WatchPAT Sensor Error — PAT Probe Not Detected

What Does This Error Mean?

A sensor error on the WatchPAT means the PAT (peripheral arterial tonometry) probe worn on your finger is not being detected or is not making proper contact. The device needs a good signal from the finger probe to record the sleep study data.

Affected Models

WatchPAT ONE
WatchPAT 300
WatchPAT 200

Common Causes

Finger probe is not snapped onto the finger properly
Probe placed on the wrong finger (should be index or middle finger of non-dominant hand)
Nail polish or gel nails blocking the optical sensor
Finger is too cold, reducing peripheral circulation signal
Probe is damaged or its optical sensor is dirty

How to Fix It

Re-attach the finger probe firmly

The PAT probe clips onto the fingertip. Make sure it is fully seated with the optical window directly over the finger pad, not on a fingernail.
Use the correct finger

Place the probe on the index or middle finger of your non-dominant hand (not the thumb or little finger). Refer to the setup guide provided with the device.
Remove nail polish if present

Nail polish, gel nails, acrylic nails, or nail art can block the optical sensor that reads your arterial pulse. Remove polish from the test finger if possible.
Warm up your hands

Cold hands reduce peripheral blood flow, making it harder for the sensor to get a reliable signal. Warm your hands for a few minutes before attaching the probe.
Check the probe for damage

Inspect the optical window on the probe for scratches, moisture, or dirt. Gently clean it with a dry cloth if needed.

When to Call a Professional

Contact the clinic or hospital that prescribed the WatchPAT test — they will advise whether to retry or reschedule.

WatchPAT Sensor Error — Finger Probe Not Reading

The WatchPAT is a home sleep apnea test device made by Itamar Medical, an Israeli medical technology company. It is prescribed by sleep clinics as an alternative to a full hospital sleep study.

The PAT probe worn on your fingertip measures peripheral arterial tone — tiny changes in blood vessel diameter in the finger that correspond to breathing events during sleep. It is the core measurement of the WatchPAT system.

Most Common Fix

Re-attach the probe firmly and make sure there is no nail polish on the test finger. These two factors account for the majority of sensor errors.

If the Problem Recurs

Contact the prescribing clinic or hospital. For WatchPAT ONE (the disposable single-use version), a replacement device may be provided. For WatchPAT 300 and 200, the probe sensor may need to be replaced.

Frequently Asked Questions

Can I use the WatchPAT on my dominant hand?

The non-dominant hand is preferred because it moves less during sleep, which reduces motion artefacts in the recording. Using the dominant hand is acceptable if the non-dominant hand has a medical reason it cannot be used.

I got a sensor error midway through my sleep study. Is the test ruined?

Not necessarily. WatchPAT devices attempt to record as much valid data as possible. Depending on how long the probe was reading correctly before the error, the study may still be interpretable. Your sleep clinic will advise after reviewing the data.