Describe the pathophysiology of asthma.
Extrinsic
- pathogenesis of underlying inflammation is clear
- type I hypersensitivity develops
- allergen trigger mucosal mast cells to release mediators
- open epithelial junction
- antigen penetrates submucosal layer
- increased release of inflammatory mediators
- inflammatory cells attracted to area
- inflammatory mediators cause bronchial muscle
contraction, mucosal swelling, mucous production and
nerve stimulation resulting in bronchoconstriction
Intrinsic
- unclear but theorised associated with respiratory viral
respiratory infection or inhaled pollutants
-
Describe the clinical manifestations of asthma.
Episodic dyspnea
Cough
Wheezing (difficulty with expiration, whistling noise)
Explain how ventilatory function is measured by spirometry to evaluate airway obstruction in asthma.
.
Identify the factors that predispose people to respiratory infection.
- Contact,
- droplet,
- inhaling the germs.
- Family members are sick.
- Cystic fibrosis increases chances.
- Nasogastric tube.
Name the causative organisms of most upper respiratory tract infections.
rhino-, corona- and adenoviruses
Streptococcus pyogenes
Give 2 reasons why treatment of the common cold is solely to reduce symptoms.
It is viral so anti-biotics don’t work.
To give comfort whilst getting better.
Describe the cause of pharyngitis and a potentially serious complication.
Rhino, corona and adenoviruses.
- It can cause scarlet fever,
- Acute rheumatic fever,
- Acute glomerulonephritis.
- bronchitis
- pneumonia
- secondary bacterial infections
Explain why vaccinations for influenza are not protective for long and describe the basics of treatment for influenza.
There are multiple strains of influenza and the virus (Myxovirus) undergoes antigenic shift (mutation)
- The basic treatment for influenza to take anti-viral drugs.
- Get the vaccine regularly
- Paracetamol
- Drink water
- Rest
- Supportive
Describe the pathogenesis of lobar and bronchopneumonia.
Microorganisms reach lung via inhalation, aspiration of oropharyngeal secretions or spread from blood stream
Lobar pneumonia
- infection and consolidation confined to 1 or 2 lobes
Bronchopneumonia
- consolidation and infection occurs throughout lungs
Explain why aspiration of gastric fluid causes serious damage to the lungs.
Aspiration of gastric fluids can carry bacteria into the lungs. Pneumonia often develops.
Define pneumothorax
Partial or entire collapse of affected lung due to air in the pleural space.
Explain why tension pneumothorax is life-threatening
The air cannot get out of the lung and therefore puts pressure on the heart.
Describe how pleural effusions develop and why they are often associated with dyspnoea.
They are caused by pneumonia.
Fluid accumulation in the pleural space prevents full lung inflation → hypoxemia and dyspnea. Pain with breathing may occur with inflammatory causes.
Define asthma
A chronic disorder of reversible airway obstruction
Diagnoses of asthma
Patient history
Airway responsiveness assessed via inhalation challenge test with histamine, cholinergic agonists or cold air
Lung function tests are used to measure peak expiratory flow and the FEV1/FVC ratio
Define pneumonia
Infection and inflammation within the lungs
Name the most common causative organism of pneumonia
Bacteria, virus, fungi
Indicate the significance of pneumonia as a hospital-acquired condition.
15- 30% of cases are hospital acquired.
Leading cause of death in infants and elderly
Major cause of death throughout world
Major cause of intensive care mortality
Risk factors of pneumonia
lung disease (e.g. COPD), smoking, immobilisation, altered consciousness, immune suppression, alcoholism
elderly children underdeveloped nations, malnourished, crowded and unhygienic environments
Clinical manifestations of pneumonia
Fever cough (progresses to productive cough) chest pain breathlessness, rapid/shallow breathing rales
2 causes of pneumothorax
Spontaneous
- Rupture of bleb or blister on lung surface secondary to asthma or infection/malignancy. Usually occurs in young people.
Traumatic
- Penetrating chest trauma and non-penetrating trauma (fractured rib) damage the pleural space and lung tissue (may also cause haemothorax).
Define pleural effusions
Abnormal collection of fluid in the pleural cavity.
Difference in severity between upper and lower respiratory infections.
Upper respiratory tract infections (URTIs) – usually not
life threatening
Lower respiratory tract is normally sterile, thus infections
often serious
What categories do the strains on influenza affect
Influenza A affects humans and wide range of animals. Cause of epidemics and pandemics.
Influenza B only affects humans. Cause epidemics but not pandemics
What are the antigens on the surface envelope of Myxovirus
haemagglutinin (H)
neuraminidase (N)
Difference between antigenic drift and antigenic shift
Antigenic drift are small constant changes in H and N
Antigenic shift are major, sudden and unpredictable changes in H and N that lead to a new strain of virus
Pathogenesis of Influenza
Transmission by droplet, highly infectious
Virus adheres to upper respiratory tract epithelium via the H proteins.
1 to 3 days – fever, chills, malaise, muscle pain; runny nose, sore throat and cough may follow; recovery in 1
to 3 weeks
Acute Bronchitis
- Caused by virus
- Initial symptoms similar to pneumonia
- Self-limiting
- Treatment symptomatic – no antibiotics
- Bacterial bronchitis occurs with underlying disease
Bronchiolitis
Childhood form of bronchitis
• under 2 yrs
• Respiratory Syncytial Virus (RSV) most common cause
• Highly infectious
• Fever, coryza, cough, asthma-like symptoms
• Healthy infants recover well while premature infants with low birth weight may display severe and possibly fatal progression
Disorders which limit expiratory flow
asthma bronchitis emphysema brochiectasis cystic fibrosis
Cystic fibrosis
- Autosomal recessive condition linked to gene mutation of transmembrane regulator (CFTR) that functions as a chloride ion channel
- Cl- is retained in cells which leads to water and Na+ absorption from mucosal surface leading to ↑ viscosity of mucous
- Clinical manifestations include excessive secretion viscous fluid from epithelial glands of respiratory, gastrointestinal and genitourinary tracts
- Excessive secretions cause accumulation of viscous bronchial mucous, impaired mucociliary clearance and lung infections
- Major cause of chronic (non-reversible) respiratory disease in children
Define atelectasis
collapse of lung segment
Define transudate fluid
clear fluid from congested lungs due to heart failure, renal and/or liver disorder.
Define haemothorax
escape of blood into pleural space due to chest trauma,
malignancy and/or vessel rupture.
Define exudate fluid
protein and inflammatory cells that arise from infection, cancer or DVT.
Use of prophylactic anti-inflammatory drugs
- Preventative measure for asthma
- Crucial for moderate to severe asthma and taken on a
regular basis:
Use of bronchodilators
symptomatic relief
Use of glucocorticoids
Beclomethasone (inhaled) and Prednisone (oral)
↓inflammatory mediators
↓inflammatory cell infiltration
↓ oedema and mucous secretions
↑β2 receptors and sensitivity to β2 agonists
• Inhaled drug avoids severe adverse effects
Types of prophylactic anti-inflammatory drugs
– Glucocorticoids (anti-inflammatory)
– Leukotriene (pro-inflammatory) modifiers
– Cromolyn (mast cell stabiliser)
– IgE antagonists
Types of bronchodilators
– Beta2 adrenergic agonists
– Methylxanthines (↓ airflow obstruction, airway
hyperresponsiveness, and airway inflammation)
– Anticholinergics
Use of leukotriene modifier
– introduced late 90’s; well tolerated
– leukotriene receptor antagonist
– used for intrinsic/extrinsic asthma and allergic rhinitis
Use of Cromolyn
– ↓histamine release and ↓inflammatory cell activity
– low incidence of adverse effects
– less effective than corticosteroids
Use of IgE antagonist
– second line drug
– monoclonal antibody attaches/inhibits IgE
– associated with a number of adverse effects including
anaphylaxis
Use of Methylxanthines
– Widespread use diminished as other treatments safer
– Mechanism of smooth muscle relaxation is unclear,
provide less effective but longer duration of action than
β2 agonists
– Adverse effects include vomiting, diarrhoea,
restlessness, insomnia
Use of Muscarinic Antagonists
– Recommended for COPD but also used for asthma,
– Administered via inhalation which localises drug in lungs
and thus avoids adverse effects
Types of inhalers
Metered-Dose Inhalers (MDI’s) – hand held pressurised devices – require hand-breath coordination – 10% of the drug released reaches lungs – use of a spacer improves delivery
Dry-Powder Inhalers (DPI’s)
– not pressurised/ breath activated
– little coordination required
– 20% of dose reaches lungs
Classification of asthma
Intermittent Mild Moderate Severe
≤ 2 d/wk 2-7 d/wk daily Through the day
Why does frequent use of bronchodilators cause tachycardia
While the drug is selective for beta 2 receptors it does have some beta 1 (cardiac receptors) action. Therefore in higher doses some beta 1 stimulation occurs leading to tachycardia.
