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Biomedical subjects

N C Miller

Publications and source records attributed to N C Miller.

At least 19 recordsLinked to original sources
PubMed1998

Universal hepatitis B vaccination: hospital factors influencing first-dose uptake for neonates in Darwin.

A universal neonatal hepatitis B vaccination program was introduced in the Northern Territory in 1990. We compared live births with vaccine usage to determine the uptake of the first dose of hepatitis B vaccine under this new policy and to identify hospital factors that influenced this rate. Attitudes and vaccine administration practices were determined through interviews, using standard questions with midwifery and paediatric nursing staff at both hospitals. Hepatitis B vaccines dispensed at Hospital A indicated a 96 per cent coverage of neonates in 1993 and 93 per cent in 1994. Vaccination at Hospital B indicated 71 per cent coverage in 1993 and 77 per cent in 1994. Differences in vaccine uptake appeared to be influenced by the use of standing drug orders, the nursing staff's attitudes and knowledge, and misinformation among health professionals. Education programs for health professionals and parents need to be established before the introduction of a universal hepatitis B vaccination policy for it to be well accepted. Standing orders for hepatitis B vaccine in postnatal wards allow nursing staff to promote it and thus maximise coverage rates.

Attitude to Health↗
PubMed1998

The role of inertial particle collectors in evaluating pharmaceutical aerosol delivery systems.

Design theory for cascade impactors is well developed, and design principles can be summarized quite succinctly. The key geometric parameters of three commonly used impactors have been compared to design guidelines. Calibration theory and practice have undergone improvement in recent years. Published results show distinctly different characteristics for three commonly used impactors, and conformance to modern design recommendations results in desirable performance characteristics. A consideration of the sensitivity of stage collection efficiency characteristics to geometric variables and flow rate indicates that measurement of certain physical dimensions is sufficient to assure that impactor performance matches that of a properly calibrated unit. Flow rate is an important operating variable that is more likely to fall out of its calibrated range than important dimensional variables resulting from instrument manufacturing. In practice, data from impactors are frequently treated as though the impactors have ideal collection characteristics. The practical effects of impactor nonideal performance can be demonstrated by model calculations, and these show the necessity of data inversion to obtain a size distribution. The process is not straightforward for unknown distributions. There are much smaller differences between ideal and real performance for an impactor complying with design guidelines, thus, the cutoff characteristics are sharp.

Aerosols↗
PubMed1997

Effect of drug load and plate coating on the particle size distribution of a commercial albuterol metered dose inhaler (MDI) determined using the Andersen and Marple-Miller cascade impactors.

PURPOSE: The purpose of this study is to investigate the effect of drug load, the coating of impactor stages, and the design of cascade impactors on albuterol MDIs particle size distribution measurements. The results of the investigation will be used to explain the "loading effect" recently reported. METHODS: Particle size distribution parameters of a commercial albuterol MDI were measured using both Andersen (AI) and Marple-Miller (MMI) Cascade Impactors, where plates were either left uncoated or coated with silicone or glycerin. A previously validated HPLC-EC method was used for the assay of albuterol collected by the impactor and in single spray content determinations. RESULTS: Coating impactor collection plates had an impact on measured MMAD and GSD values for single puff measurements but very little or no effect for the multi puff measurements. Due to particle bounce, the percent of albuterol fine particles deposited in the filter and impactor finer stages (< 1.10 microns in AI and < 1.25 microns in MMI) in uncoated single puff experiments was much higher in comparison to either coated single puff or multi-puff (coated and uncoated) measurements. CONCLUSIONS: Evaluation of drug load and plate coating are necessary to determine whether observed particle size distributions are representative of the generated aerosol or are the result of particle bounce and reentrainment. In order to minimize particle bounce, especially for single puff determinations, it may be useful to apply a thin layer of a sticky coating agent to the surfaces of impactor plates.

Adrenergic beta-Agonists↗
PubMed1996

A cascade impactor entry port for MDI sprays with collection characteristics imitating a physical model of the human throat.

PURPOSE: This work was performed in order to compare and contrast results obtained from cascade impactor measurements on metered dose inhalers (MDIs) using a variety of inlet ports. METHODS: The collection characteristics of four cascade impactor ports (a physical model of the human throat, a simplified geometry intended to mimic the physical model, and two currently-used ports) were measured on a variety of MDI formulations. RESULTS: The portion of the MDI spray which collects on the entry port depends in a complicated fashion on the characteristics of the formulation; in these studies the fraction of the total dose which was collected on the port ranged between about 20% and 90% of the total emitted dose. The collection characteristics of the simplified geometry closely corresponded to the physical model. The length of the flow path between the port and the impactor was varied, and found not to have a strong effect on the measured size distribution passing the port. CONCLUSIONS: Ranking of various MDI formulations according to performance criteria as measured with a cascade impactor should be expected to depend on the particular inlet port which is used.

Administration, Inhalation↗
PubMed1996

Cold chain in a hot climate.

We monitored the temperatures of batches of vaccine during transport and storage from a national warehouse to five Northern Territory vaccination clinics. Electronic temperature monitors were placed with vaccines, and were programmed to record the temperature every 30 minutes for up to three months. A diary was attached to each vaccine batch to record each change in location. The temperature recordings covered 8369 hours. There were regular temperature deviations outside the recommended range. In the hot climate of the Northern Territory, freezing is the greatest threat to vaccine potency. Recommendations from the study include: routine use of cold chain indicators, increased vaccine turnover and storage of vaccines within an operational temperature range of 4 to 8 degrees C. Research is needed to investigate the efficacy of heat-stable vaccines when stored at ambient temperatures and in air-conditioned environments.

Climate↗
PubMed1995

Development and evaluation of a pulsed nebulizer with predictable dosing characteristics.

A metered dose nebulizer assembly with the capability for repeatable doses is described, comprising a commercial disposable nebulizer and a timing circuit to control the duration of air supply. Data on performance of the nebulizer apparatus under typical operating conditions are presented, using cromolyn sodium as a model compound. Repeat doses from the apparatus typically show less than 10% relative standard deviation.

Aerosols↗
PubMed1995

Characteristics of frequent pediatric emergency department users.

The purpose of this study was to examine the medical and demographic characteristics of patients who frequently seek emergency care at a pediatric emergency department (ED). Registration information of ED visits during the study period from 11/1/87 to 5/31/92 (4.6 years) was stored in a data base. Patients with 10 or more ED visits during this study period were considered to be "frequent" ED users. Outpatient and inpatient medical records of these patients were manually reviewed. Demographics, chronic conditions, and the acute conditions for each ED visit were coded and analyzed. During the study period, there were 79,049 ED patient visits under 21 years of age. Of the patients born after 1970, there were 47,451 visits by patients seen one or two times, 25,883 visits by patients seen three to nine times, and 5178 visits by 357 patients seen in the ED ten times or more. Ninety-nine patients were seen more than 15 times, 39 patients were seen more than 20 times, 17 patients were seen more than 25 times, and 10 patients were seen more than 30 times. Two hundred sixty-five of the 357 frequent ED users (74%) had chronic disease conditions. Two hundred and twenty-three of them had good functional status, 25 had mild or moderate impairment in carrying out activities of daily living, and 17 had severe impairment of function. The most common chronic medical conditions were recurrent wheezing (226), neurologic conditions (33), gastrointestinal conditions (13), cardiac conditions (12), and endocrine conditions (9). The other 92 were assessed as healthy children. Patients' immunization status were up to date as of the last ED visit during the study period in 329 patients (92%). Pediatricians were the primary care providers in 339 patients (95%). Medical insurance status of patients follows: private insurance (38%), military (0.3%), Medicaid or state assistance (60%), and no insurance (1.4%). Polynesian ethnic groups were over-represented in the cohort of frequent ED users. We conclude that cultural differences appeared to be an important factor associated with frequent ED use by healthy persons. Medical care resources as measured by immunizations, insurance, and identification of a primary care physician did not appear to be deficient in this cohort of frequent ED users. Since recurrent wheezing is a dominant chronic condition among frequent ED users, pediatric emergency medicine training programs may consider the inclusion of the chronic management of wheezing in their curriculum.

Acute Disease↗
PubMed1994

Should aboriginals in the "top end" of the Northern Territory be vaccinated against hepatitis A?

OBJECTIVE: To determine the level of immunity to hepatitis A virus infection in rural Australian Aboriginal populations in the "Top End" of the Northern Territory. METHODS: A total of 344 sera, for which details of donors' age, sex and domicile were available, were collected and tested for hepatitis A total antibody in a delinked seroprevalence study. RESULTS: Overall, 337/344 samples (97.97%) tested positive for hepatitis A total antibodies--18/20 samples (90%) in the 1-5 year age group; 85/88 (96.6%) in the 6-10 year age group; 98/98 (100%) in the 11-15 year age group; 32/33 (97.0%) in the 16-20 year age group and 104/105 (99%) in the older than 20 year age group. CONCLUSION: Hepatitis A is hyperendemic in the rural Aboriginal communities studied and the virus is acquired predominantly in the first five years of life. Symptomatic hepatitis A infection is uncommon in this population. We suggest that hepatitis A vaccination for rural Aboriginal children is not indicated as it would not reduce clinical disease rates and may produce a cohort whose immunity could decrease over the following 10 years. Although vaccination is appropriate for non-immune individuals working in remote communities, emphasis must be placed on the inequities in health infrastructure and education underlying the high transmission rates in Aboriginal children.

Adolescent↗
PubMed1994

Are childhood immunization programmes in Australia at risk? Investigation of the cold chain in the Northern Territory.

Since vaccines may lose their potency if transported or stored outside the recommended temperature range (2-8 degrees C), we carried out a study in the Darwin area of the Northern Territory of Australia to determine the links in the cold chain, including the extent of vaccine monitoring, and whether the vaccines were being exposed to unsafe temperatures. Sabin oral poliomyelitis vaccine (OPV) and recombinant hepatitis-B (HB) vaccine were selected for special monitoring. A total of 127 vials of OPV and 144 vials of HB vaccine were dispatched during October, November and December 1990 to the government, independent health services and general practitioner surgeries which routinely administer these vaccines. We distributed the two vaccines with MonitorMark time/temperature and Coldside indicator tags attached to cards for recording the date, location and temperature exposures each time the vaccines were moved or used. A total of 65% of the OPV and 41% of the HB vaccine monitor cards were returned for analysis. The vaccines were transported and stored at one to four locations prior to being administered. Some 23% of tagged OPV was exposed for 48 hours or more to a temperature > 10 degrees C; 47.5% of tagged HB vaccines were exposed to -3 degrees C or less, the majority of them during storage in health facilities or clinics. Exposures were independent of distance from the distribution centre, mode of transport, or type of facility. Our results show that the vaccines were often exposed to temperatures outside the recommended range during transport and storage, putting them at risk of loss of potency.(ABSTRACT TRUNCATED AT 250 WORDS)

Child↗
PubMed1993

Changes in the treatment of wheezing children in the emergency department.

This study prospectively examined the pharmacologic treatment of all wheezing children presenting to a pediatric emergency department from December 1987 to September 1991 (10,091 cases). There were increasing trends in rate of hospitalization, use of oxygen saturation measurements, use of corticosteroids and beta agents at discharge, and use of aerosolized bronchodilators administered in the emergency department. This cohort shows decreasing trends in use of theophylline and the use of subcutaneous bronchodilators administered in the emergency department. Increasing patient severity could not be confirmed in this cohort. The increase in use of corticosteroids in wheezing children is well supported in the literature. The use of theophylline appears to have significantly declined while there is still some controversy over its recommendations in the literature.

Adolescent↗
PubMed1993

Control of a community outbreak of measles which started in a poorly immunised high school population.

An outbreak of measles occurred in Darwin from February to March 1991. The first case was in a 13-year-old high school student who had returned from a holiday overseas. She was symptomatic on the second day of the new school term. She infected an infant while both waited in a doctor's surgery. Outbreak control measures were instituted 18 days later when the Communicable Diseases Centre was first alerted of cases through the laboratory notification scheme. Through active surveillance, we identified 76 cases of measles, of whom 92 per cent (70 cases) were under 20 years of age. Of these, 46 were students at the index high school in which the attack rate was 39.2 per 1,000. They transmitted the disease to six unvaccinated siblings aged 11 to 18 years, resulting in a secondary attack rate of 113 per 1,000 in this age group (relative risk of disease in siblings 2.8, 95 per cent confidence interval 1.2 to 6.2). The outbreak affected one other high school, a number of primary schools, one tertiary institution, and nine children under five years. Only four of the cases had a verified history of previous immunisation against measles. The outbreak was arrested within two weeks of instituting community-wide control measures. Inadequate immunisation coverage among school-aged children and delays in notification contributed to the severity of the outbreak. Improved measles surveillance systems, including telephone notification of clinical cases are needed so that control measures can be instituted immediately within the household and in the community.

Adolescent↗
PubMed1992

Oxygen saturation changes during the pediatric emergency department treatment of wheezing.

This study examined the oxygen saturation (OSAT) changes measured by pulse oximetry during emergency department (ED) bronchodilator treatment of wheezing patients. Data were collected prospectively on two cohorts (November 1987 to November 1988, 2,468 patients; and December 1988 to October 1990, 4,913 patients) presenting to a pediatric ED with wheezing-associated respiratory illnesses. Initial, posttreatment, and discharge OSAT was recorded in many of these patients. Improvement in OSAT following ED bronchodilator administration was noted in most patient groups. Initial OSAT was indicative of severity as measured by the need for hospitalization and the number of bronchodilator treatments administered in the ED. Subcutaneous epinephrine and aerosolized albuterol were compared in OSAT improvement and side effects. Aerosolized albuterol was not shown to be superior to epinephrine. Improvements in OSAT following bronchodilator administration documents the presence of relative preexisting hypoxemia which is reversed to some degree with bronchodilators. Pulse oximetry is an objective means of assessing asthma severity.

Adolescent↗
PubMed1992

Assessment of the twin impinger for size measurement of metered-dose inhaler sprays.

The calibration of the first stage of the twin-stage impinger, an instrument proposed for use in measuring the spray size from metered-dose inhalers, was performed with monodisperse aerosols by a standard technique for cascade impactors. The mean cut point was found to be not particularly sensitive to operating variables which may be expected to occur in practice. The cut point was close to that reported previously, although the collection efficiency curve was found to be slightly sharper. Calculations are reported on the expected results of measurements on aerosols in a two-stage instrument with an idealized perfect collection efficiency curve as well as the curve measured for the twin impinger. These results indicate that important characteristics of spray size distribution cannot be distinguished with an ideal two-stage instrument; the twin impinger is less capable than an ideal instrument.

Aerosols↗
PubMed1992

Comparative absorption of atropine from a metered-dose inhaler and an intramuscular injection.

The inhalation of atropine sulfate from a pressurized metered-dose inhaler was investigated in a nonrandomized four-period rising-dose study. Eight healthy, nonsmoking subjects received 1.7, 3.4, and 5.2 mg of atropine sulfate by inhalation and 1.67 mg of atropine free base (equivalent to 2 mg of atropine sulfate) by intramuscular (i.m.) injection. Serum atropine sulfate concentrations were measured over a 24-h period by gas chromatography/mass spectrometry. Mean serum concentrations increased nonproportionally as the inhaled dose increased. Mean peak concentrations were 4.9, 6.1, and 7.9 ng/ml for the inhaled doses and 8.4 ng/ml for the i.m. dose. Typical anticholinergic effects were seen after all doses.

Absorption↗
PubMed1988

Test method for evaluation of loss of prime in metered-dose aerosols.

A new test method is described for assessing the loss of prime in metered-dose aerosols. Two representative metered-dose valve designs and two storage positions were used to assess the utility of this test method at three different sites. Loss of prime, defined as a valve delivery 15% below the mean, was detected in three of the four test configurations. The first significant loss of prime in this study was observed at the two-week time point for valves without drain tanks stored in the upright position. Onset of loss of prime was shown to be dependent on valve design as well as storage position, thus alternate valves or storage conditions should yield different results. This test method appeared to be reproducible over the three test sites, with a slight variation in results attributed to differences in storage conditions and agitation during sample handling. This test method intentionally excluded agitation which is in sharp contrast to the normal "shake well before use" instruction to the patient. Following one priming actuation, all of the valves returned to their mean valve delivery.

Aerosols↗