Asthma Management Handbook

Completing secondary assessments and reassessing severity


When practical after starting treatment, complete clinical assessments and reassess severity.

Table. Secondary severity assessment of acute asthma in adults and children 6 years and over Opens in a new window Please view and print this figure separately:

Table. Secondary severity assessment of acute asthma in children aged 1-5 years Opens in a new window Please view and print this figure separately:

How this recommendation was developed


Based on clinical experience and expert opinion (informed by evidence, where available).

Last reviewed version 2.0

Complete a brief history, including:

  • reliever taken for this episode (dose, number of doses, time of last dose)
  • current asthma medicines (regular and as-needed, including type of devices used)
  • assessment of adherence to preventer (if prescribed)
  • what triggered this episode, if known (e.g. allergies, immediate hypersensitivity, medicines, respiratory infections
  • coexisting heart or lung disease, including chronic obstructive pulmonary disease
  • assess smoking status and exposure to second-hand smoke.
  • acute asthma is rarely triggered by food allergies, but confirmed food allergy is a recognised risk factor for asthma-related death.
How this recommendation was developed


Based on clinical experience and expert opinion (informed by evidence, where available).

Last reviewed version 2.0

In adults, start oxygen therapy if SpO2 <92%.

Titrate to target SpO2 93–95%

  • In adults, avoid over-oxygenation (SpO2 >95%), because this increases the risk of hypercapnoea.
How this recommendation was developed

Adapted from existing guidance

Based on reliable clinical practice guideline(s) or position statement(s):

  • Beasley et al. 20151

Last reviewed version 2.0

In children, start oxygen therapy if SpO2 <95%.

Titrate to target SpO2 >95%.

How this recommendation was developed


Based on clinical experience and expert opinion (informed by evidence, where available).

Last reviewed version 2.0

Arrange chest X-ray if pneumonia, atelectasis, pneumothorax or pneumomediastinum is suspected.

Note: Chest X-ray is not needed in most cases of acute asthma

How this recommendation was developed


Based on clinical experience and expert opinion (informed by evidence, where available).

Last reviewed version 2.0

Consider arterial blood gas analysis for adults with SpO2 <92%.

  • The risk of hypercapnoea is increased in older adults with asthma or asthma–COPD overlap.
How this recommendation was developed

Adapted from existing guidance

Based on reliable clinical practice guideline(s) or position statement(s)

  • Beasley et al. 20151

Last reviewed version 2.0

More information

Assessment of oxygen status in acute asthma

Hypoxia is the main cause of deaths due to acute asthma.2

Routine objective assessment of oxygen saturation at initial assessment of acute asthma is needed because clinical signs may not correlate with hypoxaemia.

Pulse oximetry is the internationally accepted method for routine assessment of oxygen status in patients with acute asthma. It should be available in all situations in which oxygen is used.1

Pulse oximetry does not detect hypercapnoea, so blood gas analysis is necessary if hypercapnoea is suspected in patients with severe or life-threatening acute asthma. Thoracic Society of Australia and New Zealand clinical practice guidelines for acute oxygen use in adults1 recommend that arterial blood gas analysis should be considered if oxygen saturation falls below 92% and in those at risk of hypercapnoea. Venous blood gas analysis can be used to assess acid–base balance and lactate,1 but performs poorly in identifying hypercapnoea.3

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Oxygen therapy in acute asthma

Oxygen is a treatment for hypoxaemia, not breathlessness.1 Oxygen has not been shown to improve the sensation of breathlessness in non-hypoxaemic patients.1 When oxygen supplementation is used, pulse oximetry is necessary to monitor oxygen status and titrate to target.

The aim of titrated oxygen therapy in acute care is to achieve adequate oxygen saturation without causing hypercapnoea.1 Adults with acute asthma and those with overlapping asthma and COPD are at greater risk of hypercapnoeic respiratory failure.

Drying of the upper airway is a potential complication of oxygen therapy,4, 5 and might contribute to bronchoconstriction.5

Few studies have investigated optimal oxygen supplementation protocols for patients with asthma.


In adults with acute asthma, titrated oxygen therapy using pulse oximetry to maintain oxygen saturation at 93–95% while avoiding hyperoxaemia achieves better physiological outcomes than 100% oxygen at high flow rate (8 L/min).6 High-concentration and high-flow oxygen therapy cause a clinically significant increase in blood CO2 concentration in adults with acute asthma.6, 7

Thoracic Society of Australia and New Zealand (TSANZ) clinical practice guidelines for acute oxygen use in adults1 recommend that, in patients with COPD, oxygen should be administered if the SpO2 is less than 88%, and titrated to a target SpO2 range of 88–92%. For other acute medical conditions, the TSANZ guidelines recommend that oxygen should be administered if the SpO2 is less than 92%, and titrated to a target SpO2 range of 92–96%.

Humidification of oxygen via high flow nasal cannulae may improve comfort and tolerance.1


There is very little evidence available to inform recommendations for oxygen saturation targets in children with asthma.8 Studies in infants with bronchiolitis suggest that targets as low as >90%9 or >92%10 may be achieve similar clinical outcomes as higher targets. Recommendations for oxygen saturation targets during supplemental oxygen vary between clinical guidelines and vary between protocols used in Australian hospitals.

Humidified oxygen can be considered if necessary. Humidification is usually not needed for low flow oxygen (<4 L/minute in children or 2 L/minute in infants) for short term. Humidification may be considered if the oxygen is required for longer than 48 hours or if the nasal passages are becoming uncomfortable or dry.4

Guidance on oxygen delivery techniques and practical issues is available from Sydney Children's Hospital Network and The Royal Children's Hospital Melbourne.

Humidified oxygen via high-flow nasal cannulae

Humidified high flow nasal oxygen is a system that has the ability to provide a humidified high-flow mix of air and oxygen via a specialised nasal cannula system. It is able to deliver positive end expiratory pressure of approximately 4–8 cm H20.

Delivery of high-flow oxygen via nasal cannulae is increasingly common practice in Australian emergency rooms. There is very little evidence to support its use in acute asthma treatment,1 but it does not appear to be associated with significant risks.

It has been reported to be feasible and safe in children with severe acute asthma in ICU,11 and at least as effective as conventional oxygen therapy in children with acute asthma with inadequate response to initial bronchodilator treatment.11 No published studies have evaluated its use in adults with acute asthma.

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Heliox in acute asthma

The rationale for its use of heliox (mixture of helium and oxygen in various proportions) in patients with asthma is that the low density may improve airflow in the presence of turbulence within the airways.12 It has negligible adverse effects.12

When giving nebulised bronchodilators in acute asthma, the use of heliox to drive the nebuliser may be more effective than oxygen for improving lung function and reducing hospital admission rates in adults and children.13, 14 However, overall evidence for benefits in the treatment of children with acute asthma is inconclusive.12

Heliox may not have any benefit for patients with severe asthma requiring mechanical ventilation.15

Heliox is not commonly used in Australian emergency departments and is not routinely available.

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Spirometry in acute asthma

Spirometry is used alongside clinical assessment and oximetry to assess severity of acute asthma and response to treatment. Clinical assessment alone may underestimate the severity of airflow limitation.16

However, no recent clinical trials have compared outcomes of spirometry-guided treatment of acute asthma with non-spirometry-guided treatment.

A study in adults with acute asthma found that, on its own, FEV1 (measured by spirometry) at 1 hour after admission to the emergency department did not closely correlate with clinicians’ decision for or against hospital admission, as assessed clinically.16 However, the combination at 1 hour of FEV1 and the patient’s ability to lie flat was significantly predictive of the decision for hospital admission.16

In adults with poor response to initial bronchodilator treatment, dyspnoea scores at 3 hours from presentation may predict relapse or clinicians’ assessment of the need for hospitalisation better than FEV1, but neither is a strong predictor.17

In children with acute asthma, clinical severity scores may be more sensitive than spirometry to detect change clinical status beyond the first 2 hours of treatment.18 The value of performing spirometry in children before hospital discharge is unclear.19

Feasibility and technique

Although some clinical guidelines recommend spirometry before treatment to assess baseline lung function, most children with severe acute asthma and many with mild-to-moderate acute asthma cannot perform spirometry at this time.20 Younger children (most children under 6 years) are unlikely to be able to perform spirometry, even when they do not have a flare-up.

Most adults with acute asthma can perform spirometry within the first hour of admission to the emergency department.21 (Hospital staff and primary care health professionals may need specific training in spirometry technique to be able to obtain acceptable spirometry in patients with acute asthma.21)

It may not be feasible to apply standard spirometry technique and manoeuvre acceptability criteria in patients with acute asthma:20, 21

  • 80% of patients older than 12 years with acute asthma can perform an FEV1 manoeuvre. A forced exhalation from total lung capacity for 2 seconds is sufficient and provides useful information about the severity of airflow obstruction
  • two attempts may suffice if patients are unable to make three attempts
  • variability between manoeuvres of < 10% should be considered acceptable
  • patients may not be able to tolerate nose clips
  • patients are unlikely to be able to exhale for long enough to demonstrate the time-volume plateau. Although patients should aim for forced exhalation of at least 6 seconds, 2 seconds is acceptable for measuring FEV1 in clinical assessment during acute asthma. A spirometry manoeuvre might be considered acceptable if back-extrapolated volume is either < 5% of FVC or 0.15 L (whichever is greater), or a time to peak flow < 120 ms.

Table. Tips for performing spirometry in patients with acute asthma

  • Ask the patient to sit straight upright, either in a chair or on a stretcher with their legs over the side.
  • Make sure the person forms a tight seal around the mouthpiece.
  • Tell the patient to take as deep a breath as possible, then blast out air as fast and hard as they can, then keep blowing until asked to stop. Aim for exhalation of maximal force for at least 2 seconds (6 seconds if FVC is measured).

You may need to give the patient lots of coaching, repeat instructions, and give immediate feedback on technique.

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Peak expiratory flow measurement in acute asthma

Peak expiratory flow rate obtained using a peak flow meter underestimates the severity of airflow limitation in patients with acute asthma, compared with FEV1 obtained by spirometry.22

Peak expiratory flow is not a sensitive measure of small clinical improvements as perceived by the patient.23

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Instruments for assessing acute asthma

Validated scoring systems for assessing the severity of acute asthma, response to treatment, and predicting the need for hospital admission are used in research studies and by some clinicians. These include:

  • Pediatric Respiratory Assessment Measure (PRAM)24 for assessing acute asthma severity and response to treatment in children and adolescents, based on oxygen saturation, effort of breathing (suprasternal retraction and scalene muscle contraction), air entry (assessed by auscultation of the chest) and wheezing
  • the CHOP classification tree for predicting need for hospitalisation in adults,25 based on change in peak expiratory flow severity category, history of acute admission for asthma (‘ever hospitalisation’), oxygen saturation while breathing room air, and initial peak expiratory flow.

These instruments are not routinely used in Australian emergency departments.

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