Cardiovascular engineering
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The esophageal Doppler monitor (EDM) is a clinically useful device for minimally invasive assessment of cardiac output, preload, afterload, and contractility. An empirical model, based upon the logistic function, has been developed. Use of this model illustrates how the EDM could estimate the net effect of aortic and non-aortic contributions to inertia, resistance, and elastance within real time. ⋯ Furthermore, the effects of inertia, resistance, and elastance, on mean blood pressure during systole, can be quantified. These additional parameters could offer insight for clinicians, as well as researchers, and may be beneficial in further examining and utilizing clinical hemodynamics with the EDM. These additional measurements also underscore the need to integrate the EDM with existing and future monitoring equipment.
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The objective of this 14-pig study was designed to determine the amount of lung ventilation obtainable by only rhythmic chest compression (100/min, 100 lbs). Tidal volume (TV), dead space (DS), and respiration rate (R) were measured with normal breathing and with rhythmic chest compression during ventricular fibrillation. The ratio of TV/DS was calculated in both cases. ⋯ With spontaneous breathing, the minute alveolar volume was 5.48 +/- 2.1 l/min. With only chest-compression breathing, the alveolar ventilation was -1.49 +/- 0.64 l/min. The negative minute alveolar volume and fractional ratio reveals that TV was less than the dead space indicating that chest-compression alone does not ventilate the lungs.