Reducing chest injuries in automobile collisions: rib fracture timing and implications for thoracic injury criteria

The purpose of this study was to quantify the biomechanical response of the human thorax during dynamic shoulder belt loading representative of that seen in a severe automotive collision. Two post-mortem human surrogates (PMHSs) (one male and one female) were instrumented with 26 single-axis strain gages on the ribs, sternum, and clavicle. The thorax of each PMHS was placed on a custom spine support bracket designed to support the thorax on either side of the spinous process, thereby allowing free motion at the costovertebral joints. In addition, the support bracket raised the thorax above the flat base plate, which could otherwise constrain the deformation and motion of the posterior region of the rib cage. The thorax of each PMHS was then loaded using a custom table-top belt loading system that generated thoracic displacement rates representative of a severe automotive collision, 1.3 m/s for the male PMHS and 1.0 m/s for the female PMHS. The rib fracture timing data, determined by analyzing the strain gage time histories, showed that severe thoracic injury (AIS = 3) occurred at 16% chest compression for the male and 12% chest compression for the female. However, these values are well below the current thoracic injury criteria of 29% chest compression for the male and 23% chest compression for the female. This data illustrates that serious thoracic injury (AIS = 3) occurs at lower chest compressions than the current ATD thoracic injury criteria. Overall, this study provides critical data that can be used in the design and validation of advanced ATDs and finite element models, as well as the establishment of improved, more stringent thoracic injury criteria.

Rib fracture timing in dynamic belt tests with human cadavers

The purpose of this article is to present data from dynamic belt loading tests on the thorax of human cadavers where the exact timing of all rib fractures is known. To quantify rib fracture timing, a total of 47 strain gages were placed throughout the thorax of two human cadavers (one male, one female). To simulate thoracic loading observed in a severe car crash, a custom table-top belt loading device was developed. The belt loading pulse was configured to result in approximately 40% chest compression during a 150 ms load and unload cycle. The time histories of each strain gage were analyzed to determine the time of each rib fracture which was then directly compared with the reaction loads and chest displacements at that exact time, thereby creating a noncensored data set. In both cadavers, all rib fractures occurred within the first 35% compression of the thorax. As a general trend, fractures on the left side of the thorax, where the passenger belt passed over the abdomen, occurred first followed by fractures to the upper ribs on the right side of the thorax. By utilizing this technique, the exact timing of each injury level can be characterized relative to the mechanical parameters. For example, using rib fractures as the parameter for Abbreviated Injury Scale (AIS) scores in the female test, it was shown that AIS 1 injury occurred at a chest compression of 21.1%, AIS 2 at 21.6%, AIS 3 at 22.0%, and AIS 4 at 33.3%.

American College of Preventive Medicine Practice Policy Statement. Screening for elevated blood lead levels in children

Abstract: Based on a review of the current literature and recommendations, the American College of Preventive Medicine presents a practice policy statement on screening for elevated blood lead levels in children.

A cost-effectiveness analysis of newborn hearing screening strategies

CONTEXT

Congenital hearing loss affects between 1 and 3 out of every 1,000 children. Screening of all neonates has been made possible by the development of portable automated devices. Universal screening is a 2-stage screening process using automated transient-evoked otoacoustic emissions, followed when indicated by automated auditory brain response testing. Targeted screening reserves the 2-stage screening process for those infants at risk for congenital hearing loss.

OBJECTIVE

To compare the expected costs and benefits of targeted screening with universal screening for the detection of significant bilateral congenital hearing loss.

DESIGN

Cost-effectiveness analysis from the health care system perspective. including costs directly related to screening and initial follow-up evaluation.

MAIN OUTCOME MEASURES

Number of cases identified, number of false positives, and cost per case.

RESULTS

For every 100,000 newborns screened, universal screening detects 86 of 110 cases of congenital hearing loss, at a cost of $11,650 per case identified. Targeted screening identifies 51 of 110 cases, at $3,120 per case identified. Universal screening produces 320 false-positive results, 304 more than targeted screening. Switching to universal screening from targeted screening would cost an additional $23, 930 for each extra case detected.

CONCLUSIONS

Universal screening detects more cases of congenital hearing loss, at the expense of both greater cost and more false-positive screening results. Little is known about the negative impact of false-positive screening and about the benefits of early intervention for congenital hearing loss. Those who advocate adoption of universal screening should be aware not only of the direct costs of universal screening, but of the indirect costs and strategies to increase the benefits of screening.

A systematic review of vision screening tests for the detection of amblyopia

OBJECTIVE

To review the test characteristics and the quality of evidence regarding available screening tests for the detection of amblyopia in preschool-aged children to help primary care practitioners select a screening strategy.

DESIGN

Systematic review of published studies.

DATA SOURCES

The MEDLINE database was searched from 1966 through January 1999 using a broad and inclusive strategy. A total of 9551 citations were identified.

STUDY SELECTION

All studies that compared the results of commercially available screening tests in preschool-aged children to ophthalmologic examination.

DATA EXTRACTION

The setting of the study, the age of the population, the type of screening test, criteria for a positive screen, criteria for the ophthalmologic examination, test characteristics, and measures of reliability were abstracted by 2 reviewers for each selected study.

DATA SYNTHESIS

Four eligible articles were identified that studied the test characteristics of 3 screening tests. None of these studies were performed in a primary care setting. Each study used different criteria for failure of the ophthalmologic examination. None of the studies measured observer or test reliability.

CONCLUSIONS

Few high-quality data exist regarding the performance of preschool vision screening. Important future work should include the development of a consensus gold standard ophthalmologic examination and evaluation of screening tests in the primary care setting.

Cost-effectiveness analysis of lead poisoning screening strategies following the 1997 guidelines of the Centers for Disease Control and Prevention

OBJECTIVE

To compare blood lead (BPb) poisoning screening strategies in light of the 1997 recommendations by the Centers for Disease Control and Prevention, Atlanta, Ga.

DESIGN

Cost-effectiveness analysis from the perspective of the health care system to compare the following 4 screening strategies: (1) universal screening of venous BPb levels; (2) universal screening of capillary BPb levels; (3) targeted screening of venous BPb levels for those at risk; and (4) targeted screening of capillary BPb levels for those at risk. Costs of follow-up testing and treatment were included in the model.

RESULTS

Only universal venous screening detected all BPb levels of at least 0.48 micromol/L (10 microg/dL). Universal capillary screening detected between 93.2% and 95.5% of cases, depending on the prevalence of elevated BPb levels. Targeted screening was the least sensitive strategy for detecting cases. Venous testing identified between 77.3% and 77.9% of cases, and capillary testing detected between 72.7% and 72.8% of cases. In high-prevalence populations, universal venous screening minimized the cost per case ($490). In low- and medium-prevalence populations, targeted screening using venous testing minimized the cost per case ($729 and $556, respectively). In all populations, regardless of screening strategy, venous testing resulted in a lower cost per case than capillary testing. Sensitivity analyses of all parameters in this model demonstrated that this conclusion is robust.

CONCLUSIONS

Universal screening detects all cases of lead poisoning and is the most cost-effective strategy in high-prevalence populations. In populations with lower prevalence, the cost per case detected using targeted screening is less than that of universal screening. The benefit of detecting a greater number of cases using universal screening must be weighed against the extra cost of screening. Regardless of whether a strategy of universal or targeted screening is used, the cost per case using venous testing is less than that of capillary testing.