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Biomedical subjects

Jon G Ayres

Publications and source records attributed to Jon G Ayres.

12 recordsLinked to original sources
PubMed2006

Changes in vagal tone with posture in asthma are related to changes in ventilatory pattern.

BACKGROUND: Posturally induced changes in minute ventilation in patients may be autonomically driven. This study aimed to test whether changes in autonomic tone with posture differed between normal and asthmatic subjects and whether this related to changes in indices of ventilation. METHODS: Ten patients with type 1 brittle asthma (BA), 10 with non-brittle, severe asthma (SA), 10 with mild asthma (MA) and 10 normal individuals were studied lying flat, at 60 degrees head up tilt and flat again each for 30min, assessing end-tidal CO(2) (ETCO(2)), respiratory rate and autonomic tone by heart rate variability. RESULTS: Parasympathetic tone (as high-frequency [HF] power) fell on tilt in all four groups, all showing increases in LF (low frequency)/HF ratio (sympatho-vagal balance) on tilt (BA, 2.03-4.9; SA, 3.3-8.2; MA, 1.5-4.9; normals, 2.3-6.6). ETCO(2) on tilt fell significantly in all 3 asthma groups (BA, DeltaETCO(2) -0.4, 95% CIs -0.18 to -0.75, P=0.005; SA, -0.7, 95% CIs -0.27 to -1.16, P=0.004; MA, -0.5, 95% CIs -0.14 to -0.78, P=0.01) but not in normals (-0.1, 95% CIs +0.23 to -0.49). The fall in ETCO(2) on tilt correlated with the fall in HF power in all three asthma groups but not in normal subjects. CONCLUSION: Changes in vagal tone posture are seen on tilt in both normal and asthmatic subjects which relate to changes in ETCO(2) only in asthmatic subjects. This provides support for the hypothesis that hyper-ventilatory response to postural change in asthma is autonomically influenced.

Adult↗
PubMed2006

Community-acquired pneumonia on the intensive care unit: secondary analysis of 17,869 cases in the ICNARC Case Mix Programme Database.

INTRODUCTION: This paper describes the case mix, outcome and activity for admissions to intensive care units (ICUs) with community-acquired pneumonia (CAP). METHODS: We conducted a secondary analysis of a high quality clinical database, the Intensive Care National Audit & Research Centre (ICNARC) Case Mix Programme Database, of 301,871 admissions to 172 adult ICUs across England, Wales and Northern Ireland, 1995 to 2004. Cases of CAP were identified from pneumonia admissions excluding nosocomial pneumonias and the immuno-compromised. It was not possible to review data from the time of hospital admission; therefore, some patients who developed hospital-acquired/nosocomial pneumonia may have been included. RESULTS: We identified 17,869 cases of CAP (5.9% of all ICU admissions). There was a 128% increase in admissions for CAP from 12.8 per unit to 29.2 per unit during the study period compared to only a 24% rise in total ICU admissions (p < 0.001). Eighty-five percent of admissions were from within the same hospital. Fifty-nine percent of cases were admitted to the ICU < 2 days, 21.5% between 2 and 7 days, and 19.5% > 7 days after hospital admission. Between 1995 and 1999 and 2000 and 2004 there was a rise in admissions from accident and emergency (14.8% to 16.8%; p < 0.001) and high dependency units (6.9% to 11.9%; p < 0.001) within the same hospital, those aged > 74 (18.5 to 26.1%; p < 0.001), and mean APACHE II score (6.83 to 6.91; p < 0.001). There was a fall in past history of severe respiratory problems (8.7% to 6.4%; p < 0.001), renal replacement therapy (1.6% to 1.2%; p < 0.01), steroid treatment (3.4% to 2.8%; p < 0.05), sedation/paralysis (50.2% to 40.4%; p < 0.001), cardiopulmonary resuscitation prior to admission (7.5% to 5.5%; p < 0.001), and septic shock (7.3% to 6.6%; p < 0.001). ICU mortality was 34.9% and ultimate hospital mortality 49.4%. Mortality was 46.3% in those admitted to the ICU within 2 days of hospital admission rising to 50.4% in those admitted at 2 to 7 days and 57.6% in those admitted after 7 days following hospital admission. CONCLUSION: CAP makes up a small, but important and rising, proportion of adult ICU admissions. Survival of over half of all cases vindicates the use of ICU facilities in CAP management. Nevertheless, overall mortality remains high, especially in those admitted later in their hospital stay.

Adolescent↗
PubMed2005

Occupational asthmagens.

Occupational asthma is caused by exposure to a workplace irritant. It is one of the few subtypes of asthma where a cure can be achieved by removing the cause, or the individual, from the workplace. The agent implicated is frequently obvious to the investigating clinician, although at times it may remain elusive. This review will discuss the definition of occupational asthma and asthmagens, the working environments under which they are commonly found, and what should be done on discovery of an occupational asthmagen.

Journal Article↗
PubMed2004

Bronchodilator treatment and deaths from asthma: case-control study.

OBJECTIVE: To investigate the association between bronchodilator treatment and death from asthma. DESIGN: Case-control study. SETTING: 33 health authorities or health boards in Great Britain. PARTICIPANTS: 532 patients under age 65 who died from asthma and 532 controls with a hospital admission for asthma matched for period, age, and area. MAIN OUTCOME MEASURES: Odds ratios for deaths from asthma associated with prescription of bronchodilators and other treatment, with sensitivity analyses adjusting for age at onset, previous hospital admissions, associated chronic obstructive lung disease, and number of other drug categories. RESULTS: After full adjustment, there were no significant associations with drugs prescribed in the 4-12 months before the index date. For prescriptions in the 1-5 years before, mortality was positively associated with inhaled short acting beta2 agonists (odds ratio 2.05, 95% confidence interval 1.26 to 3.33) and inversely associated with antibiotics (0.59, 0.39 to 0.89). The former association seemed to be confined to those aged 45-64, and the association with antibiotics was more pronounced in those under 45. Significant age interactions across all periods suggested inverse associations with oral steroids confined to the under 45 age group. An inverse association with long acting beta2 agonists and a positive association with methylxanthines in the 1-5 year period were non-significant. CONCLUSION: There was no evidence of adverse effects on mortality with medium to long term use of inhaled long acting beta2 agonist drugs. The association with short acting beta(2) agonists has several explanations, only one of which may be a direct adverse effect.

Adolescent↗
PubMed2004

Characteristics and outcome for admissions to adult, general critical care units with acute severe asthma: a secondary analysis of the ICNARC Case Mix Programme Database.

INTRODUCTION: This report describes the case mix, outcome and activity (duration of intensive care unit [ICU] and hospital stay, inter-hospital transfer, and readmissions to the ICU) for admissions to ICUs for acute severe asthma, and investigates the effect of case mix factors on outcome. METHODS: We conducted a secondary analysis of data from a high-quality clinical database (the Intensive Care National Audit and Research Centre [ICNARC] Case Mix Programme Database) of 129,647 admissions to 128 adult, general critical care units across England, Wales and Northern Ireland over the period 1995-2001. RESULTS: Asthma accounted for 2152 (1.7%) admissions, and in 57% mechanical ventilation was employed during the first 24 hours in the ICU. A total of 147 (7.1%) patients died in intensive care and 199 (9.8%) died before discharge from hospital. The mean age was 43.6 years, and the ratio of women to men was 2:1. Median length of stay was 1.5 days in the ICU and 8 days in hospital. Older age, female sex, having received cardiopulmonary resuscitation (CPR) within 24 hours before admission, having suffered a neurological insult during the first 24 hours in the ICU, higher heart rate, and hypercapnia were associated with greater risk for in-hospital death after adjusting for Acute Physiology and Chronic Health Evaluation II score. CPR before admission, neurological insult, hypoxaemia and hypercapnia were associated with receipt of mechanical ventilation after adjusting for Acute Physiology and Chronic Health Evaluation II score. CONCLUSION: ICU admission for asthma is relatively uncommon but remains associated with appreciable in-hospital mortality. The greatest determinant of poor hospital survival in asthma patients was receipt of CPR within 24 hours before admission to ICU. Clinical management of these patients should be directed at preventing cardiac arrest before admission.

APACHE↗
PubMed2004

Brittle asthma.

Asthma is recognised as a heterogeneous disease and, within this heterogeneity, brittle asthma is identified as a distinct phenotype. Two types of brittle asthma have been recognised in adults: type 1, showing more than 40% diurnal variability in PEF rate on most days over long periods and type 2, with acute severe attacks on a background of apparently good asthma control. The exact incidence of these phenotypes in adults is unknown but both seem to carry an increased risk of death and considerable morbidity. Adults with brittle asthma are generally atopic, with a high degree of psychosocial morbidity. This phenotype has not been recognised to the same degree in children, although we believe that such children exist and probably present the same management problems as their adult counterparts. The management of brittle asthma is, as for all patients with complex disease, holistic, with the removal of important causal factors ensuring compliance and providing adequate education. Steroid therapy remains the mainstay of treatment but the balance has to be struck between the benefits and side-effects of both inhaled and oral corticosteroids. Continuous subcutaneous terbutaline has been shown to be effective in controlling PEF variability but there are side effects and it must be used with due caution.

Adolescent↗
PubMed2004

Measuring exhaled nitric oxide levels in adults: the importance of atopy and airway responsiveness.

BACKGROUND: Raised exhaled nitric oxide (Feno) levels have been associated with asthma. However, we have found that in children, Feno was increased in atopic children with increased airway responsiveness (AR), and this was independent of a diagnosis of asthma. STUDY OBJECTIVES: The current study was designed to test the hypothesis that in adults there is no association between Feno and asthma after controlling for atopy and AR. MEASUREMENTS: One hundred fifteen adults (77 women; mean age, 41 years) underwent an assessment that included Feno measurements, spirometry, skin-prick testing, blood eosinophil count, and inhaled histamine challenge (results are expressed as a dose-response slope [DRS]). RESULTS: When only atopic individuals were considered (n = 73), Feno was positively associated with the DRS (p = 0.003), male gender (0.02), and negatively associated with current smoking (p = 0.09). Only male gender (p = 0.03) was associated with Feno among nonatopic individuals (n = 36). In multivariate analysis, there was no association between Feno and current asthma, current wheeze, or asthma ever. CONCLUSIONS: We conclude that in adult subjects, elevated Feno measurements are associated with a phenotype characterized by atopy and increased AR regardless of the presence of asthma or asthma-like symptoms.

Adult↗
PubMed2004

Assessment of bronchial responsiveness following exposure to inhaled occupational and environmental agents.

Inhalation of a range of agents can result in airway inflammation and/or irritation. This may result in occupational asthma or reactive airways dysfunction syndrome. Reactive airways dysfunction syndrome follows a single large exposure to a chemical agent but is now frequently embraced under the wider term of irritant-induced asthma, a term that also includes asthma due to persistent, lower dose irritant exposures. Bronchial hyperresponsiveness is a hallmark of both occupational asthma and reactive airways dysfunction syndrome, although some patients with occupational asthma may occasionally have typical clinical features without increased bronchial hyperresponsiveness. Following removal of the causal agent in occupational asthma, bronchial hyperresponsiveness generally returns towards normal over a 2-year period, although some individuals demonstrate increased bronchial hyperresponsiveness for longer. Measurement of specific bronchial hyperresponsiveness to the primary causal agent in occupational asthma is used diagnostically but not for assessing prognosis. Bronchial hyperresponsiveness to inhaled methacholine can be measured across individual workshifts to assess work-related change. It may also be measured at the end of a work period when exposure has occurred, and compared with values following a period away from work. There have been no direct, systematic comparisons of changes in methacholine responsiveness in the diagnosis of occupational asthma compared with the more frequently used serial peak flow measurements. Patients with reactive airways dysfunction syndrome classically exhibit non-specific bronchial hyperresponsiveness, which can be readily measured by evaluating responses to inhaled methacholine. Bronchial hyperresponsiveness in reactive airways dysfunction syndrome can persist for many years after initial exposure and serial changes can be used to assess recovery and subsequent disability over time.

Administration, Inhalation↗
PubMed2003

Exposure to metal fume and infectious pneumonia.

To test the hypothesis that inhalation of metal fume reversibly increases susceptibility to pneumonia, the authors conducted a case-control study. Men aged 20-64 years, admitted to 11 hospitals in West Midlands, England, with community-acquired pneumonia during 1996-1999 were interviewed about their lifetime occupational history, exposure to metal fume, and potential confounding factors. Similar information was collected from controls admitted to the same hospitals with nonrespiratory illness. For cases, exposures were timed relative to the onset of their illness (on average, 6 months before interview). Exposure histories for controls were censored 6 months before interview. Interviews were completed by 525 cases and 1,122 controls (response rates of 74% and 99%). Pneumonia was associated with reported occupational exposure to metal fume in the previous year (adjusted odds ratio (OR) = 1.6, 95% confidence interval (CI): 1.1, 2.4) but not in earlier periods (OR = 1.1). The risk was highest for lobar pneumonia and recent exposure to ferrous fume (OR = 2.3, 95% CI: 1.2, 4.3). The association was not specific to any one microorganism. These findings support the hypothesis that ferrous and possibly other metal fumes reversibly predispose to infectious pneumonia. Research should now focus on the underlying mechanisms and prevention.

Adult↗
PubMed2003

The association of daily sulfur dioxide air pollution levels with hospital admissions for cardiovascular diseases in Europe (The Aphea-II study).

The objective of this study is to assess the short-term effect of sulfur dioxide (SO(2)) air pollution levels on hospital admissions for cardiovascular diseases. Daily mean hospital admissions for cardiovascular diseases, ischemic heart diseases (IHDs), and stroke in seven European areas (the cities of Birmingham, London, Milan, Paris, Rome, and Stockholm, and in The Netherlands) participating in the multicenter European study of air pollution (Aphea-II), were measured. Time series analysis of daily hospital admission counts was performed using poison autoregressive models. A summary regression coefficient for all cities was provided. Daily numbers of all cardiovascular admissions except stroke, and particularly IHDs, rose significantly with an increase of daily SO(2)levels of the same day and day before. After adjusting for PM(10)(i.e. particles with size <10 microm), the association of SO(2)with IHD admissions remained significant (i.e. an increase of 0.7%; 95% confidence interval=0.1-1.3, per each 10 microg/m(3)increase of SO(2)) among subjects younger than 65 years, but not among subjects older than 65. In the older group the increase was only significant for particles (1.3%; CI 0.7-1.8, per each increase in 10 microg/m(3)of PM(10)). This study provides new evidence for the effects of urban air pollution on cardiac diseases in Europe, and suggests that SO(2)pollution may play an independent role in triggering ischemic cardiac events. From a Public Health perspective these results suggest that reduction in SO(2)levels in European cities could imply a reduction of admissions for IHDs.

Adult↗