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

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.