-Original-

Thoracoabdominal Compression Model of Traumatic Asphyxia to Identify Mechanisms of Respiratory Failure in Fatal Crowd Accidents

Tomokazu Motomura¹, Hisashi Matsumoto¹, Hiroyuki Yokota², Mototsugu Suzuki³, Tetsuya Nishimoto³ and Sadayuki Ujihashi⁴

¹Department of Emergency and Critical Care Medicine, Shock and Trauma Center, Nippon Medical School Chiba Hokusoh Hospital, Chiba, Japan
²Department of Emergency and Critical Care Medicine, Nippon Medical School, Tokyo, Japan
³Biomechanics Research Unit, Nihon University, Fukushima, Japan
⁴Nippon Bunri University, Oita, Japan

Background: Traumatic asphyxia is a major cause of death in fatal crowd disasters, but the relationships between compression site, load magnitude, load time, and medical outcomes are unclear. This study estimated thoracoabdominal compression conditions (load magnitude, load time) that could result in respiratory failure in adults.
Methods: Eight load patterns-A (chest load: 0 kg, abdominal load: 10 kg), B (0, 20), C (10, 0), D (10, 10), E (10, 20), F (20, 0), G (20, 10), and H (20, 20)-were applied to 14 healthy women. Blood pressure, heart rate, respiratory rate, SpO₂, tidal volume, vital capacity, respiratory phase, and modified Borg dyspnea score were measured over time. Breathing Intolerance Index (BITI) was also calculated.
Results: Vital capacity decreased in patterns C, D, E, F, G, and H. BITI reached the critical range of ≥0.15 (at which respiratory failure occurs after about 45 min) after 14 min in pattern G and 2 min in pattern H. A vital capacity ≤1.85 L and a modified Borg scale score ≥8.3 corresponded to a BITI of ≥0.15 and were regarded as equivalent to reaching the critical range. Furthermore, change in chest load was positively correlated with BITI when abdominal load remained constant.
Conclusions: In women, respiratory failure can occur within 1 h from respiratory muscle fatigue, even when total thoracoabdominal load is only about 60% of body weight. A vital capacity ≤1.85 L and modified Borg scale score ≥8.3 can be regarded as indices for predicting respiratory failure.

J Nippon Med Sch 2019; 86: 310-321

Keywords
traumatic asphyxia, crowd accident, stampede, respiratory failure, Breathing Intolerance Index (BITI)

Correspondence to
Tomokazu Motomura, MD, Department of Emergency and Critical Care Medicine, Shock and Trauma Center, Nippon Medical School Chiba Hokusoh Hospital, 1715 Kamagari, Inzai, Chiba 270-1694, Japan
xcjwg823@yahoo.co.jp

Received, November 5, 2018
Accepted, July 24, 2019