Complexity of chronic asthma and chronic obstructive pulmonary disease: implications for risk assessment, and disease progression and control

Although assessment of asthma control is important to guide treatment, it is difficult since the temporal pattern and risk of exacerbations are often unpredictable. In this Review, we summarise the classic methods to assess control with unidimensional and multidimensional approaches. Next, we show how ideas from the science of complexity can explain the seemingly unpredictable nature of bronchial asthma and emphysema, with implications for chronic obstructive pulmonary disease. We show that fluctuation analysis, a method used in statistical physics, can be used to gain insight into asthma as a dynamic disease of the respiratory system, viewed as a set of interacting subsystems (eg, inflammatory, immunological, and mechanical). The basis of the fluctuation analysis methods is the quantification of the long-term temporal history of lung function parameters. We summarise how this analysis can be used to assess the risk of future asthma episodes, with implications for asthma severity and control both in children and adults.

Increased airway smooth muscle mass in children with asthma, cystic fibrosis, and non-cystic fibrosis bronchiectasis

RATIONALE: Structural alterations to airway smooth muscle (ASM) are a feature of asthma and cystic fibrosis (CF) in adults. OBJECTIVES: We investigated whether increase in ASM mass is already present in children with chronic inflammatory lung disease. METHODS: Fiberoptic bronchoscopy was performed in 78 children (median age [IQR], 11.3 [8.5-13.8] yr): 24 with asthma, 27 with CF, 16 with non-CF bronchiectasis (BX), and 11 control children without lower respiratory tract disease. Endobronchial biopsy ASM content and myocyte number and size were quantified using stereology. MEASUREMENTS AND MAIN RESULTS: The median (IQR) volume fraction of subepithelial tissue occupied by ASM was increased in the children with asthma (0.27 [0.12-0.49]; P < 0.0001), CF (0.12 [0.06-0.21]; P < 0.01), and BX (0.16 [0.04-0.21]; P < 0.01) compared with control subjects (0.04 [0.02-0.05]). ASM content was related to bronchodilator responsiveness in the asthmatic group (r = 0.66, P < 0.01). Median (IQR) myocyte number (cells per mm(2) of reticular basement membrane) was 8,204 (5,270-11,749; P < 0.05) in children with asthma, 4,504 (2,838-8,962; not significant) in children with CF, 4,971 (3,476-10,057; not significant) in children with BX, and 1,944 (1,596-6,318) in control subjects. Mean (SD) myocyte size (mum(3)) was 3,344 (801; P < 0.01) in children with asthma, 3,264 (809; P < 0.01) in children with CF, 3,177 (873; P < 0.05) in children with BX, and 1,927 (386) in control subjects. In all disease groups, the volume fraction of ASM in subepithelial tissue was related to myocyte number (asthma: r = 0.84, P < 0.001; CF: r = 0.81, P < 0.01; BX: r = 0.95, P < 0.001), but not to myocyte size. CONCLUSIONS: Increases in ASM (both number and size) occur in children with chronic inflammatory lung diseases that include CF, asthma, and BX.

Eicosanoids in exhaled breath condensates in the assessment of childhood asthma

The value of measurements of eicosanoids in exhaled breath condensate (EBC) for the evaluation of childhood asthma is still inconclusive most likely because of the limited value of the methods used. In this case-control study in 48 asthmatic and 20 healthy children, we aimed to characterize the baseline profile of the inflammatory mediators cysteinyl leukotrienes (cysLTs), 9(alpha)11(beta)PGF(2), PGE(2), PGF(2alpha), 8-isoprostane (8-iso-PGF(2alpha)) within EBC in asthmatic compared with healthy children using new methods. In addition, we investigated their relation to other inflammatory markers. The assessment included collection of EBC, measurement of fractional exhaled nitric oxide (FE(NO)) and evaluation of urinary excretion of leukotriene E(4.) cysLTs were measured directly in EBC by radioimmunoassay and prostanoids were measured using gas chromatography negative-ion chemical ionization mass spectrometry. Only cysLT levels were significantly higher in asthmatic compared with healthy children (p = 0.002). No significant differences in cysLTs were found between steroid naïve and patients receiving inhaled corticosteroids. In contrast, FE(NO) was significantly higher in steroid naïve compared with steroid-treated asthmatic and healthy children (p = 0.04 and 0.024, respectively). The diagnostic accuracy of cysLTs in EBC for asthma was 73.6% for the whole group and 78.2% for steroid-naïve asthmatic children. The accuracy to classify asthmatic for FE(NO) was poor (62.9%) for the whole group, but improved to 79.9% when only steroid-naïve asthmatic children were taken into consideration. cysLTs in EBC is an inflammatory marker which distinguishes asthmatics, as a whole group, from healthy children.

Routine vaccination against pertussis and the risk of childhood asthma: a population-based cohort study

BACKGROUND: In industrialized countries vaccination coverage remains suboptimal, partly because of perception of an increased risk of asthma. Epidemiologic studies of the association between childhood vaccinations and asthma have provided conflicting results, possibly for methodologic reasons such as unreliable vaccination data, biased reporting, and reverse causation. A recent review stressed the need for additional, adequately controlled large-scale studies. OBJECTIVE: Our goal was to determine if routine childhood vaccination against pertussis was associated with subsequent development of childhood wheezing disorders and asthma in a large population-based cohort study. METHODS: In 6811 children from the general population born between 1993 and 1997 in Leicestershire, United Kingdom, respiratory symptom data from repeated questionnaire surveys up to 2003 were linked to independently collected vaccination data from the National Health Service database. We compared incident wheeze and asthma between children of different vaccination status (complete, partial, and no vaccination against pertussis) by computing hazard ratios. Analyses were based on 6048 children, 23 201 person-years of follow-up, and 2426 cases of new-onset wheeze. RESULTS: There was no evidence for an increased risk of wheeze or asthma in children vaccinated against pertussis compared with nonvaccinated children. Adjusted hazard ratios comparing fully and partially vaccinated with nonvaccinated children were close to one for both incident wheeze and asthma. CONCLUSION: This study provides no evidence of an association between vaccination against pertussis in infancy and an increased risk of later wheeze or asthma and does not support claims that vaccination against pertussis might significantly increase the risk of childhood asthma.

Allergic rhinitis in patients with asthma: the Swiss LARA (Link Allergic Rhinitis in Asthma) survey

OBJECTIVE: To determine the characteristics of asthma (A) and allergic rhinitis (AR) among asthma patients in primary care practice. RESEARCH DESIGN AND METHODS: Primary care physicians, pulmonologists, and allergologists were asked to recruit consecutive asthma patients with or without allergic rhinitis from their daily practice. Cross-sectional data on symptoms, severity, treatment and impact on quality of life of A and AR were recorded and examined using descriptive statistics. Patients with and without AR were then compared. RESULTS: 1244 asthma patients were included by 211 physicians. Asthma was controlled in 19%, partially controlled in 27% and not controlled in 54%. Asthma treatment was generally based on inhaled corticosteroids (ICS) with or without long acting beta 2 agonists (78%). A leukotriene receptor antagonist (LTRA) was used by 46% of the patients. Overall, 950 (76%) asthma patients had AR (A + AR) and 294 (24%) did not (A - AR). Compared to patients with A - AR, A + AR patients were generally younger (mean age +/- standard deviation: 42 +/- 16 vs. 50 +/- 19 years, p < 0.001) and fewer used ICS (75% vs. 88%, p < 0.001). LTRA usage was similar in both groups (46% vs. 48%). Asthma was uncontrolled in 53% of A + AR and 57% of A - AR patients. Allergic rhinitis was treated with a mean of 1.9 specific AR medications: antihistamines (77%), nasal steroids (66%) and/or vasoconstrictors (38%), and/or LTRA (42%). Rhinorrhoea, nasal obstruction, or nasal itching were the most frequently reported AR symptoms and the greatest reported degree of impairment was in daily activities/sports (55%). CONCLUSIONS: Allergic rhinitis was more common among younger asthma patients, increased the burden of symptoms and the need for additional medication but was associated with improved asthma control. However, most asthma patients remained suboptimally controlled regardl-ess of concomitant AR.

[Acute asthma attacks in childhood]

The diagnosis of an acute asthmatic attack in a child is made on a clinical basis. The severity of the exacerbation can be assessed by physical examination and measurement of the transcutaneous oxygenation saturation. A blood gas analysis can be helpful in this assessment. A child with a severe asthma exacerbation should be promptly referred to an emergency department of a hospital. Oxygen should be given to keep the oxygen saturation above 92% and short-acting, selective beta-2 agonists should be administered. Beta-2 agonists can be delivered by intermittent nebulization, continuous nebulization or by metered dose inhaler (MDI) with a spacer They can also be given intravenously in patients who are unresponsive to escalating therapy. The early administration of systemic corticosteroids is essential for the management of acute asthma in children. When tolerated, systemic corticoseroids can be given orally but inhaled corticosteroids are not recommended. Oxygen delivery, beta-2 agonists and steroid therapy are the mainstay of emergency treatment. Hypovolemia should be corrected either intravenously or orally. Administration of multiple doses of ipratropium bromide has been shown to decrease the hospitalization rate in children and adolescents with severe asthma. Clinical response to initial treatment is the main criterion for hospital admission. Patients with failure to respond to treatment should be transferred to an intensive care unit. A critical aspect of management of the acute asthma attack in a child is the prevention of similar attacks in the future.

Risk of severe asthma episodes predicted from fluctuation analysis of airway function

Asthma is an increasing health problem worldwide, but the long-term temporal pattern of clinical symptoms is not understood and predicting asthma episodes is not generally possible. We analyse the time series of peak expiratory flows, a standard measurement of airway function that has been assessed twice daily in a large asthmatic population during a long-term crossover clinical trial. Here we introduce an approach to predict the risk of worsening airflow obstruction by calculating the conditional probability that, given the current airway condition, a severe obstruction will occur within 30 days. We find that, compared with a placebo, a regular long-acting bronchodilator (salmeterol) that is widely used to improve asthma control decreases the risk of airway obstruction. Unexpectedly, however, a regular short-acting beta2-agonist bronchodilator (albuterol) increases this risk. Furthermore, we find that the time series of peak expiratory flows show long-range correlations that change significantly with disease severity, approaching a random process with increased variability in the most severe cases. Using a nonlinear stochastic model, we show that both the increased variability and the loss of correlations augment the risk of unstable airway function. The characterization of fluctuations in airway function provides a quantitative basis for objective risk prediction of asthma episodes and for evaluating the effectiveness of therapy.