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

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This article is extracted from the LANCET and was published in September 2008. It deals with asthma and COPD (chronic obstructive pulmonary disease) and particularly about their risk assessment, their progression and their control. Two most common chronic respiratory diseases but their pathogenesis and their progression are not fully understood. We can notice that these two diseases are similar for many points that's another reason to study them together. A multidimensional approach with the analysis of several parameters seems to be necessary.

The acknowledgment of disease severity and control are very important because they form the basis of asthma treatment. To have an objective characterization of the lung function we use spirometry with measures of FEV1, FVC and especially FEV1/FVC ratio for children.
Risk is difficult to assess. Moreover it's not always associated with disease severity. Thus, we have to find some markers to predict exacerbations. Few new recent studies use the analysis of the lung function particularly bronchial hyper-reactivity which can guide the treatment. Other markers like fractional exhaled NO concentration are useful without forgetting environmental risk factors. So it seems that a multidimensional approach is necessary and in practice we use a probabilistic method based on the several interacting components of the lung web. With this novelty, we can have a comprehensive understanding of different asthma phenotypes for example.

Extraits

[...] So it seems that a multidimensional approach is necessary and in practice we use a probabilistic method based on the several interacting components of the lung web. With this novelty, we can have a comprehensive understanding of different asthma phenotypes for example. UNPREDICTABILITY OF DISEASE PROGRESSION But clinicians always have difficulties to predict exacerbations, fluctuations with time. It remains elusive. Moreover the problem is the possible crisis and relapses we often can observe. In fact, respiratory system seems to be very complex and we must consider all time-varying stimuli which interact in way non-linear with immunological, mechanical and inflammatory components. [...]

[...] For measures we use a function of the time scale τ and the long-range correlation exponent α (High value: stable system, low value: unpredictable lung function). Airway have a fractal organization embedded in elastic parenchyma. Fluctuations at different spatial scales are similar. Thus, it explains why forces at the microscopic scale can launch a cascade of events that propagate through macroscopically large proportions of the system and it's irreversible. So, we can, for example, approach the progression of emphysema with the distributions of mechanical forces in the parenchyma which induce destruction of the elastic fibre network of the lung with time. [...]

[...] In fact, there are some short-term effects but also some long-term effects like genetic parameters and memory effects too (inflammatory, immunological, mechanical and neuro-respiratory control). Thus, we can observe that symptoms fluctuate. Measures: To characterize lung function, we often use spirometry with indices like FEV1(forced expiratory volume in FVC(forced vital capacity), the FEV1/FEV ratio and PEF(peak expiratory flow). Main findings: Clinicians use a probabilistic approach to monitor and treat their patients. The main problem is the unpredictability of disease progression and the possible evolution in sudden steps both in asthma and COPD. [...]

[...] Its main interest: To explain research about two most common chronic respiratory diseases, asthma and chronic obstructive pulmonary disease; especially their progression, their control and the risk assessment which are not fully understood. And we can notice these two diseases are similar for many points that's why we study them together. Methods: First the classic method of assessment is presented: it's a reductionist approach based on the observation of frequency and intensity of symptoms to find the trigger which causes inflammation, bronchial hyper- reactivity and airway obstruction. [...]

[...] When they have a short-acting effect, they can induce instability and so increase the risk of exacerbations but when they're long-acting, they have a benefit effect on the evolution of disease. Conclusion: In short, we can present the 3 models of analysis of disease for monitoring exacerbations: classic model, multidimensional approach and finally the fluctuation analysis approach→figure6 So it seems necessary to consider the combination of several clinical and physiological parameters. Moreover, we mustn't forget importance of clinical experience. Patients' history provide interesting informations for the assessment of disease. [...]