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.

Estimation of conditions evoking fracture in finger bones under pinch loading based on finite element analysis.

A finger finite element (FE) model was created from CT images of a Japanese male in order to obtain a shape-biofidelic model. Material properties and articulation characteristics of the model were taken from the literature. To predict bone fracture and realistically represent the fracture pattern under various loading conditions, the ESI-Wilkins-Kamoulakos rupture model in PAM-CRASH (ESI Group S.A., Paris, France) was utilized in this study with parameter values of the rupture model determined by compression testing and simulation of porcine fibula. A finger pinch simulation was then conducted to validate the finger FE model. The force-displacement curve and fracture load from the pinch simulation was compared to the result of finger pinch test using cadavers. Simulation results are coincident with the test result, indicating that the finger FE model can be used in an analysis of finger bone fracture during pinch accident. With this model, several pinch simulations were conducted with different pinching object's stiffness and pinching energy. Conditions for evoking finger bone fracture under pinch loading were then estimated based on these results. This study offers a novel method to predict possible hazards of manufactured goods during the design process, thus finger injury due to pinch loading can be avoided.

Neck injury mechanisms during direct face impact.

STUDY DESIGN: Digitized measurements of the intervertebral motions using cervical cineradiographs of 10 volunteers during direct impacts applied to their faces. OBJECTIVES: To clarify the cervical spine motion during direct face impact and postulate some mechanisms of neck injuries. SUMMARY OF BACKGROUND DATA: Neck injury occurs mostly in traffic or falling accidents. Hyperextension of the neck is considered the most common mechanism of the injury because most victims have lacerations or contusions on their faces. METHODS: A low-level backward impact load was applied to 10 healthy male volunteers' faces at the forehead and maxilla via a strap using a free-falling small mass. Cervical vertebral motion was recorded by radiograph cineradiography during the impact. RESULTS: The upper cervical spine showed a flexion motion for both conditions. Consequently, the cervical spine had an S-shaped curvature similar to that in cervical retraction. Intervertebral motions of the cervical spine were evaluated using an radiograph frame taken at the maximum cervical retraction. For the forehead load, intervertebral motion at C1-C2 was flexion, and motions of the lower cervical spine were extension. For the maxilla load, intervertebral motions from occiput-C1 through C4-C5 were flexion. The inflection point of the curvature was influenced by the impact location. CONCLUSION: We detected a flexion motion of the upper or middle cervical spine during direct face impact. In an actual accident, if the cervical spine is forced into similar motion, we speculate that neck injury would occur in this retraction-like curvature of the cervical spine.

Cervical vertebral motions and biomechanical responses to direct loading of human head.

There is little known data characterizing the biomechanical responses of the human head and neck under direct head loading conditions. However, the evaluation of the appropriateness of current crash test dummy head-neck systems is easily accomplished. Such an effort, using experimental means, generates and provides characterizations of human head-neck response to several direct head loading conditions. Low-level impact loads were applied to the head and face of volunteers and dummies. The resultant forces and moments at the occipital condyle were calculated. For the volunteers, activation of the neck musculature was determined using electromyography (EMG). In addition, cervical vertebral motions of the volunteers have been taken by means of X-ray cineradiography. The Ethics Committee of Tsukuba University approved the protocol of the experiments in advance. External force of about 210 N was applied to the head and face of five volunteers with an average age of 25 for the duration of 100 msec or so, via a strap at one of four locations in various directions: (1) an upward load applied to the chin, (2) a rearward load applied to the chin without facial mask, (3) a rearward load applied to the chin with the facial mask, and (4) a rearward load applied to the forehead. The same impact force as those for the human volunteers was also applied to HY-III, THOR, and BioRID. We found that cervical vertebral motions differ markedly according to the difference in impact loading condition. Some particular characteristics are also found, such as the flexion or extension of the upper cervical vertebrae (C0, C1, and C2) or middle cervical vertebrae (C3-C4), showing that the modes of cervical vertebral motions are markedly different among the different loading conditions. We also found that the biofidelity of dummies to neck response characteristics of the volunteers at the low-level impact loads is in the order of BioRID, THOR, and HY-III. It is relevant in this regard that the BioRID dummy was designed for a low-severity impact environment, whereas THOR and HY-III were optimized for higher-severity impacts.