Asthma Flashcards
Asthma : Pathophysiology
- Exposure to allergen in the environment triggers an inflammatory response
- Causing smooth muscles of the bronchioles to constrict in response
- Reversible obstruction of the airway
Asthma : Risk factors
- Atopy - eczema, hay fever
- Hygiene hypothesis
- Family history - childhood asthma diagnosed before age 12 likely 2nd to genetic cause whereas adult asthma likely to be 2nd to environment
Asthma : Symptoms
- Cough - worse at night and early morning ‘diurnal’
- Chest tightness and breathlessness
- Wheezing
- Increased mucus production
Asthma : Diagnosis < 5
< 5 years }** Dx is based on clinical judgement **
- FHx of Asthma, atopy
- Clinically asthmatic symptoms
Asthma : Diagnosis - 5-16 years
- First line : Spirometry with bronchodilator reversibility.
If negative;
- Second line : FeNO test
Asthma : Diagnosis -> 16 years
Adults > 17 years = Spirometry (BDR) + FeNO for dx
Asthma : Spirometry results
Obstructive disease
1. FEV1 : Significantly reduced
2. FVC : Normal
- Pre bronchodilator : FEV1/FVC < 70%
- Post bronchodilator : FEV1/FVC improves 12% / 200mls or more
} Indicates + for Asthma due to reversibility
Asthma : FeNO test explanation
Definition : FeNO test measures the amount of NO exhaled in the breath
- Eisenophils are a type of white blood cells secreted in response to allergic reactions
- Eisenophils produce nitric oxide as a by product
- Level of inflammation correlates with the level of eisenophils hence the amount of NO exhaled.
Asthma : FeNO test - Asthma
FeNO results
* Adults >40 parts per billion (ppb) = positive for asthma
* Children > 35 parts per billion (ppb) = positive asthma
Asthma : NSAID therapy
Avoid NSAIDs e.g. Aspirin in patients with Asthma
MOA :
1. NSAIDs inhibit COX enzyme which produces prostaglandins
- Inhibition of COX results in increased production of leukotrienes which is an inflammatory chemical
- This triggers inflammation and bronchoconstriction in the lungs of asthmatic patients
Asthma : Mx : Step 1
Mx : Short acting beta agonist ‘SABA’
Escalate if;
If SABA used > 3x a week
Asthma : SABA
Short acting beta agonist ‘SABA’
- *MOA *: act on beta-2 adrenergic receptors on the smooth muscle of bronchioles and cause dilation of airways
- Indication : helps to relieve short term symptoms of chest tightness and wheezing
- Onset : within 15 minutes, lasts up to 4 hours
- Examples : Salbutamol, Terbutaline
5.* CI *: Avoid SABA and non cardio-selective beta blocker } bind to B2 in bronchioles
Asthma : Mx : Step 2
Step 2 - Add ICS
SABA + low dose inhaled corticosteroid (ICS)
Asthma : SE of inhaled steroids
- Oral/Pharyngeal thrush - ‘Oral candidiasis’
Asthma : Mx : Step 3
Step 3 - Add LTRA
SABA and low dose inhaled corticosteroid (ICS) + LTRA
Asthma : Leukotrine receptor antagonist
Leukotrine receptor antagonists
MOA :
1. Block the action of leukotrienes which are inflammatory chemicals in asthma
2. Reduces airway inflammation and helps to control asthma
3. Bronchodilate the airway
Indication: used in longterm asthma management to improve overall asthma symptoms and reduce use of SABA.
Examples: Montelukast
Asthma : Mx : Step 4
Step 4 - Add LABA
SABA + Low dose ICS + Long-acting beta antagonist
Asthma : LABA
MOA: Bind to B2 receptors in smooth muscle of bronchioles allowing for relaxation of airways
Indication : Longer duration of action of bronchodilation of around 12 hours or more
Helps improve symptoms for a longer period of time.
Examples : Formoterol - Salmeterol
Asthma : Mx : Step 5
Step 5 - Switch from LABA and ICS to MART regimen inhaler
MART therapy ( combination inhaler of fast acting LABA + Low dose ICS )
+/ SABA +/- LTRA
Asthma : Mx : Step 6
Step 6
- Increase from low to moderate dose of ICS
SABA + MART (LABA - fast acting + medium dose ICS) +/- LTRA
Asthma : Mx : Step 7
Step 7 - trial the one of the following along with SABA +/ LTRA ;
* High dose ICS inhaler (separate not a part of MART)
* LAMA (tiotropium bromide)
* Theophylline
Asthma Mx- <5 years
- SABA
- SABA + an 8-week trial of paediatric MODERATE-dose inhaled corticosteroid (ICS)
- Review in 8 weeks
No improvement : alternative dx
Resolved
-Reoccur within 4 weeks } Restart ICS at low dose ICS as first line maintenance
-Reoccur >4 weeks } Repeat 8 week trail of moderate dose ICS - SABA + Low dose ICS + LTRA
- Stop LTRA and refer to paediatric asthma specialist
Asthma : Theophylline
MOA :
1. Bronchodilator and phosphodiesterase inhibitor
1. Inhibits phosphodiesterase enzyme which breaks down cyclic AMP
1. Increase cAMP relaxes the airways and causes bronchodilator
1. Also blocks adenosine receptors, as adenosine can cause bronchoconstriction
Asthma : Step down
- Annual asthma review - taper down inhaler steroid therapy by 25-50% every 3 months
Asthma : Acute Asthma : Moderate sx
- PEFR 50 - 75%
- Normal speech
- RR < 25
- Pulse < 110bpm
Asthma : Acute Asthma : Severe sx
- PEFR 33-50
- Can’t complete a sentence
- RR>25
- Pulse > 110bpm
Asthma : Acute Asthma : Life threatening sx
- PEFR < 33%
- Oxygen sats < 92%
- Normal CO22, reduced respiratory effort
- Hypotension, Bradycardia
- Confusion
Asthma : Acute Asthma : Management
- Oxygen therapy - if very unwell, 15l non rebreathe
- SABA with nebulisere.g. Salbutamol, Terbutaline
- Corticosteroid - 40-50mg of prednisolone for 5 days
-
Nebulised Ipratropium bromide - short acting muscaranic antagonist
1.** IV magnesium sulphate** - severe/life-threatening asthma - Consider IV Aminophylline post senior r/v
- If still remains unresponsive - for ITU/HDU
Asthma : Acute Asthma : Criteria for discharge
- No nebuliser or oxygen for 12-24 hours
- Inhaler technique checked
- PEF >75% of best or predicted
