Secondary severity assessment

Following the initial severity assessment and initiation of treatment, perform a more detailed secondary severity assessment as outlined in Secondary severity assessment of acute asthma to determine ongoing management.

Assessment of response to treatment is an ongoing process; tailor the frequency of assessment to the severity of the exacerbation. Repeat secondary severity assessment frequently within the first hour (eg after each dose of salbutamol). In more severe cases, remain at the bedside until the patient is stabilised.

Secondary assessment of acute asthma should also take into account any risk factors for fatal asthma—see Risk factors for potentially fatal asthma.

Table 1. Secondary severity assessment of acute asthma
Mild to moderate: all of the following	Severe: any of the following	Life-threatening: any of the following
consciousness
alert	may be the same as mild to moderate and does not determine severity	reduced consciousness (eg drowsy or unconscious)
speech
can finish a sentence in one breath	children 1 to 5 years: may be the same as mild to moderate and does not determine severity adults: unable to complete sentences in one breath	can’t speak or can only speak single words because of dyspnoea
posture
can walk (or, if an infant, crawl)	difficulty lying flat because of dyspnoea sitting hunched forward (‘tripoding’) tiring	collapsed or exhausted
breathing
respiratory distress is not severe	increased work of breathing with use of accessory muscles (eg tracheal tug, intercostal or subcostal recession, marked abdominal breathing, chest wall recession in children)	severe respiratory distress or poor respiratory effort
skin colour
normal	may be the same as mild to moderate and does not determine severity	cyanosis (not always present)
respiratory rate [NB1]
normal	tachypnoea	tachypnoea bradypnoea (indicates respiratory exhaustion)
heart rate [NB1]
normal	tachycardia	cardiac arrhythmia or bradycardia (may occur just before respiratory arrest)
chest auscultation
wheeze persistent cough (not always present)	may be the same as mild to moderate and does not determine severity	‘silent chest’ due to reduced air entry
oxygen saturation (pulse oximetry)
SpO₂ more than 94%	SpO₂ 90 to 94%	SpO₂ less than 90% or clinical cyanosis
arterial blood gas analysis (only applicable to adults)
not indicated	may be indicated if not improving as expected [NB2]	PaO₂ lower than 60 mmHg on room air PaCO₂ higher than 45 mmHg or PaCO₂ within normal range [NB2] pH less than 7.35 [NB3]
lung function tests (only applicable to adults)
FEV₁ or PEF more than 40% predicted or personal best	FEV₁ or PEF less than 40% predicted or personal best	not indicated (usually not able to be performed)
asthma history
assess risk factors for asthma-related death; see Risk factors for potentially fatal asthma
chest X-ray
not usually required; indicated if pneumonia, atelectasis, pneumothorax or pneumomediastinum is suspected, or if sudden deterioration
Note: FEV₁ = forced expiratory volume in 1 second; PaCO₂ = partial pressure of carbon dioxide; PaO₂ = partial pressure of oxygen; PEF = peak expiratory flow; SpO₂ = oxygen saturation measured by pulse oximetry NB1: Normal values for heart rate and respiratory rate in children vary with age; see The Royal Children’s Hospital (Melbourne) website. NB2: Do not be reassured by a normal PaCO₂ in a patient with an elevated respiratory rate. The presence of hypercapnia or normocapnia indicates that the patient is tiring and may need ventilatory support. NB3: Metabolic acidosis (often associated with hypokalaemia) may occur with increased work of breathing and with high-dose salbutamol. Adapted from the Australian Asthma Handbook © 2020 National Asthma Council Australia. Accessed 31 August 2020.

Figure 1. Risk factors for potentially fatal asthma

Risk factors for potentially fatal asthma include:

previous ventilation or admission to an intensive care unit for asthma
hospital admission for asthma in the last year
repeated emergency-department attendances in the last year
frequent short-acting beta₂ agonist use (eg more than one canister per month)
requirement for three or more classes of asthma maintenance medication
poor lung function
history of ‘brittle asthma’ (ie sudden and severe exacerbations)
confirmed food allergy
current or recent requirement for oral corticosteroid
rural or remote location.

The above factors often coexist with adverse psychosocial or behavioural factors, such as:

poor adherence to drug therapy
poor attendance at follow-up appointments
depression or other psychiatric illness
substance misuse, including smoking
denial of the serious nature of asthma or the need for regular treatment
social isolation
learning difficulties
financial or domestic problems.