Annals of biomedical engineering
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Impedance cardiography has not achieved popularity in the Intensive Care Unit (ICU) to date probably because of the limitations in technique and interpretation associated with the altered physiology of critically ill patients, and also because of interference from other machinery in the ICU. The current climate of questioning the existing technology for bedside cardiovascular assessment however spurs the need to evaluate impedance cardiography as a noninvasive alternative. Validation in noncritically ill patients is good when compared to other technologies (e.g., thermodilution, Fick, dye dilution (r greater than 0.9)). ⋯ This is thought to be a measure of contractility that is independent of preload and afterload. The ultimate test in the ICU for impedance cardiography is whether clinical outcome of critically ill patients is altered by the use of this technology. Such outcome testing is essential before the true value of impedance cardiography in the management of critically ill patients can be determined.
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Tibial external fixation frames were constructed on aluminum tube simulating tibia bone. A 20-mm gap was left at the fracture site in order to measure the structural stiffness of the frame rather than the aluminum tube. The performance of the frames were experimentally evaluated and quantified using tests which simulated the loading conditions encountered in normal walking. ⋯ Stiffnesses of various frames with different geometric configurations were compared by comparing their appropriate stiffness coefficients. Such comparison can set forth a quantitative guideline in selecting a suitable frame configuration for the type of injury and condition of fracture pattern. This type of quantitative analysis can also be useful in modifying the frame during the postoperative bone healing process.
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A totally self-contained instrument for the measurement of cardiac output is described. The microcomputer controlled instrument is based upon the principles of thermodilution and is capable of making cardiac output determinations on a minute by minute basis. ⋯ The accuracy and reproducibility of flow determinations made with the system compare favorably with those made with a conventional cardiac output monitor. This study demonstrates the feasibility of a stand-alone cardiac output computer that can provide virtually continuous measurements of blood flow without the intervention of a technician.