Journal of clinical monitoring and computing
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J Clin Monit Comput · Apr 2006
Rapid measurement of blood propofol levels: a proof of concept study.
Despite many advantages over traditional volatile anaesthetic techniques, propofol total intravenous anaesthesia (TIVA) makes up a small percentage of general anaesthetics administered. One of the reasons for this is the absence of a clinically useful method for measuring blood propofol concentrations. We have designed and tested a prototype system for rapidly measuring blood plasma levels of propofol using solid phase extraction (SPE) methodology, coupled with colorimetric and spectrometric techniques. ⋯ The results show that this methodology may be suitable for rapid and accurate clinical monitoring of propofol levels during general anaesthesia.
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J Clin Monit Comput · Apr 2006
A depth of anaesthesia index from linear regression of EEG parameters.
The field of Anaesthesia has recently witnessed numerous advances both in the drug administration and monitoring of anaesthetic state. This development has further boosted the efforts and interest of researchers in the automation of clinical Anaesthesia. The success in this direction is possible only when assessment of the depth of hypnotic component of anaesthesia is achieved accurately. This paper describes a technique to arrive at a reliable Depth of Hypnosis (DoH) index using electroencephalographic (EEG) parameters. ⋯ A combination of irregularity of EEG waveform in time-domain and band powers in frequency domain best describes the difference between awake and anesthetized states. To characterize these states, a set of optimum EEG parameters exists. These parameters must be normalized to reduce interpatient variability. The calculated graded index may be used to assist the anaesthetist in the operating theatre.
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J Clin Monit Comput · Apr 2006
Ventilator Y-piece pressure compared with intratracheal airway pressure in healthy intubated children.
Compare airway pressure measurements at the ventilator Y-piece of the breathing circuit (P( Y )) to intratracheal pressure measured at the distal end (P( T )) of the endotracheal tube (ETT) during mechanical ventilation and spontaneous breathing of intubated children. ⋯ In healthy children P( Y ) significantly overestimates PIP in the trachea during positive pressure ventilation and underestimates the intratracheal airway pressure during spontaneous inhalation. During positive pressure ventilation P( T ) better assesses the pressure generated in the airways and lungs compared to P( Y ) because P( T ) also includes the difference in airway pressure across the ETT tube due to resistance. During spontaneous inhalation, P( T ) reflects the series resistance of the ETT and ventilator circuit, while P( Y ) reflects only the resistance of the ventilator circuit, accounting for the smaller decreases in pressure. Additionally, P( Y ) underestimates the total WOBi load on the respiratory muscles. Thus, P( T ) is a more accurate reflection of pulmonary airway pressures than P( Y ) and suggests that it should be incorporated into ventilator systems to more accurately trigger the ventilator and to reduce work of breathing.
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J Clin Monit Comput · Apr 2006
The use of joint time frequency analysis to quantify the effect of ventilation on the pulse oximeter waveform.
In the process of determining oxygen saturation, the pulse oximeter functions as a photoelectric plethysmograph. By analyzing how the frequency spectrum of the pulse oximeter waveform changes over time, new clinically relevant features can be extracted. ⋯ Joint time frequency analysis of the pulse oximeter waveform can be used to determine the respiratory rate of ventilated patients and to quantify the impact of ventilation on the waveform. In addition, when applied to the pulse oximeter waveform new clinically relevant features were observed.
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J Clin Monit Comput · Feb 2006
A fully automated algorithm for the determination of respiratory rate from the photoplethysmogram.
To determine if an automatic algorithm using wavelet analysis techniques can be used to reliably determine respiratory rate from the photoplethysmogram (PPG). ⋯ Our technique allows the accurate measurement of respiratory rate from the photoplethysmogram, and leads the way for developing a simple non-invasive combined respiration and saturation monitor.