Asthma Flashcards
Describe the typical clinical features of asthma (stable and during exacerbations) seen in an acute medical setting and formulate and appropriate investigation and management plan
What are the symptoms of asthma?
Shortness of breath (Dyspnoea)
Wheeze
Cough
Chest tightness
What factors contribute towards the airway obstruction in asthma?
Oedema
Increased mucous production
Increased smooth muscle tone/ bronchoconstriction
These are due to the underlying inflammatory process which is IgE mediated and a type I hypersensitivity reaction.
What are some features that increase the likelihood of dyspnoea being due to asthma?
Wheeze, SOB, chest tightness
Diurnal variation (Worse in morning)
Triggers- Cold weather, allergen, exercise, symptoms after Beta Blocker/NSAID
History of Atopy- Atopic Dermatitis, Hay Fever, Allergy
Family history of atopy/asthma
Expiratory polyphonic wheeze
PEF improvement in FEV1 of 12% or more with Salbutamol or steroid trial (NICE say 12 for salbutamol)
FEV1/FVC<0.7
What peak flow findings suggest asthma is more likely?
Reduced FEV1
FEV1/FVC <0.7
Improvement in FEV1 of 12% or more with salbutamol or steroids
What should you ask about for potential triggers for asthma?
Cold weather Exercise Salbutamol NSAIDs Known allergens Smoking Infection Occupational Exposures- does it improve at weekend/during holidays? (Common for paint sprayers, food processors, welders and animal handlers)
What features would you want to know about for a patient presenting with acute asthma/exacerbation?
Prodrome- preceding symptoms that could indicate a cause e.g. Cough, Wheeze, GI Symptoms, Rhinorrhoea, Fevers
Speed of onset- How quickly has it worsened?
When did it first start?
Previous diagnosis with asthma?
Treatment of asthma? Compliance to this
Previous exacerbations?
Previous admission to ITU/intubation for asthma?
Possible triggers- e.g. allergen exposure, dust, building work
PEFR- Best for them
What are the findings from an asthma exacerbation on respiratory examination?
Wheeze- polyphonic expiratory wheeze
Tachypnoea
Tachycardic
Hyperinflated chest
Use of accessory muscles of respiration- SCM
Inability to complete sentences (bad sign)
What is the mechanism that leads to hyperinflation of the chest?
Premature airway closure during expiration causes inspiratory volumes to become greater than expiratory volumes- this leads to hyperinflation
What changes are seen in spirometry values during an acute exacerbation of asthma?
FEV1/FVC decreases FVC decreases RV increases FRC and TLC increase (Static volumes increase)
What PEFR % ranges guide wether the exacerbation is severe or moderate?
Moderate- PEFR 50-75%
Acute Severe Asthma- PEFR 33-50%
(Both of best predicted)
What four clinical features indicate acute severe asthma?
PEFR 33-50%
Inability to complete sentences
Tachypnoea- RR>25
HR>110
What ABG findings would you expect to see in acute severe asthma? How would this change as the patient fatigues due to the increased effort of breathing?
Low PaO2 and a Normal/Low PaCO2
Initially Type I Respiratory failure would be seen due to V/Q mismatch. The patient is hypoxic but PaCO2 is normal/low as the patient is hyper ventilating and breathing off carbon dioxide.
Progression to Type II Respiratory Failure as PaO2 <8kPA and PaCO2>6kPa. This occurs when the patient fatigues and alveolar ventilation begins to reduce. it is a very bad sign.
Why do patients with severe acute asthma fatigue when breathing?
Airway obstruction and a hyper inflated chest (meaning the chest wall is less compliant) mean the effort of breathing is increased
What is a silent chest?
This occurs when no breath sounds can be heard, the wheeze is no longer audible. This is a bad clinical sign.
What are some features of life threatening asthma?
Cyanosis Silent chest Fatiguing patient Reduced consciousness Hypotension
What measurements (ABG, O2 Sats, PEFR) indicate life threatening asthma?
Type I Respiratory Failure
O2 Sats less than 92%
PEF <33%
Why is a raised PaCO2 a very bad clinical sign?
A raised PaCO2 in addition to a PaO2 less than 8 indicates Type II respiratory failure and is a marker of near-fatal asthma. PaCO2 starts to rise when the patients ventilation reduced due to fatigue.
In an acute asthma attack what investigations should be requested?
CXR (Rule out pneumonia, pneumothorax) ABG PEFR Other Bloods Bloods- FBC, CRP, ESR, U+Es, Blood culture if appropriate Sputum culture (if suspecting infection)
For a patient presenting in GP with features of asthma (not acute severe asthma) what tests should be done to diagnose asthma?
PEFR- and PEFR monitoring over 2 weeks (A diurnal variation of more than 20 % on at least three days a week for 2 weeks is suggestive of asthma)
Spirometry- FEV1:FVC less than 0.7 suggests asthma. Usually improvement in FEV1 when salbutamol given. NICE say to regard a 12% improvement or more as a positive test.
Fractional Exhaled Nitric Oxide- 40 parts per billion is a positive finding. Produced by eosinophils in the airways and so higher levels indicate greater activity.
Skin prick tests may be done to identify potential allergens if thought to be a trigger.
What percentage FEV1/FVC indicates obstructive spirometry?
70% or less
What percentage improvement in FEV1/FVC following salbutamol is suggestive of asthma?
12% or more according to NICE
How long should patients monitor their peak flow results for to check for variability?
2-4 weeks
When should patients peak flow variability be checked for?
NICE say to monitor for peak flow variability over 2-4 weeks if there is diagnostic uncertainty after FeNo testing and they have either normal spirometry or obstructive spirometry (FEV1:FVC <0.7), reversible airway obstruction (12% or more improvement)
What percentage peak flow variability indicates a positive test)?
20%
What FeNO value is a positive result for asthma?
40 parts per billion
What are some differential diagnosis to consider when suspecting asthma?
COPD
Pneumonia
Congestive Cardiac Failure (Oedema causing breathlessness)
Pneumonothorax
PE
Large airway obstruction- foreign body, tumour
When should would a bronchial challenge test with histamine or metacholine be done?
If diagnostic uncertainty, normal spirometry, no peak flow variability with FeNO>40 or FeNO<40 with PEFR variability
Or no bronchodilator reversibility with obstructive spirometry, negative FeNO, no peak flow variability
What is a bronchial challenge test?
Histamine or metacholine are given to provoke bronchoconstriction which can be checked with spirometry.
PC20 of 8mg/ml or less is a positive result. This is a provocative concentration that is required to cause a 20% fall in FEV1.
How initially should an acute asthma be treated?
Oxygen- target saturations of 94-98%
Salbutamol 2.5-5.0 mg nebuliser (can drive with 6L or oxygen)- repeat 15-30
Steroids- Oral Prednisolone 40-50mg
Re-assess every 15 minutes
What should be added in if response is poor to oxygen, steroids and salbutamol in acute severe asthma?
Ipratropium Bromide 0.5mg/6h added to the nebuliser- add in at first step if severe or life threatening features.
What should be done if there is no improvement in an acute severe asthma attack after oxygen+steroids+salbutamol+ipratropium has been given?
Senior Review
Senior may advise to give magnesium IV (2g over 20 minutes) or aminophylline (PDE inhibitor)
In what order should the tests be carried out to check for asthma at GP?
FeNO
Spirometry (with bronchodilator reversibility)
Peak flow variability
Direct bronchial challenge test with histamine/metacholine
What criteria must be met for safe discharge?
PEFR>75%
Inhaler technique checked
Patient is stable
Steroid and bronchodilator therapy available
Should antibiotics be given for acute severe asthma?
Not routinely, only if signs of infection.
E.g. Fever, Raised WCC, Raised CRP, Raised ESR, +ve Sputum culture, Green sputum, CXR consolidation
When should follow up be done following acute sever asthma?
Within 2 days see GP or specialist nurse
Within a month see specialist nurse/physician
What features should prompt referral to ITU?
Failure to respond to initial treatments Persistent or worsening hypoxia Hypercapnia Acidosis Exhaustion and reducing respiratory effort Reduced consciousness/confusion Respiratory arrest
What should be offered first line to patients presenting in GP with suspected asthma?
1st - SABA- Salbutamol for newly diagnosed asthma. + Add in a low dose ICS as the first-line maintenance therapy to adults if indicated by symptoms three or more times per week or causing night waking at presentation.
Low dose ICS (+SABA PRN)
How soon after initiating treatment for asthma should you review the response?
4-8 weeks
If response to first line therapy (SABA+ Low dose ICS if night waking/more than 3 times per week) is no adequate what should be added for second line therapy?
Leukotriene receptor antagonist should be added as second line maintenance therapy. E.g. montelukast.
Review response in 4-8 weeks time
Note- Low dose ICS is first line maintenance therapy
LTRA+ ICS (+SABA PRN)
If response the second line therapy (Low dose ICS+ LTRA +Salbutamol PRN) what should be added?
LABA- Long acting beta agonist should be added in combination with the ICS. Discuss with the patient wether to continue with the LTRA if it has been any help.
E.g Salmeterol/Formoterol
LABA+ ICS with/out LRTA (+ SABA PRN)
If response to third line therapy (LABA+ Low dose ICS with/out LTRA (+SABA PRN)) for chronic asthma is poor what should be done?
Considerate low dose ICS + LABA within a MART (Maintenance and reliever therapy) with or without a LTRA.
Note MART can be used as a reliever therapy but if using a fixed dose SABA needs be included for symptoms relief.
What is MART when should it be offered?
MART is a combination inhaler that contains ICS and LABA. Examples include fostair MART (formoterol/beclomethasone) and symbicort MART (budesonide and formeterol).
MART inhalers can be used as a reliever therapy and so a SABA does not need to be included.
If response to fourth line therapy (Low dose ICS +LABA either as fixed dose or as part of MART regime +/- LTRA +/- SABA (if not on MART) is poor what should be done?
Up the steroid dose to a moderate maintenance dose - either continuing on a MART regime or changing to a fixed dose ICS and LABA
Note- If changing to a fixed dose SABA must be added as a reliever therapy. If on a MART this can be used as a reliever therapy.
If response to a moderate steroid dose (either within MART or as fixed dose ICS +LABA (with salbutamol) +/- LTRA) what should be done?
Increase ICS to a high maintenance dose as part of a fixed dose regime (must add in SABA if leaving MART)
Trial of an additional drug-
- LAMA e.g. Ipratropium/Tiatropium. Long acting anti-muscarinics.
- Theophyline (aminophyline is metabolised to this) PDE inhibitor that causes increases in cAMP and reduces bronchoconstriction.
Refer onwards to a specialist in asthma. Other options include omalziumab which is anti-IgE for patients with persistent allergic asthma. given as a SC injection every 2-4 weeks.
