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Biomedical subjects

W A Kennedy

Publications and source records attributed to W A Kennedy.

4 recordsLinked to original sources
PubMed1992

Occluded-ear simulator with variable acoustic properties.

Ear simulators were designed to replicate acoustical characteristics of the average adult ear. Due to variability of ear-canal geometry and eardrum impedance among individuals, the possibility of any one person exhibiting such "average" characteristics--especially if that person is a child and/or has a conductive pathology--is remote. Thus, ear simulators have been of only peripheral value when prescribing a hearing aid (a high output impedance device) to fit the acoustical requirements of a particular patient. Reported herein is development of a programmable artificial ear (PAE) that can account for individual differences in ear-canal geometry and eardrum impedance. It consists of a 2.0-cc coupler, microphone, amplifier, computer, PAE code, and a computer card and/or software for digitization and Fourier transformation. Required input data includes ear-canal dimensions, eardrum impedance, and output impedance of the hearing aid being tested. Sound-pressure recordings produced in the 2.0-cc coupler by the hearing aid are adjusted by the computer to what they would have been had the recordings been made at the eardrum of a particular patient wearing the same hearing aid. Good agreement was observed between experiment and theory for one test case involving a totally occluding miniature earphone.

Acoustic Impedance Tests↗
PubMed1991

Endotoxin concentrations in cerebrospinal fluid correlate with clinical severity and neurologic outcome of Haemophilus influenzae type B meningitis.

Endotoxin concentrations were measured in paired samples of cerebrospinal fluid from 38 patients with Haemophilus influenzae type b meningitis. On admission, the median concentration of endotoxin in cerebrospinal fluid was 104 ng/mL and decreased rapidly in follow-up samples. From 17 to 48 hours after admission, 50% of the patients had concentrations of less than 1 ng/mL. Endotoxin concentrations correlated significantly with concentrations of interleukin 1 beta, protein, and glucose in cerebrospinal fluid, duration of secondary fever, and neurologic abnormalities during hospitalization and on follow-up examinations. Twenty-eight percent of patients with endotoxin concentrations of 100 ng/mL or more on admission had long-term complications, compared with none of those with lower endotoxin concentrations (relative risk, 2.31; 95% confidence interval, 1.53 to 3.48). These results indicate that quantitation of endotoxin in cerebrospinal fluid could be a valuable aid in identifying those children at increased risk of complications during Haemophilus influenzae type b meningitis and provide additional evidence that the Haemophilus influenzae type b meningitis lipo-oligosaccharide is important in the pathogenesis of meningitis.

Animals↗
PubMed1991

The role of corticosteroid therapy in children with pneumococcal meningitis.

The records of 97 infants and children with pneumococcal meningitis treated in Dallas, Tex, from 1984 to 1990 were reviewed to determine whether corticosteroid therapy improved disease outcome as has been demonstrated in patients with Haemophilus meningitis. Forty-one patients received corticosteroid therapy, 39 of whom were given dexamethasone in the conventional 4-day regimen. There were no significant differences in the demographic and clinical characteristics of steroid- and non-steroid-treated patients. In addition, there were no significant differences between treatment groups with regard to presence of seizures, subdural effusions, hydrocephalus, and positive cerebrospinal fluid cultures 24 hours after the start of treatment. When steroid therapy was given before or concurrently with antibiotic therapy, none of 30 steroid-treated vs 16 of 52 non-steroid-treated patients developed evidence of neurologic or cardiovascular instability after the first parenteral antibiotic dose was given. Among 86 survivors examined, significantly fewer steroid-treated patients had an adverse neurologic long-term outcome, including hearing impairment, compared with non-steroid-treated patients (four of 35 vs 14 of 43). This was also true for those patients with overwhelming meningeal infection. We believe that corticosteroid therapy is also beneficial in infants and children with pneumococcal meningitis.

Adolescent↗