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Biomedical subjects

D L Harm

Publications and source records attributed to D L Harm.

27 records · Page 2Linked to original sources
PubMed1985

Improving the ability of peak expiratory flow rates to predict asthma.

A major problem in the behavioral management of childhood asthma concerns recognition of the early signs of impending episode. An objective measure commonly used to aid recognition of early warning signs is the peak expiratory flow rate (PEFR). This study examined the ability of PEFRs to predict asthma within a 12-hour period; the prediction method used was based on prior and conditional posterior probabilities. Twenty-five children with asthma recorded their PEFR twice daily, and also recorded the date and time of their asthma episodes. Conditional posterior probabilities and the ratio of hits to misses were computed for each subject at successively lower flow rates. The average improvement in predictability from the prior probability to the highest posterior probability was 491%. The ratio of hits to misses and the number of episodes predicted, however, decreased as the posterior probability increased. Selection of the PEFR at lower posterior probabilities resulted in fewer prediction errors and led to prediction of a higher number of episodes than selection of the PEFR at the highest posterior probability.

Adolescent↗
PubMed1985

Effects of instructions on pulmonary function values.

This study examined the influence of specific components of standard forced expiratory maneuver instructions on spirometric values. Thirty-six subjects received instructions and practice in performing the forced expiratory maneuver prior to experimental manipulation of instructions. Instructions to begin with a maximal inhalation and then to blow into the spirometer as hard, fast, and long as possible were reiterated prior to every maneuver. During the instruction manipulation period, subjects were additionally instructed to blow either harder, faster, or longer. Overall, instructions to blow harder resulted in the most stable pattern of increase in all measures (IC, FVC, FEV1, FEF25-75%, and FEV1/FVC); instructions to blow longer consistently led to decreases in some values.

Adolescent↗
PubMedDate not supplied

Self-motion perception: assessment by computer-generated animations.

The goal of this research is more precise description of adaptation to sensory rearrangements, including microgravity, by development of improved procedures for assessing spatial orientation perception. Thirty-six subjects reported perceived self-motion following exposure to complex inertial-visual motion. Twelve subjects were assigned to each of 3 perceptual reporting procedures: (a) animation movie selection, (b) written report selection and (c) verbal report generation. The question addressed was: do reports produced by these procedures differ with respect to complexity and reliability? Following repeated (within-day and across-day) exposures to 4 different "motion profiles," subjects either (a) selected movies presented on a laptop computer, or (b) selected written descriptions from a booklet, or (c) generated self-motion verbal descriptions that corresponded most closely with their motion experience. One "complexity" and 2 reliability "scores" were calculated. Contrary to expectations, reliability and complexity scores were essentially equivalent for the animation movie selection and written report selection procedures. Verbal report generation subjects exhibited less complexity than did subjects in the other conditions and their reports were often ambiguous. The results suggest that, when selecting from carefully written descriptions and following appropriate training, people may be better able to describe their self-motion experience with words than is usually believed.

Aerospace Medicine↗
PubMedDate not supplied

Psychophysical scaling of circular vection (CV) produced by optokinetic (OKN) motion: individual differences and effects of practice.

Vection (V) refers to the compelling visual illusion of self-motion experienced by stationary individuals when viewing moving visual surrounds. The phenomenon is of theoretical interest because of its relevance for understanding the neural basis of ordinary self-motion perception, and of practical importance because it is the experience that makes simulation, virtual reality displays, and entertainment devices more vicarious. This experiment was performed to address whether an optokinetically induced vection illusion exhibits monotonic and stable psychometric properties and whether individuals differ reliably in these (V) perceptions. Subjects were exposed to varying velocities of the circular vection (CV) display in an optokinetic (OKN) drum 2 meters in diameter in 5 one-hour daily sessions extending over a 1 week period. For grouped data, psychophysical scalings of velocity estimates showed that exponents in a Stevens' type power function were essentially linear (slope = 0.95) and largely stable over sessions. Latencies were slightly longer for the slowest and fastest induction stimuli, and the trend over sessions for average latency was longer as a function of practice implying time course adaptation effects. Test-retest reliabilities for individual slope and intercept measures were moderately strong (r = 0.45) and showed no evidence of superdiagonal form. This implies stability of the individual circularvection (CV) sensitivities. Because the individual CV scores were stable, reliabilities were improved by averaging 4 sessions in order to provide a stronger retest reliability (r = 0.80). Individual latency responses were highly reliable (r = 0.80). Mean CV latency and motion sickness symptoms were greater in males than in females. These individual differences in CV could be predictive of other outcomes, such as susceptibility to disorientation or motion sickness, and for CNS localization of visual-vestibular interactions in the experience of self-motion.

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