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Abstract
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Pressurization of the cardiovascular system of cadavers during impact testing is accomplished in order to study the effects of surges in hydraulic pressure on the organs of the thorax and on the great vessels. The surges in hydraulic pressure are those that result from the decelerative forces such as might be experienced in automobile collisions. Other investigators have had problems with the pressurization of the cardiovascular system of cadavers with a normal saline solution in such tests because fluid loss from the capillaries of cadavers has been a significant problem.
SwRI has developed a method for minimizing the fluid loss from the capillaries when the supradiaphragmatic arterial system is to be pressurized to average diastolic pressure, 80 mm. Hg, by normal saline. This is accomplished by distending the supradiaphragmatic arterial system of the cadaver via a catheter introduced into the aorta with flow to the lower aorta being obturated by a distended intraaortic Miller-Abbot tube balloon placed at or near the diaphragm. In testing in other laboratories the saline solution introduced via this catheter leaked out of the capillaries almost as rapidly as it was introduced, thereby increasing supradiaphragmatic mass through fluid accumulation in lungs, head, neck, and arms. Since large increases in supradiaphragmatic mass will influence the "g" forces produced in deceleration and thus influence the injuries produced, it is important to minimize fluid accumulation in the tissues. A simple expedient to eliminate this problem is to introduce a 250-400 cc bolus of polyethylene bead suspension into the aorta just prior to pressurization with the saline solution. The bead size varies from 4 microns to 50 microns so that when the saline for pressurization is introduced, the beads are impacted in the pre- capillary arterioles (average diameter 30 microns) in the capillaries (average diameter 8 microns) preventing passage and thus leakage of the normal saline.
This expedient has been utilized on four cadavers to date and found to be completely effective in that on autopsy no edema of head, trunk, neck, or arms could be found, and there was no accumulation of fluid in lung parenchyma or pleural cavity. Prior to impact, the intra-aortic pressure was easily maintained at 80 to 110 mm. Hg with less than 1000 cc of normal saline solution. |