Recommendations
Urgent
Assess airway, breathing, and circulation.[1]
Determine the severity of the asthma exacerbation. Life-threatening asthma is any one of the following in a patient with severe asthma:[13]
Silent chest
Cyanosis
Poor respiratory effort
Arrhythmia
Hypotension
Exhaustion
Altered consciousness
Peak expiratory flow (PEF) <33% of best or predicted
Oxygen saturation (SpO2) <92%
Partial pressure of oxygen (PaO2) <8 kPa (<60 mmHg)
‘Normal’ partial pressure of carbon dioxide (PaCO2) 4.6 to 6.0 kPa (35-45 mmHg)
Raised PaCO2 is a marker of near-fatal asthma.
If the patient has any features indicating a life-threatening asthma exacerbation, measure arterial blood gas. No other investigations are immediately required prior to starting management.[13]
Is it asthma? Consider alternative causes of acute breathlessness, which may require urgent management, such as:
Heart failure[1]
Paradoxical vocal fold motion (also known as inducible laryngeal obstruction)[1]
Inhaled foreign body[1]
Pulmonary embolism[1]
COPD.
In the community:[13]
Arrange immediate admission to hospital for the patient with life-threatening or acute severe asthma (including pregnant patients).
Have a high level of suspicion for acute severe asthma or life-threatening asthma in any patient presenting for an emergency asthma consultation (i.e., regard them as having acute severe asthma until shown otherwise).
Key Recommendations
Check for the classic triad of cough, breathlessness, and wheeze. The presentation can vary and the symptoms are not specific.
Be aware that the patient can deteriorate very quickly.
Measure PEF, respiratory rate, and oxygen saturation as the main initial investigations.[13] If the patient has any features indicating a life-threatening asthma exacerbation, measure arterial blood gas.[13]
Perform a primary survey, assessing the patient’s airway, breathing, and circulation.[1]
Be aware that the patient with asthma who has respiratory symptoms can deteriorate quickly.[13]
Assess symptoms. Check for the classic triad of:
Breathlessness
Specifically, an increase in shortness of breath (including too breathless to complete sentences in one breath).
Look for progressive worsening.[1] The degree of breathlessness is an aid in determining the severity of the exacerbation.
Cough
Wheeze
The patient is also likely to present with any of the following:[1][13]
Progressive chest tightness
A symptom of impaired airflow.
Progressive decrease in lung function (a decrease in home PEF measurements)
Tachypnoea
A sign of dyspnoea and airflow obstruction.
Tachycardia
Silent chest
Accessory muscle use
Look for accessory muscle use as this is a sign of respiratory distress.
Altered consciousness
Cyanosis[13]
Indicates severe hypoxaemia.
An indication of a life-threatening exacerbation.[13]
Collapse.[13]
Ask about a prodrome of symptoms, such as:
Nocturnal awakening with the ‘classic triad’ of symptoms (cough, breathlessness, and wheeze)
Exertional symptoms
Nasal symptoms
Skin symptoms (e.g., eczema).
Note that none of the listed symptoms, singly or together, are specific and their presence or absence does not confirm or exclude an exacerbation of asthma.[13] An exacerbation represents a change in the patient’s symptoms and/or lung function compared to their normal state.[47] There is an objective decrease from baseline in measures of pulmonary function, such as PEF rate and forced expiratory volume in one second (FEV1).
Practical tip
The patient may perceive airflow limitation poorly. There may be a significant decline in lung function without a change in symptoms. Likewise, the patient may have marked symptoms with little change in measured airflow limitation.
Check for signs of other conditions that could explain acute breathlessness, including:
Heart failure[1]
Paradoxical vocal fold motion (also known as inducible laryngeal obstruction)[1]
Inhaled foreign body[1]
Pulmonary embolism[1]
Pneumonia
Pneumothorax
COPD
Anaphylaxis. See our topic pages for these conditions for more information.
Check for other conditions that may cause cough and wheeze, and lead to shortness of breath, with or without asthma, such as a viral infection. In practice, acute viral bronchiolitis is difficult to differentiate from a viral exacerbation of asthma. Establish whether there is a secure prior history of asthma.
Check for any comorbid conditions or complicating factors, such as pneumothorax, anaphylaxis, or pneumonia.[1] Note that pneumothorax, pneumonia, and COPD could also be differential diagnoses. See Differentials and Complications.
Practical tip
The patient with life-threatening or severe asthma may not be distressed and may not show all of the abnormalities listed above. Be alert to the presence of any of the signs and symptoms.
Take a brief history at the same time as starting therapy (for treatment information see Management recommendations).[1] Ask about:
Time of onset and possible cause of the current exacerbation[1]
Severity of acute asthma symptoms[1]
Ask if the symptoms limit the patient’s ability to exercise or disturb their sleep.
Any current symptoms of anaphylaxis[1]
Anaphylaxis is an important alternative or complicating diagnosis to consider (especially if the patient has a history of suspected or confirmed anaphylaxis, which is a risk factor for asthma-related death).[1] Food-induced anaphylaxis commonly presents as a life-threatening asthma exacerbation.[1]
Risk factors for asthma exacerbation:[1][13]
History of previous asthma attacks
In particular, near-fatal asthma requiring intubation or mechanical ventilation, or hospitalisation or emergency care for asthma in the last year.
Poor control
Inappropriate or excessive short-acting beta-2 agonist use
Age[13]
Elderly patients may be more at risk and require specialist care.
Reports indicate that people aged 18-29 have a high prevalence of poorly controlled asthma and an increased likelihood of an exacerbation.[48]
Female sex[13]
Reduced lung function
A decrease in home PEF measurements.
The Global Initiative for Asthma (GINA) advises that a low FEV₁, especially <60% predicted, is an important risk factor for exacerbations, even if the patient has few asthma symptoms.[1]
Obesity
Smoking (including e-cigarettes/vapes)
Depression, other psychological disease, or major psychosocial or socioeconomic problems
A history of anaphylaxis[13]
Food allergy
Comorbid gastro-oesophageal reflux disease
COPD[13]
Raised FeNO at routine reviews
Blood eosinophilia
High blood eosinophil count, reflecting type 2 inflammation, is a risk factor for asthma exacerbations.[51]
Poor adherence with prescribed preventer (controller) medication, or poor engagement with routine asthma review or follow-up
High bronchodilator reversibility[1]
Chronic rhinosinusitis.[1]
All current asthma reliever and preventer (controller) medications, including doses and devices prescribed, and whether a spacer is used.[1] Ask:
About adherence pattern, any recent changes to treatment (e.g., dose) including any changes made in response to the exacerbation, and response to current therapy[1]
If the patient uses or has recently stopped using oral corticosteroids
If the patient is currently using inhaled corticosteroids
How frequently short-acting beta-2 agonists are used.
Triggers, such as:[1]
Infections (e.g., viral respiratory infections)
Allergens (e.g., pollen, food and occupational allergens)
Irritants (e.g., smoke, fumes, pollution)
Medicines (e.g., non-steroidal anti-inflammatory drugs [NSAIDs], aspirin, beta-blockers).
Pregnancy
Pregnancy increases the risk of exacerbations even if the patient has few asthma symptoms.[1]
Exacerbations are associated with worse outcomes in pregnant women and their babies (causing pre-term delivery and low birth weight).[1][13][52] Acute severe asthma in pregnancy is an emergency and should be treated vigorously.[13] See Management Recommendations.
Identify patients with any of the following features. Patients with severe asthma and one of the following features are at increased risk of fatal or near-fatal asthma:[13]
Non-adherence with treatment
Failure to attend appointments
Requiring frequent home visits
Psychiatric illness
Alcohol or drug abuse
Obesity
Learning difficulties
Employment or income issues
Social isolation
Current or recent major tranquiliser use.
Note that GINA identifies the following risk factors for asthma-related death (irrespective of asthma severity):[1]
A history of near-fatal asthma requiring intubation and mechanical ventilation
Hospitalisation or emergency care visit for asthma in the past year
Currently using or having recently stopped using oral corticosteroids
Not currently using inhaled corticosteroids (ICS)
Over-use of short-acting beta-2 agonists, especially use of one or more inhalers of salbutamol (or equivalent) monthly on average, or use of nebulised short-acting beta-2 agonist
Poor adherence with ICS-containing drugs and/or poor adherence with (or lack of) a written asthma action plan
A history of psychiatric disease or psychosocial problems
Food allergy (or anaphylaxis) in a patient with asthma
Several comorbidities including pneumonia, diabetes, and arrhythmias are independently associated with an increased risk of death after hospitalisation for an exacerbation.
Assess the patient’s level of consciousness.[1] Use a standard tool, such as the Glasgow Coma Scale. [ Glasgow Coma Scale Opens in new window ]
Assess the patient’s speech[1]
Can the patient speak in full sentences? Do they struggle to complete words?
Assess the patient’s respiratory effort.
Is there accessory muscle use?[1]
Listen to the patient’s chest and check for wheeze.[1] Check for stridor.
Take particular note if the patient has a silent chest.
Stridor may indicate an alternative aetiology of the clinical presentation, such as vocal cord dysfunction.
Check for cyanosis.[13]
Assess for the presence of complicating factors such as anaphylaxis, pneumonia, atelectasis, pneumothorax and pneumomediastinum, and consider whether there are signs of alternative causes of acute breathlessness (e.g., pulmonary embolism, heart failure).[1]
In particular, keep in mind the signs and symptoms that may indicate life-threatening or severe acute asthma. See Severity assessment below.
Measure respiratory rate.[1][13]
Respiration ≥25 breaths/minute indicates acute severe asthma.[13]
Pulse ≥110 beats per minute indicates acute severe asthma.[13]
Check temperature and blood pressure.[1]
Continue to monitor pulse and respiratory rate.[13]
Determine the severity of the exacerbation. Note that none of the listed symptoms, singly or together, are specific and their presence or absence does not confirm or exclude an exacerbation of asthma.[13]
Life-threatening asthma is any one of the following in a patient with severe asthma:[13]
Silent chest
Cyanosis
Poor respiratory effort
Arrhythmia
Hypotension
Exhaustion
Altered consciousness
PEF <33% of best or predicted
SpO2 <92%
PaO2 <8 kPa (<60 mmHg)
‘Normal’ PaCO2 (4.6-6.0 kPa [35-45 mmHg])
Raised PaCO2 is a marker of near-fatal asthma.
Acute severe asthma is a patient presenting with any one of the following (and no features of life-threatening asthma):[13]
Patient can’t complete a sentence without taking a breath
Respiratory rate ≥25/minute
Pulse rate ≥ 110 beats per minute
PEF 33% to 50% of best (use % predicted if recent best unknown).
Indications for moderate asthma are:[13]
Speech normal
Respiratory rate <25 breaths/minute
Pulse rate <110 beats per minute
PEF >50% to 75% of best or predicted.
In the community, arrange immediate hospital admission via an ambulance for any patient with possible life-threatening asthma and for patients withacute severe asthma (including pregnant patients).[13] See Severity assessment section above. Alert the receiving hospital unit.
Admit to hospital patients with features of acute severe asthma present after initial treatment or patients with previous episodes of near-fatal asthma.[13]
People with asthma who have respiratory symptoms are at risk of becoming seriously unwell very quickly.[13]
These patients should have immediate access to a health professional trained in the emergency treatment of asthma.[13]
Appropriate treatment should be started (where available) while transfer to hospital is arranged.[1] Stay with the patient until the ambulance arrives.[13]
The patient may receive a short-acting beta-2 agonist via oxygen-driven nebuliser in the ambulance.[13]
Most asthma deaths occur before admission to hospital.[13]
Have a high level of suspicion for acute severe asthma or life-threatening asthma in any patient presenting for an emergency asthma consultation (i.e., regard them as having acute severe asthma until shown otherwise).[13]
Consider other factors, such as failure to respond to treatment, comorbidities, or social circumstances, when considering which patients to refer.[13]
Bear in mind that moderate exacerbations can often be treated in the community.[1][13]
If the patient has any features indicating a life-threatening asthma exacerbation, measure arterial blood gas. No other investigations are immediately required prior to starting management.[13]
In hospital, perform the following initial investigations:[13]
Arterial blood gas
Peak expiratory flow
Pulse oximetry.
In the community, perform:
Peak expiratory flow
Pulse oximetry.
Arterial blood gas (in hospital)
Measure arterial blood gas in the patient with SpO2 <92% on pulse oximetry (irrespective of whether the patient is on air or oxygen) or other features of life-threatening asthma.[13]
SpO2 <92% on pulse oximetry is associated with a risk of hypercapnia.[13]
Also perform an arterial blood gas if:[13]
PEF <50% at 15-20 minutes of treatment
There are signs of severe asthma or PEF <50% at 60 minutes of treatment.
The following on arterial blood gas indicate more severe asthma:[13]
‘Normal’ or raised PaCO2 (>4.6 kPa [35 mmHg])
Severe hypoxia (PaO2 <8 kPa [60 mmHg])
Low pH (or high H+).
Repeat arterial blood gas within 60 minutes of starting treatment, if:[13]
initial PaO2 <8 kPa (60 mmHg) unless subsequent SpO2 >92%, or
PaCO2 ‘normal’ or raised, or
the patient deteriorates.
Peak flow (in the community and in hospital)
Measure PEF (before initiating treatment, if possible to do this without inappropriately delaying management) to help assess severity and direct decisions about management.[1][13] In acute settings, PEF may be more reliable than symptoms for determining exacerbation severity.[1] Consider the following peak flow criteria:[13]
Life-threatening asthma: PEF <33% of best or predicted
Acute severe asthma: PEF 33% to 50% of best or predicted
Moderate asthma: PEF >50% to 75% of best or predicted
Consider PEF in the context of other markers of severity. PEF alone does not determine the severity of an exacerbation. See Severity assessment section above.
Practical tip
Bear in mind that PEF depends on effort from the patient and may therefore vary in patients depending on the effort involved.
Measure PEF 15 to 30 minutes after starting treatment and continue to monitor PEF according to the patient’s response to treatment.[13] Repeat PEF measurements after bronchodilator therapy and at least four times throughout the patient’s hospital stay, if admitted.[13] Different peak-flow meters give different readings, so use the same (or a similar type of) meter as much as possible.
FEV1 is a valid measure of airway calibre, but PEF is considered more clinically useful and is more readily available in acute care.[13]
How to use a peak flow meter to obtain a peak expiratory flow measurement.
Pulse oximetry (in the community and in hospital)
Assess and record oxygen saturation on air using pulse oximetry.[13]
Life-threatening asthma: SpO2 <92%
Acute severe asthma: SpO2 ≥92%
Moderate asthma: SpO2 ≥92%
Pulse oximetry should be closely monitored during acute management.[1] Use pulse oximetry to determine the adequacy of oxygen therapy and the need for arterial blood gas measurement.[13]
Measure arterial blood gas in the patient with SpO2 <92% (irrespective of whether the patient is on air or oxygen) or other features of life-threatening asthma.[13] SpO2 <92% on pulse oximetry is associated with a risk of hypercapnia.[13]
Treat urgently (with aggressive therapy) any patients with saturations <90%.[1] See Management recommendations.
Bear in mind that pulse oximetry will not detect hypercapnia.[13] Also note that pulse oximetry may overestimate oxygen saturation in patients with dark skin colour.[1]
Do not delay supplemental oxygen when indicated if pulse oximetry is not readily available but commence monitoring as soon as available.[13]
Chest x-ray (in hospital)
Do not routinely request a chest x-ray as an investigation but consider if a complicating or alternative pulmonary pathology is suspected.[1][13]
Request a chest x-ray if there is:[13]
Suspected pneumomediastinum or pneumothorax
Suspected pneumonia/consolidation
Life-threatening asthma
Failure to respond to treatment satisfactorily
Requirement for ventilation.
In the emergency department, order a chest x-ray if there are signs of severe asthma or PEF <50% after 60 minutes.[13]
Full blood count (in hospital)
Indicated in acute exacerbations when complicating factors (e.g., pneumonia) are suspected from the history and examination. Assess for evidence of infection and/or eosinophilia. Raised WBC count could indicate evidence of infection.
Urea and electrolytes (in hospital)
Assess for electrolyte abnormalities which may need correction. In particular, look for deranged potassium, which often falls with beta-2-agonist use.
C-reactive protein (in hospital)
Assess for evidence of infection.
Theophylline levels (in hospital)
Check in a patient already taking oral theophylline. Elevated if theophylline toxicity.
ECG (in hospital)
Check to rule out arrhythmia and as baseline in case aminophylline is needed.
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