International journal of clinical monitoring and computing
-
Int J Clin Monit Comput · Jan 1988
'Anestheticography': on-line monitoring and documentation of inhalational anesthesia.
The safe practice of inhalational anesthesia requires control over the amount of volatile anesthetic delivered to the patient. With minimal fresh gas flow this is facilitated by continuous monitoring and recording of the agent's concentration ('Anestheticography'). Alterations brought about by routine clinical maneuvers become visible. ⋯ Initiating emergence by closing the vaporizer during minimal flow led to a slow decrease in concentration whilst at a flow of 61/min the inspiratory isoflurane concentration rapidly decreased to subanesthetic levels. Insertion of a charcoal filter into the inspiratory limb of the breathing circuit immediately dropped the inspiratory concentration to undetectable levels. 'Anestheticography' is a useful means of monitoring and documentation of inhalational anesthetic. With the use of a charcoal filter all advantages of minimal flow anesthesia can be realized throughout the entire anesthetic, including emergence.
-
Int J Clin Monit Comput · Jan 1988
Phase space electroencephalography (EEG): a new mode of intraoperative EEG analysis.
Intraoperative monitoring of electroencephalography (EEG) data can help assess brain integrity and/or depth of anesthesia. We demonstrate a computer generated technique which provides a visually robust display of EEG data plotted as 'phase space trajectories' and a mathematically derived parameter ('dimensionality') which may correlate with depth of anesthesia. Application of nonlinear mathematical analysis, used to describe complex dynamical systems, can characterize 'phase space' EEG patterns by identifying attractors (geometrical patterns in phase space corresponding to specific ordered EEG data subjects) and by quantifying the degree of order and chaos (calculation of dimensionality). ⋯ In this paper we describe and demonstrate phase space trajectories generated for sine waves, mixtures of sine waves, and white noise (random chaotic events). We also present EEG phase space trajectories and dimensionality calculations from a patient undergoing surgery and general anesthesia in 3 recognizable states: awake, anesthetized, and burst suppression. Phase space trajectories of the three states are visually distinguishable, and dimensionality calculations indicate that EEG progresses from 'chaos' (awake) to progressively more 'ordered' attractors (anesthetized and burst suppression).
-
Int J Clin Monit Comput · Jan 1987
Extravascular lung water measurement by double indicator dilution in shock and respiratory failure.
Clinical quantitation of water accumulation in the lungs is imprecise. The technique of measuring extravascular lung water (EVLW) with double indicator dilution utilizing cold indocyanine green dye has become practical with the addition of a microprocessor. The technique, insertion of a special thermistor tipped arterial catheter and potential problems are described. ⋯ On the other hand 19 patients with Adult Respiratory Distress Syndrome (ARDS) had marked increases in EVLW from normal of 5-8 ml/kg to 10.7 to 14.4 ml/kg. No further increases in EVLW were observed in eight ARDS patients requiring fluid resuscitation for associated hypovolemia and hypoperfusion. We feel that measurement of EVLW in critically ill patients offers an opportunity to study the pathophysiology of pulmonary failure.
-
Int J Clin Monit Comput · Jan 1987
Historical ArticlePulse oximetry: historical review and Ohmeda functional analysis.
Oximetry relies on the detection of the spectral properties of oxygenated and reduced hemoglobin. In vitro bench analysis capabilities have spurred the desire to accomplish accurate in vivo measurement through various techniques. The 1930-40s were a particularly active period for oximetry culminating in the development of pulse oximeters in the 1970s. ⋯ Arterial oxygen saturation readings are derived from the ratio of pulse-added signals of red and infrared light energy passed through tissue. Data manipulation that includes empirically derived constants produces numerical data that is clinically useful. A photo-plethysmographic waveform display of actual oximeter signal closes the loop between man and machine.