Asthma Flashcards
What is asthma clinical diagnosis based on? (2)
- A history of recurrent episodes of wheeze, chest tightness, breathlessness, and/or cough, particularly at night
- Evidence of generalized and variable airflow obstruction, which may be detected as intermittent wheeze on examination or via tests such as peak expiratory flow (PEF) measurement.
Asthma pathophysiology
- Chronic eosinophilic bronchitis/ bronchiolitis
- Airway inflammation with cellular infiltration by Th2 cells, lymphocytes, eosinophils and mast cells.
- 25% asthma non-eosinophilic. Neutrophilic airway inflammation makes up the largest portion of this group, driven by persistent airway infection.
- Airway obstruction occurs due to a combination of:
- Inflammatory cell infiltration
- Mucus hypersecretion with mucus plug formation
- ## Airway smooth muscle contraction
- This may become irreversible over time due to:
- Basement membrane thickening, collagen deposition, and epithelial desquamation
- Airway remodelling occurs in chronic disease, with smooth muscle hypertrophy and hyperplasia.
Asthma clinical features
- Cough
- Shortness of breath
- Wheeze
- Chest tightness
- These symptoms are:
- variable
- intermittent
- worse at night
- associated with specific triggers e.g. pollens, pets, cold air
Other features related to asthma
- Nasal symptoms–obstruction, rhinorrhoea, hyposmia
- Atopic dermatitis/eczema/hay fever
- Allergies, including food allergy
- Reflux/gastro-oesophageal reflux disease (GORD) disease (treating reflux may improve symptoms that have been wrongly attributed to asthma, particularly cough)
- Laryngo/pharyngeal reflux (hoarse voice, throat clearing, acid in throat)
- Triggers, including exercise, menstruation
- Social situation/stresses
- Aspirin sensitivity (associated with later-onset asthma and nasal polyps)
- Family history.
Asthma diagnostic features
- Symptoms (cough, wheeze, breathlessness)
- Day-to-day peak flow variability (>15% variability or reversibility to inhaled beta2 agonist).
- Airway hyperresponsiveness
Diagnosis can be considered with:
- Recurrent cough, episodic breathlessness and wheeze
- Chest tightness
- Isolated or nocturnal cough
- Exercise-induced cough or breathlessness
- Hyperventilation syndrome
What is Samter’s triad
Aspirin + nasal polyps + aspirin hypersensitivity
More common in women
Asthma spirometry
- peak flow and spirometry
- airway obstruction leads to decreased pef and fev1 but should be normal between episodes of bronchospasm. If persistently normal, unlikely to be asthma.
- diagnosis likely if:
- 20% diurnal PEF variation on >3 days/week
- FEV1 >15% decrease after 6 mins of exercise
- FEV1 >15% increase after 2 week trial of oral steroid e.g. prednisolone 30mg od
- bronchodilator reversibility testing FEV1 >15% increase after a single dose of SABA e.g. salbutamol by MDI or spacer
- a 400ml improvement is strongly suggestive of asthma.
Other asthma investigations
- blood tests
- FBC - expecting eosinophilia
- IgE
- Fractional exhaled nitric oxide concentration (FeNO)
- > 50 ppb likely to be eosinophilic airway inflammation
asthma differentials
- upper airway obstruction
- breathlessness, noisy stridor, low PEF out of proportion to FEV1
- foreign body aspiration
- tumour, especially tracheal
- congestive cardiac failure
- young patient with a murmur
- vocal cord dysfunction
- hyperventilation syndrome
- chronic thromboembolic
disease or primary pulmonary hypertension - interstitial lung disease
- Churg strauss and other eosinophilic lung diseases
- bronchiolitis
- GORD
Risk factors for fatal or near-fatal asthma
- Previous near-fatal asthma, e.g. previous ventilation or respiratory acidosis
- Three or more classes of asthma medication
- Repeated A&E attendances (especially within the last 12 months)
- Previous admission for asthma (especially within the last 12 months)
- High β2agonist use
- Adverse behavioural or psychosocial features such as:
- Non-adherence with asthma medications or follow-up
- Self discharge from hospital
- Alcohol or drug abuse
- History of psychiatric illness
Initial assessment of acute asthma
- Clinical features e.g. tachypnoea, tachycardia, silent chest
- PEF expressed as a percentage predicted or, more usefully, percentage of the patient’s best PEF (within 2 years)
- Pulse oximetry
- Arterial blood gases are required in patients with a SpO2<92%. In acute asthma the pCO2is initially low due to hyperventilation. A normal CO2may indicate fatigue
- Life-threatening or near-fatal asthma attacks require hospital admission.
How can acute asthma be classified
- moderate
- PEF >50-75%
- speech normal
- RR <25
- Pulse < 110
- severe
- PEF 33-50%
- Can’t complete sentences
- RR >25
- Pulse >110
- life threatening
- PEF <33%
- Oxygen sats <92%
- PaO2 <8kPa
- Normal CO2
- Silent chest
- cyanosis
- poor respiratory effort
- bradycardia/ arrhythmia/ hypotension
- exhaustion
- altered conscious level
- near fatal
- raised PaCO2
Acute asthma mx
A - ensure no obstruction
B - high flow O2 15L non-rebreathe mask
C - IV access
Monitor:
- PEF on arrival, 15-30 mins after starting treatment and regularly thereafter
- O2 saturation, maintain 94-98
- ABG for pH and PaCO2
- HR and RR
- Glucose and potassium
- CXR
- CO2 retention requires ICU review for invasive ventilatory support
Treatment:
- B2 agonist - inhaled or nebulised salbutamol
- give repeated doses or continuous
- risk of hypokalaemia
- anticholinergic - nebulised ipratropium bromide
- steroids - oral prednisolone for atleast 5 days or until recovery
- IV magnesium sulphate
- IV aminophylline
- loading dose followed by continuous infusion
- cardiac monitoring required
- antibiotics - if infective exacerbation
- IV fluids and correct hypokalaemia
- IM adrenaline if peri arrest
- liaise with ICU early
When to discuss acute asthma with ICU
- Worsening PEF despite treatment
- Worsening hypoxia
- Hypercapnia (or rising CO2even if not yet >6 kPa)
- Falling pH
- Exhaustion/poor respiratory effort
- Drowsiness/confusion
- Respiratory arrest
When to discharge
- Reduced beta2 agonist dose
- off nebulised drugs and on inhalers >24hrs
- PEF >75%
- minimal PEF diurnal variation
- check inhaler technique and safety netting
- GP review within 2 days, chest clinic appointment within 1 month
