Asthma: Aetiologies, Symptoms, Aids to Diagnosis and Management Flashcards
What is obstructive airways disease?
Obstructive airways disease refers to conditions that cause narrowing of the large, medium-sized, and small airways (bronchi), leading to difficulties in breathing. Examples of obstructive airways diseases include asthma, COPD (chronic obstructive pulmonary disease), and bronchiectasis.
What are the consequences of obstructive airways disease?
Obstructive airways diseases result in air trapping and hyperinflation, making it harder for air to flow out of the lungs during expiration.
What is spirometry?
Spirometry is a common diagnostic test used to assess lung function. It measures the amount and speed of air that can be inhaled and exhaled.
How is obstructive airways disease diagnosed using spirometry?
In obstructive airways disease, spirometry typically shows a decreased forced expiratory volume in 1 second (FEV1), with a relatively preserved forced vital capacity (FVC). This leads to a decreased FEV1/FVC ratio, which is commonly defined as less than 70%.
FEV1 = Forced Expiratory Volume in 1 second.
FVC = Forced Vital Capacity.
How is asthma defined?
Asthma is a reversible, obstructive airways disease characterized by inflammation, hyper-responsiveness, and narrowing of the bronchial tree. It occurs in susceptible individuals due to various triggers.
What are the main characteristics of asthma?
Asthma is characterized by recurrent attacks of breathlessness and wheezing. The severity and frequency of these attacks can vary from person to person.
How is asthma diagnosed?
There are no consistent diagnostic criteria for asthma. Diagnosis is typically based on the presence of symptoms such as wheezing, breathlessness, chest tightness, and cough. Additionally, there is usually evidence of variable airflow obstruction.
What is the epidemiology of asthma?
In the UK, the mortality rate for asthma is around 4 per 100,000 individuals.
What is the etiology of asthma?
Asthma has a multifactorial etiology. It occurs when a genetically susceptible individual with atopy (a tendency to produce high amounts of Immunoglobulin E, IgE) is exposed to certain environmental factors. Atopy is often associated with a high prevalence of asthma, allergic rhinitis, urticaria, and eczema.
What is atopy?
Atopy refers to the tendency of individuals to produce high levels of IgE antibodies when exposed to small amounts of an antigen. Atopic individuals often demonstrate positive reactions to antigens on skin prick testing, indicating their sensitivity or allergy to specific allergens.
How can atopy be measured or demonstrated?
Atopy can be measured by detecting specific IgE antibodies to allergens in the serum. This can be done through blood tests. Additionally, skin prick testing can be used to demonstrate allergies to specific allergens by observing positive reactions on the skin.
What is the process of airway inflammation in asthma?
Airway inflammation in asthma involves the sensitization of atopic individuals followed by inhalation of allergens. It results in a two-phase response: an early reaction occurring within 20 minutes and a late reaction occurring 6-12 hours later. T-helper lymphocytes, particularly Th2 cells, regulate the inflammatory response by secreting pro-inflammatory interleukins and stimulating the release of IgE antibodies by plasma cells.
How do IgE antibodies contribute to the pathophysiology of asthma?
IgE antibodies bind to receptors on mast cells and eosinophils, triggering the release of histamine, prostaglandins, and cysteinyl leukotrienes. These mediators cause bronchoconstriction of the airways, which occurs within minutes of exposure to allergens. The targets of these mediators serve as therapeutic targets in asthma management.
What are the characteristics of the late phase response in asthma?
The late phase response in asthma involves the infiltration of the smooth muscle layer by various immune cells, desquamation of epithelial cells, mucus gland hyperplasia, hypertrophy and hyperplasia of airway smooth muscle, increased permeability of blood vessels, increased mucus production, mucus plugging, and acute inflammation resulting in edema. These processes contribute to airway narrowing and obstruction.
What are the consequences of chronic and severe asthma?
In chronic and severe asthma, there is remodeling of the airways with collagen deposition and fibrosis of the airway wall, leading to fixed narrowing. Eosinophils are associated with acute asthma, while neutrophils are associated with persistent airway inflammation and “steroid-dependent” asthma.
What are some environmental triggers for acute asthma?
Environmental triggers for acute asthma include animal dander, house dust mites (HDM), grass and tree pollen, mold, viral and bacterial infections, atmospheric pollution (such as ozone, sulfur dioxide, nitrogen oxide, fumes), thunderstorms, perfumes, hair sprays, plug-ins, cigarette smoking (active and passive), indoor fires, chlorine (from swimming pools or cleaning products), paints, and exposure to cold air or sudden changes in temperature.
Which drugs can trigger acute asthma?
Certain drugs can trigger acute asthma, including aspirin, non-steroidal anti-inflammatory drugs (NSAIDs), and beta-blockers. These medications may cause bronchoconstriction and worsen asthma symptoms in susceptible individuals.
What are some physiological triggers for acute asthma?
Physiological triggers for acute asthma include pregnancy, the premenstrual period, and exercise. These factors can lead to increased airway responsiveness and exacerbate asthma symptoms in susceptible individuals.
What is occupational asthma?
Occupational asthma refers to asthma that is triggered or worsened by exposure to specific substances or conditions in the workplace. Various occupational agents such as chemicals, dust, fumes, and allergens can induce or exacerbate asthma symptoms in susceptible individuals.
What are the symptoms of acute asthma during exacerbations?
During exacerbations of acute asthma, individuals may experience breathlessness, chest tightness, wheezing (a high-pitched whistling sound during breathing), and coughing. These symptoms can be distressing and indicate a worsening of asthma.
What are the symptoms of acute asthma between exacerbations?
Between exacerbations, individuals with asthma may experience periods of being completely well. They may also have mild chest tightness, occasional wheezing, or a dry cough. Some individuals may have cough-variant asthma, where cough is the predominant symptom.
Is there a diurnal variability of symptoms in acute asthma?
Yes, there is diurnal variability in asthma symptoms. Asthma symptoms tend to be worse at night and in the early morning. This pattern is linked to the body’s circadian rhythm, and individuals may experience increased bronchial constriction and inflammation during these times.
What signs may be present during an acute asthma exacerbation?
During an acute asthma exacerbation, clinical examination may reveal signs such as tachypnea (rapid breathing) and tachycardia (elevated heart rate). These signs indicate increased effort in breathing and the body’s response to reduced airway function.
What are the characteristic respiratory sounds in acute asthma exacerbation?
Acute asthma exacerbation is often accompanied by polyphonic wheezing, which is the presence of wheezing sounds during both inspiration and expiration. These wheezes are caused by the narrowing of the airways and the turbulent airflow passing through them.
What signs suggest hyperinflation in acute asthma?
In severe cases of acute asthma, signs of hyperinflation may be observed. These can include cyanosis (bluish discoloration of the skin and mucous membranes due to inadequate oxygenation), a silent chest (reduced breath sounds), and bradycardia (a slow heart rate). These signs indicate severe airway obstruction and compromised respiratory function.
What blood tests are commonly used in the investigation of suspected asthma?
In the investigation of suspected asthma, blood tests such as a full blood count may be performed. A raised eosinophil count is often observed in asthma, indicating the presence of eosinophilic inflammation. Additionally, tests measuring IgE levels, such as the radioallergosorbent test (RAST), may be conducted if a specific allergy is suspected.
What diagnostic tests can be used to assess lung function in asthma?
Several diagnostic tests are used to assess lung function in asthma. These include spirometry, which measures the volume and flow of air during forced breathing maneuvers. A full lung function test with reversibility to bronchodilator, such as salbutamol, can also be performed to determine the degree of airflow obstruction and assess the response to bronchodilator therapy. Methacholine or histamine provocation tests may be used to assess airway hyperresponsiveness, which is a characteristic feature of asthma.
What imaging tests may be conducted in the investigation of suspected asthma?
Imaging tests such as a chest X-ray (CXR) and high-resolution computed tomography (HRCT) may be conducted in the investigation of suspected asthma. CXR can help identify other respiratory conditions that may mimic asthma, while HRCT is useful for evaluating lung structure and assessing the presence of conditions like emphysema or bronchiectasis, which can coexist with asthma.
What other tests can be performed in the investigation of suspected asthma?
Other tests that can be performed in the investigation of suspected asthma include sputum analysis, which involves examining the sputum for microbiological factors and conducting a differential cell count. This helps identify any underlying infections or inflammation. Peak flow measurements and PEF (peak expiratory flow) homework, where the patient records their PEF measurements in the morning and evening for several weeks, can provide valuable information about diurnal variation and variability, which are characteristic features of asthma.
What spirometry results indicate airflow obstruction in asthma?
Spirometry is a commonly used test to assess lung function in asthma. The spirometry results that indicate airflow obstruction include reduced forced expiratory volume in 1 second (FEV1) and a decreased ratio of FEV1 to forced vital capacity (FVC), with an FEV1/FVC ratio less than 70%. These findings suggest the presence of airflow limitation and obstruction in the large and small airways.
How is reversibility to bronchodilator assessed in spirometry?
Reversibility to bronchodilator is assessed in spirometry by measuring the change in lung function after administering a bronchodilator medication, such as inhaled salbutamol. The criteria for reversibility include an increase in FEV1 by at least 15% of the baseline value or by more than 200 ml, measured 20 minutes after the administration of 200 mcg of inhaled salbutamol. Patients with asthma typically show significant reversibility, whereas patients with chronic obstructive pulmonary disease (COPD) show little to no reversibility.
What are the lung function test findings in asthma?
In asthma, lung function tests may reveal an increase in total lung capacity (TLC) and residual volume (RV) due to air trapping caused by the narrowing of the airways. However, the transfer factor or diffusing capacity (TLCO/DLCO) is usually normal in asthma, indicating that the ability of the lungs to transfer oxygen from inhaled air into the bloodstream is not significantly affected.
What is Fractional Exhaled Nitric Oxide (FeNO)?
Fractional Exhaled Nitric Oxide (FeNO) is a measure of airway eosinophilic inflammation, which is commonly associated with asthma. It is a non-invasive test that measures the level of nitric oxide in the breath. Elevated FeNO levels (> 40 ppb) are suggestive of airway inflammation and support the diagnosis of asthma. FeNO testing can be performed in both general practitioner (GP) offices and hospital clinics. It can also be used to monitor treatment response and assess compliance in asthma management.
What are the imaging options for asthma?
When imaging is required for asthma evaluation, two common options are available: chest X-ray (CXR) and high-resolution computed tomography (HRCT).
Chest X-ray (CXR):
CXR findings may be normal in mild asthma.
In more severe cases, CXR may show hyperinflation with increased lung volumes and flattened diaphragms.
Other CXR features may include the visualization of 6 anterior ribs or 10 posterior ribs in the mid-clavicular line and a more vertical and narrow heart.
High-resolution computed tomography (HRCT):
HRCT is more sensitive than CXR in detecting abnormalities in asthma.
It can show air trapping, which is a characteristic feature of asthma due to narrowed airways.
HRCT may also provide additional information about bronchial wall thickening, mucus plugging, and other structural changes in the airways.
What are some key strategies for managing asthma?
Avoiding allergens if possible, utilizing inhaled therapy, and considering oral therapy.
What are the aims of pharmacological management in asthma?
Achieving symptom control: minimal symptoms during day and night, minimal need for a reliever, and no limitation of physical activity.
Attaining the best possible pulmonary function: FEV1 or PEF > 80% predicted or best.
Preventing exacerbations.
Reducing morbidity and mortality.
Minimizing side effects.
How does the British Thoracic Society (BTS) provide guidelines for asthma management?
The BTS provides comprehensive guidelines that outline evidence-based recommendations for the management of asthma.
What does the management of acute exacerbation of asthma involve?
The management of acute exacerbation of asthma includes prompt assessment, administration of appropriate bronchodilators and corticosteroids, oxygen therapy if needed, and monitoring of respiratory function.
Which receptors are present in the bronchial mucosa?
β2-adrenoceptors are found in the smooth muscle of the airways from the trachea to the terminal bronchioles. Muscarinic cholinergic receptors also receive parasympathetic nerve supply
What are the routes of medication administration for the lungs?
Inhaled: Medications can be delivered through inhalers or nebulizers, allowing direct deposition into the lungs. The technique of inhalation is important for effective drug delivery.
Oral: Medications taken orally are absorbed in the gut. This route is not technique-dependent.
Intravenous: Medications administered intravenously have systemic effects throughout the body. This route is not technique-dependent but may have more side effects.
Intramuscular: Medications injected into the muscle tissue.
Subcutaneous: Medications injected beneath the skin.
How do inhalers and nebulizers contribute to drug deposition in the lungs?
Inhalers and nebulizers directly deposit the drug into the lungs, allowing for rapid absorption of the medication.