PubMed Health⌕ Search

Biomedical subjects

H Neufeld

Publications and source records attributed to H Neufeld.

At least 19 recordsLinked to original sources
PubMed2003

Isospin violation in epsilon'.

On the basis of a next-to-leading-order calculation in chiral perturbation theory, the first complete analysis of isospin breaking for direct CP violation in K0-->2 pi decays is performed. We find a destructive interference between three different sources of isospin violation in the CP violation parameter epsilon'. Within the uncertainties of large-N(c) estimates for the low-energy constants, the isospin violating correction for epsilon' is below 15%.

Journal Article↗
PubMed2001

[Word generation in bilinguals--fMRI study with implications for language and memory processes].

For over a century the cerebral representation of language functions is a matter of debate. In Neuroscience language is regarded as one of the most lateralized cognitive functions. Thus, while the language which is acquired first in most cases is processed by the left hemisphere some studies in brain damaged but also experimental investigations propose a pivotal role of the right hemisphere in second language processing. By the advent of modern neuroimaging it is now possible to study language lateralization and bilinguality also in healthy subjects. We studied first and second language abilities in a group of bilingual, healthy individuals by means of functional magnetic resonance imaging (fMRI) with a word-fluency paradigm. While we found a predominantly left prefrontal activity during both first and also second language processing an additional right prefrontal activation was registered during the use of second language. Our findings are discussed on the basis of an interaction between language and memory processes.

Adult↗
PubMed1999

Retrograde amnesia for world knowledge and preserved memory for autobiographic events. A case report.

A patient (PC) with severe and chronic retrograde amnesia for world knowledge (tested with famous events and famous faces), but unimpaired autobiographical memory is described. The 64-year-old man had traumatic brain injury four years prior to the present evaluation. Current brain imaging showed principally damage involving the infero-lateral prefrontal and the lateral temporal regions of the left-hemisphere. PC was of average intelligence, had no depression and only minor language problems, but manifested some additional anterograde memory deficits and performed subaverage in various frontal lobe-sensitive tests. Patient PC represents one of the very few cases with a preserved retrograde episodic and an impaired retrograde knowledge system, showing a dissociation between preserved retrieval of autobiographical events and amnesia for nonpersonal famous events. It is hypothesized that the sparing of autobiographical memories can be linked to the integrity of the right frontal and temporo-polar cortices.

Amnesia, Retrograde↗
PubMed1997

Using self-reported questionnaire data to prioritize OSA patients for polysomnography.

Many laboratories have large numbers of patients with suspected obstructive sleep apnea (OSA) waiting to be tested. We assessed the use of simple clinical data to detect those patients with an apnea index <20 (low AI) who could be studied less emergently. Using questionnaires completed by patients prior to evaluation, we collected data on 354 consecutive patients (281 males, 73 females; mean age 48.6 years) referred for OSA and assessed with polysomnography (PSG). The questionnaires included the Epworth sleepiness scale (ESS), height, weight, age, and a history of observed apnea. Analysis of receiver operating characteristics curves revealed that both body mass index (BMI) [area under curve = 0.7258, standard error (SE) = 0.03, p < 0.01] and ESS (area under curve = 0.5581, SE = 0.03, p = 0.03) were significantly better than chance alone in detecting people with AI < 20. ESS < or =12 was found in 37.9% of the subjects but 39.6% of those expected to have a low AI using ESS had an AI > or =20. A BMI < or =28 was found in 24.9% of the subjects; 14.8% of those expected to have a low AI using BMI had an AI > or =20. Combining these variables improved accuracy but resulted in smaller groups; a cut-off of ESS < or =12 and BMI < or =28 resulted in a group of 33 (9.3% of subjects), only two (6%) of whom were falsely called low AI. Adding to this the fact that apnea had not been observed resulted in a group of nine patients (2.5% of subjects), none of whom had an AI > or =20. Thus there is a tradeoff; the more variables used, the greater the accuracy but the smaller the percent of cases selected to have low AI. However, in laboratories with hundreds of patients waiting to be tested, any procedure better than chance to help prioritize patients seems worthwhile.

Appointments and Schedules↗
PubMed1996

Treatment of obstructive sleep apnea with a self-titrating continuous positive airway pressure (CPAP) system.

Conventional manually adjusted continuous positive airway pressure (CPAP) is an effective therapy for sleep-disordered breathing. We prospectively investigated the efficacy of a self-titrating nasal CPAP system in the acute treatment of obstructive sleep apnea (OSA) syndrome. Twenty patients with moderately severe OSA [apnea hypopnea index (AHI) > 15/hour] were enrolled in a randomized, controlled, prospective clinical trial. An initial diagnostic sleep study was performed, followed by randomization to a manually adjusted CPAP titration on one night and self titrating CPAP on the other night. On the conventional CPAP night, the CPAP was manually adjusted until abolition of all apneas and electroencephalographic (EEG) arousals, whereas the self-titrating CPAP was set in automatic mode at lights out. The self-titrating CPAP system utilized an algorithm based on airway vibration patterns to detect airway stability. The AHI decreased from 50.8 +/- 28.8/hour [mean +/- standard deviation (SD)] at baseline to 3.8 +/- 3.1/hour (p < 0.005) during manually adjusted and 6.1 +/- 5.3/hour (p < 0.005) during self-titrating CPAP. The arousal index (Ar-I) decreased from 34.1 +/- 23.1/hour (baseline) to 11.2 +/- 5.0/hour on manual adjustment (p < 0.005) and 11.3 +/- 0.3/hour on self titration (p < 0.005), whereas total sleep time was unchanged. No significant differences in any measure of oxygenation or sleep architecture were observed between the manually adjusted and self-titrating CPAP nights except that the lowest arterial oxygen saturation (SaO2) was higher with manual titration (84.4 +/- 4.2% vs. 79.9 +/- 9.7%, p < 0.05). The maximum pressure required for abolition of apneas and arousals was significantly lower (p < 0.05) during the self-titrating study (10.1 +/- 3.8 cmH2O) as compared to manually adjusted CPAP (12.3 +/- 3.9 cmH2O). Failure to increase pressure and failure to maintain minimum pressure occurred in 7 of the 20 subjects during the self-titrating study. This required manual resetting of the system in five subjects, but the system self-corrected in two subjects. An unsupervised study would have resulted in undertreatment of OSA. Based on a single-night laboratory study, self-titrating CPAP was well tolerated and improved OSA and sleep architecture comparable to manually adjusted CPAP. The future modifications of this prototype will require further research to assess its efficacy and safety in the laboratory and home environments before its recommendation for general long-term use.

Adult↗
PubMed1991

Subjective versus objective evaluation of hypnotic efficacy: experience with zolpidem.

There is little published literature on the correlation between subjective and objective efficacy of hypnotics. We wanted to determine whether there was a correlation between the patient's subjective evaluation of the efficacy of the hypnotic with the polysomnographic (PSG) findings. We studied 16 patients with chronic insomnia (sleep latency, greater than or equal to 30 minutes; total sleep time, greater than 240 but less than 420 minutes) for 11 nights who took placebos on nights 1 and 2, zolpidem (imidazopyridine) on nights 3-9 and placebo on nights 10 and 11. Patients completed a questionnaire each morning following PSG, which evaluated subjective sleep quality, sleep latency and total sleep time. These data were compared to PSG findings to answer specific questions about sleep latency reduction, efficacy of the hypnotic after a week's use, sleep quality after discontinuing the drug, and any correlation between subjective and objective measures. PSG findings indicated a shortened sleep latency, increased total sleep time, decreased total wake time and increased sleep efficiency when patients ingested zolpidem 30 minutes before bedtime. We found that after 7 nights (nights 3-9) the drug was still effective in reducing sleep latency and increasing total sleep time. Upon withdrawal (nights 10 and 11) sleep returned to baseline (nights 1 and 2). Subjectively, the patients confirmed those findings on the questionnaire, as well as a subjective reduction in the number of awakenings and, interestingly, a subjective increase in the time spent awake after sleep. Many of the objective variables we examined correlated highly with the subjective variables. While on zolpidem, subjects believed and were objectively shown to have a decreased sleep latency, increased total sleep time and decreased time awake before persistent sleep, although they tended to overestimate sleep latency and time spent awake before persistent sleep and underestimated total sleep time. Although the correlation between objective and subjective measures was high for the group, in individual patients there was an impressive difference between the two, and the highest coefficient of variation between a subjective and objective measures was 0.453. No correlations were found with subjective measures of refreshing quality of sleep, decrease in number of awakenings, how sleepy patients felt in the morning or their ability to concentrate in the morning. Thus, we believe the PSG remains the keystone in the evaluation of hypnotic efficacy.

Adult↗
PubMed1985

Intrathoracic and abdominal pressure variations as an efficient method for cardiopulmonary resuscitation: studies in dogs compared with computer model results.

Intrathoracic pressure variations are currently proposed as the main flow-generation mechanisms in standard and modified cardiopulmonary resuscitation (CPR) techniques. A method of changing pressure within the thorax and abdomen without any degree of heart compression was developed and tested in dogs. Intrathoracic and abdominal pressure waves were induced by cyclic inflation and deflation of the lungs and of perithoracic and periabdominal balloons. Various modes of CPR, depending on the rate of cycling, the use of a periabdominal balloon inflation, and a delay between the abdominal and thoracic pressure waves, were studied during ventricular fibrillation. During artificial systole (high intrathoracic pressure phase), the pressure which developed in the right ventricle (96.7 +/- 20.5 mmHg) was higher than the pressure in the aorta (89.3 +/- 20.5 mmHg, p less than 0.001). In artificial diastole (low intrathoracic pressure phase), the right ventricular pressure (11.7 +/- 2.6 mmHg) was lower than the aortic pressure (17.5 +/- 3.3 mmHg, p less than 0.001). The average flow in the carotid artery was 21.7 +/- 7.8 ml . min-1, which was 18 +/- 6% of the baseline carotid flow before CPR. Three different factors were found to improve the efficiency of CPR: periabdominal balloon inflation simultaneous with the intrathoracic pressure waves; increased frequency of the pressure waves from 60 to 100 cycles per minute; and inflation of the periabdominal balloon 50 to 100 ms before the thoracic balloon. Blood-gas and acid-base balance analysis during CPR revealed well-oxygenated arterial blood with a marked respiratory alkalosis and a slowly developing metabolic acidosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Abdomen↗
PubMed1984

Cerebrovascular accidents in infants and children with congenital cyanotic heart disease.

The red blood cell (RBC) counts and indices of 12 patients with congenital cyanotic heart diseases (CCHD) who had had cerebrovascular accidents (CVA) (study group) were compared with those of 41 infants and children with CCHD who had not had CVA (control group); the groups were matched for age and type of CCHD. The patients in the study group were found to have nonsignificantly lower hemoglobin levels and similar hematocrit levels, in comparison with the control group. On the other hand, significantly lower RBC indices were found among the patients of the study group in comparison with the control group. The arterial oxyhemoglobin concentration, studied in six patients of the study group, was not found to be significantly lower than that of the patients in the control group. Thus, we conclude that relative anemia with microcytosis is associated with the occurrence of CVA in children with CCHD.

Cerebrovascular Disorders↗
PubMed1980

Myocardial infarction in a young woman with systemic lupus erythematosus.

We describe the case of a young woman with systemic lupus erythematosus (SLE) who suffered an acute myocardial infarction (MI). The patient was treated by corticosteroids in addition to the usual management for acute MI. The role of arteritis in producing the infarction is also discussed.

Adult↗
PubMed1978

Secondary malignant neoplasms in patients with Hodgkin's disease.

Retrospective analysis of 232 cases of Hodgkin's disease (HD) treated at the University of Manitoba from Jan. 1, 1965, to Dec 31, 1973, and followed up to 44.3 months disclosed five cases of secondary malignant neoplasms. Two cases of acute leukemia were discovered compared with an expected value of 0.05 in our community. All neoplasms developed in the mixed cellularity group, representing only 28% of the HD cases. Combinations of radiotherapy and chemotherapy may have increased the incidence of leukemia, but its frequency does not appear high enough to abandon combined modality treatment.

Adult↗
PubMed1978

Endocarditis and ventricular septal defect: surgical vs. conservative treatment.

Three patients with ventricular septal defect and bacterial endocarditis are reported. Because of the very frequent spontaneous closure of the defect, especially in children, and the rarity and benign nature of bacterial endocarditis superimposed on ventricular septal defect, it is suggested that the condition be treated conservatively. An exception to this is the rare case with recurrent endocarditis, mainly in older individuals, in whom surgery may be contemplated.

Adolescent↗