J. Weinman

A photoelectric approach to the study of peripheral circulation

Abstract Living tissue is transparent to red and infrared radiation in the spectral range at which measurements of extinction coefficients of oxygenated and nonoxygenated blood are generally made. The extinction coefficient of nonhemolyzed blood in this region is much higher than that of the tissue. Incandescent lamps are cheap sources of these wavelengths, and photoconductive cells are extremely sensitive detectors. Therefore, if tissue is illuminated by light in this spectral region, one can expect to be able to detect the varying amount of blood in the tissue due to pulsating flow and vasomotor action. To convert changes in resistance of the photoconductive cells to voltages, simple electrical circuits had to be devised. Photocells and light-sources are built into one small unit which can be easily attached to any part of the body. Light passing through the tissue or scattered in it can be detected. Because of the high sensitivity of the cells, light filters can be used, and changes in flow due to venous or arterial blood can be studied. Experiments were performed in order to test the validity of the proposed method.

High fidelity ECG in the diagnosis of occult coronary artery disease: a study of patients with normal conventional ECG.

High fidelity (HF) electrocardiography (ECGY) was performed on four groups of patients with a normal resting electrocardiogram (ECG). Two groups (A and B) consisted of normal subjects over or under the age of 40, while the other two groups of patients (C and D) underwent coronary arteriography because of chest pain. HR ECG components within the initial portion of the QRS complex were significantly more common among patients with advanced coronary disease. The difference between the normal groups and the group with documented coronary artery disease (CAD) became more significant when the number of leads showing the HF ECG components was counted. Precordial leads were more sensitive in predicting the presence or absence of CAD than limb leads. HF ECG components in the terminal portion of the QRS complex did not differentiate between normals and patients with coronary artery disease, unless the number of leads showing these HF ECG components was considered. It seems that abnormal HF ECG components can point to minor areas of fibrosis caused by coronary artery disease even if the resting conventional ECG is normal.

Assessment of the Atrial Contribution to Cardiac Performance by a Noninvasive Photoplethysmographic Technique

Atrial contribution to ventricular performance was assessed by a non-invasive photoplethysmographic technique in two patients with complete atrioventricular block. The amplitude of the dorsalis pedis

Biomedical engineering: A critical re-appraisal

SommaireL’Auteur considére que le rôle actuel du Génie Biologique et Médical consiste à entretenir la coöpération entre plusieurs disciplines, et conclut que cette fonction pourrait être transitoire.ZusammenfassungDer Autor betrachtet die gegenwärtige Bedeutung der biomedizinischen Technik für die Förderung der Zusammenarbeit zwischen den Disziplinen. Er hält diese Funktion für wahrscheinlich zeitlich begrenzt.