No abstract

The objective of this study was to measure the force exerted by 83 trained CPR rescuers and 104 untrained adult laypersons (college students and staff). A bathroom scale was used to measure the force exerted by these subjects with their hands on the bathroom scale in the CPR position. The weight range for both groups was the same. Of the trained rescuers, 60% pressed with more than 125 lbs, whereas only 37% of the laypersons pressed with more than 125 lbs. In view of the American Heart Association (AHA) guidelines (2000) to depress the chest 1.5 to 2 inches, which requires 100-125 lbs, it would appear that most laypersons do not exert enough force for effective CPR.

A patient with a history of Prinzmetal angina, refractory ventricular fibrillation, cardiac arrest with an implantable cardioverter-defibrillator, and obesity presented to the emergency department at 17 weeks gestational age with a chief complaint of angina and multiple episodes of defibrillation. A T3/4 thoracic epidural was placed to assess the effectiveness of a partial chemical sympathectomy in alleviating symptoms of angina as well as decreasing the amount of defibrillation episodes. Once this proved to be beneficial in accomplishing both of these goals, a more specific approach was designed. A continuous stellate ganglion block was then placed controlling both her angina and preventing further episodes of defibrillation long enough for her pregnancy to progress beyond 24 weeks gestational age.

Hydroxyapatite (HA) whisker reinforced polyetheretherketone (PEEK) composites have been investigated as bioactive materials for load-bearing orthopedic implants with tailored mechanical properties governed by the volume fraction, morphology, and preferred orientation of the HA whisker reinforcements. Therefore, the objective of this study was to establish key structtire-property relationships and predictive capabilities for the design of HA whisker reinforced PEEK composites and, more generally, discontinuous short fiber-reinforced composite materials. HA whisker reinforced PEEK composites exhibited anisotropic elastic constants due to a preferred orientation of the HA whiskers induced during compression molding. Experimental measurements for both the preferred orientation of HA whiskers and composite elastic constants were greatest in the flow direction during molding (3-axis, C^j), followed by the transverse (2-axis, C22) and pressing (Iaxis, Cji) directions. Moreover, experimental measurements for the elastic anisotropy and degree of preferred orientation in the same specimen plane were correlated. A micromechanicai model accounted for the preferred orientation of HA whiskers using two-dimensional implementations of the measured orientation distribution function (ODF) and was able to more accurately predict the orthotropic elastic constants compared to common, idealized assumptions of randomly oriented or perfectly aligned reinforcements. Model predictions using the 3-2 plane ODF, and the average of the 3-1 and 3-2 plane ODFs, were in close agreement with the corresponding measured elastic constants, exhibiting less than 5% average absolute error. Model predictions for C// using the 3-1 plane ODF were ¡ess accurate, with greater than 10% error. This study demonstrated the ability to accurately predict differences in orthotropic elastic constants due to changes in the reinforcement orientation distribution, which will aid in the design of HA whisker reinforced PEEK composites and, more generally, discontintious short fiberreinforced composites. [DOI: 1O.1115/1,4(X)5421]