BRONCHIAL ASTHMA[Symptoms / Asthma Triggers / Pathogenesis / Confirmatory Pulmonary Function Tests / Risk Factors / Complications]


                       It is a disease characterized by recent attacks of breathlessness and wheezing, which vary in severity and frequency from person to person. Between the attacks, patient's breathing is normal. Worldwide, around 250,000 people die every year as a result of asthma.


Symptoms

     *Wheezing (a whistling sound arising from the lung during breathing)

     *Tightness in the chest

     *Shortness of breath

     *Trouble sleeping caused by shortness of breath, coughing or  wheezing

     *Coughing or wheezing attacks that are worsened by a respiratory virus, such as a cold or the flu.


Asthma Triggers

         Exposure to various irritants and substances that trigger allergies (allergens) can trigger signs and symptoms of asthma. Asthma triggers are different from person to person and can include:

     *Airborne substances, such as pollen, dust mites, mold spores, pet dander or particles of cockroach waste.

     *Respiratory infections, such as the common cold

     *Physical activity (exercise-induced asthma)

     *Cold air 

     *Air pollutants and irritants, such as smoke 


Pathogenesis

        The pathology of bronchial asthma consist of reversible bronchial narrowing associated with spasm of smooth muscle in the wall of airways (bronchi). The airway hyper-responsiveness is the fundamental disorder. The airway smooth muscle shows an exaggerated response to a variety of triggers such as seasonal outdoor allergens (pollen) or allergens derived from house dust, mites present in carpets, bets or domestic animals or cockroaches.

         There is a genetic predisposition to bronchial asthma. A substantial percentage of asthmatic patients have elevated IGL levels (a sign of allergic predisposition) and history of additional allergic disorders.

          Histological examination of small bronchi reveals epithelial damage, hypertrophy and hyperplasia of bronchial smooth muscle, enlargement of mucous glands, increased number of goblet cells and infiltration of bronchial wall with eosinophils and lymphocytes. The inflamed tissues respond to any of the triggers by release of mediators such as histamine and bradykinin by the mast cells and eosinophils in the bronchial mucous. These mediators produce bronchospasm and increased mucus secretion. The combined effect of bronchoconstriction and increased airways and increased airway resistance, especially during expiratory phase. During asthmatic attack, though breathing difficulty is felt during inspiratory phases, it becomes worse during expiratory phases of respiratory phases of respiratory cycles.

Histological changes in the bronchiole in bronchial asthma

Confirmatory Pulmonary Functions Tests

     *Forced vital capacity (FVC) is decreased

     *Forced expiratory volume 1st second / vital capacity ratio (FEV / FVC ratio) is decreased

     *Peak expiratory flow rate (PEFR) decreased.

     *Increase in FEV / VC ratio and PEFR when tested after inhalation of a bronchodilator drug


Risk Factors

     *Family history

     *Viral respiratory infections during infancy and childhood

     *Other allergies: Having an allergic condition, such as eczema or allergic rhinitis is a risk factor for developing asthma.

     *Smoking

     *Air pollution 

     *Obesity


Complications

Frequent attacks of bronchial asthma interfere with day-to-day life.

Acute severe asthma may progress to a life-threatening condition known as status asthmaticus.

COPD (emphysema) in later life


Pathophysiology basis of treatment: 

       An attack of bronchial asthma can be terminated by administration of a bronchodilator drug.

Decreased FEV1 / FVC ratio in obstructive lung disease