Resp: Asthma treatment, Hypersensitivity pneumonitis, Bronchiectasis, Cystic fibrosis Flashcards
How is asthma treated
- Bronchodilators
SABA: Salbutamol (partial agonist)
Terbutaline
LABA (12 hours): Salmeterol Formoterol 2. Muscarinic antagonists 3. Methylxanthines 4. Anti-infllamtory steroids
Why are LABAs more longer acting
They are more lipophilic so remain in tissue for longer
What receptor does salbutamol bind to
B2
Where is B1 found
Heart
Where is B3 found
Adipose tissue
Pharmacology of B2 agonists
- Bind to B2 receptor coupled with Gs proteins
- Adenyl cyclase converts ATP to cyclic AMP
- Increases cyclic AMP to bronchodilation
ALSO inhibit mast cell activity
Why should B2 agonists not be given in high concentration
- They may develop B2-recpetor desensitisation
Name a short-acting muscuranic antagonist
Ipratropium
Name a long-acting muscuranic antagonist
- Tiotropium
What receptor do anti-muscurinic receptors bind to
M3
Pharmacology of M3 receptor binding
- ACh binds to M3 receptor bound to Gq protein resulting in phospholipase C converting phosphate to DAG
- Protein Kinase C production results in smooth muscle contraction
Why are methylxanthines given
- Phosphodiesterase inhibitor prevents conversion of cyclic AMP to 5’-AMP resulting in a build up of cyclic-AMP and thus increased smooth muscle relaxation
Name some methylxanthines
- LONG-ACTING: Theophylline (non selective so effects many systems) and aminophylline
What anti-inflammatory steroids are given to the patient
- Inhaled corticosteroids
When are inhaled corticosteroids given
- Patients who has a regular persistent symptoms
Name two types of corticosteroids
- Mineralocorticoids (aldosterone - Na retention)
2. Glucocorticoids (hydrocortisone - ensures glucose levels are correct and has anti-inflammatory properties)
Examples of inhaled corticosteroids
- Prednisolone
- Beclomatasone
- Budesonide
How do glucocorticoids suppress asthmatic attacks
- Gene transcription
Where is glucocorticoids receptor found
Promotor region of DNA has zinc fingers that anchor receptors to DNA and recognise discrete sequences on Glucocorticoid reposes element (either increases or decreases transcription)
Result of a negative GRE
SUPPRESSION OF CYTOKINES (TNF. IL-5, IL-3)
Result of a positive GRE
Results in increased lipocortin which inhibits PLA2:
DECREASED arachidonic acid
Causes a DECREASE in prostaglandins and leukotrienes
Reduced inflammation nd symptoms
Side-effects of corticosteroids
- Susceptibility to infection due to cytokine suppression
2. OSTEOPOROSIS and muscle wasting
Alternatives to corticosteroids
- Leukotriene receptor antagonist (montelukast)
2. Steroid-sparing agents
Name some steroid-sparing agents
- METHOTREXATE
- CICLOSPORIN
- IV immunoglobulin
- Anti-IgE monoclonal antibody (omalizumab)
Describe the structure of medication regime in a asthmatics
- SABA
- SABA + ICS (or leukotriene receptor antagonist)
- SABA + LABA + ICS
- SABA + LABA + ICS + 4th Drug (anti-IgE monoclonal)
What is hypersensitivity pneumonitis
- A type of interstitial lung disease
Where extracellular matrix deposition of complexes in lungs distal to bronchioles
What is the lung interstitum
The tissue and space around the air sacs of the lungs
What causes hypersensitivity pneumonitis
- Allergic reaction affecting small airways and alveoli in response to inhaled antigen or following ingestion of a causative drug
Pathophysiology of hypersensitivity pneumonitis
- Allergic response causes deposition of immune complexes (TYPE 3 hypersensitivity)
- Inflammation as complements are activated
- Inflammation attracts and activates alveolar and interstitial macrophages so that continued antigenic exposure results in the progressive development of pulmonary fibrosis
- Acutely, alveoli is infiltrated with inflammatory cells
- Chronically, granuloma forms and obliterative bronchiolitis occurs
What characteristic is seen in hypersensitivity
FARMERS LUNG
causes farmers lung
- Fungus in mouldy hay inhaled
- Type II hypersensitivity occurs
- Acute dyspnoea and coughs
- Early feature of bronchiolitis
- Later, chronic inflammatory cells are seen in the intersttium together with non-caveating granulomas
- Eventually results in pulmonary fibrosis
Risk factors of hypersensitivity pneumonitis
- Famers
- Bird/pigeon keepers
- Cheese-workers
- Malt-workers
- Humidifier fever
- Pre-existing lung disease
- Regular use of hot tubs
What fungus causes farmers lung
- Micropolyspora fauna
2. Aspergillus umbrosuus
What causes hypersensitivity pneumonitis
- Avian proteins in droppings
What causes hypersensitivity pneumonitis in cheese-workers
Penicillium casei
What causes hypersensitivity pneumonitis in malt-workers
Aspergillus clavatus
Clinical presentation of hypersensitivity pneumonitis
ACUTE:
- Fever
- RIgors
- Myalgia
- Dry Cough
- Dyspneoa
- Crackles
- Chest-wheeze
Resolves after removal of antigen
Subacute: Occurs at lower-level exposure
1. Less sever symptoms of acute and is repeated
Recurrent pneumonia
Improvement seen in weeks
Chronic: Cyanosis and clubbing
Weight loss
Increasing dyspnoea
Type I respiratory failure
Differential diagnosis of hypersensitivity pneumonitis
- Infection
- Connective tissue disorders (causes interstitial lung disease)
- Pulmonary fibrosis
- Asthma
How is hypersensitivity pneumonitis diagnosed
- CXR
- FBC
- Lung function test
- Bronchoalveolar lavage
What is seen in a chest X-ray for hypersensitivity pneumonitis
- Fibrotic shadow in upper zone of the lung
2. Diffuse small nodules and increased reticular shadowing may be present but not specific
What is seen in the FBC for hypersensitivity pneumonitis
- Raised white cell count
2. Increased ESR
What is seen on live function test for hypersensitivity pneumonitis
- Reversible restrictive defect
2. Reduced gas transfer during acute attacks
What is seen in bronchoalveolar lavage for hypersensitivity pneumonitis
- Analysis of lymphocyte count and CD4/CD8 ratio
How is hypersensitivity pneumonitis treated
ACUTE:
- Remove allergen
- Give O2 (35-60%)
- Oral prednisolone
CHRONIC:
- Avoid exposure to allergen
- Long term steroids can often achieve CXR and physiological improvement
- Corticosteroids (Prednisolone)
What can cause bronchial carcinomas
- ASBESTOS
- Polycyclic hydrocarbons
- Radon in mines
Define pneumoconiosis
- Accumulation of dust in the lungs and reaction of the tissue in its presence
Pathophysiology of pneumoconiosis
- Particles are ingested by alveolar macrophages in small airways causing them to die and releasing enzymes = fibrosis
What is simple pneumoconiosis
Production of fine micro nodular shadowing in CXR