Target Oxygen Saturation During an Asthma Attack
During an asthma attack, oxygen should be administered to maintain an oxygen saturation (SpO2) of greater than 90%, with a target range of 94-98% for most patients. 1
General Principles of Oxygen Therapy in Asthma
- Oxygen administration is a primary treatment for all asthma exacerbations, alongside inhaled β2-agonists and systemic corticosteroids 1
- Oxygen should be delivered through nasal cannulae or mask to maintain the target saturation levels 1
- Oxygen saturation should be continuously monitored until a clear response to bronchodilator therapy has occurred 1
Specific Target Ranges
- Standard target range for asthma patients: 94-98% 1
- Special populations requiring higher targets:
Clinical Decision Making Based on Oxygen Saturation
- Initial oxygen saturation ≤90% indicates increased severity and risk of a complicated hospital course 2
- SpO2 levels <94% are associated with increased severity of asthma attacks 3
- SpO2 levels ≤92% are associated with a 6.3-fold greater relative risk for requiring additional treatment 3
Oxygen Delivery Methods
For mild to moderate exacerbations:
- Nasal cannulae at 2-6 L/min (preferred) or
- Simple face mask at 5-10 L/min 1
For severe exacerbations with saturation below 85%:
- Start with a reservoir mask at 15 L/min 1
Monitoring Considerations
- Pulse oximetry should be used to guide oxygen therapy throughout treatment 1
- Desaturation can occur during various activities including coughing, eating, and sleeping in patients with acute asthma 4
- Tachypnea and tachycardia are more common indicators of hypoxemia than visible cyanosis 1
Nebulizer Therapy and Oxygen
- For patients with asthma, nebulizers should be driven by oxygen at a flow rate of >6 L/min 1
- After nebulizer treatment is complete, return the patient to their usual oxygen delivery device 1
- If oxygen-driven nebulizers are not available, use an air-driven nebulizer with supplemental oxygen via nasal cannulae 1
Common Pitfalls to Avoid
- Do not discontinue oxygen therapy to obtain room air measurements in patients who clearly require oxygen 1
- Do not delay transport to hospital when administering bronchodilator treatments in pre-hospital settings 1
- Be aware that bronchodilator therapy itself may sometimes cause pulmonary vasodilation leading to V/Q mismatch and reduced blood oxygen levels 1
- Remember that pulse oximetry alone is not sufficient for self-monitoring of asthma exacerbations at home without professional guidance 5
Special Considerations
- In patients with hemoglobinopathies, standard oxygen saturation targets may not apply, and individualized targets based on oxygen dissociation curves may be needed 6
- For patients with risk factors for hypercapnic respiratory failure (e.g., COPD), a lower target range of 88-92% may be appropriate after blood gas assessment 1