The effect of age on bronchodilator responsiveness

A comparative analysis of the bronchodilatador response measured by impulse oscillometry and spirometry in asthmatic children living at high altitude

OBJECTIVE

Although the assessment of a bronchodilator response (BDR) is a routine and important procedure when performing lung function tests, comparisons between spirometric and oscillometric BDRs in asthmatic children living at high altitude have not been previously reported. The aim of the present study was to compare spirometric and oscillometric BDRs in children living at high altitude, and to identify independent predictors of spirometric and oscillometric BDRs.

METHODS

Between January and December, 2015, asthmatic children aged between 5 and 17 years old performed impulse oscillometry (IOS) and spirometry during the same visit before and after albuterol administration. The data were analyzed, and children were classified into those positive for oscillometric BDR only, those positive for spirometric BDR only, those positive for both BDRs, and those negative for both BDRs.

RESULTS

Ninety-three asthmatic children (56 boys, 37 girls), with a median (IQR) age of 11 (8-13) years, made up the study population. Among the total of 93 participants, 13 (14.0%), 4 (4.3%), 0 (0%), and 76 (81.7%) were positive for spirometric BDR only, positive for oscillometric BDR only, positive for both BDRs, and negative for both BDRs, respectively. Age and baseline lung function were identified as significant predictors of positive spirometric BDR.

CONCLUSIONS

The present study shows poor concordance between positive spirometric and oscillometric BDRs, with a greater proportion of patients with a spirometric BDR when compared to those with positive oscillometric BDR. Additionally, age and baseline lung function are useful for predicting spirometric BDR results.

Bronchodilator Dose Responsiveness in Children and Adolescents: Clinical Features and Association with Future Asthma Exacerbations

BACKGROUND

Bronchodilator reversibility measures are often associated with poor asthma outcomes in children. Whether bronchodilator dose responsiveness is similarly useful in children is unclear.

OBJECTIVE

We hypothesized that children and adolescents requiring higher doses of bronchodilator to achieve maximal bronchodilation would have unique risk factors and increased risk of future exacerbation.

METHODS

Children (6-11 years, N = 299) and adolescents (12-21 years, N = 331) with confirmed asthma underwent clinical phenotyping procedures and a test of maximal bronchodilation with escalating doses of albuterol sulfate up to 720 mcg. Outcome measures were assessed at 12 months and included exacerbations treated with systemic corticosteroids, emergency department (ED) visits, and hospitalizations for asthma.

RESULTS

A total of 6.7% of children and 9.3% of adolescents had poor bronchodilator dose responsiveness, defined as attainment of maximal forced expiratory volume in 1 second with 720 mcg albuterol. Risk factors included type 2 inflammation, prior exacerbations, and greater asthma severity; historical pneumonia and tobacco exposure were also risk factors in children. Children and adolescents with poor bronchodilator dose responsiveness did not have increased current symptoms or impaired quality of life, but had approximately 2-fold increased odds of exacerbation or ED visit and approximately 3-fold increased odds of hospitalization by 12 months, independent of airflow obstruction.

CONCLUSIONS

Bronchodilator dose responsiveness may be useful for phenotyping and may be of utility in practice and future studies focused on asthma outcomes or quantification of treatment responses. In children and adolescents, this phenotype of poor bronchodilator responsiveness may be associated with periods of relatively stable disease yet marked airway constriction in response to triggers, including tobacco smoke, respiratory infections/pneumonia, and aeroallergens.

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.

Population pharmacodynamic model of bronchodilator response to inhaled albuterol in children and adults with asthma

BACKGROUND

Because interpatient variability in bronchodilation from inhaled albuterol is large and clinically important, we characterized the albuterol dose/response relationship by pharmacodynamic modeling and quantified variability.

METHODS

Eighty-one patients with asthma (24% African American [AA]; 8 to 65 years old; baseline FEV1, 40 to 80% of predicted) received 180 microg of albuterol from a metered-dose inhaler (MDI), and then 90 microg every 15 min until maximum improvement or 540 microg was administered; all then received 2.5 mg of nebulized albuterol. FEV1 was measured 15 min after each dose. The population cumulative dose/response data were fitted with a sigmoid maximum effect of albuterol (Emax) [maximum percentage of predicted FEV1 effect] model by nonlinear mixed-effects modeling. The influence of covariates on maximum percentage of predicted FEV1 reached after albuterol administration (Rmax) and cumulative dose of albuterol required to bring about 50% of maximum effect of albuterol (ED50) and differences between AA and white patients were explored.

RESULTS

ED50 was 141 microg, and Emax was 24.0%. Coefficients of variation for ED50 and Emax were 40% and 56%, respectively. Ethnicity was a statistically significant covariate (p < 0.05). AA and white patients reached 82.4% and 91.9% of predicted FEV1, respectively (p = 0.0004); and absolute improvement in percentage of predicted FEV1 was 16.6% in AA patients vs 26.7% in white patients (p < 0.0003). There were no baseline characteristic differences between AA and white patients. Nebulized albuterol increased FEV1 > or = 200 mL in 21% of participants. Heart rate and BP were unchanged from baseline after maximal albuterol doses.

CONCLUSIONS

Our model predicts that 180 microg of albuterol by MDI produces a 14.4% increase in percentage of predicted FEV1 over baseline (11.7% in AA patients, and 17.5% in white patients). Emax varies widely between asthmatic patients. AA patients are less responsive to maximal doses of inhaled albuterol than white patients.

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.

Evaluation of bronchial hyperresponsiveness by monitoring of transcutaneous oxygen tension and arterial oxygen saturation during methacholine challenge in asthmatic children

BACKGROUND

Bronchial hyperresponsiveness (BHR) is a key feature of asthma, but the measurement of BHR is hampered by the fact that most tests of airway caliber are difficult to conduct at a young age. Methacholine-induced bronchoconstriction is associated with significant hypoxemia, which can be assessed noninvasively by transcutaneous oxygen pressure (tcPO2) and pulse oximetry. Evaluating BHR by monitoring tcPO2 instead of respiratory resistance (Rrs) has been used over a wide age range in childhood.

OBJECTIVE

To investigate whether there is a consistent relationship between changes in arterial oxygen saturation (SaO2) and respiratory resistance (Rrs) similar to the relationship between tcPO2 and Rrs during methacholine challenge in young children and to assess the usefulness of SaO2 as a parameter for the indirect measurement of BHR.

METHOD

We performed methacholine inhalation challenge by monitoring SaO2, tcPO2 and Rrs in 37 asthmatic children 5 to 7 years of age. Consecutive doses of methacholine were doubled until a 10% decrease in tcPO2 from the baseline was reached. We recorded the cumulative dose of methacholine (Dmin) at the inflection point of tcPO2 (Dmin-tcPO2), SaO2 (Dmin-SaO2), and Rrs(Dmin-Rrs).

RESULTS

The mean value of Dmin-Rrs was 4.27 +/- 2.02 units, the mean value of Dmin-tcPO2 was 4.48 +/- 2.01 units, and the mean value of Dmin-SaO2 was 4.57 +/- 0.20 units. Inhalation of increasing doses of methacholine raised Rrs curvilinearly and depressed tcPO2 and SaO2. There were no significant differences between any of the parameters. There were significant relationships between Dmin-tcPO2 and Dmin-Rrs (r = 0.914, p < 0.001) and between Dmin-SaO2 and Dmin-Rrs (r = 0.905, p < 0.001) and a relationship between Dmin-tcPO2 and Dmin-SaO2 (r = 0.949, p < 0.001).

CONCLUSION

We concluded that measurement of SaO2 and/or tcPO2 during methacholine inhalation challenge may be used to assess bronchial hyperresponsiveness. This study showed that both SaO2 and tcPO2 monitoring are safe, useful, and tolerable for use in children who are too young to cooperate with lung function tests.

Does bronchodilator responsiveness in infants with bronchiolitis depend on age?

OBJECTIVE

To assess the relation between age and bronchodilator responsiveness in infants with bronchiolitis.

STUDY DESIGN

In 41 infants (age, 2 to 18 months) with bronchiolitis, lung function was measured with the raised volume rapid thoracoabdominal compression technique before and after salbutamol inhalation. Lung function was quantified in terms of timed volumes (FEV(0.5), FEV(0.75), and FEV(1.0)). A significant change was defined as a postbronchodilator value that differed from baseline by more than twice the within-subject coefficient of variation.

RESULTS

For the group, postbronchodilator values did not differ significantly from baseline (DeltaFEV(0.5), 3.8% +/- 9.3%; DeltaFEV(0.75), 3.5% +/- 9.5%; and DeltaFEV(1.0), 4.0 +/- 9.8%). Eleven subjects showed significantly increased timed volumes; 3 presented with a decreased lung function; the remaining patients failed to show a significant change. The mean age of subjects with improved lung function did not differ significantly from the mean age of those with no or paradoxical responses (9.7 +/- 4.7 vs 8.1 +/- 4.1 months); there was no correlation of age with the size of the bronchodilator response.

CONCLUSIONS

The results of the current study indicate that bronchodilator responsiveness in infants with bronchiolitis is not age-dependent.

Current drug therapies: relievers and preventers

What we know: The different wheezing phenotypes in early childhood may influence the response to therapy. beta-Agonists are effective in acute asthma from the first year of life and anticholinergics have been shown to provide additional benefit from at least 18 months of age. Non-steroidal preventer medications provide some benefit in early childhood asthma, but response is variable and dependent on severity. Inhaled corticosteroids are the most effective preventer medication in children with persistent asthma, but have not been shown to be effective in children with episodic viral wheeze. There is no convincing evidence to suggest that inhaled corticosteroids influence long-term outcome in childhood asthma. What we need to know: Can we distinguish different wheezing phenotypes at presentation (using clinical features or other markers of airway inflammation or airway hyperresponsiveness) in order to target therapy? What are the relative benefits of reliever and preventer medications in treating different wheezing phenotypes, and do all wheezing phenotypes require treatment? What is the dose-response curve for inhaled corticosteroids in infants and young children with asthma? Are infants and young children more susceptible than older children to growth suppression or other side effects from inhaled corticosteroids? Can early treatment with inhaled corticosteroids or non-steroidal medications influence long-term outcome in terms of asthma development and/or loss of lung function?

Choices of therapy for exercise-induced asthma in children

Cough and wheezing interferes with sport and other forms of physical activity in half of asthmatic children. Airway obstruction can be induced by a standard exercise test in over 70% of children with asthma. A beta-adrenergic agonist or cromone taken by inhalation beforehand will usually inhibit bronchoconstriction provoked by a free running exercise test. The duration of protective effect with salbutamol, terbutaline and cromones is less than 4 h. The long acting beta-adrenergic agonists formoterol and salmeterol give protection against exercise-induced airway obstruction for up to 12 h, which implies that treatment given in the morning will offer protection from the effects of physical activity throughout the day. However, the duration of protective effect after a morning dose declines if these compounds are given regularly. Leukotriene receptor antagonists (LRAs) also provide good protection against exercise-induced asthma. Regular administration of LRAs is not associated with tolerance and loss of protective effect. The oral route makes for unobtrusive administration and this may help adherence to prescribed regimens.

Infant lung function, bronchial responsiveness and the development of asthma

Infants who wheeze are likely to have narrowed or overly compliant airways rather than atopy. After around 3 years of age, airway responsiveness and atopy are associated with the development of wheeze and the diagnosis of asthma. Anti- or proinflammatory genes are likely to be responsible for at least part of the predisposition to wheeze seen in older children, but further studies are needed to clarify this situation.

Forced expiratory maneuvers in children aged 3 to 5 years

There is no consensus about reproducibility and reliability of spirometry in young children. We evaluated forced expiratory maneuvers from 98 children aged 3 to 5 years with a variety of respiratory disorders before and after bronchodilator treatment. Forced vital capacity (FVC) and forced expiratory volume in 1 sec (FEV1) were analyzed for reproducibility by the American Thoracic Society criteria and for reliability based on the coefficient of variation (CV%). Over 90% of the patients cooperated, however, while 95% could exhale for at least 1 second, very few generated an FEV1 on all 6 "best" efforts. This clearly improved with age. Of all patients nearly 60% performed reproducible pre- and postbronchodilator sets of FVC but only 32% performed reproducible sets of FEV1. Based on the CV%, those patients who could reproducibly perform an FVC and FEV1 did it quite reliably (mean CV%, 9.38 and 7.01 for FVC and FEV1, respectively). We conclude that while some very young children can perform spirometry, reliability of performance cannot be assumed in this age group.