Pathophysiology of Asthma: Causes, Effects, Prevalence and Risk Factors, Functional Diagnosis and Control

By | 23/02/2018
pathophysiology of asthma attack

Asthma is a complex inflammatory respiratory disease caused by many inflammatory cells and mediators. It refers to chronic inflammatory disease of the respiratory tract.

The pathogenesis of asthma involves various cells and mediators of inflammation, conditioned in part by genetic factors and with bronchial hyperresponsiveness and an entirely or partially reversible airflow obstruction, and either by a drug or spontaneous action.

It is a chronic and persistent inflammatory disease of the airways, involving several cell types such as mast cells, eosinophils and T lymphocytes.

This causes recurrent episodes of wheezing, dyspnoea, and cough, particularly at night and in the morning upon awakening.

Also, there is high variability in the time given mainly by environmental factors. From an anatomical and functional point of view, these could be:

  • Diffuse bronchial obstruction of variable intensity, which is at least partially reversible spontaneously or with the intervention of therapeutic measures.
  • Airway hyperreactivity to different stimuli (due to chronic inflammation)

In most cases, there is a family or personal history of atopic dermatitis, allergic rhinitis or family members with bronchial asthma, which suggests a significant component of genetic susceptibility associated with environmental factors that trigger the disease.

Epidemiologically, 20% of children are asthmatic and 5% of adults. The lethality is 0.03% per year, which is not negligible due to the prevalence of the disease.

Some classified asthma:

  • Pathologically, as multiple inflammatory effects, including bronchoconstriction and mucus hypersecretion caused due to thickening of airway due to inflammation and overdeveloped glands in the lungs.
  • Physiologically, as inflammatory cells and mediators that are a hindrance to the free flow of air through the respiratory tract.

Both environmental, as well as genetic factors, may influence inflammation causing asthma.

It is a chronic disease that may become fatal over the time. Hence, sufferers need proper diagnosis and treatment at the right time.

Causes of Asthma

There are many causes responsible for asthma and inflammation, broadly being environmental and genetic factors. Besides, there are other factors too.

  • Allergens found in the environment, foods or any other substance is likely to trigger inflammation and cause asthma.
  • Some medicines may act as a stimulus.
  • Family history or infection from birth.
  • Specific inflammatory cells such as mast cells, dendritic cell, and eosinophils among others.
  • Hormonal changes may also lead to such respiratory ailment.
  • A low immune system.
  • Psychological problems, anxiety, stress or depression, may also be one among the other submissive causes of asthma.

Effects

The inflammatory cells, genetic, environmental and other factors affect the respiratory tract acutely and might lead to immense destruction to not only the air passage but also the human being as a whole over the time.

However, proper treatment and regular checkup will help in stabilizing the problem to an adequate level.

The effects are quite chronic and result in complex and varied pathophysiological changes in the respiratory passage.

It may further, also, affect some neural mechanism under some extreme conditions.

Some of the pathophysiological effects of asthma are:

  • Bronchoconstriction
  • Mucus hypersecretion
  • Plasma Exudation
  • Vascular responses
  • Fibrosis
  • Structural changes in the air passage

Airway obstruction is due to a combination of factors that include:

  • Smooth airway muscle spasm
  • Edema of the mucosa of the airways
  • Increased mucus secretion
  • Cellular infiltration, especially by eosinophils, on the walls of the airways
  • Injury and desquamation of airway epithelium.

Prevalence and risk factors

The prevalence of wheezing in pre-school children is approximately 25% to 38%, but in most cases, wheezing is transient and is resolved over five years of age.

The ISAAC study (6) shows that, at a national level, the prevalence of asthmatic symptoms in children has remained constant over the past eight years.

In children aged 13-14 years (9.3% in 1993 and 9.2% in 2002); While it has experienced a significant increase in the 6-7 year group (6.2% in 1993 and 9.4% in 2003).

Geographically, there is also a considerable variability for Spain. Thus, it varies from 5.5% from Pamplona to 15.4% from Cadiz.

The EISL (International Study of Wheezing in Infants) study (7) determines the prevalence of recurrent wheeze and other related aspects during the first year of life.

The prevalence of recurrent wheezing during the first year of life varies by region, being higher in Latin America (21.4%) than in Europe (15.0%).

The percentage of severe episodes of recurrent wheezing was more than 60% in Latin Americans; While in Europe, this figure exceeds 40%. As for hospital admissions for recurrent wheezing, they are almost 30% in Latin America and around 15% in Europe.

Experts have identified many inflammatory mediators in the airway secretions of patients with asthma contribute to bronchoconstriction, mucus secretion, and microvascular hyperpermeability.

The latter, a standard component of inflammatory reactions, causes submucosal edema, increases airway resistance, and contributes to increased bronchial hyperreactivity.

Functional diagnosis

Spirometry.

The diagnosis of asthma is straightforward when wheezing is detected in the child and responds to bronchodilator treatment, but the diagnosis is often uncertain when we resort exclusively to symptoms.

In children of school age, a bronchodilation test, the study of variability in the PEF or a bronchial provocation test can be used to confirm the diagnosis.

Spirometry is a simple and readily available tool for assessing lung function. It is useful for the diagnosis and follow-up of asthma in children over six years.

Pulmonary function tests in children less than six years of age require at least passive patient co-operation, even if there is no coordination.

However, although these tests have value in clinical and epidemiological research, their importance in contributing to the clinical management of the child at these ages is at least uncertain.

Asthma control

There is considerable interest in controlling not only the clinical manifestations of asthma but also the inflammation and pathophysiology of the disease.

The goal of treatment should be to achieve and maintain control over extended periods of time.

Therefore, assessment of asthma control should include, not only control of clinical manifestations (such as diurnal or nocturnal symptoms, nocturnal awakening, maintenance of lung function, use of rescue medication, limitation of activity; Table XI).

It should also include the predicted future risk control of patients, such as exacerbations, accelerated decline in lung function and possible side effects of treatment.