Asthma and TB Flashcards
What is asthma?
Chronic inflammatory disorder of the airways resulting in;
- Reversible airway obstruction
- Inflammation, bronchoconstriction, mucus
Describe the pahogenesis of asthma?
Environmental Trigger is breathed in leading to inflammation triggered by TH2 cells
This then leads to a type 1 hypersensitivity reaction
This includes;
- Smooth muscle contraction
- Mucus production
- inflammatory cell infiltration
These then lead to: Remodelling = damaged epithelium and increased SM thickness
List some common triggers of asthma
Indoor allergens: - Pets - House dust mite - Mould/fungus Outdoor allergens: - Pollens - Tabacco Smoke - Pollutants
Others: Cold, Exercise and medications (BBlockers)
What time of respiratory defect is asthma?
Obstructive
FEV1/FVC ratio is usually below 70%
List common symptoms of asthma
recurrent:
- wheeze
- breathlessness
- chest tightness
- cough (usually dry)
what is a wheeze?
High pitched, expiratory muscial sound
From narrowed airways (can be compression or obstruction)
Describe distinctive characteristics about a asthmatics cough
worse at night
dry
exercise induced
When difficulty breathing is found in response to triggers what can you assess?
Respiratory Rate Tracheal Tug Recession Nasal Flaring Accessory muscle use
How else would you confirm a diagnoses other than assessing; Respiratory rate Tracheal tug Recession Nasal Flaring Accessory muscle use?
Full Hx; symptoms?
PMH- Eczma, hay fever
FH- atopy, smoking (if parent smokes during pregnancy, can cause damage to developing lungs)
SH- mould in home, farm, wood burning fire, pets
DH- some medications can make it worse
Respiratory examination would include
Inspection
Palpation
Percussion
Asucultation
What can be used to assess respiratory defect?
spirometry
Vitalograph; FEV1/FVC
Flow Volume curve
Reversibility- before and after bronchodilator
Treatment of asthma
trial Bronchodilators for a month and review
- do symptoms get better?
- do their peak flows get better?
if yes, continue to treat as asthma
Spirometry is gold standard for diagnosis
Management of asthma
Education - how to use inhalers properly
Prevention- change pillows and bedsheets, fresh air etc.
What is a SABA?
Short Acting Beta Agonist
helps relax smooth muscles
quick relief
How does Salbutamol work?
Salbutamol is a B2-adrenoreceptor selective agonist it binds to the receptor and reverses or opposes bronchoconstriction
Compare Salbutmaol and Salmeterol?
Salbutamol has B2 selective efficacy
Salmeterol has no selectivity but it has higher affinity for B2, its selectivity is therefore based on affinity
Describe the mechanism by which BBlockers work?
Beta adrenoreceptor antagonists or B-Blockers block the action of the B1 adrenoreceptor in the heart blocking the sympathetic action decreasing the slope of the pacemaker potential in the SA node
At what point would a pt need a step up from a SABA?
If used more than 3x wk or if nocturnal symptoms more than once a week
What is the step up from a SABA?
Steriod- preventer
Reduces inflammatory cells
Inhibits inflammatory mediators
When is a LABA used?
Used in pateitns who still have asthma symptoms despite steroid use
Slower onset or action therefore NOT for acute asthma attack
What is the treatment of an acute asthma attack?
Oxygen
Salbutamol nebulisers, atrovent nebulisers ‘back to back’
IV access
May need to intubate and ITU admission
Details about Mycobacterium Tuberculosis
Non-motile rod shaped bacteria
Obligate aerobe
Long-chain fatty (mycolic) acids, complex waxes and glycolipids in cell wall:
- Structural rigidity
- staining characteristics –> Alcohol fast stain
relatively slow growing
Generation time 15h-20h (takes longer to culture)
How is TB transmitted?
Respiratory droplets
what is a giant cell?
What giant cell is present with TB?
Multinucelate cells made by fusion of macrophages
Langhans (nucleus around the edges)
What is granulomatous inflamation?
What is a granuloma?
What do granulomas arise with?
Chronic inflammation with granulomas present
A granuloma is a collection of immune cells mainly macrophages
persistent low grade antigenic stimulation e.g. TB
and hypersensitivity
What will be in the center of a granuloma in TB?
Caseous necrosis
What are sites of Extrapulmonary TB?
Who are they found more often in?
Larynx Lymph nodes pleura brain Kidneys Bones & joint Found more often in: - HIV + or other immunosuppressed persons - Young children
Where are caseating granulomata found?
in the lung parenchyma and mediastinal lymph nodes
Compare Latent TB infection and TB disease
Latent TB
- inactive, contained tubercle bacilli in the body
- TFT or IFN gamma test results usually positive
- CXR usually normal
- Sputum smears and cultures negative
- no symptoms
- not infectious
Not a case of TB
TB Disease
- Active, multiplying tubercle bacilli in the body
TST or blood test results usally positive
- CXR usually abnormal
- Psutum smears and cultures may be positive
- Symptoms such as cough, fever, weight loss
- often infectious before treatment
A case of TB
What is the test for TB?
The Mantoux test/Tuberculin sensitivity test
tuberculin injected intradermally. the induration is read 48-72 hours later
Cheap
subject to interpretation
what is interferon gamma releasing assays?
used to support the diagnosis of TB
Detection of antigen specific IFN-gamma production
T spot TB
Quantiferon Gold
No cross-reaction with BCG
cannot distinguish between latent and active TB
Similar problems with sensitivity and specificity
