Biomedical subjects
R N Scott
Publications and source records attributed to R N Scott.
Melphalan concentration and distribution in the tissues of tumour-bearing limbs treated by isolated limb perfusion.
Levels of melphalan (L-phenylalanine mustard) were measured in the tissues of tumour-bearing limbs treated by isolated limb perfusion (ILP). 41 samples of melanoma tissue, normal fat and skin were excised from 15 patients during ILP. A high performance liquid chromatography assay was used to measure melphalan concentrations. Levels of melphalan were higher in tumour than in fat (P < 0.01, Wilcoxon signed-ranks test), and not significantly different from levels in adjacent skin. In 2 cases there was significant regional toxicity in the treated limb, but this was not related to the levels of melphalan measured in the tissues of the limb. It is encouraging that the concentrations of melphalan which were achieved in large necrotic nodules by ILP were similar to those in well-perfused normal skin.
The pharmacokinetic advantages of isolated limb perfusion with melphalan for malignant melanoma.
We describe melphalan pharmacokinetics in 26 patients treated by isolated limb perfusion (ILP). Group A (n = 11) were treated with a bolus of melphalan (1.5 mg kg-1), and in a phase I study the dose was increased to 1.75 mg kg-1. The higher dose was given as a bolus to Group B (n = 9), and by divided dose to Group C (n = 6). Using high performance liquid chromatography (HPLC) the concentrations of melphalan in the arterial and venous perfusate (during ILP) and in the systemic circulation (during and after ILP) were measured. Areas under the concentration time curves for perfusate (AUCa, AUCv) and systemic (AUCs) data were calculated. In all three groups the peak concentrations of melphalan were much higher in the perfusate than in the systemic circulation. The pharmacokinetic advantages of ILP can be quantified by the ratio of AUCa/AUCs, median value 37.8 (2.1-131). AUCa and AUCv were both significantly greater in Group B than in Group A (P values less than 0.01, Mann-Whitney). In Groups B and C acceptable 'toxic' reactions occurred but were not simply related to melphalan levels. Our phase I study has allowed us to increase the dose of melphalan to 1.75 mg kg-1, but we found no pharmacokinetic advantage from divided dose administration.
Pilonidal abscess of the penis.
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Psychological morbidity in the first year after breast surgery.
In this prospective study, the psychological morbidity associated with the treatment of breast cancer was assessed. The study population comprised all patients referred to one centre with a recently diagnosed breast lump, who were to undergo surgery. Psychological morbidity was assessed preoperatively and at 6 and 12 months postoperatively by modified Rotterdam Symptom Checklist. Three hundred and twenty patients completed all three questionnaires: 93 women undergoing mastectomy, 73 women having conservation therapy for breast cancer and 156 women having biopsy for benign breast disease. Patients with a breast malignancy smaller than 4 cm in diameter were treated by lumpectomy and radiotherapy, anti-oestrogen therapy or chemotherapy alone or in combination. Psychological morbidity among patients with malignant disease was significantly greater than that seen in the group with benign disease. Among cancer patients, a significant decrease in anxiety and depression occurred during the year following surgery. The study failed to demonstrate any psychological advantage associated with breast conservation.
Noise characteristics of stainless-steel surface electrodes.
Bioelectric events measured with surface electrodes are subject to noise components which may be significant in comparison with low-level biological signals such as evoked neuroelectric potentials, and myoelectric potentials. In an effort to better understand noise arising from these electrodes, electrode and measurement system noise is modelled. The effect of electrode surface area on electrode impedance and noise is studied using circular stainless-steel electrodes of varying diameters. The main contributions of the work are the development of a model for stainless-steel electrode noise as a function of electrode area, and demonstrating that, for the band-width of interest to evoked neuroelectric and myoelectric signals (8-10,000 Hz), the primary noise components are thermal and amplifier current generated. The magnitudes of both of these depend on the electrode impedance magnitude. Electrode impedance is shown to be a power function of both electrode diameter and frequency, consistent with a capacitive electrode model.
Control performance characteristics of myoelectric signal with additive interference.
Myoelectric signal is an important source of control information for powered prostheses. A commonly used performance measure for the signal processors of such control systems is the ratio of processor output mean to variance. This ratio (SNR) is a function of a number of factors including physiological parameters and additive interference. The paper investigates the effects of motor unit physiological parameters and interference on control performance, with particular reference to SNR. Performance equations are derived and verified with in vivo experiments. The results show a complex interaction among the physiological parameters and interference. A particular point of interest is the misleading SNR values that can occur under certain recruitment and interference conditions.
Myoelectric control systems research at the Bio-Engineering Institute, University of New Brunswick.
Myoelectric controls research began at the University of New Brunswick in 1960, and has continued without interruption since that time. The Bio-Engineering Institute has emphasized control systems which meet special clinical needs. These have included systems for amputees with only a single muscle remnant with which to control a prosthesis and, more recently, systems which provide the best possible appearance for children and for infants as young as 15 months of age. Throughout this work, however, the Institute has maintained a fundamental interest in the problem of control of complex multifunction prostheses. With recent developments in electromechanical systems this more advanced controls research will find clinical application shortly.
Feedback in myoelectric prostheses.
This article briefly reviews the history of the use of feedback in artificial limbs. It suggests that researchers have concentrated unduly upon the use of feedback to control prehensile force or joint angle and advocates a broader perspective. In that context, the article presents a comprehensive view of the need for feedback in myoelectric prostheses. The difficulties of designing transducers to meet the stringent demands of prosthetics applications are considered, and problems inherent in several alternatives are identified. Various means of conveying feedback information to the amputee are reviewed in some detail. The concept of feedback in control systems is introduced in the context of closed-loop control of a prosthesis. The surprisingly good performance of skilled users of myoelectric prostheses is noteworthy implying that the distinction between sensory and proprioceptive feedback may be somewhat artificial. By integrating these two feedback types a satisfactory feedback system may become an attainable goal.
Low temperature performance of electric hands.
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A comparison of simultaneous measurements of systolic function in the baboon by electromagnetic flowmeter and high frame rate ECG-gated blood pool scintigraphy.
Left ventricular (LV) systolic timing and relative volume variations were simultaneously measured by electromagnetic flowmeter (EMF) and high frame rate ECG-gated blood pool scintigraphy in five baboons. No significant differences (p greater than 0.1, paired t test) were observed in the time (from R wave) to peak aortic flow (maximum LV ejection rate), time to cessation of aortic flow (end-systole) or in the duration of aortic flow (LV ejection time). A small (approximately 15 msec) but significant systematic difference (p less than 0.02) was noted in the time to onset of aortic flow. The shape of each scintigraphic time-activity curve during systole was compared to an equivalent curve synthesized from 10 EMF flow profiles obtained in the same baboon. Comparison of these paired curves over systolic ejection yielded an average correlation or r = 0.95 (range 0.90--0.99). The ratio of peak flow to stroke volume determined from these data did not differ significantly (p greater than 0.05). In the baboon, quantitative high temporal resolution ECG-gated scintigraphy appears to reflect closely the detailed timing and relative magnitude variation of LV volume during the entire period of systolic ejection. We conclude that the assumptions underlying the scintigraphic method are valid in the baboon during the ejection interval.
Some experience in fitting a myoelectrically controlled hand which has a sense of touch.
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Education and certification of biomedical engineers in Canada.
The education of biomedical engineers in Canada is discussed, with reference to the Canadian health care system and related industry. Information on specific educational programmes, with enrollment data, is presented. The paper concludes with brief comments on the certification of clinical engineers in Canada.
Operator error in multistate myoelectric control systems.
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A nonstationary model for the electromyogram.
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Brochial stump closure techniques following pneumonectomy: A serial comparative study.
Three methods of closing bronchial stumps were evaluated in 90 dogs undergoing left pneumonectomy:interrupted 3-0 silk sutures, interrupted 3-0 nylon sutures, and stapling with an automatic device. The dogs were sacrificed at 24 hours, 3, 5, 7, 10, and 14 days after pneumonectomy. Brochial stump leakage pressures and histological studies were performed on all specimens. Differences in the exudative reaction between silk and staple closures were significant on day 5(238.19+/- 23.28 SD PMN's/HPF in silk closures, 34.95+/- 20.37 SD PMN's/HPF in staple closures) and therafter(P less than 0.001). The reaction to nylon was intermediate between silk and staple. Collagen levels were highest at all periods for staple closures. Staple leakage pressures were greater than silk or nylon(day 5: 145.3 mm Hg +/- 64.9 SD in staple closures, 40.2 mm Hg +/- 15.4 SD in silk closures). These results have clinical relevance to the selection of suture materials for stump closures.
A serial comparison of bronchial stump closure techniques following pneumonectomy.
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Practical considerations for the use of a pulmonary artery thermistor catheter.
The use of a pulmonary artery thermistor catheter for pressure measurement and thermodilution cardiac output determination was evaluated in 11 dogs. Pulmonary artery wedge pressure was a reliable index of left atrial pressure at end-expiratory pressures less than 10 cm. H2O. Fluctuations in pulmonary artery temperature occurred at a frequency equal to the respiratory rate and an amplitude of 0.010 to 0.086 degrees C. Changes in amplitude were associated with changes in ventilatory waveform, respiratory rate, and level of anesthesia. Intermittent and continuous positive-pressure ventilation generally dampened and reversed the pulmonary artery temperature pattern exhibited during spontaneous breathing. This suggested that when end expiration is used to time indicator injection, cardiac output will be underestimated during spontaneous breathing and overestimated during continuous or intermittent positive-pressure ventilation. When indicator was injected at the same point in the ventilatory cycle, successive values of cardiac output deviated from one another by 0.0 to 6.7 percent. Deviations as large as 14 percent resulted if sequential injections were out of phase by half a respiratory cycle. These deviations can be minimized by injecting indicator at the same point in the respiratory cycle, if it is not feasible to measure cardiac output during apnea. The clinical utility of a pulmonary artery thermistor catheter can be optimized through appreciation of its specific strengths and limitations.