Methods for determining pediatric thoracic force-deflection characteristics from cardiopulmonary resuscitation.

The Children's Hospital of Philadelphia, 3535 Market Street, 11th Floor, Philadelphia, PA 19104, USA.
Stapp car crash journal 12/2008; 52:83-105.
Source: PubMed


Accurate pediatric thoracic force and deflection data are critical to develop biofidelic pediatric anthropomorphic test devices (ATDs) used in designing motor vehicle safety systems for child occupants. Typically, post-mortem human subject (PMHS) experiments are conducted to gather such data. However, there are few pediatric PMHS available for impact research, therefore novel methods are required to determine pediatric biomechanical data from children. In this study, we have leveraged the application of chest compressions provided in the clinical environment during pediatric cardiopulmonary resuscitation (CPR) to collect this fundamental data. The maximum deflection of the chest during CPR is in the range of chest deflections in PMHS impact experiments and therefore CPR exercises the chest in ways that are meaningful for biofidelity assessment. Thus, the goal of this study was to measure the force-deflection characteristics of the thorax of children and young adults during CPR. To do so, a force and deflection sensor was integrated into a patient monitor-defibrillator used during CPR in the Pediatric Intensive Care Unit and Emergency Department of a children's hospital. The sensor was interposed between the chest of the patient and hands of the rescuer during CPR compressions. Following a CPR event, thoracic force and deflection data were downloaded from the monitor-defibrillator for analysis. Each compression cycle was fit to a parallel spring-damper model, wherein stiffness and damping were linearly dependent on chest deflection. Average maximum chest deflection, force at maximum deflection, linear stiffness, and elastic and viscous model forces are reported for each subject and correlated with age. Eighteen subjects (11 females) ages 8 to 22 years were enrolled in the study and each received a mean of 2000 (Standard Deviation 2339) chest compressions during CPR. Average maximum chest deflection and corresponding force were 39 +/- 5 mm and 309 +/- 55 N respectively. When combined with our previous study of adult CPR data, and other data from the literature, our findings suggest that the stiffness of the thorax increases from youth to middle age, and then decreases in the elderly. CPR has the potential to provide data from a wide range of human subjects with which to study the effect of age on mechanics of thoracic deformation. Future studies will expand the sample size and age range of data collected to further explore the age-related changes in thoracic mechanics.

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    • "The cartilage is most elastic in youth and becomes stiffer as the cartilage calcifies with age. Together, these factors results in a structural stiffness that gradually increases from youth to middle age [24] "
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    • "Similar trends have been found in other experimental test series in which a broad age range is included in the sample. Maltese and colleagues [17] report the stiffness of child thoraces based on cardiopulmonary resuscitation techniques. They present a compilation of data from their study, from [18] and [19], that depicts an age-associated trend in thorax stiffness in which an increase in peak force is observed until the end of the young adult period, at which point the force declines. "
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    • "Conclusion An anatomically detailed, high-resolution 10-year-old FE thorax model was developed and validated against data obtained from the real-world CPR. The CPR experiment was performed at a relatively low speed, with a maximum loading rate of 250 mm/s (Maltese et al. 2008). Although tissue material properties were scaled from adults, the 10-year-old FE model was validated during a loading event for which inertial effects were minimal. "
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