Treatment of Severe Hypoxemia

Initial Assessment and Management

The British Thoracic Society recommends that all patients with severe hypoxemia (SpO2 <85%) require immediate oxygen therapy and urgent clinical assessment to identify and treat the underlying cause 2, 3
The British Thoracic Society suggests checking arterial blood gases (ABGs) within 1 hour of initiating oxygen therapy to assess for hypercapnia and guide further management 2, 4
For critically ill patients or those with shock/hypotension, the British Thoracic Society recommends obtaining arterial blood samples rather than capillary samples 3

The British Thoracic Society recommends initial treatment with a reservoir mask at 15 L/min oxygen flow for patients without risk of hypercapnic respiratory failure 1, 2
The British Thoracic Society suggests titrating down to maintain a target saturation of 94-98% using nasal cannulae at 1-6 L/min or a simple face mask at 5-10 L/min once the patient is stabilized 1, 2
For patients with risk of hypercapnic respiratory failure, the British Thoracic Society recommends initial treatment with a 24% Venturi mask at 2-3 L/min or a 28% Venturi mask at 4 L/min or nasal cannulae at 1-2 L/min 1
The British Thoracic Society suggests a target saturation range of 88-92% for patients with risk of hypercapnic respiratory failure 1, 5

The British Thoracic Society identifies COPD and other conditions causing fixed airflow obstruction as risk factors for hypercapnic respiratory failure 1
The British Thoracic Society also identifies cystic fibrosis, neuromuscular disease or neurological conditions affecting respiratory muscles, and chest wall deformities or morbid obesity as risk factors for hypercapnic respiratory failure 1

The British Thoracic Society recommends a target saturation of 85-88% for patients with paraquat poisoning or bleomycin lung injury 1
The British Thoracic Society suggests that patients with high respiratory rates should receive oxygen via a Venturi mask at a flow rate exceeding their peak tidal and exertional inspiratory flow 6
The British Thoracic Society recommends against oxygen therapy for patients with intractable breathlessness in palliative care settings who are not hypoxemic (SpO2 ≥92%) 7

The British Thoracic Society recommends recording oxygen saturation, delivery system, and flow rate on the patient's monitoring chart 8
The British Thoracic Society suggests adjusting oxygen delivery device and flow rate to maintain target saturation range 8
The British Thoracic Society recommends urgent clinical reassessment if oxygen requirements increase 3
The British Thoracic Society suggests considering non-invasive ventilation for patients with persistent hypoxemia despite oxygen therapy, especially those with COPD exacerbations 5