Biomedical subjects

C W Turner

Publications and source records attributed to C W Turner.

At least 19 recordsLinked to original sources

PubMed1992

Family support, physical impairment, and adherence in hemodialysis: an investigation of main and buffering effects.

Patient noncompliance is a pervasive problem among end-stage renal disease (ESRD) patients. Previous studies have implicated social support as an important correlate of adherence behavior in other chronic illness groups, but little research has examined this relationship in a hemodialysis population. The present study examined the main and interactive effects of social support in the family and illness-related physical impairment with regard to patient compliance in a sample of 78 hemodialysis patients. Results indicated that patients holding perceptions of a more supportive family environment exhibited significantly more favorable adherence to fluid-intake restrictions than did patients reporting less family support. Family support was not associated with adherence to dietary restrictions. The effect of family support on fluid-intake adherence was not moderated by level of physical impairment. This pattern suggests that the influence of support on adherence is more attributable to a main or direct effect, as opposed to a buffering process in the face of increased physical impairment.

Activities of Daily Living↗

PubMed1992

Detection and recognition of stop consonants by normal-hearing and hearing-impaired listeners.

This study examined the possibility that hearing-impaired listeners, in addition to displaying poorer-than-normal recognition of speech presented in background noise, require a larger signal-to-noise ratio for the detection of the speech sounds. Psychometric functions for the detection and recognition of stop consonants were obtained from both normal-hearing and hearing-impaired listeners. Expressing the speech levels in terms of their short-term spectra, the detection of consonants for both subject groups occurred at the same signal-to-noise ratio. In contrast, the hearing-impaired listeners displayed poorer recognition performance than the normal-hearing listeners. These results imply that the higher signal-to-noise ratios required for a given level of recognition by some subjects with hearing loss are not due in part to a deficit in detection of the signals in the masking noise, but rather are due exclusively to a deficit in recognition.

Adult↗

PubMed1992

Intensity discrimination in forward masking.

A nonmonotonic intensity discrimination function was recently reported in which a midlevel hump occurred for 25-ms sinusoidal standards ranging from 20 to 100 dB SPL and presented 100 ms after an intense narrow-band noise forward masker [F.-G. Zeng et al., Hear. Res. 55, 223-230 (1991)]. This paper provides additional data on how the midlevel hump is affected by three factors of forward masking: signal delay, masker level, and frequency. Specifically, just-noticeable differences (jnd's) in intensity were obtained at signal delays of 50, 200, and 400 ms. Results show that at the midlevels the forward-masked intensity jnd's did not recover to their unmasked values, even at the 400-ms signal delay. The longer the signal delay, the smaller this midlevel hump. This slow recovery of the midlevel jnd's is consistent with the finding that low-spontaneous rate (SR) neurons have a slow recovery from forward masking [E. M. Relkin and J. R. Doucet, Hear. Res. 55, 215-222 (1991)]. The large midlevel effect decreased sharply as masker level was reduced from 90 to 60 dB SPL, and disappeared for masker levels less than 40 dB SPL. A frequency selectivity effect for the large midlevel jnd effect was also observed, as maskers with frequency components 2 to 3 oct away from the signal frequency did not affect the jnd's. Overall, the present data are consistent with the hypothesis of Zeng et al. (1991) that low-SR neurons are involved in the midlevel hump of intensity discrimination in forward masking.

Adult↗

PubMed1992

Frequency discrimination in forward and backward masking.

Frequency difference limens for pure tones preceded by a forward masker or followed by a backward masker were obtained across a wide range of signal levels. Relkin and Doucet [Hear. Res. 55, 215-222 (1991)] have shown that at a masker-signal delay of 100 ms, the thresholds of high-SR (spontaneous rate) auditory-nerve fibers are recovered, while the low-SR fiber thresholds are not. Therefore, forward-masked frequency discrimination potentially offers a method to investigate the role of low-SR fibers in the coding of frequency. It has been shown that when an intense forward masker is presented 100 ms before a pure-tone signal, intensity difference limens are elevated for mid-level signals [Zeng et al., Hear. Res. 55, 223-230 (1991)]. However, Plack and Viemeister [J. Acoust. Soc. Am. 92, 3097-3101 (1992)] have shown that a similar elevation in the intensity difference limen is obtained under conditions of backward masking, where selective adaptation of the auditory neurons would not be expected to occur. A condition of backward-masked frequency discrimination was therefore included to investigate the role of interference resulting from adding additional stimuli to a discrimination task. For signals at 1000 and 6000 Hz, there was no effect of a forward masker upon frequency difference limens. For the backward-masked conditions, an elevation of the frequency difference limen was observed at all signal levels, demonstrating that the effects of forward and backward maskers upon frequency discrimination are dissimilar and suggesting that cognitive effects are present in backward-masked discrimination tasks.(ABSTRACT TRUNCATED AT 250 WORDS)

Auditory Perception↗

PubMed1992

Iliad's role in the generalization of learning across a medical domain.

Medical informatics could facilitate more effective analysis and use of clinical knowledge by means of expert systems. To be most effective, such systems should be constructed in a manner which is consistent with physicians' cognitive processes. Our past five years' work with a system called Iliad indicates that it provides effective medical training and education. The current research extends our previous work by using a wider array of training and test cases. We also evaluated whether training on specific cases could generalize to improved testing performance on related cases, which featured similar complaints and pathophysiologic mechanisms, but different final diagnoses. In their junior internal medicine clerkship, students (n = 100) completed 1300 Iliad training cases covering 48 diagnoses. The findings indicated improved problem solving on the specifically trained cases as well as the generalization cases. We discuss a possible training model for expert systems such as Iliad.

Computer-Assisted Instruction↗

PubMed1992

Comparison of different information content models by using two strategies: development of the best information algorithm for Iliad.

Iliad is a diagnostic expert system for internal medicine. Iliad's "best information" mode is used to determine the most cost-effective findings to pursue next at any stage of a work-up. The "best information" algorithm combines an information content calculation together with a cost factor. The calculations then provide a rank-ordering of the alternative patient findings according to cost-effectiveness. The authors evaluated five information content models under two different strategies. The first, the single-frame strategy, considers findings only within the context of each individual disease frame. The second, the across-frame strategy, considers the information that a single finding could provide across several diseases. The study found that (1) a version of Shannon's information model performed the best under both strategies---this finding confirms the result of a previous independent study, (2) the across-frame strategy was preferred over the single-frame strategy.

Algorithms↗

PubMed1992

A modified harvest technique for cord blood hematopoietic stem cells.

Human umbilical cord blood is an excellent source of hematopoietic stem cells for research and bone marrow transplantation. We have developed a modified technique which effectively flushes and collects placental derived stem cells. Catheters were inserted into the umbilical artery and vein. Using this sterile and closed system technique, 10 saline diluted cord blood harvests had hematocrits of 16% to 25%, total mononuclear cell counts of 1.17 to 34.4 x 10(8) and volumes of 105-245 ml. The averaged extrapolated colony forming units from five cord blood harvests were as follows: CFU-GM 5.2 x 10(5) (9.96 x 10(4) to 1.24 x 10(6)), BFU-E 8.82 x 10(5) (2.40 x 10(4) to 1.61 x 10(6)) and CFU-GEMM 1.37 x 10(5) (7.33 x 10(3) to 3.18 x 10(5)). This quick technique avoids needle exposure and collects a significant volume of stem cells.

Bone Marrow Transplantation↗

PubMed1991

Iliad training enhances medical students' diagnostic skills.

Iliad is a computerized, expert system for internal medical diagnosis. The system is designed to teach diagnostic skills by means of simulated patient case presentations. We report the results of a controlled trial in which junior students were randomly assigned to received Iliad training on one of two different simulated case mixes. Each group was subsequently tested in both their "trained" and "untrained" case domain. The testing consisted of computerized, simulated patient cases for which no training feedback was provided. Outcome variables were designed to measure the students' performance on these test cases. The results indicate that students made fewer diagnostic errors and more conclusively confirmed their diagnostic hypotheses when they were tested in their trained domain. We conclude that expert systems such as Iliad can effectively teach diagnostic skills by supplementing trainees' actual case experience with computerized simulations.

Clinical Clerkship↗

PubMed1991

Firstborn adolescent daughters and mothers with and without premenstrual syndrome: a comparison.

Firstborn adolescent daughters and their mothers with and without premenstrual syndrome (PMS) were evaluated for two menstrual cycles in order to compare menstrual, postmenstrual (follicular), and premenstrual (luteal) symptomatology. Physical and psychological symptoms were evaluated according to the Premenstrual Assessment Form (PAF) and the Utah PMS Calendar II. The onset of the luteal phase was defined as the day of the midcycle surge of luteinizing hormone (LH), determined by utilizing the CUE Ovulation Predictor. The PAF showed that 1) irrespective of diagnosis, severity of symptoms was not significantly different between adolescents and adults; however, 2) when daughters and mothers were grouped according to mother's diagnosis, the PMS mother/daughter dyads experienced significantly more premenstrual symptoms when compared to the non-PMS mother/daughter dyads. Furthermore, the PMS Calendar revealed menstrual cycle phase delineation. There were no significant differences in severity of symptoms between adults and adolescents during the postmenstrual (follicular) phase and the premenstrual (luteal) phase. However, the adolescents experienced significantly more symptoms during the menstrual phase than the adults. 1) There were no significant differences in severity of adolescents' menstrual symptoms and their premenstrual (luteal) symptoms; 2) the number and severity of luteal phase symptoms were significantly greater for the women with PMS and their daughters than women without PMS and their daughters.

Adolescent↗

PubMed1991

Recovery from prior stimulation. II: Effects upon intensity discrimination.

We obtained just-noticeable differences (jnds) for the intensity of pure tones following a forward masker. The masker was a 100-ms burst of narrow-band noise centered at 1000 Hz presented at 90 dB SPL; the pure-tone signal was at 1000 Hz and was 25 ms in duration. The masker-signal delay was 100 ms. Under these conditions, there is no threshold shift for the detection of the pure-tone signal following the forward masker. In contrast with the absence of a forward-masker effect upon detection thresholds, unusually large midlevel (40-60 dB SPL) jnds were observed. These large midlevel jnds were measured as a function of signal delay, revealing that they are not completely recovered to the normal (unmasked) values by 400 ms. We interpret these data as a consequence of the slower recovery of low-spontaneous rate, high-threshold neurons following prior stimulation (Relkin and Doucet, 1990). These experiments may therefore provide psychophysical evidence that the low-spontaneous rate, high-threshold neurons are a necessary physiological component in the coding of the large dynamic range for intensity. In addition, the present data provide evidence that the assumption that the effect of forward masking is limited to 100-200 ms is inappropriate, as this recovery time does not necessarily apply to suprathreshold tasks.

Acoustic Stimulation↗

PubMed1991

Health locus of control and depression in end-stage renal disease.

Research on the association between health locus of control and depression in chronic illness has produced contradictory findings, perhaps because of a failure to consider contextual variables. In this study of 96 hemodialysis patients, the belief that one's health is controllable was associated with less depression among Ss who had not previously experienced a failed renal transplant. This belief was associated with greater depression for Ss who had returned to dialysis following an unsuccessful transplant. This interactive effect occurred among severely ill Ss, but health locus of control was unrelated to depression among Ss with less severe disease. This pattern occurred both when control perceptions reflected a belief in the Ss' own or powerful others' (i.e., health care providers) ability to influence health outcomes. Results underscore the adaptive value of congruence between control beliefs and objective circumstances in chronic illness.

Adult↗

PubMed1991

Reasons for the trend toward null findings in research on Type A behavior.

The findings of many studies conducted before 1978 suggest that Type A behavior (TAB) contributes to the development of coronary heart disease (CHD). In contrast, many recent studies have found no association between these variables. Through meta-analysis, several reasons for null findings are identified. First, a type of range restriction bias, disease-based spectrum (DBS) bias, produced many null findings. A study is vulnerable to DBS bias when researchers select only high-risk or diseased Ss for study. Second, self-report measures of TAB were often associated with null findings. Finally, null results were found for all studies that used fatal myocardial infarction as a disease criterion. In addition to identifying the reasons for null findings, this research suggests that TAB, as assessed by the structured interview, is associated with CHD. More Type As (70%) were found in diseased populations of middle-aged men than in healthy populations of middle-aged men (46%).

Coronary Artery Disease↗

PubMed1991

Effects of different frequency response strategies upon recognition and preference for audible speech stimuli.

The purpose of this study was to examine whether the amount of low- versus high-frequency amplification should change as a function of input level, as is done in some recently developed hearing aids. Adults with high-frequency sensorineural hearing loss served as subjects. Both identification performance and preference judgments for audible CV syllables were assessed as a function of input level for three different signal processing conditions both in quiet and in noise. The first signal processing condition was a conventional high-pass frequency response that did not change its transfer function as the input level increased; the second condition was similar to a typical adaptive frequency response (AFR) hearing aid: a high-pass frequency response that became increasingly high-pass as the input level increased; the third condition was similar to the K-Amp hearing aid recommended by Killion (1988): a high-pass frequency response that became more broadband as the input level increased. Results indicated no significant differences among the three different processing conditions for syllable recognition and a strong listener preference for the syllables presented via the conventional amplification scheme.

Acoustics↗

PubMed1991

Binaural loudness matches in unilaterally impaired listeners.

Binaural loudness matching data using a 21FC adaptive procedure were obtained in high-frequency, unilateral cochlear-impaired listeners. The matches were obtained at frequencies where both ears had similarly normal thresholds, and also at other frequencies where the impaired ear had various degrees of hearing loss. In these listeners, one presumed difference between the ears is the limited or altered spread of excitation in the impaired ear. In agreement with previous studies using other approaches (Hellman, 1974, 1978; Hellman & Meiselman, 1986; Moore, Glasberg, Hess & Birchall, 1985; Schneider & Parker, 1987), the results of the present study suggest that both the range and the slope of loudness growth function are not dependent on the spread of excitation, but instead are related primarily to the degree of threshold elevation at the test frequency. Following this suggestion, a spread-of-excitation-independent model, based upon a group of neurons with the same characteristic frequency (CF) but different thresholds, is proposed to account for loudness growth in both normal and recruitment cases. In particular, it is shown quantitatively that a compressed distribution of thresholds due to threshold elevation may be responsible for loudness recruitment in sensorineural hearing loss.

Adult↗

PubMed1991

Growth of masking in sensorineural hearing loss.

The purpose of the present study was to measure the growth of masking in both normal-hearing and sensorineural hearing-impaired subjects. The masker was a narrow band of noise centered at 1,000 Hz, and masked thresholds for signal frequencies both above and below the masker frequency were obtained for a range of masker levels. For signal frequencies above the masker frequency, the slopes of the growth of masking functions were greater than 1 dB/dB for the normal-hearing group, while for the hearing-impaired subjects the slopes were less than those of the normal subjects, and in many cases slopes were less than 1. The slope of masking was inversely related to the threshold at the signal frequency. These data support the concept that a loss of nonlinearity at the signal place is responsible for the slower growth of masking in hearing-impaired subjects for signal frequencies greater than the masker. In addition, the slower-than-normal growth of masking of the hearing-impaired subjects suggests that some hearing aid signal-processing strategies which provide greater amounts of high-frequency emphasis at high input levels may not be appropriate.

Acoustics↗

PubMed1991

Health science information management. An approach to improving QA and clinical practice.

To help quality assurance (QA) professionals and clinical practitioners keep up with advances in health care knowledge and technology, we describe a prototype Health Science Information Management (HSIM) publication. We conceptualize HSIM to include: (a) identification of unique science information needs; (b) rapid retrieval of valid needed information; and (c) use the information to improve health care benefits. To more adequately accomplish these functions, we suggest that five specific categories of information will be essential: (1) reports of recent advances in Science Information Management methods; (2) original reports of Science Information Syntheses (SISs) providing information immediately applicable for QA; (3) previously published reports of "classic" SISs relevant to QA; (4) reviews of new technologies and products immediately applicable to quality management; (5) cumulative indexing of the above methods and products. Making the above information available to QA professionals might substantially improve the impact of quality management.

Abstracting and Indexing↗

PubMed1991

Exploring a new best information algorithm for Iliad.

Iliad is a diagnostic expert system for internal medicine. One important feature that Iliad offers is the ability to analyze a particular patient case and to determine the most cost-effective method for pursuing the work-up. Iliad's current "best information" algorithm has not been previously validated and compared to other potential algorithms. Therefore, this paper presents a comparison of four new algorithms to the current algorithm. The basis for this comparison was eighteen "vignette" cases derived from real patient cases from the University of Utah Medical Center. The results indicated that the current algorithm can be significantly improved. More promising algorithms are suggested for future investigation.

Algorithms↗

PubMed1991

Iliad training effects: a cognitive model and empirical findings.

Iliad is a diagnostic expert system consisting of an "inference engine" (collection of rules and procedures for making decisions) and a "knowledge base" (collection of medical facts). Iliad's internal medicine knowledge base recognizes 5000 medical findings and covers 1150 diagnostic conditions in 10 subspecialty fields. We used Iliad's simulator mode to train diagnostic skills in junior-year medical students. The results corroborate previous findings documenting Iliad's teaching efficacy. Recent developments in cognitive psychology provide a framework for explaining Iliad's training effects.

Clinical Clerkship↗