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Oxygen Therapy in Acute Illness (BTS 2017 / TSANZ 2022)

Oxygen Therapy in Acute Illness (BTS 2017 / TSANZ 2022): Adult who may need oxygen → Assess SpO2, RR, HR, BP and conscious state → Special cases: the us...

Pathway Overview

22 steps

Algorithm Steps

22 total

  1. 01Start

    Adult who may need oxygen

    Acutely ill or breathless adult with suspected or confirmed hypoxaemia. Not for children or neonates.

  2. 02Action

    Assess SpO2, RR, HR, BP and conscious state

    Do not stop oxygen to get a room-air SpO2 if the patient clearly needs oxygen.

    • Record SpO2 with the device and flow (L/min) or FiO2
    • Tachypnoea and tachycardia are earlier signs of hypoxaemia than cyanosis
    • ABG if critically ill, at risk of hypercapnia, SpO2 falling or oximetry unreliable
    • Oxygen treats hypoxaemia, not breathlessness alone
  3. 03Warning

    Special cases: the usual SpO2 target does not apply

    Adults only. Cluster headache, sickle cell crisis and pneumothorax: follow condition-specific guidance. Poisoning advice: Poisons Information Centre 13 11 26.

    • CO poisoning: reservoir mask 15 L/min whatever the SpO2 (aim 100%); check COHb; discuss hyperbaric O2 with a hyperbaric unit
    • Paraquat poisoning or prior bleomycin: O2 only if SpO2 below 85%; reduce or stop if above 88%
    • Oximetry unreliable (dark skin, poor perfusion, COHb, MetHb): check ABG
  4. 04Decision

    Critical illness or peri-arrest?

    Cardiac arrest, shock, sepsis, major trauma, drowning, anaphylaxis, major pulmonary haemorrhage, status epilepticus or major head injury.

  5. If Yes
    1. 05Action

      Critical illness: reservoir mask 15 L/min now

      Also if at risk of hypercapnia, until ABG and senior review. Call senior or ICU help now.

      • Cardiac arrest: highest feasible oxygen during CPR
      • When SpO2 is reliable: step oxygen down to the target in the next steps
      • Early ABG
    2. 06Decision

      At risk of hypercapnic respiratory failure?

      COPD (known or suspected), BMI above 40, cystic fibrosis, bronchiectasis, chest wall or neuromuscular disease, previous NIV or intubation, oxygen alert card.

      • Known COPD, or suspected: over 50, long-term smoker, chronic breathlessness on minor exertion
      • Morbid obesity (BMI above 40)
      • Cystic fibrosis; bronchiectasis with fixed airflow obstruction
      • Chest wall deformity or neuromuscular disease
      • Previous hypercapnic failure (NIV or IMV); home oxygen or oxygen alert card
    3. If Yes
      1. 07Action

        Hypercapnia risk: target SpO2 88-92%

        Start oxygen only if SpO2 is below 88%. ABG now. Critical illness: keep the reservoir mask until ABG and senior review. Use the target on the patient's oxygen alert card if there is one.

        • Not critically ill and SpO2 88% or more: oxygen not initially needed
        • ABG now; repeat at 30-60 min even if the first is normal
        • Home oxygen users: a senior may set a patient-specific target
      2. 08Action

        Hypercapnia risk: 24% Venturi 2-3 L/min or 28% Venturi 4 L/min

        Or nasal cannulae 1-2 L/min. Drive nebulisers with air, and keep oxygen going by nasal cannulae.

        • RR above 30: set Venturi flow up to 50% above the pack minimum (FiO2 does not change)
        • SpO2 below 88% on 28% Venturi: step up FiO2 to keep 88-92%, repeat ABG, senior review
        • When stable: consider a change to nasal cannulae
      3. 09Decision

        ABG: pH below 7.35 and PaCO2 above 45 mmHg?

        Respiratory acidosis. Repeat ABG at 30-60 min, or sooner if worse.

      4. If Yes
        1. 10Action

          Respiratory acidosis: keep SpO2 88-92% and consider NIV

          Start NIV if acidosis persists 30 min after standard medical treatment. Senior or ICU review now. Do not stop oxygen suddenly.

          • Excess oxygen suspected: step down to the lowest oxygen that keeps 88-92% (24-28% Venturi or nasal 1-2 L/min)
          • Sudden cessation of oxygen can cause life-threatening rebound hypoxaemia
          • NIV not possible or failing: senior decision on intubation and ceiling of care
        2. 11Outcome

          Higher-level respiratory support

          HFNO, NIV or invasive ventilation in HDU or ICU, by senior decision.

        If No
        1. 12Action

          No respiratory acidosis: set the target from the ABG

          PaCO2 raised with pH 7.35 or more (chronic hypercapnia): keep 88-92%.

          • PaCO2 normal and no previous NIV or IMV: target may rise to 92-96% (BTS: 94-98%), unless usual stable SpO2 is lower
          • Recheck ABG at 30-60 min for rising PaCO2 or falling pH
        2. 13Action

          Monitor and titrate to the target

          Watch SpO2 for at least 5 min after each change. Step oxygen down when SpO2 is above target.

          • Senior review if FiO2 0.40 or more; ICU review if FiO2 0.50 or more
          • SpO2 fall of 3% or more, even within range: reassess the patient
          • Use an early warning score that counts FiO2 and SpO2
          • Hypercapnia risk: score SpO2 against the 88-92% target
        3. 14Decision

          SpO2 in target on the same or less oxygen?

          Rising oxygen need means the patient is getting worse.

        4. If Yes
          1. 15Action

            Stable in target: continue and plan weaning

            Keep the oxygen prescription with the target range active.

            • Check SpO2 against the target at each observation round
            • Treat the cause of hypoxaemia
            • On a Venturi mask and stable: consider a change to nasal cannulae
          2. 16Outcome

            Wean and stop oxygen

            Step down gradually to nasal 2 L/min (hypercapnia risk: 1 L/min or 24% Venturi 2 L/min), then stop. In hypercapnic patients do not stop oxygen suddenly (rebound hypoxaemia).

            • Stop when clinically stable on low-concentration oxygen and SpO2 in target on 2 consecutive checks
            • Check SpO2 on air at 5 min and at 1 hour
            • SpO2 falls below target: restart the lowest oxygen that kept the target
            • Keep the target-range prescription active
          If No
          1. 17Warning

            Not in target or needs more oxygen: escalate now

            Senior review now. Review the diagnosis. Check ABG.

            • ICU review if FiO2 0.50 or more or simple mask 8 L/min or more
            • Severe hypoxaemic failure: consider humidified high-flow nasal oxygen
            • pH below 7.35 and PaCO2 above 45 mmHg: consider NIV or intubation
          2. Path rejoins step 11Shared downstream outcome
      If No
      1. 18Action

        No hypercapnia risk: target SpO2 92-96%

        TSANZ 2022 (Australia, NZ). BTS 2017 (UK) uses 94-98%. Start oxygen only if SpO2 is below 92%.

        • SpO2 92% or more: oxygen not routinely needed
        • Write the target range on the oxygen prescription
        • Do not give oxygen to push SpO2 above the target
      2. 19Decision

        No hypercapnia risk: choose device by SpO2

        SpO2 bands are before oxygen. Start low and step up until SpO2 is in the target range. Already on a reservoir mask for critical illness: step down only when SpO2 is above target.

      3. SpO2 85-91%
      4. 20Action

        SpO2 85-91%: nasal cannulae 2-4 L/min

        Preferred device for most patients. Titrate to target.

        • FiO2 about 0.24-0.35 at 1-4 L/min
        • BTS flow range 2-6 L/min
        • Patient can eat, talk and use inhalers with cannulae in place
      5. Path rejoins step 13Shared downstream outcome
      6. Cannulae not enough
      7. 21Action

        Cannulae not enough: simple face mask 5-10 L/min

        Do not use below 5 L/min (CO2 rebreathing).

        • FiO2 about 0.35-0.60 at 5-10 L/min
        • Needs 6 L/min or more: senior review
        • Needs 8 L/min or more: ICU review
      8. Path rejoins step 13Shared downstream outcome
      9. SpO2 below 85% or mask not enough
      10. 22Action

        SpO2 below 85% or mask not enough: reservoir mask 15 L/min

        Only if not at risk of hypercapnia. Needs urgent senior review.

        • FiO2 above 0.60; keep the reservoir bag inflated
        • Severe hypoxaemic failure: consider humidified high-flow nasal oxygen
        • Step down as soon as SpO2 is in the target range
      11. Path rejoins step 13Shared downstream outcome
    If No
    1. Path rejoins step 06Shared downstream outcome

Guideline Source

BTS Guideline for Oxygen Use in Adults in Healthcare and Emergency Settings

DOI: 10.1136/thoraxjnl-2016-209729View Guideline

Clinical Safety Information

Clinical Decision Support — Not a Substitute for Clinical Judgment

Individual patient factors may require deviation from these recommendations.

Known Limitations

  • Adults only. The usual SpO2 targets do not apply in CO poisoning, paraquat or bleomycin exposure, cluster headache or sickle cell crisis.
  • Targets follow TSANZ 2022 (92-96%; 88-92% if at risk of hypercapnia). BTS 2017 (UK) uses 94-98% and 88-92%. Follow local policy.
  • Does not give HFNO or NIV settings, and does not cover mechanically ventilated patients.
  • Palliative care: oxygen for comfort follows different goals.
  • A new BTS guideline on target oxygen saturations is in development (publication expected 2026).

Contraindicated Populations

NeonatesChildrenCarbon monoxide poisoning (reservoir mask 15 L/min whatever the SpO2)Paraquat poisoning or prior bleomycin (lower SpO2 target)Palliative care with comfort-only goals

Applicable Regions

AUNZUKGlobal

AU: TSANZ 2022: target SpO2 92-96% for most adults; 88-92% if at risk of hypercapnia.

NZ: TSANZ 2022: target SpO2 92-96% for most adults; 88-92% if at risk of hypercapnia.

UK: BTS 2017: target SpO2 94-98% for most acutely ill adults; 88-92% if at risk of hypercapnia.

Global: Principles apply globally; device availability varies.

Version 2Next review: 2027-09-30

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Frequently Asked Questions

What is the Oxygen Therapy in Acute Illness (BTS 2017 / TSANZ 2022)?

The Oxygen Therapy in Acute Illness (BTS 2017 / TSANZ 2022) is a management clinical algorithm for Pulmonary Medicine. It provides a structured decision tree to guide clinical decision-making, based on BTS Guideline for Oxygen Use in Adults in Healthcare and Emergency Settings.

What guideline is the Oxygen Therapy in Acute Illness (BTS 2017 / TSANZ 2022) based on?

This algorithm is based on BTS Guideline for Oxygen Use in Adults in Healthcare and Emergency Settings (DOI: 10.1136/thoraxjnl-2016-209729).

What are the limitations of the Oxygen Therapy in Acute Illness (BTS 2017 / TSANZ 2022)?

Known limitations include: Adults only. The usual SpO2 targets do not apply in CO poisoning, paraquat or bleomycin exposure, cluster headache or sickle cell crisis.; Targets follow TSANZ 2022 (92-96%; 88-92% if at risk of hypercapnia). BTS 2017 (UK) uses 94-98% and 88-92%. Follow local policy.; Does not give HFNO or NIV settings, and does not cover mechanically ventilated patients.; Palliative care: oxygen for comfort follows different goals.; A new BTS guideline on target oxygen saturations is in development (publication expected 2026).. Individual patient factors may require deviation from these recommendations.

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