A reduction in peak flow may indicate a life‐threatening situation and so should receive urgent medical attention (Wilkinson et al. [215]). For example, a PEF below 50% of the reference value indicates acute severe asthma and a PEF below 33% indicates acute life‐threatening asthma (Dakin et al. [50]). The treatment provided will be aimed at increasing air flow and oxygenation (Frew et al. [65]). Oxygen therapy is usually given with the aim of keeping oxygen saturations at a target saturation range (Sprigings and Chambers [189]). In patients who are known, or suspected, to have hypercapnia, oxygen therapy should target saturations of 88–92% (see Chapter c12: Respiratory care, CPR and blood transfusion for methods of oxygen administration).

Patients will require arterial blood gas samples to be taken at the earliest opportunity to enable their condition to be more thoroughly assessed (Adam et al. [2], O'Driscoll et al. [147]). Medication can be used to try to improve air flow and will usually include a combination of inhaled bronchodilators and steroids (British Thoracic Society [30], NICE [137]).

It should be noted whether the patient has experienced or been in contact with any of the following prior to the exacerbation:

The patient may require additional investigations, such as a chest X‐ray and blood and sputum tests (Frew et al. [65], West and Luks [210]).

Patient education is vital so that patients can manage their own condition (NICE [137]). This will include information on exacerbating factors, smoking cessation and when to access medical help (NICE [135]). Written personalized action plans used as part of self‐management education have been shown to improve health outcomes for people with asthma, with particularly good evidence for those with moderate to severe disease; patients report improved outcomes such as self‐efficacy, knowledge and confidence (British Thoracic Society [30]).