Low intensity vagal nerve stimulation lowers human thermal pain thresholds

The effect of vagal nerve stimulation (VNS) on thermal pain sensation was studied in eight subjects who had vagal nerve stimulators surgically implanted for purposes of seizure control. Prior to their involvement in the study, all subjects had the intensity of their VNS (30 Hz, 0.5 ms, 1.0-2.75 mA) adjusted upwards until achieving their desired clinical effect of reduced seizures. Thermal pain thresholds were determined using a Medoc TSA-2001 with a thermode applied to the skin of the forearm. During VNS at settings 100% of those used clinically to control their seizures, subjects showed a statistically significant decrease in their thermal pain threshold of 1.1+/-0.4 degrees C. Acute effects of graded VNS on thermal pain thresholds were determined in seven of the subjects after cessation of chronic VNS. Two thermal threshold measurements were obtained while the subject received sham stimulation (0 mA intensity), during tactile control stimulation and during 30 s of VNS at intensities approximately 33, 66 and 100% of the settings utilized to control their seizures. Tactile control stimulation was provided by electrical stimulation of the skin of the ankle with the intensity adjusted by the patient to match the intensity of any sensations felt in the neck during VNS. Subjects were not aware of the settings employed. Their stimulator was adjusted with each trial and an ascending/descending ordering of intensity was utilized with an inter-trial interval of 2 min. Thermal pain thresholds were significantly decreased in relation to tactile control stimulation at all intensities of VNS tested with the greatest effect occurring at the 66% level. Subjects were also monitored non-invasively and hemodynamic responses to VNS were determined. No significant alterations in hemodynamic variables were observed. The findings of this human study are consistent with experiments in non-human animals which demonstrate a pro-nociceptive effect of low intensity VNS.

Patient-specific platinum intracranial electrodes as a diagnostic tool in the surgical treatment of the epilepsies

A popular method of signal acquisition in the surgical treatment of the epilepsies is through the utilization of intracranial electrodes. These electrodes can be placed either epidurally or subdurally. By fabricating these intracranial electrodes on-site, a great deal of flexibility is gained because each electrode is designed to ensure an exact fit for each patient. With the use of intracranial electrodes fabricated on-site, there are none of the usual delays or limitations associated with the acquisition of commercially available electrodes, and significant cost savings are also seen.

The role of clinical engineering in the redesign of existing hospital patient monitoring systems

Clinical engineering can have a key role in the redesign of existing hospital patient monitoring systems. This paper presents a systematic approach to the process of reinstrumenting highly specialized cardiovascular operating suites. A detailed definition of system requirements is presented for both basic and specialized instrument sets. Configuration flexibility was given the utmost attention. The method presented here suggests that system requirements should reflect information gathered from direct interviews of both the clinical and support personnel. Consideration is given to all applicable codes, standards, and practices. Special attention must also be focused on proper and efficient interfacing of the components of the new system to all components of the existing system. The project described here was conducted within and supported by the University of Alabama Hospital of the University of Alabama at Birmingham.