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Biomedical subjects

T W Powell

Publications and source records attributed to T W Powell.

18 recordsLinked to original sources
PubMed1998

Antiviral therapy in a child with pediatric human immunodeficiency virus (HIV): case study of audiologic findings.

Over the past decade, much research has been conducted to determine the auditory consequences of human immunodeficiency virus (HIV) infection and acquired immune deficiency syndrome (AIDS). This research, primarily using adult patients, has focused on the involvement of the central auditory nervous system (CANS). Measures of auditory evoked potentials, particularly the auditory brainstem response (ABR), can document changes in the CANS as the disease progresses and during treatment with antiviral therapies such as zidovudine (AZT) and didanosine (ddI). This case study presents the audiologic findings for a child with HIV infection. Evaluations were performed over a 2-year period prior to the initiation of antiviral therapy and following treatment. Audiologic measures included behavioral audiometry, tympanometry, otoacoustic emissions, and ABR latency/intensity functions and rate studies. Findings indicated a gradual shortening of all ABR component latencies following the initiation of antiviral therapy. In addition, a high-frequency hearing loss was detected during the final evaluation subsequent to 19 months of treatment with AZT and ddI.

Anti-HIV Agents↗
PubMed1993

Critical values for evaluating CELF-R Receptive and Expressive Language Score discrepancies.

Psychoeducational evaluation of school-aged children may involve a comparison of examinees' language comprehension and production skills. To facilitate the diagnostic process, this paper presents a table of critical values for the Clinical Evaluation of Language Fundamentals--Revised, which can be used to evaluate the statistical significance of observed-score discrepancies. Theoretical implications of such discrepancies are also discussed.

Achievement↗
PubMed1991

Toward a technology of generalization: how many exemplars are sufficient?

This descriptive study examined the number of minimal-word-pair exemplars necessary for 19 phonologically impaired children to meet a generalization criterion. For 59% of the test cases, three exemplars were sufficient for generalization to occur. Five exemplars were sufficient in 21% of the test cases, and it was necessary to teach 10 different exemplars in 14% of the test cases. In 7% of the test cases, generalization did not occur despite treatment on 10 exemplars. Although generalization usually occurred following treatment using a small number of exemplars, there was substantial variability across individual subjects. There was no apparent relationship between specific sounds and the likelihood of generalization; however, the data from some children suggested that treatment on one sound enhances learning of subsequent sounds. The theoretical and clinical implications of these findings are discussed.

Articulation Disorders↗
PubMed1991

Stimulability as a factor in the phonological generalization of misarticulating preschool children.

The relationship among six functionally misarticulating preschool children's phoneme-specific stimulability skills, the choice of treatment targets (i.e., stimulable or nonstimulable sounds), and generalization of correct sound production was explored in this prospective study. Each subject [age range of 4:11 (years:months) to 5:6] was taught to produce [r] and one other sound that was absent from his or her phonetic inventory using a contrasting-minimal-pairs production approach. A multiple baseline across behaviors single-subject research design provided experimental control. For 86% of the 28 monitored sounds, generalization was consistent with pretreatment stimulability skills; production of stimulable sounds tended to improve regardless of treatment target. These results suggest that nonstimulable sounds are likely to require direct treatment; thus, generalization probe responses may be maximized by treating nonstimulable sounds rather than stimulable sounds.

Articulation Disorders↗
PubMed1990

Some constraints on functionally disordered phonologies: phonetic inventories and phonotactics.

The phonological systems of 40 functional misarticulators, ages 40 to 80 months were examined in terms of the nature and variation of phonetic inventories and phonotactic constraints. It was found that these properties of disordered systems were governed by severe constraints that yielded a typological characterization of such systems along with associated implicational laws. The principles governing disordered systems were also found to parallel closely the principles governing normal first language acquisition. The evidence suggests that at least these properties of disordered systems represent delays in the normal acquisition process and are not otherwise deviant. The assessment and treatment of functional disorders along with the projection of learning patterns can thus appeal to principles governing such phonological systems.

Articulation Disorders↗
PubMed1990

Listeners' familiarity and perception of an idiosyncratic phonologic pattern.

Idiosyncratic production of [l] for target /j/ (for example, production of the word "less" for "yes") was observed in a phonologically impaired preschooler. Recordings of his apparently homonymous productions of minimal pairs contrasting /j/ and /l/ were presented in random order to the child's mother and to five adult listeners who were unfamiliar with the child. No difference was seen across the listeners in their ability to identify target /l/ words. The child's mother, however, correctly identified /j/ targets more frequently than did unfamiliar listeners suggesting that familiarity enhances one's ability to decode idiosyncratic phonologic error patterns.

Articulation Disorders↗
PubMed1989

A profile analysis approach to interpretation of the Carrow Auditory-Visual Abilities Test.

This paper describes a profile analysis procedure for use with the Carrow Auditory-Visual Abilities Test (CAVAT). The visual-auditory dichotomy, supported by factor analysis, is examined at one level of analysis. Critical values derived from the standard error of measurement of the difference (Sem/D) for each battery are provided allowing the identification of reliable and abnormal visual-auditory discrepancies. At another level of analysis, a procedure for profile analysis is outlined and critical values are included to facilitate the identification of relative strengths and weaknesses at the subtest level. Test results from 2 preschool children are examined and contrasted to illustrate the utility of the CAVAT in the identification of systematic modality preferences.

Auditory Perception↗
PubMed1987

Culture of abdominal aortic aneurysm contents. An additional series.

We evaluated the microbiologic nature of aneurysm contents. Aerobic and anaerobic cultures were taken from non-blood fluid, laminar thrombus, or ulcerated plaque within aortic aneurysms operated on during an eight-year period. Positive bacterial cultures were obtained from 22 (10.4%) of 211 aneurysms. Staphylococcus epidermidis was the most common organism recovered (12/22, 54%). Bacterial colonization of the arterial wall has a possible role in the pathophysiology of prosthetic graft sepsis. These data are valuable not only in choosing appropriate prophylactic antibiotics for aneurysm repair, but also in experimental efforts to develop an infection-resistant vascular graft by directing the antimicrobial characteristics of agents selected for binding to various prosthetic flow surfaces.

Aorta, Abdominal↗
PubMed1984

Mallory-Weiss syndrome in a 10-month-old infant requiring surgery.

Mallory-Weiss syndrome is infrequent in children. Intractable hemorrhage requiring surgery has been reported in only one 6-year-old child in the English literature. We present a case of intractable hemorrhage from a Mallory-Weiss lesion in a 10-month-old infant requiring surgery. The incidence, etiology, diagnosis, and treatment of Mallory-Weiss syndrome in children is discussed in relation to this case.

Age Factors↗
PubMed1984

Generalization following the remediation of early- and later-developing consonant clusters.

Three pairs of matched subjects, ages 4:4 to 6:3 (yrs:mos), who consistently misarticulated word-initial consonant clusters were taught to produce either earlier-developing (stop + liquid) clusters or later-developing (fricative + liquid) clusters. Sixty untrained probe items were administered imitatively during baseline and periodically throughout treatment to assess articulation change over time. Five of the six subjects performed with essentially equal accuracy on both cluster categories during the final probe administration regardless of the nature of their treatment. Additional analysis revealed the liquid segment [( r] or [l]) as the apparently decisive factor in four subjects' learning patterns.

Articulation Disorders↗
PubMed1984

On the prediction of phonologic generalization learning patterns.

The purpose of this study was to obtain information on six children's misarticulation of consonant clusters in order to illustrate how certain factors influence generalization learning patterns. While all subjects evidenced generalization, individual differences in learning patterns did emerge. These patterns were explained in terms of the following three factors: (1) information about the children's unique knowledge about the phonologic system, (2) the linguistic relationships among sounds, and (3) the interaction of these factors with the treatment target. The implications of this explanation are discussed as they relate to the selection of treatment targets that will facilitate generalization.

Articulation Disorders↗
PubMed1984

Second leg ischemia. Lower extremity bypass versus amputation in patients with contralateral lower extremity amputation.

Unilateral amputees with second leg ischemia may miss consideration for anything but amputation. Justification for a reconstructive approach for these ischemic second limbs was sought from a retrospective study of 108 patients who underwent lower extremity distal bypass. Risk factors and results were compared for the 12 unilateral amputees and the 96 nonamputees. Age and relative incidence of rest pain, claudication, and tissue loss were not significantly different for the two groups. Diabetes mellitus was present in 41.6 per cent of amputees and 31.3 per cent of nonamputees. Preoperative, average ankle-brachial blood pressure ratios were equal for both groups (0.3). Angiography showed comparable distribution of patients between the two groups with regard to distal run-off vessels. Operative mortality was 8 per cent for amputees and 3 per cent for nonamputees. Cumulative survival at 25 months was 67.5 per cent for amputees and 82.4 per cent for nonamputees. Cumulative patency at 6 months was 71.5 per cent for amputees compared with 63 per cent for nonamputees and at 25 months was 58.5 per cent for amputees and 37.6 per cent for nonamputees (no significant difference). Unilateral amputees appear to have similar risks and results for lower extremity distal bypass as do nonamputees. An independent, aggressive approach for evaluation and surgical revascularization should not be overlooked for the ischemic, remaining lower extremity in the dysvascular unilateral amputee.

Amputation, Surgical↗
PubMed1983

A passive system using rifampin to create an infection-resistant vascular prosthesis.

Vascular prosthesis infection is a devastating complication of vascular operations. The development of a simple process for imparting infection resistance to vascular prosthesis material would be invaluable. Rifampin was added to the blood that was used to preclot 8 mm Dacron vascular prostheses that were used to replace the infrarenal aorta in 10 mongrel dogs. Rings of the grafts were resected after blood had flowed through them for 0 minute, 15 minutes, 60 minutes, and 24 hours. The resected graft rings were placed on culture plates that had been inoculated heavily with Staphylococcus aureus. The rate of antibiotic dialysis from the graft was determined by comparison of the inhibition rings that were produced by the graft rings at each subsequent interval. At 60 minutes, inhibition was 94% of that at time 0. Inhibition at 24 hours was 91%, which demonstrated no significant decrease from 60 minutes. Other antibiotics were screened by this technique, but none of them demonstrated inhibition at 24 hours. In a pilot study in which two dogs were given parenteral rifampin before and after operation and grafts were preclotted with blood that contained rifampin, it was suggested that there was a slight increase in inhibition at 24 hours (93%). The data indicated that rifampin that is added to the blood that is used to preclot a porous Dacron prosthesis is so slowly dialyzed from the graft that inhibition remains at 24 hours. This passive system imparts potential resistance to the prosthesis.

Animals↗
PubMed1981

Vascular access in hemophilia.

Patients with severe factor VIII deficiency hemophilia require recurrent factor VIII infusion for complications of their bleeding diathesis, resulting in depletion of peripheral infusion sites. At the University of North Carolina in Chapel Hill, many hemophiliac patients are seen yearly. Therapy for some of these patients requires recurrent administration of factor VIII concentrates. Recent experience with two patients who had exhausted peripheral venous infusion sites necessitated innovative vascular access. Our favorable experience with subcutaneous bovine heterografts prompted use of this technique. An easily cannulated infusion site resulted and facilitated factor VIII concentrate infusion. Patients with bleeding disorders represent a whole new population who may require vascular access. Our experience suggests that it is practical to expand the scope of access to include these patients.

Arteriovenous Shunt, Surgical↗
PubMedDate not supplied

Stimulability: a useful clinical tool.

Although difficult to define, stimulability is an easily measured skill that can provide valuable information for clinicians treating children with phonological disorders. In this article, we review changing trends in the definition of stimulability, standardized and nonstandardized approaches to its measurement, and clinical implications of stimulability for prognosis and treatment plan development as they have evolved over a 40-year period. Clinical application of stimulability information in caseload management and intervention is emphasized.

Child↗
PubMedDate not supplied

Stimulability considerations in the phonological treatment of a child with a persistent disorder of speech-sound production.

The term "persistent sound system disorder" has been used to describe the speech problems of a relatively small group of children that does not respond readily to treatment. This group includes children who have been given diagnoses such as development apraxia of speech. In this article, a rationale is developed for one approach to the treatment of persistent sound system disorder. This approach, which involves broadening of the phonetic inventory early in the treatment process, is contrasted with more traditional motor-programming treatments that emphasize stabilization of a restricted set of inconsistently produced sounds. The treatment procedures advocated in this article are illustrated in a case study. The article concludes with a discussion of evolving theories and technologies that are likely to impact upon the assessment and treatment of children with persistent sound system disorders in the future.

Articulation Disorders↗