Journal of clinical monitoring and computing
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J Clin Monit Comput · Oct 2007
Impact of withdrawal of 450 ml of blood on respiration-induced oscillations of the ear plethysmographic waveform.
It has been widely appreciated that ventilation-induced variations in systolic blood pressure during mechanical ventilation correlate with changes in intravascular volume. The present study assessed whether alterations in volume status likewise can be detected with noninvasive monitoring (ear plethysmograph) in non-intubated subjects (awake volunteers). ⋯ Respiration-induced changes of the ear plethysmographic waveform during spontaneous ventilation increase significantly as a consequence of withdrawal of approximately one unit of blood in healthy volunteers.
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J Clin Monit Comput · Aug 2007
Comparative StudyDetection of carbon monoxide production as a result of the interaction of five volatile anesthetics and desiccated sodalime with an electrochemical carbon monoxide sensor in an anesthetic circuit compared to gas chromatography.
There is a continuing risk of production of toxic levels of carbon monoxide (CO) as a result of interaction of volatile anesthetics and desiccated strong base carbon dioxide absorbents like soda lime. The aim of this study is to establish the reliability of detection of CO levels by an electrochemical carbon monoxide sensor compared to gas chromatography. ⋯ From these data we conclude that the ES can only be used as an indicator of CO production. When this sensor is used with sevoflurane and desiccated sodalime it is not capable of normal operation. The use of a strong base free carbon dioxide absorbent is therefore recommended.
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J Clin Monit Comput · Aug 2007
Comparative StudyCardiac output derived from left ventricular pressure during conductance catheter evaluations: an extended Modelflow method.
The Modelflow method computes cardiac output (CO) from arterial pressure (CO-MFao) by simulating a non-linear three-element Windkessel model of aortic input impedance. We present a novel technique to apply the Modelflow method to the left ventricular pressure (Plv) signal, to obtain an estimation of CO (CO-MFlv). ⋯ Cardiac output estimates by the modelflow method from aortic pressure and left ventricular pressure are interchangeable in patients without mitral and aortic abnormalities. After an initial calibration, CO-MFlv presents near zero bias and an adequate precision.
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J Clin Monit Comput · Aug 2007
Comparative StudyEvaluation of finger and forehead pulse oximeters during mild hypothermic cardiopulmonary bypass.
The purpose of this study was to examine and compare the four combination of pulse oximeters (POs) and monitoring sites, the Nihon Kohden BSS-9800 (N), the Masimo SET Radical (M), the Nellcor N550 D-25 (N-D) and the Nellcor N550 Max-Fast (N-MF) in patients with peripheral hypoperfusion. ⋯ The results suggested that N-D is most useful among four combinations of POs and monitoring sites tested in this study for monitoring SpO2 during hypoperfusion. The superiority of N-MF during hypoperfusion was not evident in the present study.
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J Clin Monit Comput · Aug 2007
Comparative StudyReliability of continuous pulse contour cardiac output measurement during hemodynamic instability.
Arterial pulse contour analysis is gaining widespread acceptance as a monitor of continuous cardiac output (CO). While this type of CO measurement is thought to provide acceptable continuous measurements, only a few studies have tested its accuracy and repeatability under unstable hemodynamic conditions. We compared continuous CO measurement using the pulse contour method (PCCO) before and after calibration with intermittent transpulmonary thermodilution cardiac output (TpCO). ⋯ In hemodynamically stable pigs, both pre- and post-calibration PCCO measurements agreed well with the intermittent transpulmonary thermodilution technique. However, during hemodynamic instability, and pre-calibration PCCO values had wide limits of agreement compared with TpCO. This was reflected by larger coefficients of variation for PCCO in hemodynamic instability. The error of PCCO measurement improved markedly after calibration, with bias and limits of agreement within clinically acceptable limits.