Asthma: Recognising a Severe Attack

Lachlan Baillie, Registered Paramedic

11 minutes ago

4 min read

Asthma is so common in Australia that it is easy to underestimate. Most attacks settle quickly with a reliever, and many patients have managed their asthma for years. But asthma still kills, and the patients most at risk are often the ones who look deceptively calm. For paramedic and nursing students, the key skill is recognising when an asthma attack has moved from uncomfortable to dangerous, and knowing that a quiet chest can be the most worrying sound of all.

Pathophysiology

Three things narrow the airways

Asthma is a chronic inflammatory condition of the airways. During an attack, three processes narrow the small airways at the same time:

Bronchoconstriction: the smooth muscle around the airways tightens.
Inflammation and swelling: the airway lining becomes swollen and leaky.
Mucus: thick secretions plug the narrowed airways.

Relievers work quickly on the first problem, but they do little for swelling and mucus. That is one reason severe attacks can be slow to respond, and why preventer medication matters so much in the long run.

Air goes in, but struggles to get out

Narrowed airways make breathing out much harder than breathing in. Air becomes trapped in the lungs with each breath, a process called dynamic hyperinflation. The chest becomes overinflated, the breathing muscles work at a mechanical disadvantage and the patient tires. Trapped air also raises the pressure inside the chest, which can reduce blood returning to the heart and lower blood pressure.

As the attack worsens, less air moves at all. Wheeze is created by air moving through narrowed airways, so when airflow becomes very poor, the wheeze can fade. This is the silent chest, and it is a sign of a life threatening attack, not an improvement.

A quieter wheeze in a patient who looks worse is not getting better. It may mean almost no air is moving.

Triggers

Common triggers include viral infections, allergens such as pollen and dust mite, smoke, cold air, exercise and missed preventer medication. In Australia, thunderstorm asthma is a recognised risk. During the Melbourne thunderstorm asthma event in November 2016, triple zero calls surged far above forecast levels and at least nine people died, including some with no previous diagnosis of asthma.

Assessment and Treatment

Recognising severity

The Australian Asthma Handbook classifies acute asthma in adults into mild to moderate, severe and life threatening. Simplified, the features look like this:

Mild to moderate: can speak in full sentences and walk, with oxygen saturation above 94%.
Severe: cannot finish a sentence in one breath, obvious respiratory distress, use of neck or intercostal muscles, tracheal tug or subcostal recession, and oxygen saturation of 94% or lower.
Life threatening: reduced consciousness or collapse, exhaustion, cyanosis, poor respiratory effort, soft or absent breath sounds, and oxygen saturation below 90%.

Any feature in a more severe category means you treat the patient at that level, even if other features look milder. Ask about previous intensive care admissions or intubation, recent hospital visits and how much reliever they have already used, because these point to a higher risk patient.

In practice: a patient sitting bolt upright, answering in two or three words, with a quiet chest and drifting attention is in a life threatening attack, even if the monitor still shows a reasonable saturation. Treat the patient, not the number.

Treatment priorities

Community asthma first aid in Australia follows four steps: sit the person upright, give four separate puffs of a reliever through a spacer, wait four minutes and repeat if needed, and call triple zero if breathing does not return to normal. As a clinician, your priorities build on this:

Sit the patient upright, stay calm and keep them calm.
Give bronchodilator therapy early and repeatedly, according to your clinical practice guidelines.
Give oxygen to correct low saturation, titrated to your guideline targets.
Escalate early for severe or life threatening features. Further treatments, which may include additional nebulised medications, intravenous medications and adrenaline, depend on your scope and guidelines.
Reassess constantly. Work of breathing, speech, conscious state and breath sounds tell you more than a single saturation reading.
Be cautious with assisted ventilation. Bagging too fast worsens air trapping, so slow rates that allow full exhalation matter.

Every patient with a severe attack needs medical review, and many need a review of their preventer use and asthma action plan once they recover.

Conclusion

Asthma attacks narrow the airways through bronchoconstriction, swelling and mucus, and trap air in the chest. Recognise severity by speech, work of breathing, conscious state and breath sounds, not just saturation. Treat early, escalate early and remember that a silent chest is a warning sign, not a recovery.

References

National Asthma Council Australia. Australian Asthma Handbook. Severity classification of exacerbations and acute asthma. https://www.asthmahandbook.org.au

Better Health Channel. Asthma emergency first aid. Victorian Department of Health. https://www.betterhealth.vic.gov.au/health/ConditionsAndTreatments/asthma-emergency-first-aid

Australian Institute for Disaster Resilience. Storm: Thunderstorm Asthma, Melbourne, Victoria, November 2016. https://knowledge.aidr.org.au/resources/storm-thunderstorm-asthma-victoria/

Global Initiative for Asthma (GINA). Global Strategy for Asthma Management and Prevention. https://ginasthma.org

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