Hudson Mask and Non-rebreather Mask
Hudson Mask
These are a low flow, variable performance device, meaning that different flow rates can be administered. Typically, the flow rates result in an FiO2 of 0.35-0.6. These masks can often be seen on the wards.
It has a lot of advantages. It is well tolerated, range of flows is titratable, higher FiO2 possible than with a standard nasal cannula, the mask itself can act as a small reservoir of oxygen, theoretically increasing the FiO2 delivered.
It does however have disadvantages. Patients are unable to eat or drink without temporarily removing the mask. Furthermore, it may dry out secretions and although in most cases it will deliver a higher flow than the nasal cannula, it will still poorly match PIFR, particularly in a patient with respiratory distress.
Below are images of the Hudson mask from two different perspectives.
Source: Images taken by Dr Keith Ip
Non-Rebreather
Non-rebreather masks are not true “high flow” devices as the oxygen flow rate from the wall is set at 15 litres/min. These masks are often used in the initial management of patients in acute respiratory distress.
As the patient’s PIFR increases, oxygen is entrained from the reservoir bag attached to the mask. A true non-rebreather mask will have an inspiratory and expiratory valve so that exhaled gas goes to the environment and inhaled gas comes only from the reservoir bag. However, as the seal is never perfect between the mask and the patient’s face there will always be some entrainment of air.
What are the advantages of a non-rebreathing mask? Much higher FiO2 delivered than devices without a reservoir or low flow devices.
The reservoir bag must be inflated or it will not deliver a high FiO2 . Like the other masks, the patient will be unable to eat or drink with the device in place, and the application of dry oxygen will dry out secretions.
Below is an image of a Non-rebreather mask:
Source: Image taken by Dr Keith Ip
Click next to move on to Higher Levels of Oxygen Delivery.
Introduction to Acute Respiratory Failure
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