Asthma Symptoms and Triggers

• Asthma involves defining the condition and describing the nature of airflow obstruction.
• Outlining asthma's pathophysiology
• Describing major precipitating factors for asthmatic attacks
• Describing asthma symptoms, signs, and their pathophysiological basis
• Describing tests to assess suspected asthma patients and their interpretation
• Outlining treatment principles for asthma

Definition of Asthma

• Defined as a chronic inflammatory disorder of the airways in susceptible individuals.
• It is characterized by widespread but variable airflow obstruction.
• It is also characterized by increased airway responsiveness to various stimuli
• Obstruction is often reversible spontaneously or with treatment.

Epidemiology of Asthma

• Asthma prevalence is increasing
• Asthma is more common in the developed world
• There is an increase in populations moving from developing to developed countries
• 5.4 million people in the UK receive treatment.
• 1.1 million children less than 4.3 million adults
• Genetic risk is a factor
• Sensitization to airborne allergens is important
• Exposure to house dust mites
• Exposure to pollens
• Exposure to air pollution
• Exposure to tobacco smoke (pre and postnatal exposure, active)
• Hygiene hypothesis is relevant

Pathophysiology of Asthma:

• Asthma involves a chronic inflammatory process driven by Th2 cells
• Macrophages process and present antigens to T lymphocytes, activating T cells, especially TH2 cells
• TH2 cells release cytokines, attracting and activating inflammatory cells like mast cells and eosinophils.
• TH2 cells also activate B cells, leading to IgE production
• In sensitized atopic asthmatics, antigen exposure results in a 2-phase response
• An immediate response that reaches maximum in about 20 minutes
• Followed by a late phase response 3-12 hours later.

The Immediate Response

• The immediate response is an example of type 1 hypersensitivity
• It's caused by the interaction of allergens and specific IgE antibodies, leading to mast cell degranulation
• This response releases mediators, including histamine, tryptase, prostaglandin D2, and leukotriene.
• The result causes bronchial smooth muscle contraction leads to bronchoconstriction.

The Late Phase Response

• The late phase response is an example of type IV hypersensitivity
• It is complex and involves inflammatory cells: eosinophils, mast cells, lymphocytes, and neutrophils
• They release mediators and cytokines, which cause airway inflammation
• Eosinophils release Leukotriene C4 and other mediators, with some being toxic to epithelial cells, causing shedding.
• Eosinophils are very sensitive to steroid therapy.

Pathology of Airways

• Airway inflammation causes reduced airway calibre due to:
• Mucosal swelling (oedema) due to vascular leak
• Thickening of bronchial walls due to inflammatory cell infiltration
• Mucous overproduction; abnormal mucus is thick, tenacious, and slow-moving
• The cough is usually dry or productive with scanty, a white sputum but in severe cases, airways are occluded by mucus plugs
• Smooth muscle contraction
• Epithelium is shed and incorporated into the thick mucus

Long Term Considerations

• Long term, poorly controlled asthma can lead to airway remodeling, some of which may not be fully reversible
• Changes may include:
• Hypertrophy and hyperplasia of smooth muscle
• Hypertrophy of mucus glands
• Thickening of the basement membrane

Effect of Airways Narrowing

• Airways narrowing causes wheezing and other clinical features of asthma
• Results in an obstructive pattern on Spirometry with decreased FEV/FVC ratio less than 70%
• Flow-volume loops show reversibility with bronchodilators or over time
• Air trapping with increased residual volume occurs

Effect on Gas Exchange

• Airway narrowing reduces ventilation of affected alveoli, causing ventilation/perfusion mismatch in the affected area.
• Hyperventilation of better-ventilated areas can't compensate for hypoxia
• It can compensate for CO2 retention by increased breathing out of CO2

Asthma Severity

• In mild to moderate asthma, the picture is one of decreased pCO2 and decreased pO2 indicating type 1 respiratory failure
• In severe attacks, there is extensive airway involvement, resulting in rise in CO2
• Exhaustion limits respiratory effort
• Blood gas analysis reveals increased pCO2 and decreased pO2, demonstrating to type 2 respiratory failure
• Increased pCO2 signifies life-threatening asthma: the patient often requires assisted ventilation

Triggers of Asthma:

• Triggers include cold air, allergens, exercise, emotional distress, fumes, chemicals and drugs such as NSAID and beta blockers.
• Airway hyperresponsiveness means non-allergic stimuli can also trigger attacks.

Symptoms of Asthma:

• Wheezing, defined by a high pitched, expiratory sound
• Wheezing originates from the narrowed airways from compression or obstruction
• Wheezing in asthma has variable intensity and tone (polyphonic)
• A cough is a symptom
• Cough is often worse at night or induced by exercise
• Cough is usually a dry cough
• Breathlessness, especially with exercise
• Chest tightness
• Variable airflow obstruction are further symptoms

Examination:

• Inspection looking for abnormalities
• Chest examination looking for a normal chest, scars, deformities and hyper-expansion (barrel chest)
• General health
• Eczema, hay fever, lethargy.
• Ability to speak
• Room setting
• Meds and Charts
• Percussion
• Hyper-resonant
• Auscultation
• Polyphonic Wheeze

Assess the Condition

• Assess the condition if a patient suspected of asthma
• Spirometry – Flow Volume Loop
• There may be a low PEFR
• A low FEV1/FVC Ratio
• There is a >12% or 200 cc increase in FEV1 following salbutamol
• Allergy Testing
• Perform Skin prick to aero-allergens, e.g. cat, dog, HDM
• Check Blood IgE levels to specific aero-allergens
• Chest X-Rays
• This is performed to exclude other diseases, inhalation of foreign body, or pneumothorax

Treatment

• Patient education is important
• Educating patients to correctly recognize their symptoms
• Educating patients to use their medication timely
• Educating patients to use services appropriately
• Make a Personal Asthma Action Plan

Primary Prevention

• Stop smoking
• Maintain fresh air
• Reduce exposure to allergens and triggers
• Weight loss
• Vaccination

Pharmacological Treatment

• Drug treatment using the BTS: British Thoracic Society stepwise approach
• 3 classes of drugs are available
• Bronchodilators: to dilate the airways making them less symptomatic
• Anti-inflammatory: to suppress the inflammation
• Biological drugs: reduce dis. activity
• The forms of drugs either oral form, injection, inhaler or nebulizer

Acute Asthma Attacks

• Assess patients for features of acute severe asthma which requires immediate treatment and hospitalisation.
• Treatment includes:
• O2 treatment: high flow high concentration up to 100%
• Nebulized B2 agonists and ipratropium delivered in oxygen
• Intravenous steroids followed by a short course of high dose oral prednisolone
• Other drugs such as magnesium sulphate and aminophylline may need to be required
• Patients with life-threatening asthma require ITU management and may require ventilation

Explore asthma's severe symptoms, triggers like allergens and exercise, and characteristic signs such as wheezing. Understand the roles of inflammation, reduced airway calibre, and nocturnal cough in asthma. Spirometry findings confirming airflow obstruction are also discussed.