Journal of clinical monitoring and computing
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In the present review we will describe and discuss the physiological and technological background necessary in understanding the dynamic parameters of fluid responsiveness and how they relate to recent softwares and algorithms' applications. We will also discuss the potential clinical applications of these parameters in the management of patients under general anesthesia and mechanical ventilation along with the potential improvements in the computational algorithms.
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J Clin Monit Comput · Feb 2011
ReviewAcid-base chemistry of plasma: consolidation of the traditional and modern approaches from a mathematical and clinical perspective.
Debate still exists as to whether the Stewart (modern) or traditional model of acid-base chemistry is best in assessing the acid-base status of critically ill patients. Recent studies have compared various parameters from the modern and traditional approaches, assessing the clinical usefulness of parameters such as base excess, anion gap, corrected anion gap, strong ion difference and strong ion gap. To compare the clinical usefulness of these parameters, and hence the different approaches, requires a clear understanding of their meaning; a task only possible through understanding the mathematical basis of the approaches. The objective of this paper is to provide this understanding, limiting the mathematics to a necessary minimum. ⋯ Although different in their concepts, the traditional and modern approaches based on mathematical models can be seen as complementary giving, in principle, the same information about the acid-base status of plasma.
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J Clin Monit Comput · Feb 2011
Dynamic behavior of BIS, M-entropy and neuroSENSE brain function monitors.
The objective of this paper is to assess the suitability of brain function monitors for use in closed-loop anesthesia or sedation delivery. In such systems, monitors used as feedback sensors should preferably be Linear and Time Invariant (LTI) in order to limit sensor-induced uncertainty which can cause degraded performance. In this paper, we evaluate the suitability of the BIS A2000 (Aspect Medical Systems, MA), the M-Entropy Monitor (GE HealthCare), and the NeuroSENSE Monitor (NeuroWave Systems Inc, OH), by verifying whether their dynamic behavior conforms to the LTI hypothesis. ⋯ While both BIS and M-Entropy monitors have been successfully used in closed-loop systems, we were unable to obtain a unique LTI model that could capture their dynamic behavior during step-wise changes in cortical activity. The uncertainty in their output during rapid changes in cortical activity impose limitations in the ability of the controller to compensate for rapid changes in patients' cortical state, and pose additional difficulties in being able to provide mathematically proof for the stability of the overall closed-loop system. Conversely, the NeuroSENSE dynamic behavior can be fully captured by a linear and time invariant transfer function, which makes it better suited for closed-loop applications.
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J Clin Monit Comput · Dec 2010
Carina as a useful and reliable radiological landmark for detection of accidental arterial placement of central venous catheters.
Central venous catheters are commonly used in the management of critically ill patients. Their insertion can be challenging in hemodynamically unstable patients and in those with altered thoracic anatomy. Although ultrasound guided insertion can reduce this problem, this facility may not be available in all locations and in all institutions. ⋯ Other recognized measures used to identify arterial puncture would be blood gas analysis of the returning blood, use of pressure transducer to identify waveform pattern and the pressures. In this article, we propose that trachea and carina can be used as a reliable radiological landmark to identify accidental arterial placement of central venous catheters. We further conclude that this information could be useful especially when dealing with post-resuscitation victims and hemodynamically unstable critically ill patients.
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J Clin Monit Comput · Dec 2010
How do changes in exhaled CO₂ measure changes in cardiac output? A numerical analysis model.
In a previous study in anesthetized animals, the slope of percent decreases in exhaled CO₂ versus percent decreases in cardiac output (Q(T) inflation of vena cava balloons) was 0.73. To examine the mechanisms underlying this exhaled CO₂-Q(T) relationship, an iterative numerical analysis computer model of non-steady state CO(2) kinetics was developed. ⋯ The numerical analysis computer model helps to delineate the mechanisms underlying how decreased Q(T) resulted in decreased exhaled CO₂. The model permitted deconvolution of the effects of simultaneous variables and the interrogation of parameters that would be difficult to measure in actual experiments.