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Biomedical subjects

Peter Davis

Publications and source records attributed to Peter Davis.

At least 37 records · Page 2Linked to original sources
PubMed2004

Continuous positive airway pressure: current controversies.

PURPOSE OF REVIEW: Continuous positive airway pressure is increasingly being used in the care of premature infants. The purpose of this review is to highlight the current controversies in the use of neonatal continuous positive airway pressure. RECENT FINDINGS: This review explores information about the devices available for delivering continuous positive airway pressure and the pressures that can be used. It also investigates the controversial issues of using continuous positive airway pressure during resuscitation of premature infants and whether infants who are going to be managed on continuous positive airway pressure should be intubated and given surfactant before continuous positive airway pressure is started. It reviews the use of continuous positive airway pressure and the prevention of chronic lung disease and the use of nasal intermittent positive pressure ventilation and the difficult area of weaning from continuous positive airway pressure. SUMMARY: Existing evidence suggests that short binasal prongs are most effective, nasal intermittent positive pressure ventilation is a useful way of augmenting neonatal continuous positive airway pressure and that very premature infants can be managed with neonatal continuous positive airway pressure in the delivery room as part of the resuscitation. Further research is required to determine whether important outcomes are improved with the use of nasal continuous positive airway pressure rather than endotracheal intubation and, if so, whether surfactant should be given to infants so managed. Definition of optimal levels of continuous positive airway pressure for infants at varying stages of their disease also requires further research.

Chronic Disease↗
PubMed2004

The New Zealand Socio-economic Index of Occupational Status: methodological revision and imputation for missing data.

OBJECTIVES: To revise and update the New Zealand Socio-economic Index (NZSEI) in the light of methodological issues in its construction, and to develop an imputation method for use where occupational information is not available. METHODS: Data were drawn from the following New Zealand national surveys: 1996 Population Census; 1996/97 and 1997/98 Household Economic Surveys; 1996/97 Household Health Survey. Three sets of statistical analyses were applied: alternating least squares to generate socio-economic scores; cluster and discriminant function analyses to identify cut-points; and regression and logistic regression to develop and test imputation methods. RESULTS: Socio-economic scores for the full-time workforce in 1996 showed a different distribution, but much the same occupational ordering, as in 1991. The introduction of part-time workers and income adjustment multipliers for self-employed workers significantly affected scores for management and agricultural titles. The application of cluster and discriminant function analyses generated six groupings that were relatively distinct occupationally. An imputation method based on an averaging of scores within age/qualification categories was found to achieve acceptable results. CONCLUSIONS: Methodological improvements in the construction of the NZSEI have enhanced its empirical robustness, while a simple imputation technique has widened the potential application of the scale.

Data Collection↗
PubMed2004

Compression, expansion, or dynamic equilibrium? The evolution of health expectancy in New Zealand.

STUDY OBJECTIVE: To evaluate the New Zealand evidence for three theories of population health change: compression of morbidity, expansion of morbidity, and dynamic equilibrium. DESIGN: Using the Sullivan method, repeated cross sectional survey information on functional limitation prevalence was combined with population mortality data and census information on the utilisation of institutional care to produce health expectancy indices for 1981 and 1996. SETTING: The adult population of New Zealand in 1981 and 1996. PARTICIPANTS: 6891 respondents to the 1981 social indicators survey; 8262 respondents to the 1996 household disability survey. MAIN RESULTS: As a proportion of overall life expectancy at age 15 the expectation of non-institutionalised mobility limitations increased from 3.5% to 6% for men, and from 4.5% to 8% for women; the expectation of agility limitation increased from 3% to 7.5% for men and from 4.5% to 8.5% for women, and the expectation of self care limitations increased from 2.0% to 4.5% for men and from 3.0% to 6.0% for women. These changes were primarily attributable to increases in the expectation of moderate functional limitation. CONCLUSION: The dynamic equilibrium scenario provides the best fit to current New Zealand evidence on changes in population health. Although an aging population is likely to lead to an increase in demand for disability support services, the fiscal impact of this increase may be partially offset by a shift from major to moderate limitations, with a consequential reduction in the average levels of support required.

Adolescent↗
PubMed2004

Comparison of private for-profit with private community-governed not-for-profit primary care services in New Zealand.

OBJECTIVE: To compare the characteristics of patients, their disease patterns, and the investigation and referral patterns in private community-governed not-for-profit and private for-profit primary care practices in New Zealand. METHODS: Observational study using a representative survey of visits to general practitioners in New Zealand. Practices were categorised according to their ownership: private for-profit or private community-governed not-for-profit. Patient socio-demographic characteristics, treated prevalence and other characteristics of presenting problems, morbidity burden, numbers of investigations and referral patterns were compared. RESULTS: Compared with for-profit practices, community-governed not-for-profit practices served a younger, largely non-European population, nearly three-quarters of whom had a means-tested benefit card (community services card), 10.5% of whom were not fluent in English, and the majority of whom lived in the 20% of areas ranked as the most deprived (by the NZDep2001 index of socio-economic deprivation). Patients visiting not-for-profit practices were diagnosed with more problems, including higher rates of asthma, diabetes and skin infections, but lower rates of chest infections. The duration of visits was also significantly longer. No differences were observed in the average number of laboratory tests ordered. The odds of specialist referral were higher in for-profit patients when confounding variables were controlled for. CONCLUSIONS: Community-governed not-for-profit practices in New Zealand serve a poor, largely non-European population who present with somewhat different rates of various problems compared with patients at for-profit practices. The study highlights for communities, policy-makers and purchasers the importance of community-governed not-for-profit practices in meeting the needs of low-income and minority population groups.

Adolescent↗
PubMed2003

Adverse events in New Zealand public hospitals II: preventability and clinical context.

AIMS: To assess the preventability and clinical context of adverse events identified in New Zealand public hospitals. METHODS: Two-stage retrospective review of 6579 medical records randomly sampled from admissions for 1998 in 13 generalist hospitals providing acute care. Initial screening and medical review according to a standardised protocol. RESULTS: Eight hundred and fifty adverse events were identified, of which over one third (315) were preventable to a significant degree. Preventability of events increased with age of patient, and was more characteristic of certain diagnostic categories. Half of all events (413/850) were both preventable and occurred in hospital, giving an occurrence rate of 6.3%. This rate increased with patient age, as did impact on patients and extended stay. There were also variations by diagnostic category. Over half of the events were associated with surgery (489) and one third with medicine (303); operative incidents were predominant in the former, drug-related in the latter, and system issues in both. Events in medicine had greater patient impact, and were less likely to have occurred in a public hospital. System errors featured prominently as an area for prevention, being associated with nearly half of all preventable in-hospital events. Consultation and education were also important, resources less so. CONCLUSIONS: Preventable adverse events have a major impact on patient outcomes and extended hospital stay. A substantial proportion of these are system related and, hence, in principle susceptible to quality improvement.

Adolescent↗
PubMed2003

Quasi-stadium laser diodes with an unstable resonator condition.

We have observed lasing in a complicated eigenmode of a quasi-stadium laser diode with an unstable resonator consisting of two curved end mirrors obeying an unstable resonator condition and two straight sidewall mirrors. The laser was fabricated by application of a reactive-ion-etching technique to a molecular beam epitaxy-grown graded-index separate-confinement heterostructure single-quantum-well GaAs/AlGaAs structure. The far-field pattern shows that the lasing mode corresponds to the complicated lowest-loss mode obtained numerically by an extended Fox-Li method.

Journal Article↗
PubMed2003

Stable oscillations of a spatially chaotic wave function in a microstadium laser.

Laser action on a single spatially chaotic wave function is obtained as a final stable state in a nonlinear dynamical model of a stadium shaped resonant cavity with an active medium. The stable single-mode lasing state corresponds to a particular metastable resonance of the cavity which wins a competition among multiple modes with positive net linear gain and has a distinct lasing threshold.

Journal Article↗
PubMed2003

Lasing on scar modes in fully chaotic microcavities.

Scar wave functions in a fully chaotic cavity are obtained numerically by an extended Fox-Li method. Lasing on the scar modes are observed in a semiconductor microcavity with a selective excitation of different scars controlled by corresponding shape of electrodes for current injection.

Journal Article↗
PubMed2002

Adverse events in New Zealand public hospitals I: occurrence and impact.

AIM: To assess the occurrence and impact of adverse events in New Zealand public hospitals. METHODS: Two-stage retrospective review of 6579 medical records, selected by systematic list sample from admissions for 1998 in 13 generalist hospitals providing acute care. After initial screening, medical records were reviewed by trained medical practitioners using a standardised protocol. RESULTS: Except for hospital stay, the sample appeared to be closely representative of New Zealand public hospital admissions for 1998 on key demographic and clinical criteria. The proportion of hospital admissions associated with an adverse event was 12.9% (incidence rate, 11.2%), of which nearly one fifth had occurred outside a public hospital (mainly doctor s rooms, patient s home, rest home, or private hospital). Most adverse events had minor patient impact, with less than 15% associated with permanent disability or death. Hospital workload was strongly affected, however, with adverse events adding an average of over nine days (median 4 days) to the expected hospital stay. There was limited evidence of patterning by diagnostic category. The elderly were disproportionately affected. CONCLUSIONS: The study provides representative base parameters that can contribute to the wider understanding, and potential improvement, of patient safety and the quality of care in New Zealand public hospitals.

Adolescent↗
PubMed2002

Co-morbidity and health outcomes in three Auckland hospitals.

AIMS: To establish the burden of co-morbid disease using the Charlson Index among hospital inpatients and its relationship to key health outcomes. METHODS: An initial screen was carried out on 1575 medical records selected by systematic list sample from admissions for 1995 in three public hospitals in the Auckland region. In the course of the administration of the instrument, screeners were required to record the occurrence of co-morbid disease using the Charlson Index. RESULTS: A third of patients had co-morbid disease, of which chronic pulmonary disease and congestive heart failure were the most frequently recorded. While the Charlson Index was associated with age of patient, length of stay, inpatient mortality, and adverse event status, the simple presence or absence of co-morbidity was as an effective predictor as the extended index. Co-morbidity was more likely to be recorded for Maori, for patients from deprived areas, and for circulatory or respiratory diagnoses. Specific co-morbid conditions were predictive of health outcomes. CONCLUSIONS: Levels of co-morbid disease established for patients using the Charlson Index in three Auckland public hospitals are similar to those recorded internationally. Co-morbidity is predictive of key health outcomes that are of clinical and managerial significance. Controlling for co-morbidity will be important in making comparisons of the quality of care.

Adolescent↗
PubMed2002

Social class mortality differences in Maori and non-Maori men aged 15-64 during the last two decades.

AIMS: This investigation uses data from 1996-97 to update previous studies of social class mortality differences in Maori and non-Maori New Zealand men aged 15-64 years. METHODS: Numerator data were obtained from the national death registrations and denominator data were from the 1976, 1986 and 1996 censi. For each social class, age standardised death rates in Maori and non-Maori men were calculated for amenable, non-amenable and all causes of mortality. RESULTS: Maori male mortality was significantly higher than non-Maori mortality in each social class and for the total population for amenable (overall RR = 5.3(CI = 4.0-6.9)), non-amenable (overall RR = 2.4(2.2-2.6)) and all causes of mortality (overall RR = 2.4(2.3-2.6)). The social class mortality differences within Maori (relative index of inequality was 3.3) were markedly greater than non-Maori class differences (RII = 1.5). CONCLUSIONS: The persistently high Maori mortality rates, when controlled for social class, indicate that the poor state of Maori health cannot be explained solely by relative socioeconomic disadvantage. The high Maori rate of potentially preventable deaths indicates that the health sector is still not meeting the serious health needs of many Maori. The social class mortality gradient within Maori underlines the need to address disparities within Maori.

Adolescent↗
PubMed2002

Socio-economic factors and mortality among 25-64 year olds followed from 1991 to 1994: the New Zealand Census-Mortality Study.

AIM: To measure the association of income, education, occupational class, small area socio-economic deprivation, car access and labour force status with mortality among 25-64 year old males and females using the 1991 census-cohort of the New Zealand Census-Mortality Study. METHODS: Mortality records for 1991-94 were anonymously and probabilistically linked to 1991 census records, thereby creating a cohort study of all New Zealand census respondents. Odds ratios of mortality comparing categories of each socio-economic factor were calculated using logistic regression. For income, education and deprivation (NZDep91) a modified relative index of inequality (RII(10:90)) was calculated. The RII(10:90) estimates the relative risk of mortality for low socio-economic people (10th percentile rank) compared to high socio-economic people (90 percentile rank) allowing direct comparisons across socio-economic factors. RESULTS: The relative risk of all-cause mortality for 25-64 year old males with an equivalised household income less than $20,000, compared to greater than $50,000, was 2.16 (95% confidence interval 1.99 to 2.34). For females, this relative risk was 1.68 (1.52 to 1.86). Using the RII(10:90) all-cause mortality was 2.22, 1.94 and 1.58 times greater among low compared to high socio-economic males for income, NZDep91 and education, respectively. For females, these RII(10:90) estimates were 1.77, 1.69 and 1.57, respectively. By cause of death, the strongest gradients were observed for respiratory diseases, followed by lung cancer, cardiovascular disease and unintentional injury. For suicide deaths, unemployed males and females had 2.70 (1.84 to 3.95) and 2.86 (1.19 to 6.85) greater rates than the employed. CONCLUSIONS: There are strong socio-economic gradients for all-cause mortality and most specific causes of mortality among both males and female adults in New Zealand, regardless of the choice of socio-economic factor. The gradients were strongest for income, followed by small area deprivation and education, and strongest for 'preventable' causes of death.

Adult↗
PubMed2002

Drinking patterns among older people in the community: hidden from medical attention?

AIMS: To determine patterns of alcohol use and misuse among community-dwelling people aged 65 years and over in Christchurch and to assess how often this comes to medical attention. METHODS: A cross-sectional survey of alcohol use and misuse was conducted followed by a self-administered postal survey among non- respondents. General practitioners (GPs) of the respondents completed a self-administered questionnaire on patients' alcohol use and misuse. RESULTS: The response rate was 58% (141/243). The prevalence of hazardous alcohol consumption in the past twelve months (AUDIT cut-off score 8 or more) was 9.9% (95% CI = 4.9-14.9) and the prevalence of lifetime alcohol dependence using DSM-IV diagnostic criteria was 24.8% (95% CI = 17.6-32.0). Men were more likely than women to report lifetime dependency and current hazardous patterns. The response rate among GPs was 77.7% (108/139). None of the GPs identified or diagnosed alcohol problems in the past twelve months among this group and reported a history of alcohol problems in only four (4.0%) patients. Those with current hazardous patterns of alcohol use were twice as likely to be admitted to hospital (RR=2.4; 95% CI 1.2-5.1) but significantly less likely to visit their GPs in the previous twelve months (RR=0.55; 95% CI 0.7-1.1). CONCLUSION: A significant proportion of community-dwelling elderly people reported patterns of alcohol consumption that put them at risk of future damage to physical or mental health. Hazardous drinkers were less likely to visit their GPs and only in a few cases, were GPs aware of such potential problems.

Age Factors↗
PubMed2002

The incidence and characteristics of neonatal irreversible lung dysplasia.

A 3-year retrospective study of 173 neonates treated with extracorporeal membrane oxygenation in the United Kingdom identified 9 cases of irreversible lung dysplasia, including alveolar capillary dysplasia (n = 5), surfactant protein B deficiency (n = 1), pulmonary hypoplasia (n = 1), pulmonary lymphangiectasis (n = 1), and combined lymphangiectasis and hypoplasia (n = 1).

Bronchopulmonary Dysplasia↗
PubMed2002

Persistent social class mortality differences in New Zealand men aged 15-64: an analysis of mortality during 1995-97.

OBJECTIVE: Social class mortality differences in New Zealand men aged 15-64 years have previously been examined for the periods 1975-77 and 1985-87 using the Elley-Irving social class scale. The objective was to repeat these analyses for 1995-97 in order to examine time trends, and to assess current social class patterns of mortality. METHODS: Age-standardised mortality rates were calculated for each social class and a weighted estimate of the social class mortality gradient was obtained. RESULTS: Male mortality declined 21% between 1985-87 and 1995-97, but the social class mortality differences have not diminished and may have even increased. The Relative Index of Inequality has increased from 1.8 in 1975-77 to 2.1 in 1985-87 and 2.3 in 1995-97. Unlike previous analyses, the relative social class mortality gradient was just as strong in the older age groups as in the younger age groups, indicating that the possible increase in social class gradient has largely occurred in the older age groups. CONCLUSIONS: These findings indicate that the potential to address the excess preventable mortality caused by socio-economic factors has not been fully realised in New Zealand. IMPLICATIONS: Social class analyses identify groups in the community that have an excess mortality that is potentially preventable. There are still major social class differences in mortality in New Zealand, and these differences may even have increased. It is important that these patterns are taken into account in public health planning and that further research is conducted to identify the mechanisms by which these differences occur.

Adolescent↗
PubMed2002

Compensation for medical injury in New Zealand: does "'no-fault" increase the level of claims making and reduce social and clinical selectivity?

The issues of patient safety and quality of care have gained policy attention with a growing appreciation of the scale and impact of medical injury in health systems. While the focus is clearly on the prevention of iatrogenic injury, the question of patient compensation is now also considered important, if only because in fault-based tort systems the fear of litigation may itself be a barrier to the disclosure and open discussion of medical error. No-fault systems, by contrast, do not require proof of culpability, and thus may both reduce barriers to compensation and increase disclosure of error. Little evidence, however, is available on the performance of such systems. This article reports on the analysis of two data sources-a sample of hospital admissions and a complete set of compensation claims for medical injury. Both are for the same year and region of New Zealand, a country that has maintained a no-fault system of accident compensation for a quarter of a century. Just over 2 percent of hospital admissions were associated with an adverse event that was potentially compensable under scheme criteria. While the claims process was well targeted, the level of claims making and receipt was low, with the ratio of successful claims to potentially compensable events being approximately 1:30. Comparison of social and clinical characteristics of the two data sets revealed a degree of selectivity. Compared with the hospital events, the typical successful claimant was younger and female and was much more likely to have experienced a surgical adverse event that, while unexpected, was not due to substandard care. It is concluded that, in interpreting these results, account needs to be taken of a number of features unique to the New Zealand system. These include: the limited payoff for a compensation claim (no pain and suffering or lump sum, free hospital care); the relative complexity of the grounds for claim (either rarity and severity or practitioner error); and a history of limited litigation for medical error. This suggests that, while the New Zealand system is well targeted, cheap, and free of financial and legal barriers, a change in legal doctrine alone has not in itself been sufficient to remove completely the selective and low level of claims making traditionally associated with patient compensation under tort.

Adult↗