Oxygen therapy

• Delivers 24-30%
• Comfortable
• Flow rate 1-4L/minute
• Used for mild hypoxaemia and use in non-acute wards

• Delivers 30-40%
• Flow rate 5-10L/minute
• Delivers slightly more oxygen than a nasal cannula but the precise FiO₂ cannot be determined so a Venturi mask is often used instead

• Delivers 24-60%
• Oxygen delivery depends on mask: this is marked on the side of the mask, along with the appropriate flow rate setting
• Often used in patients with COPD/type 2 respiratory failure so you know the precise FiO₂ you are delivering

Types of Venturi mask:

• Delivers 85-90% with 15L/minute flow rate
• Mask with a reservoir bag and valve which stops almost all rebreathing.
• Used for acutely unwell hypoxaemic patients

• Delivers up to 100% with up to 60L/minute flow rate
• The very high flow rate also creates a small positive airway pressure effect similar to CPAP
• Used in type 1 respiratory failure as an alternative to CPAP or a non-rebreather mask

• Delivers up to 100% oxygen
• Air/oxygen delivered through a tight-fitting mask at constant positive pressure to keep alveoli open
• Used in type 1 respiratory failure (e.g. due to sleep apnoea or acute LVF)

• Delivers up to 100% oxygen
• Same system but with a high positive pressure on inspiration and a lower positive pressure on expiration
• Used in type 2 respiratory failure with respiratory acidosis or exhaustion (e.g. due to COPD or neuromuscular diseases)

Delivers up to 100% oxygen. A ventilation bag or machine is attached to an artificial airway to ventilate lungs. Used in intensive care and theatre.

General points

• Intubate if GCS ≤ 8 (risk of airway not protected)
• Aim for oxygen saturations of 94-98% in most patients, but 88-92% in those at risk of hypercapnic respiratory failure (e.g. COPD)
• If a patient is requiring a high level of ward-based oxygen therapy (e.g. FiO₂ ≥40-60%) to maintain saturations, or they are in type 2 respiratory failure despite medical therapy, or they have a persistently increased work of breathing (e.g. RR≥28), involve seniors and/or intensive care for consideration of non-invasive or invasive ventilation as appropriate.
• Do an ABG on any patient with oxygen saturations of <92% or high oxygen requirements
• Humidified oxygen helps secretions and prevents

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