Recent advances in the field of externally powered prosthetics and orthotics are remarkable. The purpose of this paper is to describe typical prosthetic and orthotic appliances (mainly, artificial arms) which have been developed and fitted to patients, at least for clinical investigation, in North American and European countries. Most of these prosthetics and orthotics are using myoelectric control systems.
Although myoelectric control of externally powered prosthetic and orthotic appliances has significant limitations, such as the problems of electrodes, control sites, size and weight etc., it has still primary advantage for the amputee or paralytic, as no physical motion of the body is required for its operation.
The available choices for powering an artificial arm are electric, pneumatic and hydraulic; in Japan only the electric system is popular. There is still a controversy as to which of these is best, but there might be the possibility that hybrid combination of electrics with pneumatics or electrics with hydraulic system would be successfully available in future.
Although it is possible to demand both force and position at some control sites, further sensory information is still likely to be needed.
Further effort should be exerted to solve many serious technical difficulties and make ideal artificial limbs and substitutes for many handicapped people.

View full abstract

In measuring a bioelectric event with an amplifier, a pair of recording electrodes plays the role of a transducer. The electrical characteristics of the recording electrodes are very complicated.
Therefor, distortionless insertion of the event into the amplifier requires special consideration of the electrical characteristics of the recording electrodes and the input impedance of the bioelectric amplifier.
This paper is concerned with the general considerations of such fundamental properties of recording electrodes connected through the input impedance of a bioelectric amplifier.

View full abstract

Once the metal surface makes direct contact with the electrolyte body fluid, there forms an ionic double layer, which results in the interface characteristics between metal and fluid for the signal pass. The degree of signal distortion through this layer is dependent upon the frequency and voltage or current of the signal, fluid temperature, impurities contained in the metal, conditions of the pretreated metal surface and the concentration of the electrolytes. By using the Ag-AgCl or platinized platinum, the Warburg impedance may be rendered. Bright platinum, gold and silver, however, exhibit the dominance of the frequency dependency of the R part, which is inversely proportional to the signal frequency, and the C part is relatively constant against the frequency. For the emf system, the stableness of this interface characteristics is important to minimize, the drift in zero flow level in the long duration of time. In the sine-wave excitation, the Wagner's grounding is successfully applied. In the practical applications, zero drift is also originated from the mechanical slide or slip of the vessel wall on the electrode due to pulsation and/or respiration. The degree of zero stability may be evaluated from the signal to noise ratio, where square-wave system generates over ten times as large a signal by the same velocity as the sine-wave system against the same noise caused by the electrode characteristics. Uneven distribution of the eddy current, however, may cause more zero drift in the high frequency square-wave system than seen in sine-wave system.

View full abstract

Computer diagnosis of electrocardiogram (ECG) has been extensively studied in this country, but is not yet widely used by general practitioners. A computer programm was worked out to process a standard ECG, recorded with a popular direct-writing cardiograph. Input data for this program were prepared from measurements of 15 parameters and answers to 65 questions according to a questionnaire. This questionnaire can be filled by an ECG technician after 30 minutes' training. It takes 6 minutes on an average to fill each questionnaire.
The validity of the program was tested by samples from both textbook data (261 cases) and hospital records (335 cases). 47% of diagnoses given for textbook data proved satisfactorily consistent with human diagnosis and 25% only partly and tolerably consistent. The rest (29%) was found to be inconsistent. 75% of diagnoses given for hospital records proved satisfactorily consistent with human diagnosis, 15% only partly and tolerably consistent, and the rest (7%) inconsistent.
On the other hand, almost all ECGs (4968 cases) recorded at the Kambara General Hospital (KGH) for the past three years were statistically analysed regarding their diagnoses. Combining this result with that of textbook data analysis, at least about 70% of KGH data can be expected to be fully or tolerably analysed by the computer. Simplification of the questionnaire format was one reason for the low efficiency of arrhythmia processing ; it limited the detection of comparatively rare abnormalities. Moreover, this was not very effective in decreasing measurement errors and inter-observer variations.
Despite these shortcomings, ECG diagnostic service by this program might be valuable in its capability to process popular ECG records and in its inexpensiveness.

View full abstract

The conventional dilution method of estimating residual volume fraction (RVF) of the ventricle is based on the assumption of complete intraventricular mixing of the indicator. However, incomplete mixing in the ventricle has been observed in various ways. A dilution method is devised for estimating RVF in spite of incomplete intraventricular mixing of the indicator;
RVF=C_{γ, i}/C_{γ, i-1}/C_{γ, i}/C_{γ, i-1}+ (1-C_{γ, i}/C_{γ, i-1}) C_{γ, i}/C_{s, i}
where C_{γ, i}/C_{γ, i-1}=the ratio of the concentration of the indicator in the residual volume in the i th cardiac cycle C_{γ, i} to that in the (i-1) th cycle C_{γ, i-1}, and C_{γ, i}/C_{s, i}=the ratio of C_{γ, i} to the concentration of the indicator in the stroke volume in the i th cardiac cycle C_{s, i}. This method is used in the canine heart for assessment of the incompleteness of mixing and for comparison of RVF by the conventional and the new method. Results show that some incompleteness of mixing is generally observed, but RVF by the conventional method is considered approximately equal to that by the new method. Some model analysis of incomplete mixing is given for explanation of the experimental data.

View full abstract