Hospital Resource Utilisation by Patients with Community-Acquired Pneumonia

Little data is available on the resource utilisation of patients admitted with Community-Acquired Pneumonia (CAP) in Ireland. A retrospective review of 50 randomly-selected patients admitted to Beaumont Hospital with CAP was undertaken. The mean length of stay of patients with CAP was 12 days (+/- 16 days). All patients were emergency admissions, all had a chest x-ray, a C-reactive protein blood test, and occupied a public bed at some point during admission. Common antimicrobial therapies were intravenous (IV) amoxicillin/clavulanic acid and oral clarithromycin; 60% received physiotherapy. The estimated mean cost of CAP per patient was €14,802.17. Costs arising from admission to hospital with CAP are substantial, but efforts can be undertaken to ensure that resources are used efficiently to improve patient care such as discharge planning and fewer in-hospital ward transfers.

Eosinophil peroxidase induces the expression and function of acid-sensing ion channel-3 in allergic rhinitis: in vitro evidence in cultured epithelial cells

BACKGROUND

Acid-sensing ion channels (ASIC) are a family of acid-activated ligand-gated cation channels. As tissue acidosis is a feature of inflammatory conditions, such as allergic rhinitis (AR), we investigated the expression and function of these channels in AR.

OBJECTIVES

The aim of the study was to assess expression and function of ASIC channels in the nasal mucosa of control and AR subjects.

METHODS

Immunohistochemical localization of ASIC receptors and functional responses to lactic acid application were investigated. In vitro studies on cultured epithelial cells were performed to assess underlying mechanisms of ASIC function.

RESULTS

Lactic acid at pH 7.03 induced a significant rise in nasal fluid secretion that was inhibited by pre-treatment with the ASIC inhibitor amiloride in AR subjects (n = 19). Quantitative PCR on cDNA isolated from nasal biopsies from control and AR subjects demonstrated that ASIC-1 was equally expressed in both populations, but ASIC-3 was significantly more highly expressed in AR (P < 0.02). Immunohistochemistry confirmed significantly higher ASIC-3 protein expression on nasal epithelial cells in AR patients than controls (P < 0.01). Immunoreactivity for EPO+ eosinophils in both nasal epithelium and submucosa was more prominent in AR compared with controls. A mechanism of induction of ASIC-3 expression relevant to AR was suggested by the finding that eosinophil peroxidase (EPO), acting via ERK1/2, induced the expression of ASIC-3 in epithelial cells. Furthermore, using a quantitative functional measure of epithelial cell secretory function in vitro, EPO increased the air-surface liquid depth via an ASIC-dependent chloride secretory pathway.

CONCLUSIONS

This data suggests a possible mechanism for the observed association of eosinophils and rhinorrhoea in AR and is manifested through enhanced ASIC-3 expression.

Somnolence in adult craniopharyngioma patients is a common, heterogeneous condition that is potentially treatable

CONTEXT AND OBJECTIVE

Somnolence and obesity are prevalent in craniopharyngioma patients. We hypothesized that somnolence was because of obstructive sleep apnoea in craniopharyngioma patients.

DESIGN, PATIENTS AND MEASUREMENTS

We assessed prevalence of somnolence and sleep apnoea in 28 craniopharyngioma and 23 obese controls attending a tertiary referral centre, by means of the Epworth Sleepiness Score (ESS) and polysomnography. All subjects with sleep apnoea were offered continuous positive airway pressure therapy (CPAP) or modafinil. All craniopharyngioma patients, with unexplained somnolence, were offered modafinil.

RESULTS

Somnolence was reported by 20/28 (71·5%) craniopharyngioma patients and 4/23 (17%) obese subjects (P < 0·001). Median ESS was 7·5 (IQR 6, 10·7) in craniopharyngioma patients and 4·0 (4,8) in controls, P < 0·01. Eleven somnolent craniopharyngioma patients had obstructive sleep apnoea, in whom treatment led to a reduction in ESS by 6·4 ± 1·4, P = 0·01. Among the remaining nine patients, five were offered modafinil therapy, of whom four had benefit, three were not compliant with hormone replacement, and one died before intervention. There was no difference in the prevalence of obstructive sleep apnoea between craniopharyngioma (n = 13, 46%) and obese subjects (n = 14, 61%, P = 0·4). Body mass index (BMI) does not correlate with apnoea hypopnoea index [apnoea - hypopnoea index (AHI), r = 0·25, P = 0·08], which suggests that obesity alone does not explain the prevalence of sleep apnoea in craniopharyngioma patients.

CONCLUSIONS

Somnolence is common in craniopharyngioma patients and in the majority is because of obstructive sleep apnoea. An additional group of somnolent craniopharyngioma patients benefits from modafinil.

Therapy with omalizumab for patients with severe allergic asthma improves asthma control and reduces overall healthcare costs

BACKGROUND

Patients with asthma who have persistent symptoms despite treatment with inhaled steroids and long-acting beta agonists are considered to have severe asthma. Omalizumab is a monoclonal antibody directed against IgE, which is used as an add-on treatment for patients who have severe persistent allergic asthma.

AIMS

The aim of this study was to assess the clinical benefit and healthcare utilisation of patients who responded to omalizumab therapy and to establish an overall cost implication.

METHODS

This was an observational retrospective cohort study designed to investigate the effect of omalizumab on exacerbations of asthma before and after 6 months of treatment in Irish patients.

RESULTS

Centres who had treated patients with severe allergic asthma for the 6 months prior and post omalizumab treatment were audited with a standardised assessment tool. Sixty-three (32 male) patients were studied. In the 6 months prior to omalizumab 41 of 63 (66%) had been hospitalised, and this fell to 15 of 63 (24%), p < 0.0001 in the 6 months after treatment was started. Hospital admissions reduced from 2.4 ± 0.41 to 0.8 ± 0.37 and the mean number of bed days occupied was reduced from 16.6 ± 2.94 to 5.3 ± 2.57 days, p < 0.001. The number of oral corticosteroid doses used fell from 3.1 ± 0.27 to 1.2 ± 0.17, p < 0.001. The overall cost saving per omalizumab responder patients for 6 months was <euro>834.

CONCLUSIONS

Six months therapy with omalizumab reduced the number of bed days, the number of hospitalisations and the use of oral corticosteroids compared to the 6 months prior to commencement. Despite the cost of the additional therapy there were overall savings in health costs.

The Allergic Rhinitis and its Impact on Asthma system: a new classification of allergic rhinitis and nasal responsiveness

OBJECTIVES AND HYPOTHESIS

Allergic rhinitis has traditionally been classified into seasonal and perennial rhinitis. However, many subjects with dual sensitisation do not fit neatly into either category. Recently, the Allergic Rhinitis and its Impact on Asthma workshop has proposed a new allergic rhinitis classification, into intermittent and persistent forms. The purpose of the present study was to investigate whether the symptomatic and secretory responsiveness of allergic rhinitis sufferers correlated well with the Allergic Rhinitis and its Impact on Asthma classification, compared with the traditional classification.

STUDY DESIGN

Experimental study.

METHODS

Forty subjects with allergic rhinitis and 13 normal controls underwent a unilateral nasal bradykinin challenge protocol. Symptom scores were recorded and secretion weights measured bilaterally using filter paper disks. The symptomatic and secretory responses of allergic subjects were analysed according to both the traditional and the Allergic Rhinitis and its Impact on Asthma classifications, and the two systems were compared.

RESULTS

For both classification systems, the two groups of allergic subjects were clearly demarcated by secretory responses. However, after classification according to the traditional system, there was a lack of clear demarcation between the groups as regards symptomatic response, whereas clear demarcation of symptomatic responses was seen after using the Allergic Rhinitis and its Impact on Asthma classification.

CONCLUSIONS

In allergic rhinitis subjects, the degree of nasal responsiveness was closely related to their Allergic Rhinitis and its Impact on Asthma classification. Furthermore, this classification was not compromised by the inclusion of subjects with dual sensitisation. Thus, the Allergic Rhinitis and its Impact on Asthma classification may have advantages for future research studies on allergic rhinitis.

Recent consensus on the classification of rhinosinusitis — a way forward for research and practice?

Prior classification of rhinitis was into three categories: acute, subacute and chronic rhinosinusitis. The advantages of this classification were obvious but they were offset by some disadvantages. For example, the previous classification did not take account of the mechanisms underlying the condition or the clinical outcome. Hence, there was a need for evidence-based sinusitis classification guidelines. The American Academy of Otolaryngology-Head and Neck Surgery and other related societies published a classification of the condition and suggested clinical research strategies for patients with rhinosinusitis. The main conclusion was that sinusitis should be divided into four categories: acute (bacterial) rhinosinusitis, chronic rhinosinusitis (CRS) without polyps, CRS with polyps, and allergic fungal sinusitis. The aim of this current paper is to discuss the consensus for nomenclature, outline the proposed classification of different types of rhinosinusitis and to suggest some ways that we may audit these guidelines.

Team Objective Structured Bedside Assessment (TOSBA): a novel and feasible way of providing formative teaching and assessment

It can be challenging to teach and assess medical students successfully in the setting of a hospital ward using real patients. We describe a novel method of providing weekly formative clinical assessment and teaching to final year students on an acute medical ward: The Team Objective Structured Bedside Assessment (TOSBA). The TOSBA involves three groups of five students rotating through three ward-based stations (each station consists of an inpatient and facilitator). Each group spends 25 minutes at a bedside station where the facilitator asks consecutive students to perform one of five clinical tasks. Every student receives a standardised grade and is provided with educational feedback at each of the three stations. We report our 15-month experience using the TOSBA format to assess and teach a large number of medical students on a weekly basis. We discuss the advantages and potential drawbacks of our approach.

Screening for lung cancer using low dose CT scanning: results of 2 year follow up

BACKGROUND

Screening with low dose chest computed tomographic scanning (LDCCT) may improve survival by identifying early asymptomatic lung cancer.

METHODS

Four hundred and forty nine high risk subjects were screened with serial LDCCT scanning over 2 years. Fine needle aspiration biopsy was recommended for non-calcified nodules (NCNs) of >10 mm diameter or demonstrating interval growth.

RESULTS

NCNs were identified in 111 subjects (24.7%), three of which were lung cancer. The overall prevalence (0.4%) and incidence (1.3%) rates of lung cancer detection were low. Three of the six lung cancers detected in the study were stage 1 non-small cell lung cancer; the remainder were unresectable central tumours. By contrast, eight subjects developed extrathoracic malignancy during the study period and other incidental pathology was noted in 221 subjects (49.2%). Smoking cessation rates at 19% were higher than in the general population, but 60.8% of subjects continued to smoke.

CONCLUSION

LDCCT scanning is useful in detecting early peripheral non-small cell lung cancers but its usefulness as a screening tool is limited by low specificity and by poor sensitivity for central tumours.

Induction of nasal hyper-responsiveness by allergen challenge in allergic rhinitis: the role of afferent and efferent nerves

BACKGROUND

Hyper-responsiveness of nasal secretory function and volume changes are features of allergic rhinitis (AR) that are mediated in part by neural mechanisms. The finding of nasal hyper-responsiveness in subjects with AR who are currently symptomatic, but not in those who are currently out of season and asymptomatic, suggests that induction of neural reflexes in allergic subjects occurs as a result of allergic inflammation.

OBJECTIVES

To investigate whether allergen exposure in subjects with asymptomatic seasonal allergic rhinitis (SAR) may lead to induction of neural reflexes, and to investigate the components of the reflexes involved in this induction.

METHODS

Asymptomatic subjects with (out-of-season) SAR underwent a nasal bradykinin challenge, before and 24 h after preceding ipsilateral (n = 11) and contralateral (n = 11) antigen challenge. Challenges were performed and nasal secretions collected using filter paper disks, and changes in nasal minimal cross-sectional area (A(min)) were measured using acoustic rhinometry.

RESULTS

Preceding ipsilateral antigen challenge led to the induction of a contralateral secretory reflex (P = 0.01), which was absent in control experiments (P = 0.34). Ipsilateral secretion weights were also enhanced. Preceding contralateral antigen challenge also induced a contralateral secretory reflex (P = 0.03). Enhancement of the reduction in contralateral A(min) was also seen (P = 0.02). Ipsilateral responses were unchanged.

CONCLUSIONS

Allergen exposure in asymptomatic allergic subjects leads to induction of neural reflexes, resulting in nasal hyper-responsiveness, which persists beyond the resolution of the acute allergic response. Our data suggest that the mechanisms of allergen-induced hyper-responsiveness involve both afferent and efferent components.

An alternative technique for nasal biopsy

OBJECTIVES/HYPOTHESIS

The objective was to investigate the effectiveness of co-phenylcaine as a topical anesthetic agent for nasal mucosal biopsy.

STUDY DESIGN

A prospective study.

METHODS

Nasal mucosal biopsy specimens were taken from a site just anterior to the inferior turbinate following topical anesthesia with co-phenylcaine. All volunteers graded pain according to standard visual analogue scale (0-10) (VAS) scoring, and all were followed up after 24 hours for any epistaxis.

RESULTS

Ninety nasal biopsy specimens were removed from 41 patients in all. Eight-two percent did not report any discomfort following this procedure (VAS score, 0). Ten patients reported mild discomfort (VAS scores ranging between, 1 and 3) and only six reported pain (VAS scores ranging from 5 to 7). However, five of these patients agreed to further biopsy and documented no discomfort during the repeat procedure. Only one patient required immediate intervention for hemorrhage after the procedure. In cases in which bleeding occurred (seven patients) it was documented within the first 6 hours, was minimal in content, and was controlled with local pressure. No systemic side effects were experienced.

CONCLUSION

Co-phenylcaine is a suitable topical anesthetic agent for nasal mucosal biopsy. Removal of nasal tissue from a site anterior to the inferior turbinate can be performed under direct vision and provides sufficient tissue for histological assessment.

Screening for lung cancer using low dose CT scanning

BACKGROUND

Lung cancer is the most common cause of cancer related death in Ireland. The majority of lung cancers are inoperable at the time of diagnosis and consequently the overall 5 year survival is less than 10%. The objective of the ProActive Lung Cancer Detection (PALCAD) study was to evaluate whether low dose chest computed tomographic scanning (LDCCT) can detect early stage asymptomatic lung cancer in a high risk urban population.

METHODS

Four hundred and forty nine subjects of median age 55 years (range 50-74) with a median pack year smoking history of 45 years (range 10-160), with no previous cancer history and medically fit to undergo thoracic surgery were recruited. After informed consent, LDCCT was performed on all subjects. Non-calcified nodules (NCNs) of >/=10 mm in diameter were referred for biopsy. Follow up with interval LDCCT at 6, 12 and 24 months to exclude growth was recommended for NCNs <10 mm in diameter.

RESULTS

Six (1.3%) NCNs of >/=10 mm were detected of which one (0.23%) had non-small cell lung cancer stage 1; 145 NCNs of <10 mm were detected in 87 (19.4%) subjects. Mediastinal masses were detected in three subjects (0.7%)-one small cell lung cancer and two benign duplication cysts. Incidental pathology was noted in 276 patients (61.5%), most commonly emphysema and coronary artery calcification.

CONCLUSION

The prevalence of resectable lung cancer detected by LDCCT at baseline screening was low at 0.23%, but there was a high rate of significant incidental pathology.

An outreach programme for patients with an exacerbation of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease is a common clinical condition characterised by airflow obstruction. The clinical course of the disease is characterised by intermittent exacerbations. In Ireland exacerbations of chronic obstructive pulmonary disease are a common cause of admission to acute medical hospitals. The Beaumont Hospital COPD Outreach Programme was designed to provide care at home for patients with an exacerbation of COPD that would otherwise require hospitalisation. Patients recruited to the programme were discharged home within 72 hours of admission and reviewed by the Outreach Team over a two week period. In addition to monitoring clinical progress the Team provided education, smoking cessation and medication advice. Analysis of the outcome of the first 100 patients recruited to the study show that one third of patients admitted to Hospital with an exacerbation of COPD are eligible for this programme and the average length of Hospital stay was 2.6 days. During the fourteen day follow up there was one death (non-respiratory) and six patients were re-admitted to hospital. Forty percent of smokers had abstained from smoking at the end of three months. In summary, the COPD Outreach programme is a safe and effective alternative to acute hospital care for selected patients with exacerbations of COPD.

Function of Pulmonary Neuronal M2Muscarinic Receptors in Stable Chronic Obstructive Pulmonary Disease

Anticholinergic drugs often cause a considerable degree of bronchodilation in patients with chronic obstructive pulmonary disease (COPD). Pulmonary neuronal M(2) muscarinic receptors function to limit the magnitude of vagally induced bronchoconstriction. We hypothesized that the effectiveness of anticholinergic agents in patients with COPD may reflect increased vagal reactivity due to dysfunction of M(2) muscarinic receptors. The function of M(2) receptors and the magnitude of vagally induced bronchoconstriction were assessed in subjects with normal lung function and in subjects with COPD. A nasal cold dry air challenge was used to induce a bronchoconstriction, measured as a change in airway resistance (Raw) at 5 Hz (R5) using impulse oscillometry. In subjects with COPD R5 rose from 0.68 +/- 0.06 to 0.74 +/- 0.07 kPa/L/s after the cold dry air challenge (p < 0.01) and in the control subjects R5 rose from 0.34 +/- 0.03 to 0.39 +/- 0.03 kPa/L/s (p < 0.01). The bronchoconstriction was inhibited by pretreatment with ipratropium bromide, indicating that it was vagally mediated. In both groups of subjects pretreatment with the selective M(2) muscarinic receptor agonist pilocarpine (5 mg/ml) prevented the cold air-induced bronchoconstriction, indicating normal function of M(2) receptors. These studies indicate that M(2) muscarinic receptors are functional in subjects with stable COPD.

Substance P-induced airway hyperreactivity is mediated by neuronal M(2) receptor dysfunction

Neuronal muscarinic (M(2)) receptors inhibit release of acetylcholine from the vagus nerves. Hyperreactivity in antigen-challenged guinea pigs is due to blockade of these M(2) autoreceptors by eosinophil major basic protein (MBP) increasing the release of acetylcholine. In vivo, substance P-induced hyperactivity is vagally mediated. Because substance P induces eosinophil degranulation, we tested whether substance P-induced hyperreactivity is mediated by release of MBP and neuronal M(2) receptor dysfunction. Pathogen-free guinea pigs were anesthetized and ventilated. Thirty minutes after intravenous administration of [Sar(9),Met(O(2))(11)]- substance P, guinea pigs were hyperreactive to vagal stimulation and M(2) receptors were dysfunctional. The depletion of inflammatory cells with cyclophosphamide or the administration of an MBP antibody or a neurokinin-1 (NK(1)) receptor antagonist (SR-140333) all prevented substance P-induced M(2) dysfunction and hyperreactivity. Intravenous heparin acutely reversed M(2) receptor dysfunction and hyperreactivity. Thus substance P releases MBP from eosinophils resident in the lungs by stimulating NK(1) receptors. Substance P-induced hyperreactivity is mediated by blockade of inhibitory neuronal M(2) receptors by MBP, resulting in increased release of acetylcholine.

Eosinophils and airway nerves in asthma

In the lungs, neuronal M2 muscarinic receptors limit the release of acetylcholine from postganglionic cholinergic nerves. However, these receptors are not functional under certain circumstances in animal models of hyperreactivity such as occurs after exposure of sensitised animals to an allergen or during a respiratory tract virus infection. This loss of M2 receptor function leads to an increase in acetylcholine release from cholinergic nerves and thus is a mechanism for the vagally mediated hyperreactivity seen in these animals. Studies in animal models of hyperreactivity have shown that eosinophils localise to the airway nerves of sensitised animals after antigen challenge. Inhibiting this localisation of eosinophils either with an antibody to the eosinophil survival cytokine IL-5 or the eosinophil adhesion molecule VLA-4 prevents loss of M2 muscarinic receptor function. It is likely that eosinophil MBP is responsible for the loss of M2 receptor function, since inhibiting eosinophil MBP with an antibody or neutralising MBP with heparin prevents this loss of function. These data are also supported by ligand binding studies where it has been shown that eosinophil MBP is an allosteric antagonist at neuronal M2 muscarinic receptors. Loss of function of lung neuronal M2 muscarinic receptors may also occur under certain circumstances in patients with asthma, although the mechanisms are not yet established.

Oral corticosteroid trials in the management of stable chronic obstructive pulmonary disease

Although recent guidelines for managing chronic obstructive pulmonary disease (COPD) recommend a trial of oral corticosteroids in the initial assessment, its prognostic value remains unclear. We prospectively studied 127 adults (64% men) with stable COPD (FEV1/FVC < 60%) over 1 year. At entry, we measured lung volumes, gas transfer factor, respiratory symptoms (by questionnaire), and peripheral blood eosinophil count. Skin-prick testing was done, and spirometry after nebulized 5 mg salbutamol and, after 2 weeks, oral prednisolone. Physician A gave all patients inhaled beclomethasone dipropionate (800 mcg/day), whereas physician B prescribed this only to those with a positive oral corticosteroid trial. At 1 year, spirometry and respiratory questionnaire were repeated, with an estimate of overall symptom severity on a visual analogue scale. Follow-up data were available in 104 (82%) patients. Of these, 32 (31%) were unresponsive to salbutamol and prednisolone; 48 (46%) were responsive to beta agonists but not to corticosteroids, and 24 (23%) responded to corticosteroids and salbutamol. Patients in all groups were comparable, except that the prednisolone responders had a higher mean eosinophil count (p < 0.001) and more were ex-smokers (p < 0.001). Only the response to oral prednisolone correlated with the change in prebronchodilator FEV1 over 1 year. Oral prednisolone responders had higher FEV1 at 1 year (p < 0.02) and significantly lower symptom scores (p < 0.02). In COPD, corticosteroid trials contribute information additional to that gained from nebulized bronchodilator reversibility testing. Patients with a positive response to a corticosteroid trial are more likely to have improved symptomatically and spirometrically at 1 year.

Antigen-induced hyperreactivity to histamine: role of the vagus nerves and eosinophils

M2 muscarinic receptors limit acetylcholine release from the pulmonary parasympathetic nerves. M2 receptors are dysfunctional in antigen-challenged guinea pigs, causing increased vagally mediated bronchoconstriction. Dysfunction of these M2 receptors is due to eosinophil major basic protein, which is an antagonist for M2 receptors. Histamine-induced bronchoconstriction is composed of a vagal reflex in addition to its direct effect on airway smooth muscle. Because hyperreactivity to histamine is seen in antigen-challenged animals, we hypothesized that hyperreactivity to histamine may be due to increased vagally mediated bronchoconstriction caused by dysfunction of M2 receptors. In anesthetized, antigen-challenged guinea pigs, histamine-induced bronchoconstriction was greater than that in control guinea pigs. After vagotomy or atropine treatment, the response to histamine in antigen-challenged animals was the same as that in control animals. In antigen-challenged animals, blockade of eosinophil influx into the airways or neutralization of eosinophil major basic protein prevented the development of hyperreactivity to histamine. Thus hyperreactivity to histamine in antigen-challenged guinea pigs is vagally mediated and dependent on eosinophil major basic protein.

Role of insulin in antigen-induced airway eosinophilia and neuronal M2 muscarinic receptor dysfunction

In the lungs, neuronal M2 muscarinic receptors limit ACh release from parasympathetic nerves. In antigen-challenged animals, eosinophil proteins block these receptors, resulting in increased ACh release and vagally mediated hyperresponsiveness. In contrast, diabetic rats are hyporesponsive and have increased M2 receptor function. Because there is a low incidence of asthma among diabetic patients, we investigated whether diabetes protects neuronal M2 receptor function in antigen-challenged rats. Antigen challenge of sensitized rats decreased M2 receptor function, increased vagally mediated hyperreactivity by 75%, and caused a 10-fold increase in eosinophil accumulation around airway nerves. In antigen-challenged diabetic rats, neuronal M2 receptor function was preserved and there was no eosinophil accumulation around airway nerves. Insulin treatment of diabetic rats completely restored loss of M2 receptor function, vagally mediated hyperresponsiveness, and eosinophilia after antigen challenge. These data demonstrate that insulin is required for development of airway inflammation, loss of neuronal M2 muscarinic receptor function, and subsequent hyperresponsiveness in antigen-challenged rats and may explain decreased incidence of asthma among diabetic humans.

Pulmonary neuronal M2 muscarinic receptor function in asthma and animal models of hyperreactivity

In the lungs neuronal M2 muscarinic receptors limit acetylcholine release from postganglionic cholinergic nerves. These inhibitory M2 receptors are dysfunctional in antigen challenged guinea pigs and in humans with asthma which leads to an increase in vagally mediated hyperreactivity. In vitro, eosinophil products act as allosteric antagonists at neuronal M2 muscarinic receptors. In vivo, displacing or neutralising MBP preserves neuronal M2 muscarinic receptor function and prevents hyperreactivity. Thus, there is good evidence from animal studies that after antigen challenge pulmonary M2 muscarinic receptors become dysfunctional because MBP inhibits their function. Loss of function of pulmonary neuronal M2 muscarinic receptors has also been reported in patients with asthma, although the clinical significance of this dysfunction and the mechanisms underlying it are not yet established.

Effects of tachykinin NK1 receptor antagonists on vagal hyperreactivity and neuronal M2 muscarinic receptor function in antigen challenged guinea-pigs

1. The role of tachykinin NK1 receptors in the recruitment of eosinophils to airway nerves, loss of inhibitory neuronal M2 muscarinic receptor function and the development of vagal hyperreactivity was tested in antigen-challenged guinea-pigs. 2. In anaesthetized guinea-pigs, the muscarinic agonist, pilocarpine (1-100 microg kg(-1), i.v.), inhibited vagally induced bronchoconstriction, in control, but not in antigen-challenged guinea-pigs 24 h after antigen challenge. This indicates normal function of neuronal M2 muscarinic receptors in controls and loss of neuronal M2 receptor function in challenged guinea-pigs. Pretreatment of sensitized guinea-pigs with the NK1 receptor antagonists CP99994 (4 mg kg(-1), i.p.), SR140333 (1 mg kg(-1), s.c.) or CP96345 (15 mg kg(-1), i.p.) before antigen challenge, prevented M2 receptor dysfunction. 3. Neither administration of the NK1 antagonists after antigen challenge, nor pretreatment with an NK2 receptor antagonist, MEN10376 (5 micromol kg(-1), i.p.), before antigen challenge, prevented M2 receptor dysfunction. 4. Electrical stimulation of the vagus nerves caused a frequency-dependent (2-15 Hz, 10 V, 0.2 ms for 5 s) bronchoconstriction that was significantly increased following antigen challenge. Pretreatment with the NK1 receptor antagonists CP99994 or SR140333 before challenge prevented this increase. 5. Histamine (1-20 nmol kg(-1), i.v.) caused a dose-dependent bronchoconstriction, which was vagally mediated, and was significantly increased in antigen challenged guinea-pigs compared to controls. Pretreatment of sensitized animals with CP99994 before challenge prevented the increase in histamine-induced reactivity. 6. Bronchoalveolar lavage and histological studies showed that after antigen challenge significant numbers of eosinophils accumulated in the airways and around airway nerves. This eosinophilia was not altered by pretreatment with the NK1 receptor antagonist CP99994. 7. These data indicate that pretreatment of antigen-sensitized guinea-pigs with NK1, but not with NK2 receptor antagonists before antigen challenge prevented the development of hyperreactivity by protecting neuronal M2 receptor function. NK1 receptor antagonists do not inhibit eosinophil accumulation around airway nerves.

Pretreatment with antibody to eosinophil major basic protein prevents hyperresponsiveness by protecting neuronal M2 muscarinic receptors in antigen-challenged guinea pigs

In antigen-challenged guinea pigs there is recruitment of eosinophils into the lungs and to airway nerves, decreased function of inhibitory M2 muscarinic autoreceptors on parasympathetic nerves in the lungs, and airway hyperresponsiveness. A rabbit antibody to guinea pig eosinophil major basic protein was used to determine whether M2 muscarinic receptor dysfunction, and the subsequent hyperresponsiveness, are due to antagonism of the M2 receptor by eosinophil major basic protein. Guinea pigs were sensitized, challenged with ovalbumin and hyperresponsiveness, and M2 receptor function tested 24 h later with the muscarinic agonist pilocarpine. Antigen-challenged guinea pigs were hyperresponsive to electrical stimulation of the vagus nerves compared with controls. Likewise, loss of M2 receptor function was demonstrated since the agonist pilocarpine inhibited vagally-induced bronchoconstriction in control but not challenged animals. Pretreatment with rabbit antibody to guinea pig eosinophil major basic protein prevented hyperresponsiveness, and protected M2 receptor function in the antigen-challenged animals without inhibiting eosinophil accumulation in the lungs or around the nerves. Thus, hyperresponsiveness is a result of inhibition of neuronal M2 muscarinic receptor function by eosinophil major basic protein in antigen-challenged guinea pigs.

Localization of eosinophils to airway nerves and effect on neuronal M2 muscarinic receptor function

Neuronal M2 muscarinic receptors inhibit acetylcholine release from pulmonary parasympathetic nerves but are dysfunctional in antigen-challenged animals and asthmatics. Deletion of pulmonary eosinophils protects M2 receptor function in antigen-challenged guinea pigs. Therefore, the association of eosinophils with airway nerves was investigated. Nerve-associated eosinophils were significantly increased in challenged animals compared with controls (0.75 +/- 0.05 vs. 0.28 +/- 0.05 eosinophils/nerve). In antigen-challenged animals, eosinophil density was greatest around airway nerves, suggesting recruitment to the nerves. M2 receptor function was inversely correlated with the number of eosinophils per nerve, thus eosinophils are associated with airway nerves in antigen-challenged guinea pigs, where they impair M2 receptor function. In airways from three patients with fatal asthma, 196 of 637 eosinophils (30%) were associated with nerves, and release of eosinophil major basic protein was evident; conversely, in three control patients 1 of 11 (9%) eosinophils were in contact with nerves. Thus eosinophils and their granule proteins are also seen in association with airway nerves in patients with asthma.

Antibody to VLA-4, but not to L-selectin, protects neuronal M2 muscarinic receptors in antigen-challenged guinea pig airways

Antigen challenge of sensitized guinea pigs decreases the function of inhibitory M2 muscarinic autoreceptors on parasympathetic nerves in the lung, potentiating vagally induced bronchoconstriction. Loss of M2 receptor function is associated with the accumulation of eosinophils around airway nerves. To determine whether recruitment of eosinophils via expression of VLA-4 and L-selectin is critical for loss of M2 receptor function, guinea pigs were pretreated with monoclonal antibodies to VLA-4 (HP1/2) or L-selectin (LAM1-116). Guinea pigs were sensitized and challenged with ovalbumin, and M2 receptor function was tested. In controls, blockade of neuronal M2 muscarinic receptors by gallamine potentiated vagally induced bronchoconstriction, while in challenged animals this effect was markedly reduced, confirming M2 receptor dysfunction. Pretreatment with HP1/2, but not with LAM1-116, protected M2 receptor function in the antigen-challenged animals. HP1/2 also inhibited the development of hyperresponsiveness, and selectively inhibited accumulation of eosinophils in the lungs as measured by lavage and histology. Thus, inhibition of eosinophil influx into the lungs protects the function of M2 muscarinic receptors, and in so doing, prevents hyperresponsiveness in antigen-challenged guinea pigs.

Compliance at night with low flow oxygen therapy: a comparison of nasal cannulae and Venturi face masks

BACKGROUND

The factors that influence nocturnal compliance among patients prescribed low flow oxygen therapy were determined and tolerance of nasal cannulae and Venturi face masks compared.

METHODS

Two studies were performed: (1) a prospective study of 99 hospitalised patients prescribed low flow oxygen therapy, 49 on nasal cannulae and 50 on Venturi face mask; and (2) a prospective study of 20 separate patients with an acute respiratory disorder requiring low flow oxygen therapy who were given nasal cannulae and Venturi face mask on successive nights in random order.

RESULTS

In study 1, 49 patients dislodged their device at least once during the night. Those using Venturi face masks and those over 75 years of age had the most dislodgements. In study 2 patients also dislodged Venturi face masks more frequently (mean (SD) 2.0 (2.4)) than nasal cannulae (0.7 (1.4)). Most patients expressed a preference for nasal cannulae.

CONCLUSIONS

Nocturnal tolerance of nasal cannulae is superior to Venturi face masks, and this factor should be considered when choosing the method of oxygen delivery.

Ulcerative jejunitis: are we missing cases?

We present two cases of ulcerative jejunitis unassociated with coeliac disease. The condition is probably being underdiagnosed especially since the reduction in the investigative laparotomy.