Biomedical subjects
Publications and source records attributed to B J West.
The tendency for surgery and associated nursing care to become short-stay is driven by so many considerations (of both dubious and desirable kinds) that it may be useful to attempt a little stock-taking on previous patterns of day operating and, by consulting a crystal ball, to consider possible implications for nursing and patient aftercare.
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The mammalian lung exhibits features of a fractal tree: heterogeneity, self-similarity and the absence of a characteristic scale. The finite nature of the lung ultimately limits the range over which self-similarity scaling characteristics are applicable. However, generalization based on the scaling features of fractals, provides unique insight into geometric organization of anatomic structures. Furthermore, the mathematical theory of renormalization groups provides a description of the harmonically-modulated inverse power-law scaling observed for bronchial tree dimensions observed in different species. Compared to several mammalian species (dog, rat, hamster), the human lung shows marked differences in the phase of the harmonic modulation for both length and diameter measurements. These inter-species scaling differences suggest that evolutionary factors modify certain universal features of morphogenesis.
The natural variability in physiological form and function is herein related to the geometric concept of a fractal. The average dimensions of the branches in the tracheobronchial tree, long thought to be exponential, are shown to be an inverse power law of the generation number modulated by a harmonic variation. A similar functional form is found for the power spectrum of the QRS-complex of the healthy human heart. These results follow from the assumption that the bronchial tree and the cardiac conduction system are fractal forms. The fractal concept provides a mechanism for the morphogenesis of complex structures which are more stable than those generated by classical scaling (i.e., they are more error tolerant).
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Behavioral momentum refers to the tendency for behavior to persist following a change in environmental conditions. The greater the rate of reinforcement, the greater the behavioral momentum. The intervention for noncompliance consisted of issuing a sequence of commands with which the subject was very likely to comply (i.e., high-probability commands) immediately prior to issuing a low-probability command. In each of five experiments, the high-probability command sequence resulted in a "momentum" of compliant responding that persisted when a low-probability request was issued. Results showed the antecedent high-probability command sequence increased compliance and decreased compliance latency and task duration. "Momentum-like" effects were shown to be distinct from experimenter attention and to depend on the contiguity between the high-probability command sequence and the low-probability command.
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(1) Nonlinear mechanisms may apply both to the understanding of SA-AV node interactions and to bifurcations leading to certain types of AV block. (2) The fractal His-Purkinje system serves as the structural substrate for the generation of the broadband, inverse power-law spectrum of the stable ventricular depolarization (QRS) waveform. (3) Fractal anatomy is also seen in multiple other systems: pulmonary, hepatobiliary, renal, etc. Fractal morphogenesis may reflect a type of critical phenomenon that results in the generation of these irregular, but self-similar structures. (4) Self-similar (fractal) scaling may underlie the 1/f-like spectra seen in multiple systems (e.g., interbeat interval variability, daily neutrophil fluctuations). This fractal scaling may provide a mechanism for the "constrained randomness" that appears to underlie physiological variability and adaptability. (5) Behavior consistent with subharmonic bifurcations is seen in cardiac electrophysiology (e.g., sick sinus syndrome) and hemodynamic perturbations (e.g., swinging heart phenomenon in pericardial tamponade). (6) Ventricular tachyarrhythmias associated with sudden cardiac death (e.g., torsades de pointes, ventricular fibrillation) appear to reflect relatively periodic, not chaotic (turbulent) processes resulting from disruption of the physiologic fractal depolarization sequence. (7) Spectral analysis of Holter monitor data may help in the detection of patients at high risk for sudden death.
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An analysis of five demand conditions affecting the reluctant speech of a preschool child was conducted in the classroom. Results indicated that demand conditions that did not permit escape from academic demand tasks, ignored mute responses, prompted answers and enthusiastically praised verbal responses resulted in higher rates of speech. Further, replication of these procedures across escape conditions resulted in increased speech rates that approximated those of a non-mute peer in the same classroom. Follow-up data at 8 months indicated that in the classroom the subject spoke more often to more people using a greater number of words, subsequent to analysis and intervention. The classroom teacher also reported a marked improvement in speech rate and quality and considered the time spent in analysis worthwhile. The study provides a model for further analysis of conditions associated with reluctant speech.
The role of reinforcement in reactive self-monitoring was investigated. Subjects for this study were three mentally retarded adults employed in a sheltered workshop. Changes in productivity rates in a party hat assembly task across experimental conditions (reinforcements, self-monitoring, and self-monitoring plus reinforcement) were evaluated. Findings showed that while reinforcement alone increased productivity, it was to a lesser degree and with less consistency than when combined with self-monitoring. In addition, self-monitoring alone did not increase productivity. These results support the Rachlin and Nelson and Hayes hypotheses that reactive effects of self-monitoring are dependent upon environmental contingencies. The results also showed that self-monitoring increases the salience of reinforcement.
The average dimensions (diameter, length, and volume) of the airways in the mammalian bronchial tree, long thought to be exponential functions of the generation number, are shown to be power laws in generation number modulated by a harmonic variation. These data are satisfactorily described by means of a functional scaling relation--renormalization group property--between successive generations for the average variable of interest. This type of scaling may provide a mechanism for the morphogenesis of complex but highly stable structures.
The irregular branching pattern of the bronchial tree in multiple mammalian species is consistent with a process of morphogenetic self-similarity described by Fibonacci scaling.
Electrical activation of the ventricles via the His-Purkinje system is represented on the body surface by a waveform with a broad range of frequency components. We speculate that this process is mediated by current flow through a fractal-like conduction network and therefore that the broadband spectrum of the depolarization waveform should be scaled as a power-law distribution. The prediction is confirmed by Fourier analysis of electrocardiographic data from healthy men. This observation suggests a new dynamical link between nonlinear (fractal) structure and nonlinear function in a stable physiologic system.
New instrumentation, techniques and computers have made such large amounts of information rapidly available to ICU clinicians that there is now a danger of information overload. To help with this problem at LDS Hospital, a computerized system was implemented in the Shock-Trauma ICU. This ICU is almost totally computerized with each patient's physiologic, laboratory, drug, demographic, fluid input/output and nutritional data integrated into the patient's computer record. In the ICU, physician decision-making takes place in two situations: during rounds and on-site. For this study, data usage in decision-making was evaluated in both of these environments. The items of data used in decision-making were tabulated into six categories: bedside monitor, laboratory, drugs, input/output and IV, blood gas laboratory, observations and other. Comparisons were made between the portion of the computerized database occupied by a category and its use in decision-making. Combined laboratory data (clinical, microbiology and blood gas) made up 38 to 41% of total patient data reviewed and occupied 16.3% of the database. Observations made up 21-22% of the data reviewed and occupied 6.8% of the database. Drugs, input/output and IV data usage ranged from 13% to 23%, but occupied 36% of the database. Bedside monitor data usage was 12.5% to 22% and occupied 32.5% of the database. The 'other' category, used 2.5% to 5% of the time, made up 8.4% of the database. These results indicate that patient data collection and storage must be evaluated and optimized. This evaluation, along with implementation of the computerized ICU Rounds Report developed for optimal data presentation, will help physicians to evaluate patient status and should facilitate effective decisions.
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