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Biomedical subjects

N D Le

Publications and source records attributed to N D Le.

29 records · Page 2Linked to original sources
PubMed1996

Cohort study of Air Canada pilots: mortality, cancer incidence, and leukemia risk.

Despite the special working environment and exposures of airline pilots, data on risk of death and cancer incidence in this occupational group are limited. The authors investigated a cohort of 2,740 Air Canada pilots who contributed 62,449 person-years of observation. All male pilots employed for at least 1 year on and since January 1, 1950, were studied. The cutoff date for outcome information was December 31, 1992. Standardized mortality ratio (SMR) and standardized incidence ratio (SIR) were used to compare mortality rates and cancer incidence rates of the cohort with the respective Canadian population rates. Ninety percent confidence intervals of the SMR and SIR were calculated. Statistically significant decreased mortality was observed for all causes (SMR = 0.63, 90% confidence interval (CI) 0.56-0.70), for all cancers (SMR = 0.61, 90% CI 0.48-0.76), and for all noncancer diseases (SMR = 0.53, 90% CI 0.45-0.62). Mortality from aircraft accidents was significantly raised (SMR = 26.57, 90% CI 19.3-35.9). Significantly decreased cancer incidence was observed for all cancers (SIR = 0.71, 90% CI 0.61-0.82), rectal cancer (SIR = 0.42, 90% CI 0.14-0.96), lung cancer (SIR = 0.28, 90% CI 0.16-0.46), and bladder cancer (SIR = 0.36, 90% CI 0.12-0.82). Prostate cancer (SIR = 1.87, 90% CI 1.38-2.49) and acute myeloid leukemia (SIR = 4.72, 90% CI 2.05-9.31) were significantly increased. The preferred relative risk model for radiation-induced nonchronic lymphoid leukemia (Beir V report) was applied to the cohort by using published estimates of in-flight radiation exposures. The estimated relative risk ranged from 1.001 to 1.06 and did not differ significantly from the observed SIR (SIR = 1.88, 90% CI 0.80-3.53). However, the incidence rate of acute myeloid leukemia was significantly increased. Monitoring of in-flight radiation exposure and long-term follow-up of civil aviation crew members is needed to further assess cancer incidence and leukemia risk in this special occupational group.

Accidents, Aviation↗
PubMed1996

The reversal of profound mivacurium-induced neuromuscular blockade.

PURPOSE: Mivacurium is metabolized by plasma cholinesterase catalyzed ester hydrolysis. Acetylcholinesterase antagonists used in the reversal of muscle relaxation may also inhibit plasma cholinesterase and, therefore, delay the hydrolysis of mivacurium. The clinical interaction between acetylcholinesterase antagonists and mivacurium induced neuromuscular blockade was studied. METHOD: Intraoperative muscle relaxation was maintained with a mivacurium infusion to achieve a constant intense block (first twitch, T1, 2-3% of control). Patients were randomly divided into three groups. Patients in Group 1 received no anticholinesterase, in Group 2 neostigmine 0.07 mg.kg-1, and in Group 3 edrophonium 1 mg.kg-1. The times between termination of the mivacurium infusion (Group 1) or the administration of the anticholinesterase (Groups 2 and 3) to 25%, 50%, 75% and 95% T1 recovery, and to 50%, 70% and 90% recovery in the ratio, T4/T1 (TR) were recorded. RESULT: In the neostigmine Group, T1 recovery to 25%, 50% and 75% (2.32 +/- 1.41, 3.90 +/- 1.85 and 6.88 +/- 2.66 min) was accelerated compared with control (3.36 +/- 1.34, 5.78 +/- 2.22, and 8.58 +/- 3.60, and), but recovery to 95% (18.53 +/- 9.09 vs 13.29 +/- 5.24 min) was delayed. Also, TR recovery to 50%, 70%, and 90% was slower (14.47 +/- 8.73, 21.25 +/- 11.06 and 31.37 +/- 12.11 min vs 11.75 +/- 3.74, 13.78 +/- 4.39 and 17.86 +/- 6.44 min). However, all T1 and TR recovery times were decreased in the edrophonium group (0.88 +/- 0.51, 2.00 +/- 1.50, 4.97 +/- 2.96, and 9.35 +/- 5.24 min for T1 and 6.86 +/- 3.93, 9.05 +/- 4.51 and 12.24 +/- 6.66 min for TR). CONCLUSION: Neostigmine reversal of intense mivacurium neuromuscular block should be avoided, as this may result in prolongation of the block.

Adolescent↗
PubMed1995

Assessing viral retention and elimination in rotary dental instruments.

The authors of this article used a laboratory model of herpes simplex virus infection to assess the potential for contamination of dental handpieces by a human viral pathogen. They found that although all the handpieces in the study were fitted with anti-retraction valves, it was not until the units were flushed internally and disinfected externally that the pathogens were eliminated.

Dental High-Speed Equipment↗
PubMed1994

A clinical trial of bethanechol in patients with xerostomia after radiation therapy. A pilot study.

The effects of bethanechol in the treatment of dry mouth were assessed in patients with xerostomia after radiation therapy to the head and neck. Bethanechol possesses muscarinic and nicotinic-cholinergic activity that likely accounts for its mode of action. Bethanechol (25 mg, three times daily) was not associated with significant side effects. Statistically significant increases in whole resting saliva (p = 0.003) and whole stimulated saliva (p = 0.001) were seen. In patients with pretreatment stimulated saliva volumes greater than resting saliva volumes, a positive response to subsequent use of the sialagogue was seen.

Bethanechol↗
PubMed1993

Risk factors for oropharyngeal candidiasis in patients who receive radiation therapy for malignant conditions of the head and neck.

Twenty-seven consecutive patients receiving radiation to the head and neck were followed to assess risk factors for the development of candidiasis. One-third of the patients developed oral candidiasis during radiation therapy. Xerostomia was shown to correlate with risk of oropharyngeal infection (p = 0.033). The presence and use of oral prostheses were shown to correlate with oral colonization of Candida albicans before radiation therapy (p = 0.011). Alcohol use and smoking represent risk factors for oral colonization by Candida during radiation therapy (p = 0.023 and p = 0.045 respectively). These factors must be assessed in future studies of oropharyngeal candidiasis in radiation therapy.

Adult↗
PubMed1992

Exact likelihood evaluation in a Markov mixture model for time series of seizure counts.

This paper provides an alternative to Albert's (1991), Biometrics 47, 1371-1381) approximation to the E-step when using the EM algorithm for parameter estimation in Markov mixture models. Use of a recursive algorithm of Baum et al. (1970, Annals of Mathematical Statistics 41, 164-171) results in exact evaluation of the likelihood, optimal parameter estimates, and very efficient computation. Applications to time series of seizure counts and fetal movements clearly show the advantages of this exact approach.

Algorithms↗
PubMedDate not supplied

Surveillance of clustering near point sources.

Health authorities are often alerted to suspected cancer clusters near the vicinity of potential point sources by members of the public. A surveillance system, where administrative regions around the potential point sources are regularly monitored for high disease rates, would allow for responses which are easier to obtain, timelier, and less expensive than individual thorough investigations. The monitoring could be done by using the so-called 'focused' tests for detecting disease clustering. However, these tests, generally designed to detect clusters of a fixed size around the foci, are not particularly effective when dealing with administrative regions with substantial differences in populations. In this work, an approach which overcomes the problem to a certain extent is described. Here the selected cluster sizes are based on the populations of the administrative regions under examination. The approach is used to investigate whether cancer clustering appears in the vicinity of the pulp and paper mills in British Columbia for the years 1983-1989. The results indicate that the approach performs reasonably well in identifying cancer sites for which elevated risks have also been suggested in the epidemiologic literature. Consequently, this methodology could be utilized to provide guidance for further investigation even in the absence of local reports. Similarly, it could be readily utilized to provide timely responses to local reports.

Adolescent↗
PubMedDate not supplied

Methodological issues in the development of the Canadian Cancer Incidence Atlas.

The Canadian Cancer Incidence Atlas is among recent national atlases using incidence rather than mortality data. Methods used to assess the significance and spatial correlation of the age-standardized rates (ASIRs) for the 290 census divisions are described. The expected number of cases by area was used to determine cancer sites with sufficient cases to be mapped. ASIR significance was assessed using a simulation based on a Poisson distribution. The consistency of the observed case distributions with the Poisson distribution was examined. The bootstrap confidence interval (CI) for the ASIR developed by Swift was used in the atlas. Spatial correlation was assessed with Moran's I/I(max) and the significance determined by a simulation in order to allow for area population variation. Data quality indicators typically used for cancer registries were presented, supplemented by a registry questionnaire.

Atlases as Topic↗
PubMedDate not supplied

Topical bleomycin treatment of oral leukoplakia: a randomized double-blind clinical trial.

BACKGROUND: Oral leukoplakia and oral erythroplakia may be associated with benign and dysplastic cellular changes, and are at risk of malignant transformation. Additional means of management of these lesions is needed. The results of nonblinded trials using topical bleomycin in oral leukoplakia indicated the need for phase III study. METHODS: A prospective, double-blind, randomized trial of topical bleomycin versus placebo was conducted. Bleomycin 1% in dimethylsulphoxide (DMSO) or the carrier was applied for 5 minutes for 14 consecutive days. Clinical assessment and pre-application and post-treatment biopsies were conducted. RESULTS: Twenty-two patients were randomized. Of the patients who received bleomycin, decrease in clinical size of the lesion was achieved (p = 0.001), and histological reduction in dysplasia was seen (p = 0.094). CONCLUSIONS: The topical application of bleomycin in DMSO may represent an additional approach to management of oral leukoplakia. The treatment is well-tolerated, and may be considered when the location or extent of the lesion may make surgical excision difficult.

Administration, Topical↗
PubMedDate not supplied

Compliance with fluoride gel use in irradiated patients.

Patients who undergo radiation therapy that includes the salivary glands frequently experience severe xerostomia. The standard of care for these patients who have natural teeth has become daily application of fluoride by means of custom-fabricated carriers. The purpose of this study was to determine patient compliance with fluoride gel application using carriers. Using a structured verbal questionnaire, we interviewed 76 patients who had completed radiation therapy for head and neck cancer. Thirty of these patients were seen regularly in the dental clinic of the Cancer Agency (group 1); the remaining 46 were not seen on a regular basis (group 2). Overall, 43% of patients reported using fluoride gel regularly (once a day). In group 1, 67% of patients used fluoride regularly, as did 28% of patients in group 2 (p = 0.001). There were no significant differences between the groups in frequency of toothbrushing and use of dental floss. Compliance with the use of fluoride in carriers was not associated with differences in other oral care measures in the two groups, which suggests that fluoride application in carriers achieves limited compliance in relation to daily oral health care measures. Regular follow-up of patients after radiation therapy is needed to assess their need for, and compliance with, daily fluoride application.

Adult↗