There are two flowmeters at the front of the CPAP machine. One controls the oxygen level – this is labelled O2 FLOW. The other flowmeter is labelled TOTAL FLOW – this one sends blended oxygen and air to the baby.

To check that the flowmeters are working correctly, the CPAP should be switched on. This ensures that air is being supplied from the pump.

The CPAP should also be connected to the external oxygen concentrator to ensure that oxygen is being supplied to the oxygen flowmeter.

On each of the flowmeters, when you turn the knob in each direction, the small silver bead should move up and down the flowmeter tube to indicate the flow level on the number dial.

If the bead doesn’t move, it may be caused by damage, a leak or a build-up of dirt – or the bead might have become stuck.

First, try tapping the front of the flowmeter with your hand or with a screwdriver handle. The bead can become stuck due to static or moisture, and this action can be enough to dislodge it.

If the bead still doesn’t move up and down, we’ll need to take a closer look at the flowmeter.

For safety, switch off and unplug the CPAP machine.

Inside the CPAP casing, ease off the tubes from the connector of the flowmeter which is not working. Then undo the screws that are in line with this flowmeter. You can then release the flowmeter from the front of the CPAP casing.

Next, undo the four screws around the sides of the flowmeter cartridge. You can then ease off the control knob and unscrew the two tube connectors.

Next, pop the metal spindle out from the plastic casing.

Using a flat-head screwdriver, carefully remove the three rubber O-rings from the spindle. If there’s a build-up of debris, or they are cracked or loosened, this can affect the functioning of the flowmeter.

Clean the O-rings with a cloth, or if they are degraded, replace them with a new set.

While the flowmeter is disassembled, take the opportunity to clean each component. Use a soft, damp cloth.

This should include cleaning the metal bead and the chamber it moves in. Slide out the locking plate to access the bead, being careful not to lose it.

Then, making sure everything is dry, put all the parts back together again.

Put the flowmeter back into the CPAP casing and screw it back into position, then reattach the tubes firmly onto the connectors.

It is essential that everything is put back in exactly the same position or the CPAP machine won’t work properly.

You should also check the patient port and oxygen port for loose connections, leakages or blockages.

For each port, you can push a cotton swab through the port to ensure that it’s clear of any obstruction.

Switch the CPAP machine and oxygen supply back on. Then turn the flowmeter control knobs each way to check if the bead moves and the issue has been solved.