ASTHMA – Etiology, Risk Factors, Pathophysiology, Signs and Symptoms, Diagnostic Evaluations and Management
Asthma is a condition in which the airways become narrow and swell and produce extra mucus and characterized by airway hyper-responsiveness, hyperventilation and mucosal edema.
Exposure to various substances that trigger allergies and irritants can trigger signs and symptoms of asthma. Asthma triggers are different from person to person and can include
- Airborne allergens, such as pollen, animal dander, mold, cockroaches and dust mites
- Respiratory infections, such as the common cold
- Physical activity
- Cold air
- Air pollutants and irritants, such as smoke
- Certain medications, including beta blockers, aspirin, ibuprofen
- Strong emotions and stress
- Menstrual cycle in some women
A number of factors are thought to increase chances of developing asthma. These include:
- Having a blood relative (such as a parent or sibling) with asthma
- Having another allergic condition, such as atopic dermatitis or allergic rhinitis
- Exposure to second-hand smoke
- Mother who smoked while being pregnant
- Exposure to exhaust fumes or other types of pollution
- Exposure to occupational triggers, such as chemicals used in farming, hairdressing and manufacturing
It involves the following mechanism:
- Bronchoconstriction: in asthma, the dominant physiological event leading to clinical symptoms is airway narrowing and a subsequent interference with airflow. In acute exacerbations of asthma, bronchial smooth muscle contraction occurs quickly to narrow the airways in response to exposure to a variety of stimuli including allergens or irritants. Allergen-induced acute bronchoconstriction results from an IgE-dependent release of mediators from mast cells that includes histamine, tryptase, leukotrienes, and prostaglandins that directly contract airway smooth muscle. Aspirin and other nonsteroidal anti-inflammatory drugs can also cause acute airflow obstruction.
- Airway edema: as the disease becomes more persistent and inflammation more progressive, other factors further limits airflow. These include edema, inflammation, mucous hypersecretion and the formation of mucus plugs, as well as structural changes including hypertrophy and hyperplasia of the airway smooth muscle.
- Airway hyper-responsiveness: the mechanisms influencing airway hyper-responsiveness are multiple and include inflammation, dysfunctional neuroregulation, and structural changes.
- Airway remodeling: in some persons who have asthma, airflow limitation may be only partially reversible. Permanent structural changes can occur in the airway. These are associated with a progressive loss of lung function.
SIGNS AND SYMPTOMS
- Shortness of breath
- Chest tightness or pain
- Trouble sleeping caused by shortness of breath, coughing or wheezing
- A whistling or wheezing sound when exhaling
- Coughing or wheezing attacks
For some people, asthma symptoms flare up in certain situations:
- Exercise-induced asthma, which may be worse when the air is cold and dry
- Occupational asthma, triggered by workplace irritants, such as chemical fumes, gases or dust
- Allergy-induced asthma, triggered by particular allergens, such as pet dander, cockroacheso or pollen
- Spirometry: this test estimates the narrowing of bronchial tubes by checking how much air one can exhale after a deep breath
- Peak flow: a peak flow meter is a simple device that measures how hard you can breathe out. Lower than usual peak flow readings are a sign that lungs may not be working as well and that asthma may be getting worse.
- Methacholine challenge: methacholine is a known asthma trigger that, when inhaled, will cause mild constriction of airways. If a patient reacts to methacholine, then he/she is likely to have asthma.
- Imaging tests: a chest X-ray and high-resolution computerized tomography (CT) scan of lungs and nose cavities (sinuses) can identify any structural abnormalities of diseases that can cause or aggravate breathing problems.
- Allergy testing: this can be performed by skin test or blood test. Allergy tests can identify allergy to pets, dust, mold and pollen. If important allergy triggers are identified, this can lead to recommendation for allergen immunotherapy.
- Sputum eosinophils: this test looks for a certain white blood cells in the mixture of saliva and mucus discharge during coughing. Eosinophils are present when symptoms develop and become visible when stained with a rose-colored dye.
- Long-term asthma medications: types of long-term control medications
Inhaled corticosteroids: these anti-inflammatory drugs include fluticasone, budesonide, flunisolide, ciclesonide, beclomethasone and mometasone.
Leukotriene modifiers: these oral medications include montelukast and zileuton. These help relieve asthma symptoms for up to 24 hours
Long-acting beta agonists: these inhaled medications, which include salmeterol and formoterol, open the airways.
Theophylline: theophylline is a daily pill that helps keep the airways open by relaxing the muscles around the airways.
- Quick-relief (rescue) medications are used as needed for rapid, short-term symptom relief during an asthma attack – or before exercise. Types of quick-relief medications include:
Short-acting beta agonists: these inhaled, quick, relief bronchodilators act within minutes to rapidly ease symptoms during an asthma attack. They include albuterol, levalbuterol and pirbuterol. Short-acting beta agonists can be taken using a portable, hand-held inhaler or a nebulizer.
Ipratropium: like other bronchodilators, ipratropium acts quickly to immediately relax the airways, making it easier to breathe.
Oral and intravenous corticosteroids: these medications include prednisone and methylprednisolone, relieve airway inflammation caused by severe asthma.
- Allergy medications may help if asthma is triggered or worsened by allergies. These include:
Allergy shots (immunotherapy): allergy shots gradually reduce immune system reaction to specific allergens. Patient generally receives shots once a week for a few months, then once a month for a period of three to five years.
Omalizumab: this medication, given as an injection every two to four weeks, is specifically for people who have allergies and severe asthma. It acts by altering the immune system
Allergy medications: these include oral and nasal spray antihistamines and decongestants as well as corticosteroids and cromolyn nasal sprays.
- Use air conditioner: air conditioning reduces the amount of airborne pollen from trees, grasses and weeds that find its way indoors. Air conditioning also lowers indoor humidity and can reduce exposure to dust mites
- Decontaminate the décor: minimize dust that may worsen night-time symptoms by replacing certain items in the bedroom. For example, encase pillows, mattresses and box springs in dust proof covers. Remove carpeting and install hardwood or linoleum flooring. Use washable curtains and blinds.
- Maintain optimal humidity: dehumidify the room
- Prevent mold spores: clean damp areas in the bath, kitchen and around the house to keep mold spores from developing. Get rid of moldy leaves or damp firewood in the yard.
- Clean regularly: clean home at least once a week
- Cover nose and mouth: if asthma is worsened by cold or dry air, wearing a face mask can help.
- Ineffective Airway Clearance related to tracheobronchial obstruction
- Assess airway for patency by asking the patient to state his name
- Inspect the mouth, neck and position of trachea for potential obstruction
- Auscultate lungs for presence of normal or adventitious lung sounds
- Assess respiratory quality, rate, depth, effort and pattern
- Assess for mental status changes
- Assess changes in vital signs
- Monitor arterial blood gases (ABGs)
- Administer supplemental oxygen
- Position patient with head of bed at 45 degrees (if tolerated)
- Assist patient with coughing and deep breathing techniques (positioning, incentive spirometry, frequent position changes)
- Prepare for placement of endotracheal or surgical airway (i.e. cricothyroidectomy, tracheostomy)
- Confirm placement of the artificial airway
- Impaired Gas Exchange related to altered oxygen supply
- Assess respirations: quality, rate, pattern, depth and breathing effort
- Assess for life-threatening problems (i.e. respiratory arrest, flail chest, sucking chest wound)
- Auscultate lung sounds. Also assess for the presence of jugular vein distention (JVD) or tracheal deviation
- Assess for signs of hypoxemia
- Monitor vital signs
- Assess for changes in orientation and behavior
- Monitor ABGs
- Place a patient on continuous pulse oximetry
- Assess skin color for development of cyanosis, especially circumoral cyanosis
- Provide supplemental oxygen, via 100% O2 nonrebreather mask
- Prepare the patient for intubation