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

Home High-Flow Therapy in Patients with Chronic Respiratory Diseases: Physiological Rationale and Clinical Results

High-flow therapy (HFT) is the administration of gas flows above 15 L/min. It is a non-invasive respiratory support that delivers heated (up to 38 °C), humidified (100% Relative Humidity, RH; 44 mg H2O/L Absolute Humidity, AH), oxygen-enriched air when necessary, through a nasal cannula or a tracheostomy interface. Over the last few years, the use of HFT in critically ill hypoxemic adults has increased. Although the clinical benefit of home high-flow therapy (HHFT) remains unclear, some research findings would support the use of HHFT in chronic respiratory diseases. The aim of this review is to describe the HFT physiological principles and summarize the published clinical findings. Finally, we will discuss the differences between hospital and home implementation, as well as the various devices available for HHFT application.

A Comparative Study to Explore Static and Dynamic Lung Functions in Users and Non-Users of Air Conditioners in Bengaluru

Background

Air conditioners (AC) have become indispensable in the contemporary World. However, their effects on respiratory health need to be explored further using dynamic and static lung functions.

Objectives

The objectives were: 1. To evaluate and compare dynamic parameters (FEV1, FVC, FEV1/FVC, PEFR, and FEF25-75) in AC users and non-users of Bengaluru. 2. To evaluate and compare airway resistance and specific airway conductance as additional parameters.

Materials and Methods

After applying ATS-ERS criteria for lung disorders, 30 AC users and non-users of Bengaluru, aged 18-40 yrs were assessed using body plethysmography. A significant association of restrictive pattern was seen in AC users (9 AC users out of 60 participants, Chi-square 8.37, P = 0.0038) having an Odd's ratio of 26.95 (CI: 1.4876 to 488.3558, Z = 2.229, P = 0.0258). Airway resistance (Raw) was comparable in both groups further indicating a non-obstructive pathology.

Conclusion

AC users had a significant decrease in flow rates (PEFR and FEF25-75) as well as an association with restrictive lung disorder suggesting the need for proper ventilation and hygiene. It is crucial to develop policies to maintain indoor air quality.

Clinical review of high-flow nasal oxygen therapy in human and veterinary patients

Oxygen therapy is the first-line treatment for hypoxemic acute respiratory failure. In veterinary medicine this has traditionally been provided via mask, low-flow nasal oxygen cannulas, oxygen cages and invasive positive pressure ventilation. Traditional non-invasive modalities are limited by the maximum flow rate and fraction of inspired oxygen (FiO₂) that can be delivered, variability in oxygen delivery and patient compliance. The invasive techniques are able to provide higher FiO₂ in a more predictable manner but are limited by sedation/anesthesia requirements, potential complications and cost. High-flow nasal oxygen therapy (HFNOT) represents an alternative to conventional oxygen therapy. This modality delivers heated and humidified medical gas at adjustable flow rates, up to 60 L/min, and FiO₂, up to 100%, via nasal cannulas. It has been proposed that HFNOT improves pulmonary mechanics and reduces respiratory fatigue via reduction of anatomical dead space, provision of low-level positive end-expiratory pressure (PEEP), provision of constant FiO₂ at rates corresponding to patient requirements and through improved patient tolerance. Investigations into the use of HFNOT in veterinary patients have increased in frequency since its clinical use was first reported in dogs with acute respiratory failure in 2016. Current indications in dogs include acute respiratory failure associated with pulmonary parenchymal disease, upper airway obstruction and carbon monoxide intoxication. The use of HFNOT has also been advocated in certain conditions in cats and foals. HFNOT is also being used with increasing frequency in the treatment of a widening range of conditions in humans. Although there remains conflict regarding its use and efficacy in some patient groups, overall these reports indicate that HFNOT decreases breathing frequency and work of breathing and reduces the need for escalation of respiratory support. In addition, they provide insight into potential future veterinary applications. Complications of HFNOT have been rarely reported in humans and animals. These are usually self-limiting and typically result in lower morbidity and mortality than those associated with invasive ventilation techniques.

Long-Term Domiciliary High-Flow Nasal Therapy in Patients with Bronchiectasis: A Preliminary Retrospective Observational Case-Control Study

High-flow nasal therapy (HFNT) provides several pathophysiological benefits in chronic respiratory disorders. We aimed to evaluate the effectiveness of long-term HFNT in patients with bronchiectasis (BE).

METHODS

This is a retrospective bicentric case-control study of outpatients with BE on optimized medical treatment with a severe exacerbation requiring hospitalization in the previous year. Patients on long-term home HFNT (cases) and patients on optimized medical treatment alone (controls) were matched by age, sex, bronchiectasis severity index, and exacerbations in the previous year. Data on BE exacerbations, hospitalizations/year, mucus features, respiratory symptoms, and pulmonary function were collected. The primary outcome was the change from baseline in the exacerbation rates at 12 months between groups.

RESULTS

20 patients in the HFNT group and 20 controls were included. A significant reduction in exacerbations [-1.9 (-2.8 to -0.9), p = 0.0005] and hospitalizations [-0.7 (-1.1 to -0.3), p = 0.0006] was found in the HFNT group vs controls. A slight improvement in pulmonary function [FEV₁% +6,1% (+1% to +11.3%) (p = 0.0219), FVC% +4.6% (+0.8% to +8.3%) (p = 0.0188) and FEF_25-75% +13.4 (+11 to +15.9) (p = 0.0189) was also found in the HFNT group compared to controls.

CONCLUSIONS

In this preliminary study, long-term domiciliary HFNT improved the clinical course of patients with BE.

High-flow nasal cannula oxygen therapy for admitted COPD-patients. A retrospective cohort study

BACKGROUND

The use of High-flow nasal cannula (HFNC) is increasing in admitted COPD-patients and could provide a step in between non-invasive ventilation (NIV) and standard oxygen supply. Recent studies demonstrated that HFNC is capable of facilitating secretion removal and reduce the work of breathing. Therefore, it might be of advantage in the treatment of acute exacerbations of COPD (AECOPD). No randomized trials have assessed this for admitted COPD-patients on a regular ward and only limited data from non-randomized studies is available.

OBJECTIVES

The aim of our study was to identify the reasons to initiate treatment with HFNC in a group of COPD-patients during an exacerbation, further identify those most likely to benefit from HFNC treatment and to find factors associated with treatment success on the pulmonary ward.

MATERIAL AND METHODS

This retrospective study included COPD-patients admitted to the pulmonary ward and treated with HFNC from April 2016 until April 2019. Only patients admitted with severe acute exacerbations were included. Patients who had an indication for NIV-treatment where treated with NIV and were included only if they subsequently needed HFNC, e.g. when they did not tolerate NIV. Known asthma patients were excluded.

RESULTS

A total of 173 patients were included. Stasis of sputum was the indication most reported to initiate HFNC-treatment. Treatment was well tolerated in 83% of the patients. Cardiac and vascular co-morbidities were significantly associated with a smaller chance of successful treatment (Respectively OR = 0.435; p = 0.013 and OR = 0.493;p = 0.035). Clinical assessment judged HFNC-treatment to be successful in 61% of the patients. Furthermore, in-hospital treatment with NIV was associated with a higher chance of HFNC failure afterwards (OR = 0.439; p = 0.045).

CONCLUSION

This large retrospective study showed that HFNC-treatment in patients with an AECOPD was initiated most often for sputum stasis as primary reason. Factors associated with improved outcomes of HFNC-treatment was the absence of vascular and/or cardiac co-morbidities and no need for in-hospital NIV-treatment.

High-Flow Nasal Cannula Oxygen Therapy: Physiological Mechanisms and Clinical Applications in Children

High-flow nasal cannula (HFNC) oxygen therapy has rapidly become a popular modality of respiratory support in pediatric care. This is undoubtedly due to its ease of use and safety, which allows it to be used in a wide variety of settings, ranging from pediatric intensive care to patients' homes. HFNC devices make it possible to regulate gas flow and temperature, as well as allowing some nebulized drugs to be administered, features very useful in children, in which the balance between therapeutic effectiveness and adherence to treatment is pivotal. Although the physiological effects of HFNC are still under investigation, their mechanisms of action include delivery of fixed concentration of oxygen, generation of positive end-expiratory pressure, reduction of the work of breathing and clearance of the nasopharyngeal dead space, while providing optimal gas conditioning. Nevertheless, current evidence supports the use of HFNC mainly in moderate-to-severe bronchiolitis, whereas for asthma exacerbations and breath sleeping disorders there is a lack of randomized controlled trials comparing HFNC to continuous positive airway pressure (CPAP) and non-invasive ventilation (NIV), which are essentials for the identification of response and non-response predictors. In this regard, the development of clinical guidelines for HFNC, including flow settings, indications, and contraindications is urgently needed.

High-flow nasal cannula in children with asthma exacerbation: A review of current evidence

Asthma is the commonest obstructive airway disease and the leading cause of morbidity in children. In the pediatric population, acute exacerbations of asthma are a frequent cause of presentations and hospital admissions. An acute asthma exacerbation is potentially life-threatening; it is predominantly treated using conventional oxygen therapy with bronchodilators and systemic corticosteroids. The treatment of those who do not respond to conventional therapy is escalated to noninvasive positive pressure ventilation (NIPPV) before invasive ventilation. Although NIPPV has demonstrated benefits and safety, it still has limitations such as treatment intolerance caused mainly by discomfort and complications. High-flow oxygen therapy administered through a nasal cannula (HFNC) provides respiratory support with adequate airway humidity and has demonstrated safety and benefits in clinical practice. In the present review, we discuss HFNC and variations in HFNC use, focusing on its feasibility and current evidence of using it on children with asthma exacerbations.

Safety and efficacy of high flow nasal cannula therapy in acute hypercapnic respiratory failure - a retrospective audit

BACKGROUND

While the role of high flow nasal cannulae (HFNC) in the management of respiratory failure continues to expand, few studies describe its use in acute hypercapnic respiratory failure.

AIMS

In this retrospective study we assessed the safety and efficacy of HFNC for treatment of acute hypercapnic respiratory failure.

METHODS

Admissions with acute hypercapnic respiratory failure to a thoracic medicine unit at a tertiary centre between January and August 2018 were included if treated with either HFNC or non-invasive ventilation (NIV). The primary outcome was post-treatment change in arterial pCO₂ . Demographics, comorbidities, length of stay, readmission rate and mortality were also collected.

RESULTS

64 patients were identified, comprising 69 presentations grouped according to initial treatment: HFNC (n=24) or NIV (n=45). Patients in the NIV group had more severe blood gas derangement. In both groups, mean arterial pCO₂ improved significantly (-10 (95% CI: -14 to -6) mmHg) from baseline with no evidence of a differential effect between groups. Six (25%) patients were transitioned from HFNC to NIV, of whom 3 had comorbid obesity and 2 had sleep disordered breathing. No significant differences in hospital length of stay, 30-day readmission rate or 90-day mortality were observed.

CONCLUSIONS

HFNC may be a reasonable initial treatment for patients with mild acute hypercapnic respiratory failure who do not have comorbid obesity or sleep disordered breathing. Prospective study may help identify clinical factors or phenotypes predictive of success with this treatment modality. This article is protected by copyright. All rights reserved.

Nasal high flow oxygen in acute respiratory failure

Thermo-humidified nasal high flow (NHF) oxygen therapy is increasingly used in the management of respiratory failure. This therapy has recently gained attention as an alternative non-invasive respiratory support in several clinical scenarios, including acute and chronic settings. NHF enhances the patient's comfort and tolerance when compared with standard oxygen by supplying a heated and humidified mixture of air and oxygen at flows up to 60L/min. It can be delivered through different devices. Although few studies have compared the clinical effects of different NHF systems, the purpose of this paper is to describe the major benefits of NHF and to provide a quick guide on how to implement this therapy in daily practice. We have also included a brief description of the most frequently used NHF systems.

High flow nasal therapy versus noninvasive ventilation as initial ventilatory strategy in COPD exacerbation: a multicenter non-inferiority randomized trial

Background

The efficacy and safety of high flow nasal therapy (HFNT) in patients with acute hypercapnic exacerbation of chronic obstructive pulmonary disease (AECOPD) are unclear. Our aim was to evaluate the short-term effect of HFNT versus NIV in patients with mild-to-moderate AECOPD, with the hypothesis that HFNT is non-inferior to NIV on CO₂ clearance after 2 h of treatment.

Methods

We performed a multicenter, non-inferiority randomized trial comparing HFNT and noninvasive ventilation (NIV) in nine centers in Italy. Patients were eligible if presented with mild-to-moderate AECOPD (arterial pH 7.25–7.35, PaCO₂ ≥ 55 mmHg before ventilator support). Primary endpoint was the mean difference of PaCO₂ from baseline to 2 h (non-inferiority margin 10 mmHg) in the per-protocol analysis. Main secondary endpoints were non-inferiority of HFNT to NIV in reducing PaCO₂ at 6 h in the per-protocol and intention-to-treat analysis and rate of treatment changes.

Results

Seventy-nine patients were analyzed (80 patients randomized). Mean differences for PaCO₂ reduction from baseline to 2 h were − 6.8 mmHg (± 8.7) in the HFNT and − 9.5 mmHg (± 8.5) in the NIV group (p = 0.404). By 6 h, 32% of patients (13 out of 40) in the HFNT group switched to NIV and one to invasive ventilation. HFNT was statistically non-inferior to NIV since the 95% confidence interval (CI) upper boundary of absolute difference in mean PaCO₂ reduction did not reach the non-inferiority margin of 10 mmHg (absolute difference 2.7 mmHg; 1-sided 95% CI 6.1; p = 0.0003). Both treatments had a significant effect on PaCO₂ reductions over time, and trends were similar between groups. Similar results were found in both per-protocol at 6 h and intention-to-treat analysis.

Conclusions

HFNT was statistically non-inferior to NIV as initial ventilatory support in decreasing PaCO₂ after 2 h of treatment in patients with mild-to-moderate AECOPD, considering a non-inferiority margin of 10 mmHg. However, 32% of patients receiving HFNT required NIV by 6 h. Further trials with superiority design should evaluate efficacy toward stronger patient-related outcomes and safety of HFNT in AECOPD.

Trial registration: The study was prospectively registered on December 12, 2017, in ClinicalTrials.gov (NCT03370666).

How to treat patients with acute respiratory failure? Conventional oxygen therapy versus high-flow nasal cannula in the emergency department

Objective:

To investigate whether high-flow nasal cannula oxygen therapy could reduce the rate of endotracheal intubation and improve arterial blood gas values, vital signs, and clinical outcomes of patients with hypoxemic acute respiratory failure as compared with conventional oxygen therapy alone.

Methods:

This retrospective, observational study was performed in the 15-month study period and included adult patients with tachypnea and hypoxemia, whose vital signs and arterial blood gas were monitored. The high-flow nasal cannula oxygen group consisted of patients admitted to the emergency department with acute respiratory failure when high-flow nasal cannula oxygen treatment was available in the hospital, while the conventional oxygen therapy group consisted of patients who have presented to the emergency department with acute respiratory failure in the absence of high-flow nasal cannula oxygen device in the hospital. The primary outcome of the study was improvement in vital signs and arterial blood gas values within first and fourth hours of the treatment. The second outcome was the need for intubation in the emergency department, length of hospital stay, and hospital mortality.

Results:

The decrease in the pulse and respiratory rate of high-flow nasal cannula oxygen–treated group was significantly greater than the conventional oxygen therapy group on the first and fourth hours of treatment (p < 0.001). PaO2 values were significantly higher in the high-flow nasal cannula oxygen group at the first and fourth hours of treatment (p ⩽ 0.001). Likewise, mean SaO2 levels of patients receiving high-flow nasal cannula oxygen treatment was significantly higher than those of patients in the conventional oxygen therapy group (p = 0.006 at 1 h and p < 0.001 at 4 h). In the hypercapnic patients, the decrease in PaCO2 and increase in pH and PaO2 values were significantly greater in high-flow nasal cannula oxygen group (p < 0.001). The difference between the groups regarding the need for invasive mechanical ventilation was not statistically significant (p = 0.179).

Conclusion:

High-flow nasal cannula oxygen treatment has been associated with favorable effects in vital signs and arterial blood gas values in patients with acute respiratory failure. High-flow nasal cannula oxygen might be considered as the first-line therapy for patients with hypoxemic and/or hypercapnic acute respiratory failure.

Animal models of emphysema

OBJECTIVE

Chronic obstructive pulmonary disease (COPD) is a common chronic respiratory disease of human beings characterized by not fully reversible airflow limitation. Emphysema is the main pathological feature of COPD which causes high mortality worldwide every year and consumes a large amount of medical expenses. This paper was to review the establishment and evaluation methods of animal models of emphysema or COPD, and put forward some new ideas on animal selection, method of modeling, and model evaluation.

DATA SOURCES

The author retrieved information from the PubMed database up to July 2019, using various combinations of search terms, including emphysema, model, and animal.

STUDY SELECTION

Original articles, reviews, and other articles were searched and reviewed for animal models of emphysema.

RESULTS

This review summarized animal models of emphysema from the perspectives of animal selection, emphysema mechanism, modeling method and model evaluation, and found that passive smoking is the classic method for developing animal model of emphysema, mice are more suitable for experimental study on emphysema. Compared with pulmonary function indicators, airway inflammation indicators and oxidative stress indicators, pathomorphological indicators of lung tissue are the most important parameters for evaluating the establishment of the animal model of emphysema.

CONCLUSIONS

Mice model induced by passive smoking is the classic animal model of emphysema. Pathomorphological indicators are the most important parameters for evaluating the establishment of the animal model of emphysema.

High flow nasal therapy in perioperative medicine: from operating room to general ward

BACKGROUND

High flow nasal therapy (HFNT) is a technique in which humidified and heated gas is delivered to the airways through the nose via small nasal prongs at flows that are higher than the rates generally applied during conventional oxygen therapy. The delivered high flow rates combine mixtures of air and oxygen and enable different inspired oxygen fractions ranging from 0.21 to 1. HFNT is increasingly used in critically ill adult patients, especially hypoxemic patients in different clinical settings.

MAIN BODY

Noninvasive ventilation delivers positive pressure (end-expiratory and inspiratory pressures or continuous positive airway pressure) via different external interfaces. In contrast, HFNT produces different physiological effects that are only partially linked to the generation of expiratory positive airway pressure. HFNT and noninvasive ventilation (NIV) are interesting non-invasive supports in perioperative medicine. HFNT exhibits some advantages compared to NIV because HFNT is easier to apply and requires a lower nursing workload. Tolerance of HFNT remains a matter of intense debate, and it may be related to selected parameters. Patients receiving HFNT and their respiratory patterns should be closely monitored to avoid delays in intubation despite correct oxygenation parameters.

CONCLUSION

HFNT seems to be an interesting noninvasive support in perioperative medicine. The present review provides anesthesiologists with an overview of current evidence and practical advice on the application of HFNT in perioperative medicine in adult patients.

Use of Nasal High Flow in Stable COPD: Rationale and Physiology

High-flow nasal cannula (HFNC) is a device able to deliver heated and humidified oxygen at high flows (up to 60 L/minutes). Potential benefits of HFNC are several and include the improvement of lung mucociliary clearance, the washout of upper airway dead space, the generation of a low level of positive airway pressure (PEEP effect), the decrease in inspiratory resistance and at the same time the increase in expiratory resistance. The present review aimed to describe the evidence surrounding the use of HFNC in stable chronic obstructive pulmonary disease patients.

Change in pulmonary mechanics and the effect on breathing pattern of high flow oxygen therapy in stable hypercapnic COPD

: We studied the effects of high flow oxygen therapy (HFOT) versus non-invasive ventilation (NIV) on inspiratory effort, as assessed by measuring transdiaphragmatic pressure, breathing pattern and gas exchange. Fourteen patients with hypercapnic COPD underwent five 30-min trials: HFOT at two flow rates, both with open and closed mouth, and NIV, applied in random order. After each trial standard oxygen therapy was reinstituted for 10 min. Compared with baseline, HFOT and NIV significantly improved breathing pattern, although to different extents, and reduced inspiratory effort; however, arterial carbon dioxide oxygen tension decreased but not significantly. These results indicate a possible role for HFOT in the long-term management of patients with stable hypercapnic COPD.

TRIAL REGISTRATION NUMBER

NCT02363920.

Respiratory mechanics and plasma levels of tumor necrosis factor alpha and interleukin 6 are affected by gas humidification during mechanical ventilation in dogs

The use of dry gases during mechanical ventilation has been associated with the risk of serious airway complications. The goal of the present study was to quantify the plasma levels of TNF-alpha and IL-6 and to determine the radiological, hemodynamic, gasometric, and microscopic changes in lung mechanics in dogs subjected to short-term mechanical ventilation with and without humidification of the inhaled gas. The experiment was conducted for 24 hours in 10 dogs divided into two groups: Group I (n = 5), mechanical ventilation with dry oxygen dispensation, and Group II (n = 5), mechanical ventilation with oxygen dispensation using a moisture chamber. Variance analysis was used. No changes in physiological, hemodynamic, or gasometric, and radiographic constants were observed. Plasma TNF-alpha levels increased in group I, reaching a maximum 24 hours after mechanical ventilation was initiated (ANOVA p = 0.77). This increase was correlated to changes in mechanical ventilation. Plasma IL-6 levels decreased at 12 hours and increased again towards the end of the study (ANOVA p>0.05). Both groups exhibited a decrease in lung compliance and functional residual capacity values, but this was more pronounced in group I. Pplat increased in group I (ANOVA p = 0.02). Inhalation of dry gas caused histological lesions in the entire respiratory tract, including pulmonary parenchyma, to a greater extent than humidified gas. Humidification of inspired gases can attenuate damage associated with mechanical ventilation.

CHRM2 but not CHRM1 or CHRM3 polymorphisms are associated with asthma susceptibility in Mexican patients

Asthma is a complex disease for which genetic predisposition has been widely documented. Considerable evidence supports the hypothesis that polymorphisms in the muscarinic-cholinergic (CHRM) genes could be involved in asthma pathogenesis, bronchial hyperresponsiveness, and mucus secretion. To determine whether single nucleotide polymorphisms (SNPs) or haplotypes in CHRM1, CHRM2, or CHRM3 are associated with asthma in Mexican pediatric population. We performed a case-control study including 398 pediatric cases with asthma and 450 healthy controls. We analyzed 19 SNPs distributed among these three genes. Two of the seven SNPs located in CHRM2, the 3' untranslated region rs8191992 and rs6962027, differed significantly in allele frequencies between patients with asthma and healthy controls [odds ratio (OR) 1.42, 95 % confidence interval (95 % CI) 1.14-1.77, P = 0.001, and OR 1.50, 95 % CI 1.21-1.87, P = 0.0002, respectively]. Statistical significance remained after multiple comparison corrections (P = 0.003 and P = 0.005, respectively). The haplotypes AA and TT, containing both major and minor alleles from rs8191992 and rs6962027, also differed between cases and controls. The haplotype AA occurred at a lower frequency in cases (OR 0.67, 95 % CI 0.53-0.85, P = 0.001) whereas the haplotype TT was overrepresented in cases compared to controls (28 vs 21 %, respectively; OR 1.46, 95 % CI 1.15-1.85, P = 0.002). No association was observed between CHRM1 or CHRM3 SNPs or haplotypes and asthma. CHRM2 polymorphisms are implicated in the genetic etiology of asthma.

Tiotropium bromide for chronic obstructive pulmonary disease

Tiotropium bromide is a long-acting, once-daily inhaled anticholinergic approved for the treatment of chronic obstructive pulmonary disease (COPD). Functional and kinetic selectivity for muscarinic (M) receptors, M(1) and M(3), in the lung permit sustained bronchodilation in moderate and severe COPD. Tiotropium is associated with increased lung function, health-related quality of life and exercise tolerance, and reduced dyspnea and acute exacerbations of COPD. It has been hypothesized that tiotropium may retard the accelerated decline in lung function associated with COPD, although a recent study does not support this notion. Tiotropium is safe and well-tolerated, with few side effects. Concerns about cardiovascular side effects and increased stroke risk have been alleviated by a recent, large, multicenter, prospective, randomized trial. Herein, we discuss the pharmacology, physiology and safety profile of tiotropium, as well as the clinical studies that have demonstrated its efficacy in COPD. Additional review of airway muscarinic receptor physiology and cholinergic pathobiology relevant to COPD and asthma provides context for future experimental and therapeutic roles for tiotropium.

The effects of gas humidification with high-flow nasal cannula on cultured human airway epithelial cells

Humidification of inspired gas is important for patients receiving respiratory support. High-flow nasal cannula (HFNC) effectively provides temperature and humidity-controlled gas to the airway. We hypothesized that various levels of gas humidification would have differential effects on airway epithelial monolayers. Calu-3 monolayers were placed in environmental chambers at 37°C with relative humidity (RH) < 20% (dry), 69% (noninterventional comparator), and >90% (HFNC) for 4 and 8 hours with 10 L/min of room air. At 4 and 8 hours, cell viability and transepithelial resistance measurements were performed, apical surface fluid was collected and assayed for indices of cell inflammation and function, and cells were harvested for histology (n = 6/condition). Transepithelial resistance and cell viability decreased over time (P < 0.001) between HFNC and dry groups (P < 0.001). Total protein secretion increased at 8 hours in the dry group (P < 0.001). Secretion of interleukin (IL)-6 and IL-8 in the dry group was greater than the other groups at 8 hours (P < 0.001). Histological analysis showed increasing injury over time for the dry group. These data demonstrate that exposure to low humidity results in reduced epithelial cell function and increased inflammation.

Muscarinic receptors on airway mesenchymal cells: novel findings for an ancient target

Since ancient times, anticholinergics have been used as a bronchodilator therapy for obstructive lung diseases. Targets of these drugs are G-protein-coupled muscarinic M(1), M(2) and M(3) receptors in the airways, which have long been recognized to regulate vagally-induced airway smooth muscle contraction and mucus secretion. However, recent studies have revealed that acetylcholine also exerts pro-inflammatory, pro-proliferative and pro-fibrotic actions in the airways, which may involve muscarinic receptor stimulation on mesenchymal, epithelial and inflammatory cells. Moreover, acetylcholine in the airways may not only be derived from vagal nerves, but also from non-neuronal cells, including epithelial and inflammatory cells. Airway smooth muscle cells seem to play a major role in the effects of acetylcholine on airway function. It has become apparent that these cells are multipotent cells that may reversibly adopt (hyper)contractile, proliferative and synthetic phenotypes, which are all under control of muscarinic receptors and differentially involved in bronchoconstriction, airway remodeling and inflammation. Cholinergic contractile tone is increased by airway inflammation associated with asthma and COPD, resulting from exaggerated acetylcholine release as well as increased expression of contraction related proteins in airway smooth muscle. Moreover, muscarinic receptor stimulation promotes proliferation of airway smooth muscle cells as well as fibroblasts, and regulates cytokine, chemokine and extracellular matrix production by these cells, which may contribute to airway smooth muscle growth, airway fibrosis and inflammation. In line, animal models of chronic allergic asthma and COPD have recently demonstrated that tiotropium may potently inhibit airway inflammation and remodeling. These observations indicate that muscarinic receptors have a much larger role in the pathophysiology of obstructive airway diseases than previously thought, which may have important therapeutic implications.

Pretreatment with inhaled procaterol improves symptoms of dyspnea and quality of life in patients with severe COPD

BACKGROUND

The clinical efficacy of short-acting β(2)-agonists administered before performing daily activities in chronic obstructive pulmonary disease (COPD) is unclear. The aim of this study was to investigate the clinical effect of supplementary inhaled procaterol hydrochloride in patients with COPD.

METHODS

Thirty outpatients with moderate to severe COPD (Stage II-IV) regularly using inhaled tiotropium bromide alone and with dyspnea during daily activities were enrolled. Subjects self-administered 20 μg of inhaled procaterol before daily activities no more than four times daily. Dyspnea symptom scores, St George's Respiratory Questionnaire (SGRQ) activity domains, impulse oscillometry system parameters, and pulmonary function tests were recorded at the beginning and end of the 2-week study.

RESULTS

At baseline, more than 80% of subjects reported dyspnea when walking up a slope (100.0%), climbing stairs (100.0%), gardening (93.3%), walking on flat ground (90.0%), bathing (86.7%), getting on a bus or train (83.3%), and changing clothes (80.0%). After 2 weeks, subjects with Stage III symptoms had significantly improved dyspnea scores on walking up a slope (P = 0.047), climbing stairs (P = 0.014), gardening (P = 0.034), walking on flat ground (P = 0.006), getting on a bus or train (P = 0.039), and changing clothes (P = 0.045). Both symptom and activity SGRQ domains improved significantly in subjects with Stage III symptoms (P = 0.036 and P = 0.028, respectively). Resistance of small airways and low-frequency reactance area values improved significantly in subjects with Stage III symptoms (P = 0.003 and P = 0.004, respectively). No significant changes were found in pulmonary function tests.

CONCLUSION

Use of supplementary inhaled procaterol before performing daily activities improved dyspnea symptoms in subjects with Stage III COPD.

Physiological differences and similarities in asthma and COPD--based on respiratory function testing

Physiological differences and similarities in asthma and COPD are documented based on respiratory function testing. (1) The airflow reversibility is usually important for the diagnosis of asthma. However, patients with long disease histories may have poor reversibility. The reversibility test in COPD is useful for predicting the treatment response. (2) In some of the stable asthmatic patients without attack, the concave downslope of flow-volume curve is present. In severe COPD, the flow in the second half of the curve is smaller than that of rest-breathing. (3) Inspiratory capacity (IC) is a good estimator of air trapping and of predicting the exercise capacity in COPD or persistent asthma. (4) Peak expiratory flow (PEF) can be an important aid in both diagnosis and monitoring of asthma. PEF is not used in COPD because the main disorder is in the peripheral airway. (5) Measurements of airway responsiveness may help to a diagnosis of asthma. However, many COPD cases also have it. (6) Impulse oscillation system (IOS) revealed that the predominant airway disorders in asthma and COPD are central and peripheral respiratory resistance, respectively. However, some asthma patients have larger values of peripheral component. (7) D(LCO) reflects the extent of pathological emphysema and it is useful for the follow-up of COPD, whereas D(LCO) is not decreased in asthma. (8) The patient with widened A-aDO(2) and alveolar hypoventilation may lead to the life threatening hypoxia in severe asthma attack or severe COPD. When PaCO(2) overcomes PaO(2), the patient should immediately be treated by mechanical ventilation.

Additional effects of pranlukast in salmeterol/fluticasone combination therapy for the asthmatic distal airway in a randomized crossover study

BACKGROUND

Salmeterol/fluticasone combination (SFC) therapy is used to control inflammation in the distal airway of patients with well-controlled asthma, but the efficacy of this approach is unclear.

OBJECTIVES

The goal of the study was to evaluate the effect of pranlukast, a leukotriene receptor antagonist (LTRA), on distal airway inflammation and pulmonary resistance in patients with asthma that was well-controlled using SFC therapy alone.

METHODS

The subjects were 32 patients with well-controlled asthma (age 61.1+/-17.8 years old, Step 3 in the GINA guidelines, Asthma Control Test score 23.2+/-1.8 points) based on use of SFC therapy alone for more than 3 months. These subjects were randomly assigned to groups receiving SFC alone or SFC+LTRA (pranlukast 450 mg daily) and then switched to the opposite group after 4 weeks in a crossover manner. Eosinophilic inflammation in induced sputum samples was assessed after each treatment period. Sputum was induced by inhalation of 10% hypertonic saline for 15 min. Impulse oscillometry parameters (R5, R20, X5 and AX) and spirometry were examined during each period. The Asthma-related Quality of Life Questionnaire (AQLQ) was also administered in each period.

RESULTS

The ECP levels in late-phase sputum were significantly higher than those in early-phase sputum with SFC therapy alone (178.3+/-166.0 vs. 65.5+/-68.9 microg/l, p<0.001), whereas these values did not differ significantly with SFC+LTRA treatment (70.9+/-95.1 vs. 54.6+/-65.7, p=0.554). ECP levels in late-phase sputum with SFC therapy were also significantly higher than those with SFC+LTRA (p=0.045). The values of R5, R20, R5-R20 (kPa/(L/s)), and AX (kPa/L) all significantly improved during with SFC+LTRA treatment compared with SFC alone (median (25-75 percentile)): 0.350 (0.283-0.440) vs. 0.340 (0.280-0.378), p=0.036; 0.280 (0.233-0.365) vs. 0.270 (0.240-0.318), p=0.019; 0.050 (0.030-0.110) vs. 0.500 (0.030-0.073), p=0.032; and 0.570 (0.308-1.045) vs. 0.410 (0.263-0.820), p=0.014; respectively. Pulmonary function indexes did not differ significantly between the two treatments, but the symptom and activity limitation domains of the AQLQ were significantly improved by SFC+LTRA treatment.

CONCLUSION

This study suggests that the combination of SFC and LTRA may give better control of residual eosinophilic inflammation in the distal airway compared with SFC therapy alone.

Research in high flow therapy: mechanisms of action

Recently, heater/humidifier devices that use novel methods to condition breathing gases from an external source have been introduced. The addition of sufficient warmth and high levels of humidification to breathing gas has allowed for higher flow rates from nasal cannula devices to be applied to patients (i.e., high flow therapy). This article provides a review of the proposed mechanisms behind the efficacy of high flow therapy via nasal cannula, which include washout of nasopharyngeal dead space, attenuation of the inspiratory resistance associated with the nasopharynx, improvement in conductance and pulmonary compliance, mild distending pressure and reduction in energy expenditure for gas conditioning.

Lung function changes following methacholine inhalation in COPD

BACKGROUND

The non-specific bronchial hyper-responsiveness reported in mild to moderate COPD is usually attributed to reduced airway calibre accentuating the effect of airway smooth muscle shortening. We hypothesized that in more severe COPD the fall in forced expiratory volume in 1 second (FEV(1)) seen during methacholine challenge would result from an increase in residual volume and decrease in vital capacity rather than an increase in airways resistance.

METHODS

Twenty-five subjects with moderate to severe COPD and 10 asthmatic subjects had spirometry and oscillatory mechanics measured before methacholine challenge and at a 20% fall from baseline post challenge (PC(20)FEV(1)).

RESULTS

In the COPD subjects median PC(20) was 0.35mg/mL. Comparing baseline to PC(20) there were significant falls in forced vital capacity (FVC) (2.91 vs. 2.2L; p<0.001), slow vital capacity (3.22 vs. 2.58L; p<0.001) and IC (2.21 vs. 1.75L; p<0.001) without change in FEV(1)/FVC ratio (0.52 vs. 0.52; not significant) or in total lung capacity where this was measured. Total respiratory system resistance (R(5)) was unchanged (0.66 vs. 0.68; not significant) but total respiratory system reactance decreased significantly (-0.33 vs. -0.44; p<0.001). In contrast, the asthmatics became more obstructed and showed a proportionally smaller fall in lung volume with increase in R(5) (0.43 vs. 0.64; p<0.01).

CONCLUSIONS

In moderate to severe COPD the fall in FEV(1) with methacholine is mainly due to increases in residual volume, which may represent airway closure and new-onset expiratory flow limitation.

Isocapnic cold air challenge in patients with COPD: are there any predisposing factors?

Cold air hyperventilation is an indirect challenge (cold air challenge, CACh) with high specificity and low sensitivity in defining asthmatic subjects. A small proportion of chronic obstructive pulmonary disease (COPD) patients present with positive CACh. The aim of this prospective study was to investigate the presence of factors related to cold air challenge (CACh) in COPD patients. Factors examined were FEV(1), FEV(1)/FVC, reversibility after bronchodilation, eosinophils in induced sputum, bronchial hyperresponsiveness to methacholine and the spirometric response to tiotropium compared to placebo. We studied 92 consecutive COPD patients in order to retrieve 15 CACh positive + patients. Fifteen COPD patients with negative CACh [CACh(-)], randomly selected from the initial group, were added in order to retrieve a group of 30 patients. Spearman's correlation coefficient was used in order to evaluate possible significant correlations between CACh values and study parameters. Sixteen percent of our subjects presented CACh+. CACh values were repeatable with an intraclass correlation coefficient between the two measurements 0.980 (95% CI 0.940-0.993). The only significant correlation observed was between Delta FEV(1) after CACh [Delta(C)FEV(1)] and trough FEV(1) values post tiotropium inhalation (r(2) = 0.62, p < 0.0001). When we analyzed the response to tiotropium in the 2 separate groups we found that patients with CACh+ presented significantly lower values of trough FEV(1) compared to those with CACh(-). In conclusion, a small proportion of COPD patients present with bronchial hyperresponsiveness to CACh. The only parameter related to CACh + in our study was a smaller bronchodilating effect of tiotropium.

Aspects on pathophysiological mechanisms in COPD

Chronic obstructive pulmonary disease (COPD) is a condition which is characterized by irreversible airway obstruction due to narrowing of small airways, bronchiolitis, and destruction of the lung parenchyma, emphysema. It is the fourth most common cause of mortality in the world and is expected to be the third most common cause of death by 2020. The main cause of COPD is smoking but other exposures may be of importance. Exposure leads to airway inflammation in which a variety of cells are involved. Besides neutrophil granulocytes, macrophages and lymphocytes, airway epithelial cells are also of particular importance in the inflammatory process and in the development of emphysema. Cell trafficking orchestrated by chemokines and other chamoattractants, the proteinase-antiproteinase system, oxidative stress and airway remodelling are central processes associated with the development of COPD. Recently systemic effects of COPD have attracted attention and the importance of systemic inflammation has been recognized. This seems to have direct therapeutic implications as treatment with inhaled glucocorticosteroids has been shown to influence mortality. The increasing body of knowledge regarding the inflammatory mechanism in COPD will most likely have implications for future therapy and new drugs, specifically aimed at interaction with the inflammatory processes, are currently being developed.

Placebo response in asthma: a robust and objective phenomenon

BACKGROUND

Placebos are hypothesized to exert positive effects on medical conditions by enhancing patient expectancies. Recent reviews suggest that placebo benefits are restricted to subjective responses, like pain, but might be ineffective for objective physiologic outcomes. Nevertheless, mind-body links and placebo responsivity in asthma are widely believed to exist.

OBJECTIVE

We carried out a randomized, double-blind investigation to (1) determine whether placebo can suppress airway hyperreactivity in asthmatic subjects, (2) quantify the placebo effect, (3) identify predictors of the placebo response, and (4) determine whether physician interventions modify the placebo response.

METHODS

In a double-blind, crossover design investigation, 55 subjects with mild intermittent and persistent asthma with stable airway hyperreactivity were randomized to placebo or salmeterol before serial methacholine challenges. Subjects were additionally randomized to physician interactions that communicated either positive or neutral expectancies regarding drug effect.

RESULTS

Placebo bronchodilator administration significantly reduced bronchial hyperreactivity compared with baseline (the calculated concentration of methacholine required to induce a 20% decrease in FEV(1) nearly doubled); 18% of subjects were placebo responders by using conservative definitions. Experimental manipulation of physician behavior altered perceptions of the physician but not the magnitude or frequency of the placebo response.

CONCLUSIONS

Objective placebo effects exist in asthma. These responses are of significant magnitude and likely to be meaningful clinically. The placebo response was not modulated by alterations in physician behavior in this study.

CLINICAL IMPLICATIONS

The placebo response in patients with asthma is important in understanding the limitations of clinical research studies and in maximizing safe and effective therapies. This article confirms the existence of a strong placebo response in an objective and clinically relevant measure of disease activity.

Muscarinic receptor signaling in the pathophysiology of asthma and COPD

Anticholinergics are widely used for the treatment of COPD, and to a lesser extent for asthma. Primarily used as bronchodilators, they reverse the action of vagally derived acetylcholine on airway smooth muscle contraction. Recent novel studies suggest that the effects of anticholinergics likely extend far beyond inducing bronchodilation, as the novel anticholinergic drug tiotropium bromide can effectively inhibit accelerated decline of lung function in COPD patients. Vagal tone is increased in airway inflammation associated with asthma and COPD; this results from exaggerated acetylcholine release and enhanced expression of downstream signaling components in airway smooth muscle. Vagally derived acetylcholine also regulates mucus production in the airways. A number of recent research papers also indicate that acetylcholine, acting through muscarinic receptors, may in part regulate pathological changes associated with airway remodeling. Muscarinic receptor signalling regulates airway smooth muscle thickening and differentiation, both in vitro and in vivo. Furthermore, acetylcholine and its synthesizing enzyme, choline acetyl transferase (ChAT), are ubiquitously expressed throughout the airways. Most notably epithelial cells and inflammatory cells generate acetylcholine, and express functional muscarinic receptors. Interestingly, recent work indicates the expression and function of muscarinic receptors on neutrophils is increased in COPD. Considering the potential broad role for endogenous acetylcholine in airway biology, this review summarizes established and novel aspects of muscarinic receptor signaling in relation to the pathophysiology and treatment of asthma and COPD.

Datura stramonium in asthma treatment and possible effects on prenatal development

Southern Africa has a variety of medicinal plants, used as remedies; however, little information is available regarding the cytotoxic potential, particularly when used during pregnancy. One such plant is Datura stramonium (DS) (Solanaceae), used frequently as an anti-asmatic treatment. DS contains a variety of alkaloids including atropine and scopolamine that can cause anticholinergic poisoning if taken in large doses. Atropine and scopolamine act on the muscarinic receptors by blocking them (particularly the M(2) receptors) on airway smooth muscle and submucosal gland cells. However, this will cause a continuous release in acetylcholine (Ach). Ach also act on nicotinic receptors; however, it is known that "over exposure" of nicotinic receptors may cause desensitization. We suggest that exposure of the foetus to DS when a mother uses it for asthma, will cause a continuous release of Ach, resulting in the desensitizing of nicotinic receptors, this could ultimately result in permanent damage to the foetus. Therefore we conclude that this African herbal remedy should be used with caution during pregnancy.

Lung Mechanics and Dyspnea during Exacerbations of Chronic Obstructive Pulmonary Disease

RATIONALE

Exacerbation of chronic obstructive pulmonary disease commonly causes hospitalization. The change in lung mechanics during exacerbation and its relationship to symptoms in spontaneously breathing individuals has not been described.

OBJECTIVE

We hypothesized that changes in both airflow and lung volumes would occur during an exacerbation, but that only volume change would relate to symptomatic improvement.

METHODS

Lung mechanics and resting dyspnea were recorded in 22 hospitalized patients during recovery from exacerbation.

MEASUREMENTS

Spirometry, inspiratory capacity, respiratory system resistance and reactance, tidal breathing patterns, and expiratory flow limitation were recorded after nebulized bronchodilator therapy on the first 3 d after admission, at discharge, and 6 wk postadmission (Day 42). Prebronchodilator measurements were taken on Day 2, at discharge, and on Day 42.

MAIN RESULTS

Postbronchodilator inspiratory capacity increased 0.23 +/- 0.07 L by discharge and 0.42 +/- 0.1 L by Day 42, FEV1 rose 0.09 +/- 0.04 and 0.2 +/- 0.05 L at discharge and Day 42, respectively, and FVC increased 0.21 +/- 0.08 and 0.47 +/- 0.09 L at discharge and Day 42 (all p < 0.05). Consistent reduction in dyspnea was seen as the exacerbation resolved. Respiratory system resistance, FEV1/FVC, and expiratory flow limitation were unchanged throughout, indicating that changes in lung volume rather than airflow resistance predominated.

CONCLUSIONS

Improvement in operating lung volumes is the principal change seen as a chronic obstructive pulmonary disease exacerbation resolves and increase in inspiratory capacity is a useful guide to a reduction in dyspnea.

Tiotropium: An inhaled anticholinergic for chronic obstructive pulmonary disease

PURPOSE

The pharmacology, pharmacokinetics, clinical efficacy, adverse effects, drug interactions, dosage and administration, and formulary considerations of tiotropium are discussed.

SUMMARY

Tiotropium, a long-acting inhaled anticholinergic, recently received approval from the Food and Drug Administration for the management of chronic obstructive pulmonary disease (COPD). In patients with COPD, increased parasympathetic nervous system activity leads to bronchoconstriction and mucus secretion. Tiotropium induces relaxation of the airway smooth muscle, as does ipratropium, but differs in receptor association and dissociation rates, allowing for once-daily administration. After inhalation, tiotropium reaches maximal plasma concentrations within five minutes, but clinical improvements in forced expiratory volume in one second (FEV(1)) are maintained over 24 hours. Clinical trials of tiotropium with placebo, ipratropium, and salmeterol have demonstrated the efficacy of tiotropium in improving FEV(1) and forced vital capacity values and health-related quality of life. The most commonly observed adverse effect is dry mouth. No increase in adverse effects was observed when tiotropium was administered concomitantly with other drugs for COPD, including sympathomimetic bronchodilators and oral and inhaled corticosteroids. The combination of tiotropium and other anticholinergics has not been studied and is not recommended. The recommended dosage of tiotropium is the inhalation of an 18-mug capsule with a HandiHaler breath-actuated inhalation device once daily.

CONCLUSION

Tiotropium appears to be at least as effective as currently available alternatives in the treatment of patients with COPD who require daily bronchodilator treatment. Its simplified dosing and tolerable adverse-effect profile can potentially lead to enhanced patient compliance.

Acetylcholine: a novel regulator of airway smooth muscle remodelling?

Increased airway smooth muscle mass is a pathological feature that asthma and chronic obstructive pulmonary disease (COPD) have in common. This increase has gained renewed interest in view of recent developments showing that airway smooth muscle, instead of solely being a contractile partner, is capable of interacting dynamically with its environment, especially under inflammatory conditions. Airway smooth muscle cells are able to proliferate, to migrate, and to secrete chemokines, cytokines, extracellular matrix proteins and growth factors, and most importantly, to adapt to these functions by changing its phenotype from contractile to proliferative/synthetic. Conversely, switching to a (hyper)contractile phenotype may also occur. A vast number of inflammatory stimuli regulate these functions and exert their effects via excitatory G(q) or G(i)-coupled receptors. Since acetylcholine activates muscarinic M(2) and M(3) receptors in the airway smooth muscle cell membrane, which are coupled to G(i) and G(q) proteins, respectively, and since acetylcholine release may be enhanced in airway inflammation, a pathophysiological role of acetylcholine related to the above processes and exceeding contraction could be envisaged. In this review, evidence in favour of this hypothesis, based on recent data that show a role for muscarinic receptors in modulating airway smooth muscle proliferation, contractility and contractile protein expression is discussed. Based on these findings, we postulate that endogenous acetylcholine contributes to airway remodeling in asthma and COPD.

The role of anticholinergics in chronic obstructive pulmonary disease

Anticholinergics are the bronchodilators of choice in the management of chronic obstructive pulmonary disease (COPD). They work by blocking muscarinic receptors in airway smooth muscle. Cholinergic tone appears to be the only reversible component of COPD. With the discovery of different muscarinic receptor subtypes, the development of more selective anticholinergics is possible. A major advance in this therapeutic area has been the discovery of tiotropium bromide, which has kinetic selectivity for M3 receptors as well as a duration of action of >24 hours. Once-daily administration of tiotropium is well tolerated and has shown significant advantages over ipratropium bromide, given 4 times daily, in the control of COPD.

The airway cholinergic system: physiology and pharmacology

The present review summarizes the current knowledge of the cholinergic systems in the airways with special emphasis on the role of acetylcholine both as neurotransmitter in ganglia and postganglionic parasympathetic nerves and as non-neuronal paracrine mediator. The different cholinoceptors, various nicotinic and muscarinic receptors, as well as their signalling mechanisms are presented. The complex ganglionic and prejunctional mechanisms controlling the release of acetylcholine are explained, and it is discussed whether changes in transmitter release could be involved in airway dysfunctions. The effects of acetylcholine on different target cells, smooth muscles, nerves, surface epithelial and secretory cells as well as mast cells are described in detail, including the receptor subtypes involved in signal transmission.

The Effects of High-Flow vs Low-Flow Oxygen on Exercise in Advanced Obstructive Airways Disease

STUDY OBJECTIVES

Current options to enhance exercise performance in patients with COPD are limited. This study compared the effects of high flows of humidified oxygen to conventional low-flow oxygen (LFO) delivery at rest and during exercise in patients with COPD.

DESIGN

Prospective, nonrandomized, nonblinded study.

SETTING

Outpatient exercise laboratory.

PATIENTS

Ten patients with COPD, stable with no exacerbation, and advanced airflow obstruction (age, 54 +/- 6 years; FEV(1), 23 +/- 6% predicted [mean +/- SD]).

INTERVENTIONS

After a period of rest and baseline recordings, patients were asked to exercise on a cycle ergometer for up to 12 min. Exercising was started on LFO first; after another period of rest, the patients repeated exercising using the high-flow oxygen (HFO) system, set at 20 L/min and matched to deliver the same fraction of inspired oxygen (Fio(2)) as that of LFO delivery.

MEASUREMENTS AND RESULTS

Work of breathing and ventilatory parameters (tidal volume, respiratory rate, inspiratory time fraction, rapid shallow breathing index, pressure-time product) were measured and obtained from a pulmonary mechanics monitor. Borg dyspnea scores, pulse oximetry, blood gases, vital signs were also recorded and compared between the two delivery modes. Patients were able to exercise longer on high flows (10.0 +/- 2.4 min vs 8.2 +/- 4.3 min) with less dyspnea, better breathing pattern, and lower arterial pressure compared to LFO delivery. In addition, oxygenation was higher while receiving HFO at rest and exercise despite the matching of Fio(2).

CONCLUSION

High flows of humidified oxygen improved exercise performance in patients with COPD and severe oxygen dependency, in part by enhancing oxygenation.

Treatment of stable chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a readily diagnosable disorder that responds to treatment. Smoking cessation can reduce symptoms and prevent progression of disease. Bronchodilator therapy is key in improvement of lung function. Three classes of bronchodilators-beta agonists, anticholinergics, and theophylline-are available and can be used individually or in combination. Inhaled glucocorticoids can also improve airflow and can be combined with bronchodilators. Inhaled glucocorticoids, in addition, might reduce exacerbation frequency and severity as might some bronchodilators. Effective use of pharmacotherapy in COPD needs integration with a rehabilitation programme and successful treatment of co-morbidities, including depression and anxiety. Treatment for stable COPD can improve the function and quality of life of many patients, could reduce admissions to hospital, and has been suggested to improve survival.

Therapeutic Update: Non-Selective Beta- and Alpha-Adrenergic Blockade in Patients With Coexistent Chronic Obstructive Pulmonary Disease and Chronic Heart Failure

Patients with chronic heart failure (CHF) have a resting restrictive ventilatory defect. Any type of exercise requires patients with CHF to markedly increase their minute ventilation. Patients with chronic obstructive pulmonary disease (COPD) have airflow obstruction that leads to dynamic lung hyperinflation and reduced ventilatory response to exercise. Because exercise is associated with abnormally high minute ventilation in patients with CHF and with a limited minute ventilation increase in patients with COPD, functional capacity is severely impaired in patients with coexistent CHF and COPD. Optimal treatment of both conditions is a prerequisite to maximally improve functional capacity in patients with CHF and COPD. Unfortunately, beta-adrenergic blockade, the current cornerstone of CHF therapy, is frequently omitted in patients with CHF and COPD for fear of inducing bronchoconstriction. Furthermore, when prescribed, beta-adrenergic blockade is often attempted with a moderate dose of metoprolol tartrate, a beta-1-blocker that results in lesser clinical benefits than combined non-selective beta-blockade with carvedilol at the maximally recommended dose. Recent experience indicates that combined non-selective beta- and alpha-blockade with carvedilol is well tolerated in patients with COPD who do not have reversible airway obstruction. Alpha-adrenergic blockade may promote mild bronchodilation that offsets non-selective beta blockade-induced bronchoconstriction in patients with obstructive airway disease.

Muscarinic acetylcholine receptors and airway diseases

Parasympathetic nerves provide the dominant autonomic innervation of the airways. Release of acetylcholine from parasympathetic nerves activates postjunctional muscarinic receptors present on airway smooth muscle, submucosal glands, and blood vessels to cause bronchoconstriction, mucus secretion, and vasodilatation, respectively. Acetylcholine also feeds back onto prejunctional muscarinic receptors to enhance or inhibit further acetylcholine release. In asthma and chronic obstructive pulmonary disease, bronchoconstriction and mucus secretion is increased and the airways are hyperresponsive to contractile agents. These changes are due to increased parasympathetic nerve activity. The number and function of postjunctional muscarinic receptors in the airways are unchanged in animal models of asthma. Rather, it is the supply of acetylcholine to the postjunctional cells (smooth muscle and submucosal gland) that is increased. The increase in acetylcholine release occurs because prejunctional, inhibitory M(2) muscarinic receptors on the parasympathetic nerves are dysfunctional. M(2) muscarinic receptor dysfunction and subsequent airway hyperreactivity have been demonstrated to occur in animals in response to a variety of triggers, including antigen challenge, virus infection, ozone exposure, and vitamin A deficiency. In humans, there is evidence that loss of M(2) muscarinic receptor function is related to asthma. The mechanisms by which neuronal M(2) muscarinic receptor function is lost and its relevance to human airway disease are discussed in this review.