The National Early Warning Score 2 (NEWS2), developed by the Royal College of Physicians (RCP), is a standardised physiological scoring system designed to identify adult patients at risk of acute clinical deterioration. NEWS2 is widely used throughout the United Kingdom and internationally to support the early recognition of serious illness, facilitate timely escalation of care, and improve communication between healthcare professionals.
A major enhancement introduced with NEWS2 was the inclusion of two separate oxygen saturation (SpO₂) scoring scales. This modification allows more appropriate assessment of patients with differing oxygen saturation targets, particularly those with confirmed hypercapnic respiratory failure, for whom conventional oxygen saturation targets may be inappropriate.
Selection of the correct oxygen saturation scale is essential for accurate NEWS2 scoring and safe administration of oxygen therapy.
NEWS2 Oxygen Saturation Scale 1
Scale 1 is the standard oxygen saturation scoring system and is appropriate for the vast majority of adult patients.
It is used in individuals who do not have confirmed hypercapnic respiratory failure and who have standard oxygen saturation targets. Oxygen saturation measurements are assigned points according to predefined NEWS2 thresholds, with progressively lower saturations generating higher physiological scores and indicating increasing clinical risk.
Scale 1 is appropriate for most patients presenting with conditions such as:
- Pneumonia
- Sepsis
- Heart failure
- Acute asthma
- Pulmonary embolism
- Trauma
- Acute medical or surgical illness
For most patients, this scale supports early identification of deteriorating respiratory function and facilitates prompt clinical review.
NEWS2 Oxygen Saturation Scale 2
Scale 2 is reserved for patients with confirmed hypercapnic respiratory failure who have a prescribed target oxygen saturation range of 88–92%.
These patients are at risk of worsening carbon dioxide retention (hypercapnia) if excessive oxygen is administered. Consequently, lower target oxygen saturations are recommended to optimise oxygenation while minimising the risk of respiratory acidosis.
Patients who may require Scale 2 include:
- Confirmed chronic hypercapnic respiratory failure
- Selected patients with severe chronic obstructive pulmonary disease (COPD)
- Patients with documented long-term oxygen therapy plans specifying target saturations of 88–92%
- Other conditions where lower oxygen saturation targets have been prescribed by an appropriately qualified clinician
Importantly, Scale 2 should not be applied automatically to all patients with COPD. Its use should only follow a documented clinical decision confirming that lower oxygen saturation targets are appropriate.
Why Are Two Oxygen Saturation Scales Used?
Earlier versions of the National Early Warning Score used a single oxygen saturation scale for all patients. Clinical experience demonstrated that this approach could inadvertently encourage excessive oxygen administration in patients with chronic hypercapnic respiratory failure.
The introduction of Scale 2 enables these patients to be monitored using oxygen saturation targets appropriate to their physiological requirements while preserving the benefits of an objective early warning system. This refinement aligns NEWS2 with contemporary evidence-based oxygen prescribing practice and improves patient safety.
Supplemental Oxygen in NEWS2
NEWS2 records not only the patient’s oxygen saturation but also whether supplemental oxygen is being administered.
Patients receiving supplemental oxygen receive additional NEWS2 points, regardless of their measured oxygen saturation, because the requirement for oxygen therapy itself reflects increased physiological risk. Clinical documentation should also record the oxygen delivery device, inspired oxygen concentration where appropriate, and oxygen flow rate to support ongoing assessment and treatment decisions.
Clinical Applications
NEWS2 Oxygen Saturation Scales are routinely used across a wide range of healthcare settings, including:
- Emergency departments
- Acute medical units
- Hospital wards
- Intensive care units
- Ambulance services
- Community and urgent care teams
Repeated NEWS2 observations provide valuable trend information, allowing clinicians to identify improving or deteriorating physiological status and determine whether escalation or de-escalation of care is required.
Clinical Interpretation
The oxygen saturation component represents only one element of the overall NEWS2 score. Comprehensive assessment also includes:
- Respiratory rate
- Heart rate
- Systolic blood pressure
- Body temperature
- Level of consciousness or new confusion
- Requirement for supplemental oxygen
A high NEWS2 score does not establish a diagnosis but identifies patients at increased risk of clinical deterioration who require timely clinical review and, where appropriate, escalation of care. Conversely, a low NEWS2 score should never override significant clinical concern or replace professional judgement.
Clinical Significance
The introduction of two oxygen saturation scales represents one of the most important developments within NEWS2, ensuring that patients with differing oxygen requirements are assessed appropriately. Correct selection of Scale 1 or Scale 2, together with accurate physiological observations and comprehensive clinical assessment, enables healthcare professionals to recognise deterioration earlier, prescribe oxygen therapy safely, and support evidence-based decision-making across emergency, acute, and critical care settings.