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Biomedical subjects

P Howell

Publications and source records attributed to P Howell.

At least 37 records · Page 2Linked to original sources
PubMed1995

Carotid artery trauma: a review of contemporary trauma center experiences.

PURPOSE: Many issues surrounding the management and outcome of carotid artery injuries remain controversial. The purpose of this study was to review a large contemporary experience with such injuries in the setting of designated trauma centers. METHODS: A statewide computerized trauma registry was used to identify all patients with injuries to the common or internal carotid arteries from October 1987 to June 1993. The records of 82 such patients were retrieved and analyzed. RESULTS: Overall mortality and stroke rates were 17% and 28%, respectively. Patients presenting with coma or shock had a particularly bad prognosis (50% and 41% mortality, respectively). Internal carotid injuries resulted in mortality and stroke rates of 21% and 41%, respectively, compared with 11% each for common carotid injuries. Patients with blunt injuries had a much higher stroke rate (56% vs 15%) but had lower mortality (7% vs 22%) than did patients with penetrating injuries. Airway compromise and associated injuries did not affect prognosis. Operative repair and percutaneous balloon occlusion had the best survival and functional outcomes. CONCLUSIONS: Operative repair offers the best chances for recovery in all categories of patients regardless of injury mechanism. Ligation is useful only as a last-resort lifesaving effort. Shock and neurologic impairment are poor prognostic factors but should not negate repair.

Adolescent↗
PubMed1994

Epidural butorphanol does not reduce side effects from epidural morphine after cesarean birth.

In this prospective, double-blind, randomized study of women undergoing elective cesarean birth, the hypothesis that epidural butorphanol in various doses could effectively reduce or eliminate the side effects caused by epidural morphine was tested. Patients were randomly assigned to one of four groups. All received a standard epidural anesthetic and 20 min after delivery each received 3 mg epidural morphine with either 1 mg butorphanol (Group A), 2 mg butorphanol (Group B), 3 mg butorphanol (Group C), or 3 mL normal saline (Group D). Patient evaluations were made preoperatively and 2, 8, and 24 h after delivery. These consisted of visual analog scores for pain, satisfaction, nausea, itch, and somnolence. At each evaluation, a CO2 challenge test, using portable equipment, was performed. Data from 71 patients were analyzed and all four groups were comparable in terms of age, height, weight, level of sensory block, and volume of local anesthetic used. There were no significant differences among groups in terms of pain, satisfaction, nausea, or pruritus. Groups A, B, and C had significantly higher somnolence scores at 8 h compared to Group D (P < 0.001). There were no significant differences among groups in CO2 challenge test data at any point during the study, but overall a reduced sensitivity to CO2 after opioid administration was observed across all groups. There were no clinically significant incidents of respiratory depression. Epidural butorphanol, in doses of 1-3 mg, failed to reduce the side effects from 3 mg epidural morphine given after cesarean birth. Patients who received epidural butorphanol reported significantly higher levels of somnolence.

Anesthesia, Epidural↗
PubMed1993

Patient-controlled epidural analgesia in labour: varying bolus dose and lockout interval.

This double-blind prospective study was designed to determine the best dose variables for patient-controlled epidural analgesia (PCEA) and to compare bolus-only PCEA with continuous infusion epidural analgesia (CIEA) during the first stage of labour. Five groups of parturients self-administered 0.125% bupivacaine with 1:400,000 epinephrine and fentanyl 2.5 micrograms.ml-1 using PCA pumps programmed as follows: Group A, 2 ml bolus/10 min lockout interval (LI); Group B, 3 ml bolus/15 min LI; Group C, 4 ml bolus/20 min LI; Group D, 6 ml bolus/30 min LI; Group E, 8 ml.hr-1 continuous infusion. Hourly assessments included: VAS scores for pain and satisfaction, sensory and motor block, bupivacaine and fentanyl consumption. Blood samples were collected at birth for maternal and fetal fentanyl concentrations. Data from 68 patients showed no differences among groups in pain relief or maternal satisfaction. Most patients received excellent analgesia and those requiring extra epidural supplements were evenly distributed across groups. There was higher consumption of bupivacaine and fentanyl in Group E than in any of the other four groups: bupivacaine mg.hr-1, mean (SD), 9.4 (2.7) in Group E vs 5.2 (1.7) in Groups A-D inclusive (P < 0.0001); fentanyl microgram.hr-1, 19.6 (4.6) in group E vs 12.6 (7.5) in Groups A-D inclusive (P < 0.05). Motor block was minimal, whereas sensory levels were higher at the 3- and 4-hour assessments in Groups D and E than in all other groups (P < 0.05). Plasma fentanyl concentrations were < 0.5 ng.ml-1 in all samples and no sequelae from fentanyl were observed, apart from mild pruritus.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Cue trading in the production and perception of vowel stress.

The distinction between stressed and unstressed vowels in noun/verb pairs differentiated by stress (e.g., as in the word "misprint") is known to be cued by the acoustic attributes fundamental frequency, intensity, and duration. The role of these cues and vowel centralization measures in perception is ordered differently from that in production. It is not known what variability there is between speakers, whether the acoustic factors vary with speech clarity that a speaker produces on different occasions, or what the relationship is between the various speech attributes. Importantly, no studies have been performed in which production and perception of materials is compared with respect to these questions. In the current study, noun/verb pairs differentiated by stress were produced by four speakers, and measures of produced and perceived clarity obtained for these subjects. The importance of the acoustic factors to the contrast was modeled in perception and production, and the results compared. Additionally, the variation with produced or perceived clarity was ascertained. Finally, comparison between cue trading in production and perception was made. The results are discussed in connection with models of speech perception and production.

Adult↗
PubMed1992

Acoustic analysis and perception of vowels in children's and teenagers' stuttered speech.

The syllable repetitions of 24 child and eight teenage stutterers were investigated to assess whether the vowels neutralize and, if so, what causes this. In both groups of speakers, the vowel in CV syllable repetitions and the following fluent vowel were excised from conversational speech samples. Acoustic analyses showed the formant frequencies of vowels in syllable repetitions to be appropriate for the intended vowel and the duration of the dysfluent vowels to be shorter than those of the fluent vowels for both groups of speakers. The intensity of the fluent vowels was greater than that of the dysfluent vowels for the teenagers but not the children: For both age groups, excitation waveforms obtained by inverse filtering showed that the excitation spectra associated with dysfluent vowels fell off more rapidly with frequency than did those associated with the fluent vowels. The fundamental frequency of the children's dysfluent speech was higher than their fluent speech while there was no difference in the teenager's speech. The relationship between the intensities of the glottal volume velocities was the same as that of the speech waveforms. Perceptual tests were also conducted to assess whether duration and the differences found in the source excitation would make children's vowels sound neutral. The experiments show that in children neither vowel duration nor fundamental frequency differences cause the vowels to be perceived as neutral. The results suggest that the low intensity and characteristics of the source of excitation which cause vowels to sound neutral may only occur in late childhood. Furthermore, monitoring stuttered speech for the emergence of neutral vowels may be a way of indexing the progress of the disorder.

Adolescent↗
PubMed1991

The use of prosody in highlighting alterations in repairs from unrestricted speech.

A speaker has several ways in which he or she may highlight the fact that an error or imprecision of speech has been made and subsequently altered. The three principal ones are by signalling through the structure of the speech that surrounds the error (the repair-syntax), by the use of prosody, and through the semantic content. The role of prosody in the correction process is investigated in the current studies. Analysis of the prosody of a number of errors and their alterations drawn from unrestricted speech are reported. The analysis shows that pauses occur at the moment of interruption and that an increase in stress occurs at the start of the alteration. Pauses could indicate the moment of interruption, and stress could highlight what has been altered. Two sets of perceptual experiments were carried out to assess whether these cues are salient for listeners who hear constructions containing an error and its alteration. Two paradigms were employed in each set of experiments: (1) direct judgement about the comprehensibility of sentences containing errors and alterations, and (2) repeating a message that had an error and alteration without the error. The effects of stress and pauses on (Experiments 1A and 1B) or pauses around (Experiment 2A and 2B) the alterations were assessed. In the first set of experiments it was shown that pauses and stress help listeners process repairs. When a word is spoken in error, the speaker may repeat a section of speech immediately preceding the alteration and/or a section immediately following that word. Inclusion of these repeated sections allows assessment of whether pauses signal where the interruption occurred. The second experiment shows that the placing of the pause before the retrace, rather than at other locations, indicates to listeners where the repair starts.

Adult↗
PubMed1990

Comparison of four local extradural anaesthetic solutions for elective caesarean section.

We have examined a combination of two local anaesthetics to see if the resultant solution is superior to the agents individually. This study shows that a mixture of bupivacaine and lignocaine provided an excellent alternative to bupivacaine alone, and was superior to 2% lignocaine with adrenaline for elective Caesarean section. By reducing the dose of bupivacaine used, the combination may reduce the risk of cardiotoxicity.

Adult↗
PubMed1990

Comparison of false-positive reactions in direct-binding anti-HIV ELISA using cell lysate or recombinant antigens.

In a 2-year study of false-positive anti-HIV-1 tests in blood donors at Manchester and Lancaster Blood Banks, the reactions associated with a HIV-infected cell lysate antigen were compared with those using recombinant-antigen-based tests. In year 1 (cell lysate test) at Manchester BTS 0.21% of 119.178 donations were repeatedly reactive, compared with 0.53% of 119,004 donations in year 2 (recombinant antigen). Reactive sera were tested at Manchester PHL by three different immunoassays. Referred specimens were classified as anti-HIV positive (95-100% reactive in all the assays), equivocal or negative (negative results in all three immunoassays). Two donors were confirmed to be anti-HIV positive over the 2-year period. Most sera were negative by confirmatory immunoassays in years 1 and 2. In year 1, a study of 60 referred sera with sex- and age-matched controls showed high correlation between a reactive anti-HIV-1 screening test and indeterminate anti-HIV-1 patterns on Western blot showing reactions with HIV gag-coded proteins. In year 2, less than 10% of referred sera were reactive by Western blot, and there was no correlation between a reactive screening anti-HIV test, the strength of signal in the test or a reactive Western blot. Follow-up showed that donors whose sera were reactive in years 1 and 2 by the anti-HIV-1 screening test formed almost two different populations. Four donors with equivocal anti-HIV-1 confirmatory tests had anti-HIV 'envelope' reactions.(ABSTRACT TRUNCATED AT 250 WORDS)

Blotting, Western↗
PubMed1990

Correlation of monocyte-monolayer assay results, number of erythrocyte-bound IgG molecules, and IgG subclass composition in the study of red cell alloantibodies other than D.

Comparisons have been made between the serological and immunological characteristics of 42 blood group alloantibodies (other than D) covering twelve systems using a monocyte-monolayer assay (MMA), a radiometric antiglobulin test for antibody binding and IgG subclass determinations. The results of the MMA correlated well with the level of IgG molecules bound on incompatible cells, and the highest levels in both cases were associated with the presence of the IgG3 subclass. However, limited clinical data shows that, while in general the MMA clearly identifies the clinically significant antibodies, the correlation with the degree of clinical outcome is less well defined, and in some instances other factors may be operating to ameliorate the in vivo effect of the antibody.

Antibody Specificity↗
PubMed1990

Analysis of periodic and aperiodic components during fluent and dysfluent phases of child and adult stutterers' speech.

The syllable repetitions of 6 child and 6 adult stutterers were investigated to establish whether dysfluent speech had a higher noise-to-signal ratio than fluent speech and whether this differed between children and adults. As predicted, the stuttered speech had a higher noise level for both age groups. During dysfluencies, the level of the noise components in the children's speech was higher than in the adults.

Adult↗
PubMed1990

An electrical network model of inertially induced bone-conducted sound.

A model for the description of inertially induced bone-conducted sound has been developed and a discussion of the appropriate techniques for its representation as an electrical network is described. Predictions are made for the sound pressure produced in the meatus in the cases of normal ears and pathological ears resulting from vibration applied to the skull. Evidence from this modelling suggests that the technique may provide improved discriminability over conventional immitance measurements for some types of pathology.

Acoustics↗
PubMed1989

Serological and immunological characteristics of maternal anti-Rh(D) antibodies in predicting the severity of haemolytic disease of the newborn.

A number of factors were analyzed for their predictive value in indicating the severity of haemolytic disease of the newborn (HDN) in 72 infants. The factors investigated were: maternal antibody titre in the indirect antiglobulin test, the number of antibody molecules on sensitized standard red cells evaluated by a radiometric antiglobulin test, the IgG subclass specificity and the reactivity in monocyte-monolayer assay (MMA) and in the rosette assays with lymphocytes and granulocytes from healthy individuals. The results of the MMA correlate much better with the severity of HDN than the antibody titre. In clinically unaffected infants the reactivity in the MMA never exceeded 20%, while in the severe/very severe group it was always greater than 20% (in 95% of very severe cases even above 50%). The number of IgG-bound molecules was also shown to closely correlate with the clinical severity and there was a much greater proportion of severe/very severe cases exhibiting combined IgG1 and IgG3 specificity. Of all the evaluations performed the rosette assays with lymphocytes and granulocytes were found to be less useful in predicting the severity of HDN.

Erythroblastosis, Fetal↗
PubMed1989

Jaw movement and bone-conduction in normal listeners and a unilateral hemi-mandibulectomee.

Relative movement between the mandible and skull may compress the auditory meatus and produce an excess sound in the ear canal. To test this, measurements of sound pressure in the ear canal, and movement of the upper and lower jaw are reported on normal subjects and a unilateral hemi-mandibulectomee. On the side the unilateral hemi-mandibulectomee has a jaw and in the subjects with normal jaws, the data confirm that mandible-movement relative to the skull produces sound in the ear canal. The excess sound in the ear canal when the jaw is free to move independently of the skull can be predicted from the relative movement between them.

Bone Conduction↗
PubMed1988

The contribution of the excitatory source to the perception of neutral vowels in stuttered speech.

The vowel in part-word repetitions in stuttered speech often sounds neutralized. In the present article, measurements of the excitatory source made during such episodes of dysfluency are reported. These measurements show that, compared with fluent utterances, the glottal volume velocities are lower in amplitude and shorter in duration and that the energy occurs more towards the low-frequency end of the spectrum. In a first perceptual experiment, the effects of varying the amplitude and duration of the glottal source were assessed. The glottal volume velocity recordings of the /ae/ vowels used in the analyses were employed as driving sources for an articulatory synthesizer so that judgments about the vowel quality could be made. With dysfluent glottal sources (either as spoken or by editing a fluent source so that it was low in amplitude and brief), the vowels sounded more neutralized than with fluent glottal sources (as spoken or by editing a dysfluent source to increase its amplitude and lengthen it). In a second perceptual experiment, synthetic glottal volume velocities were used to verify these findings and to assess the influence of the low-frequency emphasis in the dysfluent speech. This experiment showed that spectral bias and duration both cause stuttered vowels to sound neutralized.

Adult↗