Login
Search

Search
Search

Oxygen Therapy and Respiratory Failure

BTS Guideline for oxygen use in adults in healthcare and emergency settings. Published: May 2017.

Background Information

There are 2 main types of respiratory failure:
  • Type 1 respiratory failure: hypoxia (PaO2 <8 kPa) with normal PaCO2
  • Type 2 (hypercapnic) respiratory failure: hypercapnia (PaCO2 >6 kPa) irrespective of oxygen level (PaO2 is usually low but can be normal)

  • COPD - main risk factor
  • Cystic fibrosis
  • Bronchiectasis
  • Severe chest wall or spinal disease (e.g. kyphoscoliosis)
  • Neuromuscular disease (e.g. ALSAmyotrophic lateral sclerosis)
  • Severe obesity

Device Flow Rate Indications Advantages Disadvantages / Cautions
Nasal Cannulae
 		 1-6 L/min (FiO2 ~24% to ~50%).
  • Low-concentration oxygen therapy for mild hypoxaemia
  • Viable alternative to venturi for patients at risk of hypercapnia
  • No risk of CO2 rebreathing
  • Comfort
  • Easy to use
  • May cause nasal irritation/soreness (Avoid >4 L/min to reduce this risk)
  • Reduced efficacy if nose is severely congested or blocked
  • Does NOT deliver fixed FiO2 
Simple face mask (aka ‘Hudson mask’) 5-10 L/min (FiO2  40-60%)
  • Suitable for patients with T1RF who require medium-concentration oxygen therapy
  • Easy to use
  • Higher oxygen delivery (vs nasal cannulae)
  • Not suitable for type 2 respiratory failure
  • Risk of rebreathing CO2  at flow rate <5 L/min
  • Does NOT deliver fixed FiO2
Non-rebreather mask (reservoir mask) Up to 15 L/min (FiO2 60-90% at 15L/min)
  • Critical illness
  • Severe hypoxaemia (<85%)
  • High oxygen concentration
  • Reservoir bag stores oxygen for nearly 100% O2 delivery
  • Not suitable for patients at risk of type 2 respiratory failure, unless critically ill
Venturi mask Refer to individual mask packaging for flow rate and FiO2
  • Precise oxygen delivery for patients at risk of type 2 respiratory failure
  • Precise oxygen delivery
  • Range of oxygen concentrations available
  • Not suitable for high-flow oxygen needs
 

Guidelines

Initial oxygen therapy (ALL patients):
  • Device: non-rebreather (reservoir) mask
  • Flow rate: 15 L/min
  • SpO2 target: 94-98% (unless in carbon monoxide poisoning where the target is 100%)

BTS defined the following conditions as 'critical illness':
  • Cardiac arrest or resuscitation
  • Shock
  • Sepsis
  • Major trauma
  • Anaphylaxis
  • Status epilepticus
  • Major head injury
  • Carbon monoxide poisoning
 

In critically ill patients who are at risk of type 2 respiratory failure, the same initial oxygen therapy (15L via non-rebreather targeting 94-98%) should be given.

Perform blood gas and adjust oxygen therapy according to the results:

  • If there is evidence of CO2 retention → adjust target to 88-92% and use controlled oxygen therapy
  • If no evidence of CO2 retention → maintain the same

Oxygen therapy depends on whether the patient is at risk of type 2 respiratory failure (see above for risk factors).
 

SpO2 target: 88-92%

Device:
  • Venturi mask (preferred), or
  • Nasal cannulae

Flow rate:
  • Venturi mask: 24% (2-3 L/min) or 28% (4 L/min)
  • Nasal cannulae: 1-2 L/min

  • ↑ PCO2 (>6.0 kPa) → continue with current oxygen therapy (88-92% target with venturi mask)
 
  • Normal PCO2 → change target to 94-98% (no restriction on the oxygen delivery device)

SpO2 target: 94-98%

Oxygen delivery device:
  • SpO2 <85% → 15L/min via non-rebreather (reservoir) mask
  • SpO2 ≥85% → nasal cannulae at 2-6 L/min or simple face mask at 5-10 L/min

References

Author: Kon M
Reviewer:
Last edited: 30/07/25