Introduction Early warning scores (EWS) use routinely measured vital signs to identify patients at risk of deterioration. The National Early Warning Score 2 (NEWS2) is mandated for use by NHS England in all acute trusts. Within NEWS2, oxygen therapy is scored using a binary approach — patients receive 2 points if they are receiving supplemental oxygen and 0 points if they are breathing room air. Examples of binary oxygen EWS are widespread, including other nationally employed EWS. Some have expressed concerns that deterioration is missed when patients require an escalating amount of supplemental oxygen in the absence of other vital sign derangements. This study aims to adapt and validate a version of NEWS2 that accounts for the amount of supplemental oxygen therapy the patient receives (NEWS2-O2). Methods We will use data from four NHS healthcare trusts across the UK to develop and validate an oxygen therapy adjusted NEWS2 score. We will also explore the time trends of oxygen requirement and other vital signs prior to deterioration. We will perform an external validation of other oxygen adjusted vital sign only EWS identified in a prior systematic review. Generalisability and implications This work will explore the quantification and handling of oxygen therapy within an EWS. We aim to provide an example to the NEWS Development Group on how oxygen can be incorporated into the next iteration of NEWS.