Impedance, monitoring

Yu CM, Wang L, ChauE, et al. Intrathoracic impedance monitoring in patients with heart failure correlation with fluid status and feasibility of early warning preceding hospitalization. Circulation. Aug 9 2005 112(6) 841-848. 

Instruments are available for measuring impedance between electrode pairs. The procedure is recommended strongly as a good practice, since high impedance leads to distortions that may be difficult to separate from actual EEG signals. In fact, electrode impedance monitors are built into some commercially available EEG devices. Note that standard DC ohmmeters should not be used, since they apply a polarizing current that can result in a buildup of noise at the skin-electrode interface. 

Vollmann D, Nagele H, Schauerte P et al. 2007. CUnical utility of intrathoracic impedance monitoring to alert patients with an implanted device of deteriorating chronic heart failure. Eur Heart / 19, 1835-1840. 

J. Wissenwasser, M.J. Vellekoop, and R. Heer, Signal Generator for Wireless Impedance Monitoring of Microbiological Systems, IEEE Transactions on Instrumentation and Measurement, vol. 60, no. 6, pp. 2039-2046, 2011. 

Luthje, L., Vollmann, D., Drescher, T., Schott, P, Zenker, D., Hasenfuss, G., Unterberg, C., 2007. Intrathoracic impedance monitoring to detect chronic heart failure deterioration relationship to changes in NT-proBNP. Eur. J. Heart Fail. 9 (6-7), 716-722. 

Thoracic fluid is associated with decreased impedance between a ventricular lead and the pacing system generator. Two preliminary clinical studies have reported varying results on the clinical utility of thoracic impedance monitoring for predicting hemodynamic status. The Medtronic Impedance Diagnostics in Heart Failure Trial (MlD-HeFT) evaluated 33 patients with Class III or IV heart failure due to systolic dysfunction (n = 25) or diastolic dysfunction (n =... 

Thoracic impedance appeared to correlate with pulmonary wedge capillary pressures and importantly impedance decreased by 11% over approxi-matey 2 weeks prior to hospitahzation for heart failure. In contrast, in a cohort study of 115 patients with ICDs that allowed thoracic impedance monitoring,... 

Ypenburg C, Bax JJ, van der Wall EE, SchaUj MJ, and van Erven L. Intrathoracic impedance monitoring to predict decompensated heart faiure. Am J Cardiol 2007 99 554-557. 

Monitoring hardware integrity (e.g., impedance monitoring in thermocoupies)... 

Literature review on electrode positions for bladder impedance monitoring... 

Influence of a sliding contact on impedance monitoring in a smart surgical milling tool... 

Impedance monitors require the trailing cable to have a pilot conductor. The pilot is a separate, small conductor, incorporated in the cable construction. The pilot conductor is used to form a continuous loop with the grounding conductor. The monitor is calibrated to the impedance of the loop formed by the pilot and grounding conductors. The device then monitors the change of impedance from the initial calibration. If the impedance of the loop increases beyond a preset value, the monitor trips its associated circuit breaker. 

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