Processing, storage and display of physiological measurements
Anaesthesia & intensive care medicine 09/2011; 12(9):426-429. DOI: 10.1016/j.mpaic.2011.06.010
In the UK, standards of monitoring required for the safe management of anaesthesia are set by the Association of Anaesthetists of Great Britain and Ireland. In the past physiological measurements of, for example, blood pressure, electrocardiograph (ECG), gas composition and airway pressures may have been performed by a collection of individual electronic machines. It is now common however to have an integrated monitoring system where signals from a variety of transducers are amplified, filtered, converted to digital form, processed by a computer and presented on a display to inform the user of both the condition of the patient and function of the anaesthesia system. It is important to have some understanding of the processes that take place between the production of the raw analogue electrical signal by a transducer and the information that is finally presented to the user.
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ABSTRACT: Introduction Recovery of balance after neuraxial anaesthesia can remain delayed after simple clinical tests have demonstrated motor recovery. Dynamic posturography tracks the small movements or sway of a person standing as still as possible on a force platform and has been investigated as an objective measure of the ability to walk following anaesthesia. These are expensive laboratory devices, limiting their clinical utility. One measured variable is path length, the cumulative distance travelled in the horizontal plane by the centre of pressure of a person standing on the platform over one minute. Path length can be measured using the Nintendo Wii-Fit Balance Board™. Methods The feasibility of intercepting raw wireless data from a Nintendo® Wii-Fit Balance Board™ using custom software to calculate path length was explored. Subsequently, path lengths were measured using both this and a laboratory platform simultaneously. In a random order 20 volunteers(a) stood for 1 min, feet together, eyes open (conventional baseline test); and (b) stood for 1 min, feet together, eyes closed (simulating residual anaesthesia with increased sway). For each device, the ratio b:a was calculated as an index of performance reduction when eyes were closed. Results Path lengths ranged from 58.50 to 242.99 cm, mean bias 9cm (Wii-Fit < laboratory platform) and 95% confidence limits of 2.5 to 15.4 cm. Ratios ranged from 1.09 to 2.68, mean bias -0.04 (Wii-Fit > laboratory platform) and 95% confidence limits of 0.04 to -0.13. Conclusions The path lengths were in close agreement and the Wii-Fit Balance Board™ may be worthy of further investigation as a tool to objectively assess readiness to ambulate following neuraxial anaesthesia.
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