Technology and health care : official journal of the European Society for Engineering and Medicine
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Technol Health Care · Jan 1999
Dynamic delay time compensation for sampling capillaries used in respiratory mass spectrometry.
In intensive care patients who receive ventilatory support or full mechanical ventilation, valuable information can be drawn from gas exchange measurements. In this setting, the most favorable method for gas exchange measurement is by simultaneous recording of gas concentrations and gas flow, and by time resolved multiplication and accumulation. This paper presents a new method to compensate for the signal delay time which occurs when a sampling capillary is used for measuring gas concentrations with a respiratory mass spectrometer or some equivalent sidestream gas analyzer. ⋯ Such changes of viscosity will influence the delay time of the capillary, because they affect its flow resistance. As a consequence they will degrade the quality of measurements when done with a simple fixed delay compensation. The method described here consists of an algorithm which enables compensation for such a temporally changing delay time due to changes in gas composition.
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Technol Health Care · Jan 1999
Reduction of the bacterial load by the silver-coated endotracheal tube (SCET), a laboratory investigation.
Microaspiration enabled by high-volume-low-pressure cuffed endotracheal tubes is the most likely explanation for ventilator-associated pneumonia. To decontaminate the secretion at the proximal end of the cuff we developed a silver-coated endotracheal tube (SCET). In an in vitro model we investigated the efficacy of SCET to lower the bacterial load of secretion and aspirate. ⋯ The release of silver ions was very rapid and was described by a mono-exponential function with a time-constant tau of about 60 minutes and a saturation concentration of 200 +/- 80 microg/l. SCET showed a significant inhibition of growth of P. aeruginosa in the continuously contaminated and mechanically ventilated oropharynx-larynx-lung model. SCET by thus might be helpful in reducing ventilator-associated pneumonia.
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Technol Health Care · Jan 1999
Review Case ReportsInterfacing the body's own sensing receptors into neural prosthesis devices.
Functional Electric Stimulation (FES) is today available as a tool in muscle activation used in picking up objects, in standing and walking, in controlling bladder emptying, and for breathing. Despite substantial progress over nearly three decades of development, many challenges remain to provide a more efficient functionality of FES systems. The most important of these is an improved control of the activated muscles. ⋯ To decide when to stimulate, we are at present carrying out experiments on pigs and cats using cuff electrodes on the pelvic nerve and sacral roots to record the neural information from bladder afferents. This information can potentially be used to inhibit unwanted bladder contractions and to trigger the FES system and thereby bladder emptying. Future research will show whether cuffs and other types of electrodes can be used to reliably extract signals from the large number of other receptors in the body to improve and expand on the use of natural sensors in clinical FES systems.