Users sometimes have the issue of missing oximetry data in their recordings. When the recording is downloaded in Noxturnal, there is no oximetry data available. There are two main causes for this issue, and they require different workarounds and present in different ways in Noxturnal and the device logs. Both causes will be explained here, how they can be identified, and the troubleshooting steps and workarounds required to minimise their impact.

Bonding Issue

This issue occurs when the Nox recorded and the Nonin 3150 BLE oximeter fail to establish and maintain a stable connection. There is a breach in the communication between the A1s and the Nonin Oximeter that causes this bonding failure. The device log will show multiple messages of Bonding Failure, as shown below.

The result is that the oximetry data is missing completely from the recording or the signals are interrupted at points where the connection failed.

This issue has been investigated internally, and the most likely causes are listed below from the most likely to the least likely:

• Low or nearly empty battery in the Nonin 3150 BLE oximeter. This is the most likely cause and the only one that could be reliably reproduced by Nox.
• Low signal quality or Bluetooth instability, e.g. When the patient's body is blocking the direct Bluetooth communication between the Nox recorder and the Nonin 3150 BLE oximeter.

The recommended mitigation for this issue is to always use new Alkaline batteries for the Nonin 3150 oximeters for each sleep study.

Unhandled Response During Configuration

This failure occurs when the configuration of the Nonin 3150 BLE Oximeter fails. The Nonin 3150 BLE includes two processing units, when this error occurs the main processing unit is in a locked state and does not process any requests received by the BLE processing unit. The Nox recorder has a stable connection with the BLE processing unit  but no communication takes place with the main processing unit.

The problem with this failure is that in Noxturnal, the user will get a successful pairing message during configuration even though the configuration failed. Noxturnal is reporting that a successful connection was established with the Nonin 3150 oximeter, but there is no check whether the configuration was actually successful. This applies to all recorders running on Firmware 3.1.1 and lower.

This issue can be identified in the device log where an unhandled response message will be shown:

When we see this message in the log, we know that the configuration failed and the oximeter data will not be collected.

Improvements in Noxturnal 7.2.0 and Firmware 3.1.2

To mitigate this issue, improvements were implemented in Noxturnal and in the firmware of the devices. An extra validation step has been added in Noxturnal 7.2.0 in combination with version 3.1.2 of the device firmware. 

The system now only reports a successful pairing if the recorder manages to pair AND successfully configure the Nonin 3150 BLE oximeter.

This change ensures that the oximeter configuration step is completed before the user is shown a successful pairing message. The Nox recorder’s screen only shows a successful checkmark when the communication with the main processing unit is successful, it is not enough to connect to the BLE unit as in previous versions.

Important note:

• This extra step does not guarantee a successful overnight recording but greatly reduces the likelihood of these configuration and unhandled response errors.
• This does not affect the Bonding issue discussed above.
• Recordings can still have missing oximetry data using the combination of Noxturnal 7.2.0 and Firmware 3.1.2 on the devices.

Summary

Missing oximetry data can result from either a Bonding issue, where the Nox recorder and Nonin 3150 BLE oximeter fail to maintain a stable Bluetooth connection, or an unhandled response during configuration, where the oximeter’s configuration fails despite appearing paired. 

The recommended mitigation for these issues is 

• Using fresh alkaline batteries in the oximeter for each study which helps prevent bonding failures
• Upgrading to Noxturnal 7.2.0 and firmware 3.1.2 which adds an extra validation step that greatly reduces configuration errors

Here is an article giving step-by-step troubleshooting guidelines aimed at Sleep Technicians.