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Primary Triage in a Mass-casualty Event Possesses a Risk of Increasing Informational Confusion: A Simulation Study Using Shannon’s Entropy

Published online by Cambridge University Press:  05 August 2016

Yasuhiko Ajimi ,
Masaru Sasaki ,
Yasuyuki Uchida ,
Ichiro Kaneko ,
Shinya Nakahara  and
Tetsuya Sakamoto
Yasuhiko Ajimi*
Affiliation:
Department of Emergency Medicine, School of Medicine, Teikyo University, Tokyo, Japan
Masaru Sasaki
Affiliation:
Tokyo Metropolitan Hiroo Hospital, Tokyo, Japan
Yasuyuki Uchida
Affiliation:
Department of Emergency Medicine, School of Medicine, Teikyo University, Tokyo, Japan
Ichiro Kaneko
Affiliation:
Department of Emergency Medicine, School of Medicine, Teikyo University, Tokyo, Japan
Shinya Nakahara
Affiliation:
Department of Emergency Medicine, School of Medicine, Teikyo University, Tokyo, Japan
Tetsuya Sakamoto
Affiliation:
Department of Emergency Medicine, School of Medicine, Teikyo University, Tokyo, Japan
*
Correspondence: Yasuhiko Ajimi, MD, DMSc Trauma & Resuscitation Center Department of Emergency Medicine School of Medicine, Teikyo University 2-11-1 Kaga, Itabashi-ku, Tokyo 173-8606, Japan, E-mail: relievedtemple436@gmail.com
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Abstract

Introduction

Primary triage in a mass-casualty event setting using low-visibility tags may lead to informational confusion and difficulty in judging triage attribution of patients. In this simulation study, informational confusion during primary triage was investigated using a method described in a prior study that applied Shannon’s Information Theory to triage.

Hypothesis

Primary triage using a low-visibility tag leads to a risk of informational confusion in prioritizing care, owing to the intermingling of pre- and post-triage patients. It is possible that Shannon’s entropy evaluates the degree of informational confusion quantitatively and improves primary triage.

Methods

The Simple Triage and Rapid Treatment (START) triage method was employed. In Setting 1, entropy of a triage area with 32 patients was calculated for the following situations: Case 1 – all 32 patients in the triage area at commencement of triage; Case 2 – 16 randomly imported patients to join 16 post-triage patients; Case 3 – eight patients imported randomly and another eight grouped separately; Case 4 – 16 patients grouped separately; Case 5 – random placement of all 32 post-triage patients; Case 6 – isolation of eight patients of minor priority level; Case 7 – division of all patients into two groups of 16; and Case 8 – separation of all patients into four categories of eight each. In Setting 2, entropies in the triage area with 32 patients were calculated continuously with each increase of four post-triage patients in Systems A and B (System A – triage conducted in random manner; and System B – triage arranged into four categories).

Results

In Setting 1, entropies in Cases 1-8 were 2.00, 3.00, 2.69, 2.00, 2.00, 1.19, 1.00, and 0.00 bits/symbol, respectively. Entropy increased with random triage. In Setting 2, entropies of System A maintained values the same as, or higher than, those before initiation of triage: 2.00 bits/symbol throughout the triage. The graphic waveform showed a concave shape and took 3.00 bits/symbol as maximal value when the probability of each category was 1/8, whereas the values in System B showed a linear decrease from 2.00 to 0.00 bits/symbol.

Conclusion

Informational confusion in a primary triage area measured using Shannon’s entropy revealed that random triage using a low-visibility tag might increase the degree of confusion. Methods for reducing entropy, such as enhancement of triage colors, may contribute to minimizing informational confusion.

AjimiY, SasakiM, UchidaY, KanekoI, NakaharaS, SakamotoT. Primary Triage in a Mass-casualty Event Possesses a Risk of Increasing Informational Confusion: A Simulation Study Using Shannon’s Entropy. Prehosp Disaster Med. 2016;31(5):498–504.

Keywords

confusionentropymass-casualty eventprimary triagetriage tag
Type
Original Research
Information
Prehospital and Disaster Medicine , Volume 31 , Issue 5 , October 2016 , pp. 498 - 504
Copyright
© World Association for Disaster and Emergency Medicine 2016 

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