Peak expiratory flow variability and exercise responsiveness in methacholine-hyperresponsive adolescents with asthma remission

Trend of Bronchial Hyperresponsiveness to Methacholine as a Cost Predictor of Mild-to-Moderate Asthma: A Twelve-Month Survey in Teenagers

Bronchial asthma is characterized by variable airflow obstruction, airway inflammation, and bronchial hyperresponsiveness (BHR) to non-specific stimuli. The role of underlying airway inflammation and of related long-lasting BHR has been suboptimally investigated in teenagers with mild-to-moderate asthma, as has the corresponding economic impact over time. The aim of the present study was to calculate the cost of mild-to-moderate atopic asthma in teenagers arising from their degree of persisting BHR over a twelve-month period.

METHODS

Patients aged 12-18 years with mild-to-moderate symptoms treated with fluticasone fumarate/vilanterol 92/22 mcg daily were retrospectively followed for 12 months. Usual spirometric parameters, BHR to methacholine (MCh), and resource consumption (visits, hospitalizations, systemic steroids and/or antibiotics courses, school days off) were assessed at recruitment (the index date) and after 6 and 12 months. Adherence to treatment was also calculated. The cost of asthma was calculated based on Italian tariffs and published papers. The trend over time in BHR and the association between response to MCh and total cost were investigated by using regression models adjusted for repeated measures.

RESULTS

106 teenagers (53 males, age 15.9 ± 1.6 years) were investigated. The annual cost of asthma proved significantly related to the BHR trend: every increment of a factor 10 in the response to MCh was associated with a saving of EUR 184.90 (95% CI -305.89 to -63.90). BHR was progressively optimized after 6 and 12 months in relation to the patients' compliance to treatment (≥70% of prescribed inhalation doses).

CONCLUSIONS

the usual spirometric parameters are largely insufficient to reflect the effects of underlying persistent inflammation in milder forms of asthma in teenagers. In terms of clinical governance, the periodic assessment of non-specific BHR is the appropriate procedure from this point of view. Non-specific BHR proves a reliable procedure for predicting and monitoring the economic impact of mild-to-moderate asthma in teenagers over time.

Complexity and emergent phenomena

Complex biological systems operate under non-equilibrium conditions and exhibit emergent properties associated with correlated spatial and temporal structures. These properties may be individually unpredictable, but tend to be governed by power-law probability distributions and/or correlation. This article reviews the concepts that are invoked in the treatment of complex systems through a wide range of respiratory-related examples. Following a brief historical overview, some of the tools to characterize structural variabilities and temporal fluctuations associated with complex systems are introduced. By invoking the concept of percolation, the notion of multiscale behavior and related modeling issues are discussed. Spatial complexity is then examined in the airway and parenchymal structures with implications for gas exchange followed by a short glimpse of complexity at the cellular and subcellular network levels. Variability and complexity in the time domain are then reviewed in relation to temporal fluctuations in airway function. Next, an attempt is given to link spatial and temporal complexities through examples of airway opening and lung tissue viscoelasticity. Specific examples of possible and more direct clinical implications are also offered through examples of optimal future treatment of fibrosis, exacerbation risk prediction in asthma, and a novel method in mechanical ventilation. Finally, the potential role of the science of complexity in the future of physiology, biology, and medicine is discussed.

Airway function, inflammation and regulatory T cell function in subjects in asthma remission

BACKGROUND

Factors associated with asthma remission need to be determined, particularly when remission occurs in adulthood.

OBJECTIVE

To evaluate airway responsiveness and inflammation in adult patients in asthma remission compared with adults with mild, persistent symptomatic asthma.

METHODS

Adenosine monophosphate and methacholine responsiveness were evaluated in 26 patients in complete remission of asthma, 16 patients in symptomatic remission of asthma, 29 mild asthmatic patients and 15 healthy controls. Blood sampling and induced sputum were also obtained to measure inflammatory parameters.

RESULTS

Perception of breathlessness at 20% fall in forced expiratory volume in 1 s was similar among groups. In subjects with symptomatic remission of asthma, responsiveness to adenosine monophosphate and methacholine was intermediate between mild asthma and complete asthma remission, with the latter group similar to controls. Asthma remission was associated with a shorter duration of disease. Blood immunoglobulin E levels were significantly increased in the asthma group, and blood eosinophils were significantly elevated in the complete asthma remission, symptomatic remission and asthma groups compared with controls. The suppressive function of regulatory T cells was lower in asthma and remission groups compared with controls.

CONCLUSION

A continuum of asthma remission was observed, with patients in complete asthma remission presenting features similar to controls, while patients in symptomatic asthma remission appeared to be in an intermediate state between complete asthma remission and symptomatic asthma. Remission was associated with a shorter disease duration. Despite remission of asthma, a decreased suppressor function of regulatory T cells was observed, which may predispose patients to future recurrence of the disease.

Prenatal arachidonic acid exposure and selected immune-related variables in childhood

Arachidonic acid (AA) is considered essential in fetal development and some of its metabolites are thought to be important mediators of the immune responses. Therefore, we studied whether prenatal exposure to AA is associated with some immune-related clinical conditions and plasma markers in childhood. In 280 children aged 7 years, atopy, lung function and plasma inflammation markers were measured and their relationships with early AA exposure were studied by linear and logistic regression analyses. AA exposure was deduced from AA concentrations in plasma phospholipids of the mothers collected at several time points during pregnancy and at delivery, and in umbilical cord plasma and arterial and venous wall phospholipids. In unadjusted regression analyses, significant positive associations were observed between maternal AA concentrations at 16 and 32 weeks of pregnancy (proxies for fetal AA exposure) and peak expiratory flow decline after maximal physical exercise and plasma fibrinogen concentrations of their children, respectively. However, after correction for relevant covariables, only trends remained. A significant negative relationship was observed between AA concentrations in cord plasma (reflecting prenatal AA exposure) and the average daily amplitude of peak expiratory flow at rest, which lost significance after appropriate adjustment. Because of these few, weak and inconsistent relationships, a major impact of early-life exposure to AA on atopy, lung function and selected plasma inflammation markers of children at 7 years of age seems unlikely.

Peak flow monitoring in clinical practice and clinical asthma trials

PURPOSE OF REVIEW

This review summarizes recent reports on peak expiratory flow (PEF) monitoring in clinical asthma trials and clinical practice.

RECENT FINDINGS

In clinical trials, summary measures such as average morning PEF provide only a fraction of the available information about asthma control and treatment response. New statistical models should improve the yield from PEF datasets. Improved criteria are needed for the diagnosis of exacerbations, and these may be developed from quality-control analysis of existing datasets. In clinical practice we must reduce the burden of monitoring and increase the ease of interpretation of PEF data. Electronic monitoring, with short message service or Internet communication, may assist with both. There is a need for standardized user-friendly PEF charts and simple statistically appropriate interpretative tools, which will facilitate the development of clinical algorithms and individualized written action plans. Normal values for diurnal variability should be updated to reflect twice daily monitoring.

SUMMARY

Current use of PEF data is limited by the burden of monitoring and the continuing use of interpretative tools that were originally developed for their practical feasibility rather than their clinical validity. Both of these problems may be improved by giving attention to methods for recording, displaying and analysing PEF data.