Effect of transcutaneous electrical nerve stimulation characteristics on clinical pain.

We compared the effects of four treatment variables on the pain reduction produced by transcutaneous electrical nerve stimulation and attempted to establish indications for TENS based on patient history and pain evaluation items. Treatment variables were the therapist and the three TENS stimulus characteristics--pulse width, frequency, and amplitude. We randomly assigned 192 consecutive adult patients suffering from painful conditions to one of four physical therapists and one of 12 stimulus characteristic combinations. We used a standard evaluation form that included a visual analog scale (VAS) to evaluate pain. Patients were given a 30-minute trial using TENS, followed by reevaluation. The VAS line length change after treatment was the criterion score for comparison of stimulus characteristic effectiveness. Although pain was reduced greatly with TENS (p = .01), a four-way analysis of variance (pulse width, frequency, amplitude, and therapist) attributed little of the treatment effect to the treatment variables or their interactions (r2 = .101). The amplitude effect, however, was borderline (p = .056), and subthreshold stimulation proved more effective than stimulation to tolerance (p = .05). Extensive multiple linear regression analyses failed to provide indications for TENS based on patient information and pain evaluation items. Therefore, pain remains the only indication for TENS, and we recommend subthreshold rather than higher amplitude stimulation on the initial TENS trial.

Data processing of the output from a Vickers M300 clinical chemistry analyser. Principles and implementation.

A suite of data processing programs is described, which takes the results' log from a Vickers Medical LTD M300 clinical chemistry analyser; corrects phasing errors; allows various types of recalibration (recalculation) of the data; and delivers the results to a general purpose laboratory data filing system (PHOENIX-ACHILLES). An important problem with the data is that results may be unphased with respect to their identification data for mechanical reasons. The principles underlying rephasing, and other requirements for handling the M300 data are described, together with the processes used by the operator. Deliberately, no ammendments were made to the supported software for the integral computer in the M300 analyser. The new software supplements the analyser by allowing the operator to summarise the corrections to the data which would have been made under manual conditions: the required corrections are then completed by the computer. About 70 working days were required to complete the program: this was much more than has been required to program data handling for several other analysers which do not have phasing problems.