Biomedical subjects
Publications and source records attributed to B L Ryack.
A portable, 12-channel electrocardiogram (ECG) recorder is described. It weighs approximately 11 pounds, can be battery operated, and provides interpretation of the ECG tracing and a computer interface. It can be used in isolated environments, emergency vehicles, or a physician's office.
The problem of escaping from a submerged helicopter is discussed. The effectiveness of illuminated escape hatches in facilitating escape has been demonstrated. The relative advantages of different types of lights are compared. Escape training, illuminating the emergency exits, and providing breathing devices should greatly enhance the chances of survival in a helicopter crash at sea.
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The effectiveness of two types of steady and flashing lights as escape hatch indicators for submerged helicopters was compared. Measurements were taken in moderately and highly turbid water. Response time was faster to the steady lights, and they were more accurately localized. Pairs of steady lights appeared to have some advantage over single lights, but this was not true for flashing lights. Subjects found it very difficult to discern how many different locations were being illuminated.
Luminance thresholds were measured for the water-immersed eye as a function of adaptation level, viewing distance, and turbidity of the water, and compared to standard adaptation curves. In water, thresholds varied as a function of initial adaptation level, and the rate of adaptation paralleled that for the eye in air. However, thresholds were about 1-2 log units higher for the water-immersed eye than for the eye in air at all adaptation levels.
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