Effects of nedocromil and salbutamol on airway reactivity in children with asthma

Beta₂-agonists for exercise-induced asthma

BACKGROUND

It is well known that physical exercise can trigger asthma symptoms and can induce bronchial obstruction in people without clinical asthma. International guidelines on asthma management recommend the use of beta2-agonists at any stage of the disease. At present, however, no consensus has been reached about the efficacy and safety of beta2-agonists in the pretreatment of exercise-induced asthma and exercise-induced bronchoconstriction. For the purpose of the present review, both of these conditions are referred to by the acronymous EIA, independently from the presence of an underlying chronic clinical disease.

OBJECTIVES

To assess the effects of inhaled short- and long-acting beta2-agonists, compared with placebo, in the pretreatment of children and adults with exercise-induced asthma (or exercise-induced bronchoconstriction).

SEARCH METHODS

Trials were identified by electronic searching of the Cochrane Airways Group Specialised Register of Trials and by handsearching of respiratory journals and meetings. Searches are current as of August 2013.

SELECTION CRITERIA

We included randomised, double-blind, placebo-controlled trials of any study design, published in full text, that assessed the effects of inhaled beta2-agonists on EIA in adults and children. We excluded studies that did not clearly state diagnostic criteria for EIA.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures as expected by The Cochrane Collaboration.

MAIN RESULTS

We included 53 trials consisting of 1139 participants. Forty-eight studies used a cross-over design, and five were performed in accordance with a parallel-group design. Forty-five studies addressed the effect of a single beta2-agonist administration, and eight focused on long-term treatment. We addressed these two different intervention regimens as different comparisons.Among primary outcomes for short-term administration, data on maximum fall in forced expiratory volume in 1 second (FEV1) showed a significant protective effect for both short-acting beta-agonists (SABA) and long-acting beta-agonists (LABA) compared with placebo, with a mean difference of -17.67% (95% confidence interval (CI) -19.51% to -15.84%, P = 0.00001, 799 participants from 72 studies). The subgroup analysis of studies performed in adults compared with those performed in children showed high heterogeneity confined to children, despite the comparable mean bronchoprotective effect.Secondary outcomes on other pulmonary function parameters confirmed a more positive and protective effect of beta2-agonists on EIA compared with placebo. Occurrence of side effects was not significantly different between beta2-agonists and placebo.Overall evaluation of the included long-term studies suggests a beta2-agonist bronchoprotective effect for the first dose of treatment. However, long-term use of both SABA and LABA induced the onset of tolerance and decreased the duration of drug effect, even after a short treatment period.

AUTHORS' CONCLUSIONS

Evidence of low to moderate quality shows that beta2-agonists, both SABA and LABA, when administered in a single dose, are effective and safe in preventing EIA.Long-term regular administration of inhaled beta2-agonists induces tolerance and lacks sufficient safety data. This finding appears to be of particular clinical relevance in view of the potential for prolonged regular use of beta2-agonists as monotherapy in the pretreatment of EIA, despite the warnings of drug agencies (FDA, EMA) regarding LABA.

Pathogenesis of exercise-induced bronchoconstriction

This article presents the various potential mechanisms responsible for the development of exercise-induced bronchoconstriction (EIB). Although the etiology of EIB is multifactorial, and the physiologic processes involved may vary between individuals (especially between those with and without asthma), drying of the small airways with an associated inflammatory response seems prerequisite for EIB. Dysregulated repair processes following exercise-induced airway epithelial injury may also serve as basis for EIB development/progression.

Exercise-induced bronchoconstriction in asthmatic children: a comparative systematic review of the available treatment options

The aim of this article is to critically review the efficacy and safety data from randomized controlled trials (RCTs) using inhaled corticosteroids (ICSs), long- or short-acting beta(2)-adrenoceptor agonists (LABAs, SABAs), parasympatholytics and oral leukotriene receptor antagonists in the management of exercise-induced bronchoconstriction (EIB) in children with persistent asthma (EIA). The studies with sufficient information on patient characteristics and outcomes were chosen using a MEDLINE search. Results from the individual searches were combined and repeated. Studies were also found by reviewing the reference lists of the articles not included in this review. Studies focusing solely on individuals with asthma and other allergic co-morbidities (i.e. a degree of bronchial reversibility) were considered in this review. To make the paper evidence-based, the design and the quality of different studies were assessed employing the Sign criteria (evidence level [EL] and grades of recommendation [GR]). No additional statistical analyses were performed. Most of studies included paediatric patients with underlying EIA. We need to distinguish children with recurrent asthma symptoms in whom EIB is also present (patients with EIA) from asthmatic subjects whose symptoms appear only as a result of exercise (patients with EIB). Further controller treatment is indicated in patients with EIA and further reliever treatment in patients with EIB. ICSs are the first-choice controller drugs for EIA in children with persistent asthma (Sign grade of recommendation [GR]:A). In children with EIA without complete control with ICSs, SABAs (GR:A), leukotriene receptor antagonists (LTRAs) [GR:A] or LABAs (GR:A) may be added to gain control. Treatment with relievers such as SABAs (GR:A), parasympatholytics (GR:B) or, eventually, LABAs (GR:A), administered 10-15 minutes before exercise is the most preferable method of preventing EIB symptoms in children; however, not as monotherapy in children with EIA. The disadvantages and controversy relating to inhaled beta(2)-adrenoceptor agonist use lie in the development of tolerance to their effect when they are used on a regular basis, and the possibility of a resulting underuse of ICSs in patients with EIA. Researchers and guidelines recommend that if any patient requires treatment with a beta(2)-adrenoceptor agonist more than twice weekly, a low dose of ICSs should be administered. Inhaled parasympatholytics may be effective as preventive relievers in some children with EIB or EIA, especially among those with increased vagal activity. LTRAs have a well balanced efficacy-safety profile in preventing the occurrence of EIB symptoms in children. Compared with LABAs, LTRAs produce persistent attenuation of EIB and possess an additional effect with rescue SABA therapy in persistent asthmatic patients with EIA. A disadvantage of LTRAs is a non-response phenomenon. There are still insufficient data on the efficacy-safety profiles of ICS/LABA combination drugs in the treatment of EIA in children to recommend this treatment without caution. Safety profiles of inhaled SABAs, anticholinergics and montelukast in approved dosages seem sufficient enough to recommend use of these drugs in the prevention of EIB symptoms in children. Many researchers agree that treatment of EIA in children should always be individualized.

Cold air-provoked respiratory symptoms: the mechanisms and management

OBJECTIVES

To describe the mechanisms and management of cold air-provoked respiratory symptoms.

STUDY DESIGN

A literature review.

METHODS

The review includes human epidemiological studies, human and animal experimental studies, as well as human studies about management of the cold air-provoked respiratory symptoms.

RESULTS

Cold air is unlikely to be a causal factor initiating respiratory diseases but a symptom trigger. In the present review, the airway responses beyond these symptoms were divided into three types. The short-term responses are those that develop within minutes in response to sudden cooling of the airways. Subjects with asthma or rhinitis are especially prone to these responses. The long-term responses are those that develop in response to repeated and long-standing cooling and drying of the airways, usually in endurance athletes. Finally, there are the physiological, reflex-mediated lower-airway responses to cooling of the skin or upper airways.

CONCLUSIONS

The mechanisms beyond cold air-provoked respiratory symptoms vary considerably and mainly depend on the individual's susceptibility and the ventilation level during the cold exposure. An understanding of these mechanisms is essential for successful management of the symptoms.

Beta2-agonists for asthma: the pediatric perspective

Inhaled beta-agonists are commonly prescribed for the treatment of wheezing disorders in infants and children. Despite this, there are concerns that these medications have potentially detrimental effects on lung health and symptoms. We will review the ontogeny of beta-agonist receptor and smooth muscle development from fetal life through infancy and childhood as well as the evidence supporting the clinical utility of beta-agonists in wheezing infants and asthmatic children. Finally, the potential detrimental effects of long- and short-acting beta-agonists in infants and children are discussed.

Effects of Different Ventilator Settings on Sleep and Inspiratory Effort in Patients with Neuromuscular Disease

Patients with neuromuscular disease (NMD) who require long-term ventilation normally have the ventilation set using empirical daytime parameters. We evaluated arterial blood gases (ABG), breathing pattern, respiratory muscle function, and sleep architecture during ventilation with two noninvasive Pressure Support Ventilation (nPSV) settings in nine patients with NMD. The two settings were randomly applied: the usual (US), with the nPSV setting titrated on simple clinical parameters, and the physiological (PHYS), tailored to the patient's respiratory effort. During wakefulness, nPSV significantly improved ABG and minute ventilation and reduced the diaphragmatic pressure-time product (PTPdi/breath), independently of the type of setting (PTPdi/breath spontaneous breathing 5.7 +/- 2.4, US 3.2 +/- 2, PHYS 3.6 +/- 1.6 cm H2O . seconds(-1), p < 0.001). However, during sleep, PHY nPSV resulted in a significant improvement of gas exchange, sleep efficiency (71.7% +/- 14 US vs. 80.6% +/- 8.3 PHYS, p < 0.01) and % of REM sleep (9.1% +/- 7 US vs. 17.3% +/- 5.4 PHYS, p < 0.01). This improvement was significantly correlated with the reduction in ineffective efforts. In NMD, nPSV is effective in improving daytime ABG and in unloading inspiratory muscles independently of whether it is set on the basis of the patient's comfort or the patient's respiratory mechanics. However, PHYS was associated with better sleep architecture and nighttime gas exchange.

Single-dose agents in the prevention of exercise-induced asthma: a descriptive review

Exercise-induced asthma (EIA) refers to the transient narrowing of the airways that occurs after vigorous exercise in 50-60% of patients with asthma. The need to condition the air inspired during exercise causes water to be lost from the airway surface, and this is thought to cause the release of inflammatory mediators (histamine, leukotrienes, and prostaglandins) from mast cells. EIA is associated with airway inflammation and its severity is markedly reduced following treatment with inhaled corticosteroids. Drugs that inhibit the release of mediators and drugs that inhibit their contractile effects are the most successful in inhibiting EIA. Single doses of short-acting beta(2)-adrenoceptor agonists, given as aerosols immediately before exercise, are very effective in the majority of patients with asthma, providing about 80% protection for up to 2 hours. Long-acting beta(2)-adrenoceptor agonists (LABAs) given in single doses can be effective for up to 12 hours when used intermittently, but tolerance to the protective effect occurs if they are taken daily. Drugs such as cromolyn sodium (sodium cromoglicate) and nedocromil given as aerosols are less effective than beta(2)-adrenoceptor agonists (beta(2)-agonists), providing 50-60% protection for only 1-2 hours, but they have some advantages. They do not induce tolerance, the aerosol dosage can be easily titrated for the individual, and the protective effect is immediate. Because they cause no significant adverse effects, multiple doses can be used in a day. Leukotriene receptor antagonists, such as montelukast and zafirlukast, are also used for the prevention of EIA and provide 50-60% protection for up to 24 hours when given as tablets. Tolerance to the protective effect does not develop with regular use. If breakthrough EIA occurs, a beta(2)-agonist can be used effectively for rescue medication. For those patients with more persistent symptoms, the use of a LABA in combination with an inhaled corticosteroid has raised a number of issues with respect to the choice of prophylactic treatment for EIA. The most important issue is the development of tolerance to the protective effect of a LABA such that extra treatment may be needed in the middle of a treatment period. Recommending extra doses of a beta(2)-agonist to control EIA is not advisable on the basis that multiple doses can enhance the severity of EIA, delay spontaneous recovery from bronchoconstriction, and enhance responses to other contractile stimuli. It is time to take into account the advantages and disadvantages of the different drugs available to prevent EIA and to recognize that there are some myths related to their use in EIA.