Bronchial Asthma 2020 PDF

Lung diseases (1) Airway diseases -- These diseases affect the airways that carry oxygen and other gases into and out of the lungs. They usually cause a narrowing or blockage of the airways. Airway diseases include asthma, chronic obstructive pulmonary disease (COPD), acute bronchitis and bronchie...

Lung diseases (1) Airway diseases -- These diseases affect the airways that carry oxygen and other gases into and out of the lungs. They usually cause a narrowing or blockage of the airways. Airway diseases include asthma, chronic obstructive pulmonary disease (COPD), acute bronchitis and bronchiectasis.  (2) Lung Diseases Affecting the Air Sacs (Alveoli): The airways eventually branch into tiny tubes (bronchioles) that dead-end into clusters of air sacs called alveoli. These air sacs make up most of the lung tissue. Lung diseases affecting the alveoli include: Pneumonia: An infection of the alveoli, usually by bacteria. Tuberculosis: A slowly progressive pneumonia caused by the bacteria Mycobacterium tuberculosis. Emphysema results from damage to the fragile connections between alveoli. Smoking is the usual cause. (Emphysema also limits airflow, affecting the airways as well.) Pulmonary edema: Fluid leaks out of the small blood vessels of the lung into the air sacs and the surrounding area. One form is caused by heart failure and back pressure in the lungs' blood vessels. Lung cancer has many forms, and may develop in any part of the lungs. Most often this is in the main part of the lung, in or near the air sacs. The type, location, and spread of lung cancer determines the treatment options. Acute respiratory distress syndrome (ARDS): Severe, sudden injury to the lungs caused by a serious illness. Life support with mechanical ventilation is usually needed to survive until the lungs recover. Pneumoconiosis: A category of conditions caused by the inhalation of a substance that injures the lungs. Examples include black lung disease from inhaled coal dust and asbestosis from inhaled asbestos dust.  (3) Lung Diseases Affecting the Interstitium The interstitium is the microscopically thin, delicate lining between the lungs' air sacs (alveoli). Tiny blood vessels run through the interstitium and allow gas exchange between the alveoli and the blood. Various lung diseases affect the interstitium: Interstitial lung disease (ILD): A broad collection of lung conditions affecting the interstitium. Sarcoidosis, idiopathic pulmonary fibrosis, and autoimmune disease are among the many types of ILD. Lung Diseases Affecting Blood Vessels (4) Lung circulation diseases -- These diseases affect the blood vessels in the lungs. They are caused by clotting, scarring, or inflammation of the blood vessels. They affect the ability of the lungs to take up oxygen and release carbon dioxide. These diseases may also affect heart function. An example of a lung circulation disease is pulmonary hypertension & pulmonary embolism.  Bronchial Asthma Bronchial asthma is a common chronic airway disease worldwide and affects approximately 26 million persons in the United States. It is the most common chronic disease in childhood, affecting an estimated 7 million children, and it is a common cause of hospitalization for children in the United States. Bronchial asthma A chronic inflammatory disorder of the airways. Many cells play a role, in particular mast cells, eosinophils, T- lymphocytes, neutrophils and epithelial cells. In susceptible individuals, this inflammation causes recurrent episodes of chest wheezing, breathlessness, chest tightness and cough. These episodes are usually associated with widespread but variable airflow obstruction that is often reversible either spontaneously or with treatment. This inflammation also, causes an associated increase in the existing bronchial hyperresponsiveness to a variety of stimuli. Pathophysiology of bronchial asthma The pathophysiology of asthma is complex and involves the following components: Airway inflammation Intermittent airflow obstruction Bronchial hyperresponsiveness Airway inflammation Some of the principal cells identified in airway inflammation include mast cells, eosinophils, epithelial cells, macrophages, and activated T lymphocytes. T lymphocytes play an important role in the regulation of airway inflammation through the release of numerous cytokines. Other constituent airway cells, such as fibroblasts, endothelial cells, and epithelial cells, contribute to the chronicity of the disease. Other factors, such as adhesion molecules (eg, selectins, integrins), are critical in directing the inflammatory changes in the airway. Finally, cell-derived mediators influence smooth muscle tone and produce structural changes and remodeling of the airway. Mast cells are increased in both the epithelium and surface secretions of asthmatics and can generate and release powerful mediators acting on smooth muscle and small blood vessels, such as histamine, tryptase, prostaglandin D2 (PGD2) and leukotriene C4 (LTC4), which cause immediate asthmatic reaction. Following the binding of allergen-specific IgE to the on mast cells , these cells activate and release effector mediators that directly cause bronchoconstriction, cellular infiltration, platelet activation, increased vascular permeability, mucosal edema and increased secretion of mucus. Besides, mast cells, other lung cells, including eosinophils, neutrophils and lymphocytes, play important roles in the immunopathogenesis of airways inflammation in asthma. Airflow obstruction Airflow obstruction can be caused by a variety of changes, including acute bronchoconstriction, airway edema, chronic mucous plug formation, and airway remodeling. Acute bronchoconstriction is the consequence of immunoglobulin E-dependent mediator release upon exposure to aeroallergens and is the primary component of the early asthmatic response. Airway edema occurs 6-24 hours following an allergen challenge and is referred to as the late asthmatic response. Chronic mucous plug formation consists of an exudate of serum proteins and cell debris that may take weeks to resolve. Airway remodeling is associated with structural changes due to long-standing inflammation and may profoundly affect the extent of reversibility of airway obstruction. Airway obstruction causes increased resistance to airflow and decreased expiratory flow rates. These changes lead to a decreased ability to expel air and may result in hyperinflation. The resulting over distention helps maintain airway patency, thereby improving expiratory flow; however, it also alters pulmonary mechanics and increases the work of breathing. Airway hyperresponsiveness Airway hyperresponsiveness or bronchial hyperreactivity in asthma is an exaggerated response to numerous exogenous and endogenous stimuli. The mechanisms involved include direct stimulation of airway smooth muscle and indirect stimulation by pharmacologically active substances from mediator-secreting cells such as mast cells or nonmyelinated sensory neurons. The degree of airway hyperresponsiveness generally correlates with the clinical severity of asthma.  Chronic inflammation of the airways is associated with increased bronchial hyper-responsiveness, which leads to bronchospasm and typical symptoms of wheezing, shortness of breath, and coughing after exposure to allergens, environmental irritants, viruses, cold air, or exercise. In some patients with chronic asthma, airflow limitation may be only partially reversible because of airway remodeling (hypertrophy and hyperplasia of smooth muscle, angiogenesis, and subepithelial fibrosis) that occurs with chronic untreated disease.  Airway narrowing in asthma result from combination of: - Smooth muscle spasm - Airway edema and inflammation - Mucus plugging Successful therapy depends upon each of these pathogenetic factor.  Classification of bronchial asthma 1...According to etiology Allergic or extrinsic asthma Non-allergic or intrinsic asthma Mixed forms 2...According to degree of severity Grade 1: Intermittent Grade 2: Persistent, mild Grade 3: Persistent, moderate Grade 4: Persistent, severe Types of Bronchial Asthma Types of bronchial asthma Child-Onset Asthma Asthma that begins during childhood is called child-onset asthma. This type of asthma happens because a child becomes sensitized to common allergens in the environment - most likely due to genetic reasons. The child is atopic - a genetically determined state of hypersensitivity to environmental allergens. Allergens are any substances that the body will treat as a foreign body, triggering an immune response. These vary widely between individuals and often include animal proteins, fungi, pollen, house- dust mites and some kind of dust. The airway cells are sensitive to particular materials making an asthmatic response more likely if the child is exposed to a certain amount of an allergen. Adult-Onset Asthma This term is used when a person develops asthma after reaching 20 years of age. Adult-onset asthma affects women more than men, and it is also much less common than child-onset asthma. It can also be triggered by some allergic material or an allergy. It is estimated that up to perhaps 50% of adult-onset asthmas are linked to allergies. However, a substantial proportion of adult-onset asthma does not seem to be triggered by exposure to allergen(s); this is called non-allergic adult-onset asthma. This non-allergic type of adult onset asthma is also known as intrinsic asthma. Exposure to a particle or chemical in certain plastics, metals, medications, or wood dust can also be a cause of adult-onset asthma.  Exercise-induced asthma If patients cough, wheeze and dyspnea during or after exercise, patients could be suffering from exercise-induced asthma. Obviously, your level of fitness is also a factor - a person who is unfit and runs fast for ten minutes is going to be out of breath. However, if your coughing, wheezing or panting does not make sense, this could be an indication of exercise-induced asthma. As with other types of asthma, a person with exercise-induced asthma will experience difficulty in getting air in and out of the lungs because of inflammation of the bronchial tubes (airways) and extra mucus. Some people only experience asthma symptoms during physical exertion. The good news is that with proper treatment, a person who suffers from exercise- induced asthma does not have to limit his/her athletic goals. With proper asthma management, one can exercise as much as desired Eighty percent of people with other types of asthma may have symptoms during exercise, but many people with exercise-induced asthma never have symptoms while they are not physically exerting themselves. Cough-Induced Asthma Cough-induced asthma is one of the most difficult asthmas to diagnose. The doctor has to eliminate other possibilities, such as chronic bronchitis, post nasal drip due to hay fever, or sinus disease. In this case the coughing can occur alone, without other asthma-type symptoms being present. The coughing can happen at any time of day or night. If it happens at night it can disrupt sleep. Occupational Asthma This type of asthma is triggered by something in the patient's place of work. Factors such as chemicals, vapors, gases, smoke, dust, fumes, or other particles can trigger asthma. It can also be caused by a virus (flu), molds, animal products, pollen, humidity and temperature. Another trigger may be stress. Occupational asthma tends to occur soon after the patients starts a new job and disappears not long after leaving that job. Nocturnal Asthma Nocturnal asthma occurs between midnight and 8 AM. It is triggered by allergens in the home such as dust and pet dander or is caused by sinus conditions. Nocturnal or nighttime asthma may occur without any daytime symptoms recognized by the patient. The patient may have wheezing or short breath when lying down and may not notice these symptoms until awoken by them in the middle of the night - usually between 2 and 4 AM. Nocturnal asthma may occur only once in a while or frequently during the week. Nighttime symptoms may also be a common problem in those with daytime asthma as well. However, when there are no daytime symptoms to suggest asthma is an underlying cause of the nighttime cough, this type of asthma will be more difficult to recognize - usually delaying proper therapy. The causes of this phenomenon are unknown, although many possibilities are under investigation. Symptoms Symptoms of bronchial asthma are: - Cough - Chest wheeze - Chest tightness - Shortness of breath (dyspnea). Bronchial Asthma Triggers Common asthma triggers include: Animals (pet hair or dander) Dust mites Certain medicines (aspirin and other NSAIDS) Changes in weather (most often cold weather) Chemicals in the air or in food Exercise Mold Pollen Respiratory infections, such as the common cold Strong emotions (stress) Tobacco smoke Many people with asthma have a personal or family history of allergies, such as hay fever (allergic rhinitis) or eczema. Others have no history of allergies. Investigations There is no single satisfactory diagnostic test for all asthmatic patients. Blood and sputum tests Patients with asthma may have an increased in the number of eosinophils in peripheral blood. The presence of large number of eosinophils in the sputum is more useful diagnostic tools. Chest x-ray There is no diagnostic feature of asthma on the chest x-ray, although during an acute episodes or in chronic severe disease overinflation is characteristic. Chest x- ray may be helpful in excluding other associated conditions. Skin–prick tests may help to identify allergens. Spirometry is important for diagnosis (obstructive defect). Treatment Asthma is treated with two types of medicines: long-term control and quick-relief medicines. Long-term control medicines help reduce airway inflammation and prevent asthma symptoms. Quick-relief, or "rescue," medicines relieve asthma symptoms that may flare up. Treatment - Stop smoking and avoid precipitants. - Bronchodilators - anti-inflammatory drugs e.g corticosteroids