Respiratory procedures: Use of a non-rebreathing oxygen mask

NON-REBREATHING OXYGEN MASKThe non-rebreathing oxygen mask enables the delivery of high concentrations of oxygen and is recommended for use in patients who are critically ill (Resuscitation Council UK, 2005). In order to ensure that the mask is functioning correctly and is used effectively, it is important to follow the manufacturer’s recommendations for simple, basic checks prior to use (Intersurgical, 2003).The aim of this article, the first in a five-part series on respiratory procedures, is to describe the correct use of a non-rebreathing mask.DESCRIPTIONThe non-rebreathing mask (sometimes called a Hudson mask) with an oxygen reservoir bag (Fig 1) can be used to deliver high concentrations of oxygen to a spontaneously breathing patient.A one-way valve diverts the oxygen flow into the reservoir bag during expiration; the contents of the reservoir bag, together with the high flow of oxygen, result in minimal entrainment of air and an inspired oxygen concentration of approximately 85% (Gwinnutt, 2006).The valve also prevents exhaled gases from entering the reservoir bag.The use of the oxygen reservoir bag helps to increase the inspired oxygen concentration by preventing oxygen loss during inspiration.It is important to ensure that a sufficient oxygen flow rate is used so the oxygen reservoir bag does not collapse during inspiration (RCUK, 2005); a flow rate of 12-15l/minute is recommended (Gwinnutt, 2006).Some non-rebreathing masks have elasticated ear loop bands. As these eliminate the need to move the patient’s head, they are used frequently in A&E departments for trauma patients.PROCEDURE- Ensure the patient is in an upright position to maximise breathing.- Request that pulse oximetry is commenced.- Check the oxygen prescription (see below).- Explain the procedure to the patient and gain informed consent.- Attach the oxygen tubing to the oxygen source.- Set the oxygen flow rate to 12-15l/minute (Fig 2).- Occlude the valve between the mask and the oxygen reservoir bag (Fig 3) and check that the reservoir bag is filling up. Remove the finger.- Squeeze the oxygen reservoir bag (Fig 4) to check the patency of the valve between the mask and the reservoir bag. If the valve is working correctly it will be possible to empty the reservoir bag. If the reservoir bag does not empty, discard it and select another mask (Smith, 2003).- Again, occlude the valve between the mask and the oxygen reservoir bag (Fig 3), and allow the reservoir bag to fill up.- Place the mask with a filled oxygen reservoir bag on the patient’s face, ensuring a tight fit (Fig 5).- Adjust the oxygen flow rate until it is sufficient to ensure that the reservoir bag deflates by approximately one-third with each breath (Smith, 2003).- Reassure the patient, who may need time to become accustomed to the mask.- Monitor the patient’s vital signs closely. In particular, assess the response to the oxygen therapy, checking respiratory rate, mechanics of breathing, colour, oxygen saturation levels and consciousness. Usually, arterial blood gas will also be monitored.- Discontinue or reduce the oxygen concentration as appropriate following advice from a suitably qualified practitioner.- Document the procedure following local protocols (Higgins, 2005; Intersurgical, 2003).RESPIRATORY RATE INDICATORSome masks have a respiratory rate indicator (Fig 6) to help healthcare practitioners monitor the patient’s respiratory rate. The indicator’s readings can be affected by:- The patient’s respiratory rate;- The orientation of the indicator;- The oxygen flow rate;- The fit of the mask to the patient’s face;- The presence of moisture in the indicator tube - this can actually stop the indicator from working (Intersurgical, 2003).Remember that the respiratory rate indicator should only be used as a guide and should not replace close monitoring of the patient’s breathing.PRESCRIPTION OF OXYGEN THERAPYIt is important to remember that oxygen is a drug and should be prescribed by an appropriately qualified practitioner. This prescription should include:- The type of oxygen delivery system;- The percentage of oxygen to be delivered (or flow rate);- The proposed duration of oxygen therapy;- Monitoring that will need to be undertaken (Smith, 2003).NMC (2004) guidelines for administration of medicines should be followed when oxygen is prescribed. However, in the emergency situation, unprescribed oxygen may need to be administered following local protocols.PROFESSIONAL RESPONSIBILITIESThis procedure should be undertaken only after approved training, supervised practice and competency assessment, and carried out in accordance with local policies and protocols.- This article has been double-blind peer-reviewed.

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