
  
  
  CONCLUSIONS
  Our results show that heart period variability analyses separate patients who die from patients who survive traumatic injury. We propose that such analyses could be employed for remote triage of injured patients in austere environments.
authors.affiliation: Department of Health and Kinesiology, The University of Texas at San Antonio, San Antonio, TX 78249, USA. william.cooke@utsa.edu
authors.forename: William H
authors.initials: WH
authors.lastname: Cooke
authors.forename: Jose
authors.initials: J
authors.lastname: Salinas
authors.forename: John G
authors.initials: JG
authors.lastname: McManus
authors.forename: Kathy L
authors.initials: KL
authors.lastname: Ryan
authors.forename: Caroline A
authors.initials: CA
authors.lastname: Rickards
authors.forename: John B
authors.initials: JB
authors.lastname: Holcomb
authors.forename: Victor A
authors.initials: VA
authors.lastname: Convertino
mesh_terms: D000328:Adult; D004562:Electrocardiography; D004632:Emergency Medical Services; D005260:Female; D005583:Fourier Analysis; D006302:Health Services Research; D006339:Heart Rate; D006801:Humans; D015601:Injury Severity Score; D008297:Male; D011379:Prognosis; D019114:Remote Consultation; D012189:Retrospective Studies; D016019:Survival Analysis; D014218:Triage / Q000379:methods*; D014947:Wounds and Injuries / Q000401:mortality* / Q000503:physiopathology*