The technology

The Nasal Alar SpO2 sensor (Xhale Assurance) is a disposable, single patient use pulse oximetry sensor that clips onto the nasal ala, the fleshy part of the side of the nose. The sensor is indicated for use in adults and children (weighing more than 30 kg) for the continuous non-invasive monitoring of peripheral oxygen saturation (SpO2) and pulse rate.

The Nasal Alar SpO2 sensor includes light-emitting diodes and a photodiode pulse oximetry sensor in a plastic nasal clip, which uses photoplethysmography signals to determine a person's SpO2 level. The sensor has soft silicone pads to hold it in place on the person's nasal alar region. It has a cable with a connector that is compatible with most pulse oximetry monitors.

The device is contraindicated for patients weighing less than 30 kg or when the sensor cannot stay in place. The device should also not be used on sites with compromised tissue or non-intact skin, or for any patient with a medical condition that decreases nasal alar blood perfusion or that increases nasal alar venous congestion or swelling.


The Nasal Alar SpO2 sensor is the only pulse oximetry sensor specifically designed to detect SpO2 levels in the blood vessels of the nasal ala. This is designed to improve sensor accuracy and reliability in people who have poor peripheral perfusion (low blood flow). This is because the nasal ala is said to maintain a good blood supply from internal carotid arteries (which supply blood to the brain). In comparison, reliable readings may not be possible in people with low peripheral perfusion using conventional digit sensors attached to a finger or toe.

Positioning of the non-adhesive sensor clip at the nasal ala is designed to allow easy and quick attachment by healthcare staff and to be better tolerated and more comfortable for patients than other sensors, especially in those who are susceptible to skin breakdown, at risk of pressure ulcers or have sensitivity to adhesives.

Current NHS pathway

Current options for continuous monitoring of SpO2 by pulse oximetry in NHS clinical settings include: digit sensors, earlobe sensors, forehead sensors or nasal bridge sensors. These sensors may be single-use or reusable devices.

NICE's guideline on recognising and responding to deterioration in hospital states that SpO2 should be measured as part of routine monitoring and by track and trigger systems; however, this guidance does not cover people in critical care or children. Other NICE guidance where pulse oximetry monitoring is recommended includes guidelines for chronic obstructive pulmonary disease, chest pain of recent onset and bronchiolitis in children.

SpO2 monitoring by pulse oximetry is classed as essential for the safe conduct of anaesthesia or sedation in the Association of Anaesthetists of Great Britain and Ireland's standards of monitoring during anaesthesia and recovery. They state that pulse oximetry monitoring should be maintained until the patient has recovered fully from anaesthesia and used for all patients who are anaesthetised or sedated, including during transfer in hospital.

The Royal College of Physicians recommends the National Early Warning Score (NEWS) for the assessment and response to acute illness: SpO2 monitoring by pulse oximetry is 1 of the 6 NEWS physiological parameters. The British Thoracic Society's guidance on emergency oxygen use in adult patients states that pulse oximetry must be available in all locations where emergency oxygen is used. The Resuscitation Council UK's guideline on pre-hospital resuscitation states that pulse oximetry should be used to assess SpO2 in all patients with a cardiac output, but highlights that in the pre-hospital settings, the combination of cold peripheries and a low cardiac output can make pulse oximetry unreliable; so if a pulse oximeter sensor placed on a finger does not measure the oxygen saturation, other anatomical sites should be used (for example toes, nose, ear lobes or tongue).

NICE is aware of the following CE-marked devices that appear to fulfil a similar function as the Nasal Alar SpO2 sensor, however they are single-use adhesive sensors placed at different anatomical locations:

Population, setting and intended user

The Nasal Alar SpO2 sensor can be used in any healthcare setting where continuous SpO2 monitoring by pulse oximetry is done. This includes secondary care settings, such as emergency wards, intensive care units and operating theatres, as well as pre-hospital settings, such as ambulances.

The sensor can be used for any person who weighs over 30 kg. The device is most likely be used as an alternative to earlobe and forehead sensors when conventional digit pulse oximeter sensors do not work or are inappropriate, such as in people with low peripheral perfusion. This condition happens when people are critically ill, but is also associated with surgery involving large fluid shifts (liver transplants, trauma, caesarean section), shock, hypothermia and certain pre-existing conditions, such as peripheral arterial disease.

The sensor should be used by healthcare professionals who are trained in pulse oximetry monitoring. As the sensor is easy to use, minimal training should be needed, because it is compatible with standard pulse oximeter monitors.


Technology costs

Each Nasal Alar SpO2 sensor costs £20.62 (excluding VAT) and can be used for a single patient for up to 7 days of monitoring. It can be purchased in a box of 24 sensors for £495.00 (excluding VAT).

Costs of standard care

Conventional finger or toe sensors for pulse oximeters can be reusable or single-use disposable items. Costs range from £40 to £250 each for a reusable sensor and £7 to £19 each for disposable sensors (NHS Supply Chain). Additional costs for disinfectant wipes and nursing time would be incurred for cleaning reusable items for use between patients.

Digit sensors may not provide reliable measurements in people with poor peripheral perfusion. Other single-use non-digit pulse oximeter sensors are available on NHS Supply Chain:

  • Nellcor forehead sensor: £16.36 each, 2 days' use (£392.59 for 24)

  • Nellcor nasal bridge sensor: £16.60 each, 2 days' use (398.30 for 24).

Resource consequences

The Nasal Alar SpO2 sensor is currently used in about 15 NHS hospitals.

Using the Nasal Alar SpO2 sensor would incur an additional cost compared with standard digit sensors which, assuming reliable SpO2 measurements, may be offset if it allows a longer duration of use, reduced nursing time or if it can provide an oximetry reading when other devices do not work. If the sensor can improve the accuracy and reliability of SpO2 measurements in people with poor peripheral perfusion, it may lead to improved medical decision-making, faster intervention in response to complications, fewer false alarms and reduced nursing time, when compared with conventional digit sensors.

The Nasal Alar SpO2 sensor can be used to monitor an individual patient for up to 7 days, compared with 2 days for single-use forehead or nasal bridge sensors. Fewer nasal alar sensors may be needed than forehead sensors for monitoring patients with low peripheral perfusion with hospital admissions over 2 days, which may lead to cost savings. Because it is a disposable single-use sensor, no nursing time or consumables are needed to disinfect it between patients, which is necessary for reusable pulse oximeter sensors to reduce the risk of healthcare-associated infections.

No changes in facilities and infrastructure would be needed to adopt the Nasal Alar SpO2 sensor, because it is compatible with standard pulse oximetry monitors. Minimal training is needed for staff using the device. This will include being shown how to apply the sensor and that it is disposable.