Asthma flash card
What is a bronchospasm?
A sudden constriction of the muscles in the walls of the bronchi
What controls the diameter of the airways?
the smooth muscles surrounding the bronchioles
What are the 2 main types of asthma?
Intrinsic and extrinsic
What is intrinsic asthma
Not triggered by external allergens, usually occurs in adulthood, arises from internal factors e.g infection, exercise
What are the symptoms of intrinsic asthma?
wheezing, shortness of breath, coughing, chest tightness
What is the pathophysiology of asthma
The airway becomes hyper-responsive, leading to an exaggerated bronchoconstrictive response to stimuli, this results in bronchoconstriction and inflammation
What is the treatment for intrinsic asthma?
Bronchodilators, inhaled corticosteroids
What is extrinsic asthma?
Caused by an allergen
What are some triggers of extrinsic asthma?
Pollen, dust mites, mold spores, food allergies
What is the pathophysiology of extrinsic asthma?
When exposed to an allergen, IgE antibodies on the surface of mast cells bind to the allergen, leading to mast cell degranulation. The next time you are exposed to the same allergen, the IgE antibodies recognise this and causes the mast cells to release chemicals such as histamine which leads to: bronchoconstriction, mucus production, inflammation
Where is mucus produced?
in the airways by goblet cells
What happens when you cough excessively?
Overstimulation of the vagus nerve, causes bronchoconstriction and bronchospasm. Because of this, air gets trapped in the lungs making it hard to breathe properly and it can lead to the collapse of the bronchi when someone tries to forcefully exhale
What is atelectasis?
when the lung tissue collapses due to the complete blockage of the airways by mucus
What is respiratory acidosis?
When there is a build up of co2 in the blood
What is IgE
Immunoglobulin - a type of antibody produced by the immune system - specifically involved in allergic reactions
What is histamine?
A chemical that causes blood vessels to become leaky - leading to oedema (swelling)
What are kinins?
Chemicals that cause the blood vessels to widen (vasodilation) and the muscles around the airways to tighten (bronchoconstriction)
What do prostaglandins do?
Cause blood vessels to narrow (vasoconstriction) which can lower blood pressure and reduce blood flow to the lungs
What happens once atelectasis has occurred?
Hypoxia is induced as air cannot diffuse through the affected areas, respiratory muscle activity increases as the demand for oxygen increases - this increased effort leads to laboured breathing
What happens when metabolic and respiratory acidosis occurs?
hypoxaemia causes the pulmonary vessels to narrow (vasoconstriction) this makes it harder for blood to flow through the lungs, increasing pressure - this increases the workload of the right side of the heart as it now has to work harder to push blood through to the lungs, which puts extra stress on the right ventricle
What happens during an asthma attack?
The number of leukocytes (white blood cells) increases, particularly eosinophils, however they are over activated, they release chemicals that cause bronchoconstriction and inflammation, resulting in long term damage and narrowing, making the individual more prone to asthma attacks
What are eosinophils?
A type of white blood cell that can help the body fight off parasites and respond to allergens. They release chemical mediators such as leukotrienes that cause the smooth muscle around the airways to tighten, increase mucus production and lead to prolonged inflammation
What are chemotactic factors?
Signals that attract white blood cells to the site of inflammation
What are cytokines?
Proteins released by mast cells that are crucial for cell-to-cell communication e.g for white blood cells to move to the inflamed area
What do mast cells do in asthma?
Release chemotactic factors and cytokines, drawing more white blood cells into the lungs and airways - this brings in more cells that increase inflammation and make the airways tighten and more swollen resulting in more airway blockage and worse hypoxia
What are short acting Beta-2 agonists?
Provide quick relief during an asthma attack e.g salbutamol
How do short acting Beta-2 agonists work?
They stimulate B2 receptors in the lungs, which causes the smooth muscle in the airways to relax (bronchodilation) and therefore easier breathing
What are long acting beta-2 agonists?
Used for maintenance in asthma management to prevent symptoms but work over a longer period. They must be used alongside anti-inflammatory medication
What are side effects of Beta-2 agonists
Tremors - due to the stimulation of B2 receptors in skeletal muscles
Uterine relaxation - due to stimulation of B2 receptors in the uterus by salbutamol - beneficial in preventing premature labour
Increased heart rate - B2 receptors in the heart
What is ipratropium bromide?
An anti-muscarinic bronchodilator
How does ipratropium bromide work?
blocks the muscarinic cholinergic receptors found in the parasympathetic nervous system. These receptors normally cause the smooth muscles in the airways to contract, narrowing the airways and making it difficult to breathe, so by blocking these ipratropium prevents the muscles from contracting, allowing the airways to stay open
What is hydrocortisone?
A glucocorticoid steroid hormone
What is hydrocortisone naturally produced by in the body?
The adrenal cortex, the outer layer of the adrenal gland
What does hydrocortisone do?
Reduces the body’s inflammatory response by inhibiting the release of inflammatory mediators e.g cytokines and prostaglandins. In the airways hydrocortisone reduces swelling, mucus production and airway narrowing by decreasing the activity of immune cells that cause inflammation. it also has immunosuppressant effects, it suppresses the activity of white blood cells, particularly lymphocytes and eosinophils, reducing their ability to cause inflammation and tissue damage
Why is oxygen essential?
for the body’s cells to produce energy through cellular respiration. Tissue oxygenation is necessary for the normal functioning of all organs and tissues in the body
What do histamines do?
Cause inflammation by vaso-dilation by binding to histamine receptors on blood vessels and in turn increased blood vessel permeability
What do anti-histamines do?
Bind to H1 receptors found in the central nervous system and peripheral tissues. Block histamine receptors so histamine can’t bind, this reduces vasodilation and permeability which helps to decrease inflammation, swelling and cold symptoms
What are some common anti-histamines?
Chlorphenamine, fexofenadine, loratadine
What is tissue perfusion?
The blood flow through the body’s tissues
Where are H1 receptors located?
Central H1 receptors - brain and spinal cord
Peripheral H1 receptors - found in tissues such as skin, lungs and blood vessels
What effects do anti-histamines have on the CNS?
Most antihistamines are known to cause CNS depression, resulting in drowsiness and sedation. in some cases, particularly in children, they may cause CNS stimulation instead, leading to symptoms like anxiety, agitation or restlessness
What anticholinergic effects do anti-histamines have?
Many antihistamines also have cholinergic properties meaning they block acetylcholine from binding to muscarinic receptors this can lead to effects such as: bronchodilation, reduction in mucus production, increased heart rate
What is cystic fibrosis?
autosomal regressive disease affecting the endocrine glands disrupting mucus production. Caused by mutations in the CFTR gene which leads to the production of stick, thick mucus, this clogs the airways and provides a fertile environment for bacterial infections leading to lung infections such as bronchiectasis
What are the treatments for cystic fibrosis?
Mucolytics - help to break down and thin the mucus
Antibiotics
What is bronchiectasis?
a chronic lung condition in which the bronchi become permanently widened and damaged due to repeated cycles of infection and inflammation, this weakens the airways preventing them from clearing mucus efficiently
Causes of bronchiectasis
Cystic fibrosis
respiratory infections
immunodeficiencies
aspiration - inhalation of foreign materials
What are the symptoms of bronchiectasis?
Chronic cough
Frequent respiratory infections
Hemoptysis - coughing up of blood
Complications of bronchiectasis
Lung damage due to the constant presence of mucus and infection, potentially resulting in respiratory failure. Treatment of this would include: airway clearance techniques, mucolytics, antibiotics, bronchodilators, surgery
What are methylxanines
Related to caffeine - provide mild to moderate relaxation of muscles in the airway to decrease bronchospasm, essentially they work as long acting bronchodilators
What do methylxanthines do?
the action of this drug is not well understood but it is thought that it inhibits the enzyme phosphodiesterase which degrades cyclic AMP, so methylxanthines tend to increase the concentration of cyclic AMP which in turn causes relaxation of smooth muscle
What are methylxanthines used for?
Used to treat respiratory diseases like asthma and COPD. They act as bronchodilators
What is an example of a methylxanthine
Theophylline
What does theophylline do?
Inhibits phosphodiesterase (which breaks down cyclic AMP) this increases the levels of cyclic AMP which leads to the relaxation of smooth muscles in the airway and bronchodilation. Theophylline also has mild anti-inflammatory effects. It can also stimulate the CNS which may enhance respiratory muscle function and help improve breathing in patients with respiratory conditions. it also increases the HR and contractility and has a diuretic effect - increases urine production
What is theophylline used for?
Used to manage chronic asthma, COPD and bronchospasm
What are leukotriene receptor antagonists? (LTRAs)
Drugs that act by suppressing the effects of leukotrienes (compounds that promote bronchoconstriction as well as mucus production and airway oedema
Examples of Leukotriene antagonists
montelukast
zafirlukast
What do leukotrienes do?
promote bronchoconstriction
increase mucus production
airway oedema
What do LTRAs do?
Block leukotriene receptors, this helps to relax the airways, reduce mucus production and alleviate airway swelling
What are LTRAs indicated for?
Long term treatment of asthma. They can be used as a maintenance therapy alongside other medications such as inhaled corticosteroids
What are side effects of leukotriene antagonists?
Fatigue
Stomach pains
Dizziness
Headache
Insomnia
What is magnesium sulphate ?
Potent bronchodilator - helps to relax the muscles around the airways and open them up.
What does magnesium sulphate do?
Acts as a calcium channel blocker at the pre-synaptic membrane. By blocking these channels, magnesium sulphate prevents calcium from entering, reducing the release of acetylcholine
What is acetylcholine and what does it do?
A neurotransmitter that when released into the synaptic cleft, binds to muscarinic receptors on the smooth muscles around the airways, causing them to narrow the airways. As magnesium sulphate reduces the amount of acetylcholine released, it helps to prevent bronchoconstriction
