In this paper are reviewed several different methods for detecting partial obstruction of peripheral airways appearing in the early stage of obstructive lung disease. The first method is based on the detection of abnormality in gas exchange efficiency by means of the analysis of arterial blood and expired gas. The methods involved in the second group are based on uneven distribution of mechanical time constants in the lungs ; one of which is related to the frequency-dependency of pulmonary resistance and compliance ; another, to the Pendelluft appearing at the airflow interruption ; another, to the phase difference between the alveolar pressure and airflow ; and still another, to the pattern analysis of the flow-volume curve. Two methods involved in the third group are based on uneven distribution of gas components in the lungs ; one deals with the classical N₂-clearance curve of Fowlers, and the other, with the measurement of “closing volume” which has recently been developed. Theoretical ground and applicability of these methods have been discussed on the basis of the clinical data.

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It is not easy to define the terms “invasive” and “non-invasive”, which are used very often recently. In the circulatory system, however, “non-invasive” examination may be regarded almost synonymous as “non-bloody” (nicht-blutig). A typical “bloody” examination of circulatory system is cardiac catheterization, which provides much important hemodynamic information. Among them, cardiac output, left ventricular ejection fraction, etc. can be determined in non-invasive ways using echocardiography, gamma camera or impedance plethysmography, but automation of measurement and calculation is required for their routine clinical use. Estimation of cardiac contractility by mechanocardiographic information can be applied only to limited situations. Noninvasive examination of coronary blood flow, detection of shunt and cardiac aneurysm and recording of His bundle electrogram are also discussed.

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The purpose of this study is to diagnose heart diseases automatically from chest X-ray films.
Cardiac shape is represented by a closed curve which is a seventh-order polynomial least-square-approximation. It is shown that the shape of the entire cardiac shadow can be represented by this model. Although this model originally has six parameters, result of principal component analysis indicates that this model can approximately be expressed (up to 98.5% in variance) by only three main components.
By reproducing cardiac shapes using three main components and diagnosing for heart diseases, the distribution of diseases is plotted in a three-dimensional space. If one is to diagnose heart disease from this distribution diagram, classification is correct for 70.0% of typical 23 cases.
Parameters used in this model can be extracted by sequentially fitting the model to an actual X-ray film. Noises such as those of the ribs and gas in stomach are eliminated in this procedure, though there are errors of 5% to 10% for three main components.

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A new multipurpose analog system has been developed, which can compute the following formula automatically and record the spatial magnitude ECG, spatial velocity ECG, spatial acceleration ECG, spatial circumference ECG and polarcardiogram very easily and quickly, using the scalar ECG (X, Y, Z) of vectorcardiographic lead as inputs.
Spatial magnitude ECG=√X²+ Y²+ Z²
Spatial velocity ECG=√ (dX/dt) ²+√ (dY/dt) ²+ (dZ/dt) ²Spatial acceleration ECG =√ (d² X/dt²) ²+ (d²Y/dt²) ²+ (d²Z/dt²) ²
Spatial circumference ECG=∫√ (dX/dt) ²+ (dY/dt) ²+ (dZ/dt) ²·dt
Time constants for the differentiating circuits were 1 msec, 5 msec and 10 msec for QRS, P and T waves respectively. Vector sum circuits applying absolute value operation introduced by Imai and Nguyen Phuoc (1972) were used in this system instead of the squaring, adding and square root circuits, and simplification of the composition of the system and the highly reliable records were obtained. Computations of the orientation curve of the polar ECG were performed following the Dower's method, and the longitude ECG (α, β and γ) and the latitude ECG (P-A, I-S and R-L)

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Theoretical consideration of electrical shock hazards caused by medical equipment have been performed based on the electromagnetic theory and Hill's neurological theory. The isometric biological tissue having an active cell and a circular electrode on it are assumed for calculation. This model is feasible to application both to macro shock and micro shock. The characteristics of electrical shock hazards obtained were as follows;
1) The threshold of shock, when commercial frequency A. C. current is applied, is equivalent to a half-value of D. C. current.
2) From commercial frequency to nearly 100 kHz, the biological tissue has constant threshold value. However, it depends on relative resistance, time constant of active cell membrane, etc., of the biological tissue.
3) When any medical equipment with high-frequency current source is especially designed, it is important to consider the frequency characteristics of catheter or lead wire which connect the equipment and the biological tissue.

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