Synopsis
Assess the severity and mechanism of sudden breathlessness, treat oxygenation and ventilation failure promptly, and select focused investigations without overlooking cardiovascular or metabolic causes.
- Assess speech, work of breathing, respiratory rate and conscious level before pursuing a diagnostic label.
- Prescribe oxygen to a target saturation, generally 94–98% or 88–92% with hypercapnic respiratory failure risk.
- A normal saturation on oxygen cannot exclude carbon-dioxide retention or respiratory fatigue.
Key red flags
New drowsiness or a falling respiratory effort during severe breathlessness can mean impending ventilatory failure and requires immediate escalation.
Investigation priorities
Assess oxygenation, carbon-dioxide handling and acid–base disturbance.
Management branches
Severe distress, hypoxaemia, fatigue or reduced consciousness makes waiting for complete investigation unsafe.
- Obtain experienced help, position to support breathing when circulation allows, clear or support the airway and deliver oxygen appropriate to the immediate threat.
- Assess whether spontaneous ventilation is effective; assist ventilation and prepare advanced airway support when effort or conscious level is inadequate rather than simply increasing oxygen flow.
Key medicines
Salbutamol for acute severe asthmaGive 5 mg by oxygen-driven nebuliser initially; repeat according to the acute-asthma response pathway, often every 15–30 minutes for a poor early response while senior reassessment proceeds.Monitor pulse, potassium and lactate with intensive treatment. Persistent tachypnoea may reflect worsening obstruction or beta-agonist-associated lactic acidosis and requires reassessment.
Prednisolone for an adult asthma attackGive 40–50 mg orally once daily until recovery, for a minimum of 5 days, provided the patient can swallow and absorb the medicine.Use an appropriate IV corticosteroid alternative if the oral route is unsuitable. Assess glucose and relevant infection risks; corticosteroids do not replace urgent ventilatory support.