A Venturi mask and a non-rebreather mask are not steps on a simple “weak to strong” scale. They are chosen for different purposes within a clinical plan. Changing between them requires assessment of the person, the oxygen source and the delivery requirements, rather than a decision based on appearance or a single oximeter reading.
Controlled oxygen delivery
A Venturi system mixes oxygen with room air through an adapter designed for a selected concentration. Its performance depends on the correct assembly, compatible source, adequate gas delivery and unobstructed entrainment openings. The printed percentage describes the intended mixture under those conditions, not a guarantee independent of how the device is used.
Controlled oxygen can be important when the team needs to manage oxygenation carefully while assessing the risk of raised carbon dioxide. The diagnosis of COPD alone does not specify an adapter or authorise a family to change settings. Blood gases and the clinical situation may be relevant.
Reservoir-mask oxygen
A non-rebreather has a reservoir bag and valves that help provide a high oxygen concentration when correctly supplied. The actual mixture still depends on the source, mask fit and breathing pattern. It does not deliver assisted breaths or replace a ventilator.
The BTS emergency-oxygen guidance places these interfaces in a monitored treatment pathway. It should not be converted into a home chart for choosing a mask from a saturation number.
What a change of mask should prompt
During hospital care, ask what the team is trying to achieve, how response is being monitored and what would require further support. A change may reflect a changing clinical situation, so it is more useful to understand the plan than to compare the names of the masks.
For home care, request the exact prescribed interface and a demonstration. Confirm that the source can support it, what a caregiver should check and whom to call. A reservoir that behaves abnormally or a patient becoming more distressed needs prompt attention according to the emergency plan. Do not tape openings, alter valves or exceed equipment limits.
Do not let a number replace assessment
An oximeter does not measure carbon dioxide or tell whether a person is becoming exhausted. New confusion, marked drowsiness, chest pain or severe breathlessness needs urgent medical help even if a displayed saturation seems acceptable. Do not delay assessment while trying successive masks.
For the practical meaning of the numbers on an adapter, see reading a Venturi mask. For distinguishing a simple mask from a reservoir design, see simple and non-rebreather masks. These explanations support a clear handover; they do not select treatment for an individual.