The patient circuit is the equipment that connects a patient to a CPAP machine. There is a specific set up for patients with COVID-19 that should be followed:

Patient interface

• The patient interface is a full-face, non-vented mask which fits over the patient’s nose and mouth and secured using straps.
• Ensure the mask is not too loose or too tight; you should be able to pass your fingers either side of the straps.
• The mask should be non-vented; this means that there is no exhalation valve which is important for infection control. The universal indication for a non-vented mask is that the elbow is blue, but other models of non-vented masks can be used in these patients and the colour of the elbow piece may vary.

Antibacterial-viral filter

• The antibacterial-viral filter fits onto the elbow of the patient interface, and filters the air that the patient exhales.

Oxygen entrainment port

• The port where oxygen can be entrained into the circuit.
• In contrast to previous guidance, the oxygen entrainment port should fit in the patient circuit after the antibacterial-viral filter, to minimise the risk of contamination should the oxygen tubing become dislodged. For further information about this alteration in guidance, see below for the most up-to-date guidelines.
• Ensure the oxygen tubing is attached to the circuit before the CPAP machine is started.

Exhalation valve

• The exhalation valve attaches to the antibacterial-viral filter and ensures the patient does not re-breath excessive levels of carbon dioxide.
• Some manufacturers have combined the oxygen entrainment port and exhalation valve.
• If using a combined oxygen and exhalation port, then this will attach into the antibacterial-viral filter. If using separate components, then the exhalation port will attach into the oxygen connector which will then attach into the antibacterial-viral filter.
• The exhalation valve MUST follow the antibacterial-viral filter in the circuit to ensure that the virus has been removed from the expelled air and therefore not released into the environment.

Standard 22mm circuit tubing

• The standard 22mm circuit tubing attaches to the back of the CPAP machine.

The full-face, non-vented face mask is the guideline suggested patient interface. It covers the patient’s nose and mouth and is secured in place using straps around the head. The elbow of the mask should be non-vented; this means that there is no exhalation valve which is important for infection control in COVID-19.

To fit the mask:

1. Identify the correct size of mask using the manufacturer’s sizing guide (S, M, L) to fit from the small of the chin to the bridge of the nose.
2. Position the lower point of the mask in the small of the chin, roll the mask up and over the face and pull the headgear around the patient’s head and secure in place with clips.
3. Adjust the tension of the straps to secure the mask in place, making sure you can fit fingers between the straps and the side of the patient’s face.
4. Attach the non-vented elbow to the antibacterial-viral filter, and the rest of the patient circuit.

To start CPAP treatment:

1. Set the CPAP machine to the correct prescription.
2. Connect the circuit to the machine in the following order; face mask, anti-bacterial viral filter, oxygen port, exhalation valve, 22mm tubing.
3. Fit the mask to the patient (see above); tight enough to prevent any leak, but not too tight to cause pressure damage to the face.
4. Connect the oxygen tube to the oxygen port and start oxygen therapy.
5. Start CPAP therapy and monitor the mask fit for leaks. If there are any leaks, adjust the straps.

Last updated 28/04/2020