Journal of clinical monitoring
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Comparative Study
Assessment of errors when expiratory condensate PCO2 is used as a proxy for mixed expired PCO2 during mechanical ventilation.
We designed a series of experiments to determine whether expiratory water condensate (PconCO2) can be used as a proxy for mixed expired gas collection. ⋯ Even with temperature correction, we failed to precisely predict PECO2 from PconCO2. For measurement of VD/VT and VCO2, we do not recommend methods that use PconCO2.
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We report the off-line calculation of the vascular compliance of the finger and suggest the continuous on-line use of this methodology as an aid to monitoring the peripheral vascular resistance. This method consists of the simultaneous analysis of the waveform signals from the pulse oximeter monitors and the arterial pressure as indicators of "volume" and pressure respectively to continuously calculate the vascular "compliance" (volume change per unit pressure change). This should be seen as a "relative compliance" as the pulse plethysmograph signal is not calibrated. This new methodology allows for continuous monitoring of peripheral vascular compliance as a beat-to-beat indicator of peripheral vascular resistance. The vaso-constrictors, phenylephrine and ephedrine, were shown to decrease the compliance as predicted. ⋯ By plotting the pulse oximeter waveforms versus the arterial waveforms, multiple volume versus pressure (relative compliance) loops were obtained. Analysis of these loops may assist in the monitoring of vascular compliance.
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A new thermodilution method for frequent (near continuous) estimation of cardiac output, without manual injection of fluid into the blood, was tested. The method utilizes a pulmonary artery catheter equipped with a fluid filled heat exchanger. The technique is based on cyclic cooling of the blood in the right atrium and measurement of the temperature changes in the pulmonary artery. ⋯ The mean coefficient of variation of repeated measurements with the near continuous thermodilution was 3.6%. Considering changes of more than 0.25 l/min to be significant, all changes in cardiac output measured by conventional thermodilution were followed by the running mean of three near continuous thermodilution estimates. This study demonstrates the feasibility of the new method to monitor cardiac output, and to detect all changes greater than 0.25 l/min.
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To show that an integrated graphic data display can shorten the time taken to detect and correctly identify critical events during anesthesia. ⋯ The results show that some simulated critical events are detected and correctly identified sooner, when an anesthesiologist views an integrated graphic display, rather than a traditional digital/waveform monitor.
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Light source-guided endotracheal intubation, whether by lighted stylet or fiber-optic laryngoscopy may potentially be improved by electrical conversion of the detected optical signal to an audio signal. The audio signal thus serves as a feedback guiding signal. ⋯ This optical-audio signal feedback system may be used to direct the lighted stylet from the oral cavity into the laryngeal-tracheal pathway. This may potentially be a more sensitive technique than the currently used visual intensity detection.