ABSTRACT
A multilayer tissue description was employed in a Monte Carlo simulation of light-tissue interaction to study photon travel through skin. Paths of photons returning to the tissue surface at a certain range from the point of entry (emitter-detector spacing) were collected. The simulation demonstrates that highly absorptive discrete layers (e.g., containing melanin or blood) tend to channel photons away. As a result, the dependence of mean depth of photon penetration on wavelength is quite different from the predictions of a homogeneous tissue model. The impact upon our understanding of pulse oximetry is discussed.
ABSTRACT
The concept of infant state refers to patterns of behavior that comprise the sleep-wake cycle. The infant's ability to organize state behavior rhythmically is indicative of central nervous system maturation and predictive of later development. This article describes the development of a noninvasive, computerized infant monitoring system that can be used to categorize the infant's sleep-wake behavior into states. Development of the system occurred in two phases: In the first phase of the study, reliability and validity of the infant monitoring system for recording continuous behavioral and physiological data were assessed. These results were then used in the second phase to develop a rule-based computer program to interpret the signal data stored on a micro-diskette and to characterize the infant's state throughout the period of monitoring. The capability of computerized data collection and analysis of infant state behavior has expanded the application of this infant monitoring system. Its use as an investigative tool in clinical research is discussed.
