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Low oxygen saturations

NEWS calls

Prescribe oxygen to a target range: 94–98% for most; 88–92% if at risk of hypercapnic respiratory failure.

NEWS2 has a separate SpO₂ scale for patients with a prescribed 88–92% target.

Act now

  1. 1

    SpO₂ <85% without hypercapnic risk: reservoir mask 15 L/min, then titrate to target.

  2. 2

    Otherwise start with nasal cannulae 2–6 L/min or simple face mask 5–10 L/min.

  3. 3

    Hypercapnic risk: 24% Venturi at 2–3 L/min or 28% at 4 L/min, target 88–92% pending gas.

Assess

  • ABCDE, work of breathing, RR, chest exam. Is the probe reading reliable?
  • Hypercapnic risk: COPD, morbid obesity, neuromuscular or chest wall disease, cystic fibrosis, bronchiectasis.

Investigations

  • Arterial blood gas if hypercapnic risk, deteriorating, or on oxygen with falling saturations.
  • CXR, ECG, FBC, CRP, U&E; consider CTPA, D-dimer only with a Wells score.

Manage

  • Treat the cause: pneumonia, pulmonary oedema, PE, pneumothorax, bronchospasm, atelectasis, opioid toxicity.
  • Hypercapnic acidosis (pH <7.35, PaCO₂ >6.5 kPa) despite treatment: consider NIV.
  • Step oxygen down once in target range; keep the target prescription in place.

Escalate when

  • Rising oxygen need, respiratory acidosis, exhaustion or reduced consciousness: senior and critical care/outreach.

Written to current guidance · sources checked 14 Nov 2026. We watch NICE for updates weekly.

Sources (2)

Reviewed by Aboodee Alhasso, MPharm MRCPharm IP on 14 Nov 2026

Calculators for this

For healthcare professionals, as an aid to clinical judgement — not a substitute for it. Follow your local policy and ask a senior when in doubt.