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Reader Feedback – Re-breather Masks

A reader has highlighted an important point about a reference made to a ‘re-breather’ oxygen mask in Case #2 (2005/33 QLD) in our December 2014 edition. This type of mask has an attached reservoir bag and at low oxygen flows, allows re-inhalation (or re-breathing) of exhaled CO2. In comparison, a ‘non-rebreather’ mask is a high concentration reservoir mask. It has a reservoir bag attached to it that is filled with oxygen. A non-rebreather mask may deliver oxygen at concentrations up to 90% when used with high flow rates of 10-15l/min. The bag is designed to prevent, not allow re-breathing (i.e. exhaled CO2 cannot be re-inhaled). Although the masks may look alike, a high flow of oxygen will prevent CO2 retention, no matter which type is used. This is vital for patients in the acute setting who require high-dose oxygen therapy.

The term ‘re-breather’ mask is sometimes erroneously used in hospital settings when referring to any mask which has a reservoir bag for delivered oxygen. Therefore, although the coroner’s finding referred to a ‘re-breather mask’, it is unclear in this case whether a ‘re-breather’ was in fact applied by the nursing staff, or whether a ‘non-rebreather’ mask was actually used.

For clarification, in the setting of hypoxia, as in this case, it is appropriate to escalate oxygen therapy by using a NON-rebreather mask with high flow oxygen and requesting senior assistance.

For further information on oxygen delivery devices, please go to: Page vi48 of the BTS guideline for emergency oxygen use in adult patients. Thorax 2008; 63:vi1-vi68. Available at:


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