What is the utility of forehead pulse oximetry (pulse ox)

From the Guidelines

Forehead pulse oximetry is a recommended alternative method for measuring blood oxygen saturation in patients with compromised peripheral circulation, such as those with Raynaud's phenomenon or poor finger perfusion, as stated in the 2023 American College of Rheumatology (ACR)/American College of Chest Physicians (CHEST) guideline 1.

Key Points

• Forehead pulse oximetry is useful in situations where traditional finger pulse oximeters cannot be used due to poor peripheral circulation.
• It involves placing a sensor on the patient's forehead to detect oxygen levels through the temporal artery.
• This method is particularly valuable in patients with severe hypotension, peripheral vascular disease, or hypothermia, where finger readings may be unreliable.
• Forehead sensors are also beneficial for continuous monitoring during sleep studies or in critical care settings, as they are less likely to be dislodged during patient movement.
• However, forehead sensors require proper positioning above the eyebrow and may be affected by venous pulsations or pressure on the temporal artery.

Clinical Considerations

• The 2023 ACR/CHEST guideline conditionally recommends monitoring with HRCT chest for patients with systemic autoimmune rheumatic diseases, particularly those with poor finger perfusion, where an ear or forehead oxygen saturation monitor is preferable 1.
• The guideline also highlights the importance of accurate oxygen saturation measurement in patients with Raynaud's phenomenon, particularly those with systemic sclerosis, where forehead pulse oximetry may be a useful alternative 1.
• The BTS guideline for oxygen use in adults in healthcare and emergency settings notes that pulse oximetry should be available to all healthcare staff managing patients receiving oxygen therapy, and they should be trained in their use 1.
• The ATS/ACCP statement on cardiopulmonary exercise testing emphasizes the importance of proper calibration and quality control for pulse oximeters, including validation with arterial oxygen saturation 1.

From the Research

Utility of Forehead Pulse Oximetry

The utility of forehead pulse oximetry can be evaluated based on its accuracy, reliability, and comparison with other monitoring sites.

• Forehead pulse oximetry has been shown to have fewer alarms and shorter durations of malfunction compared to finger pulse oximetry in emergency transport 2.
• It provides better monitoring quality in emergency care, especially during movement and in cold ambient temperatures 2.
• The forehead technique correlates well with finger SpO2 and arterial oxygen saturation (SaO2) determined by arterial blood gas analysis in healthy volunteers 3.
• However, difficulty was experienced when applying and using the sensor on critically ill patients, and the reliability of the forehead pulse oximeter sensor has not been established at low saturations 3.
• Disposable finger sensors placed on the forehead were found to be inaccurate in over half of the subjects, with an absolute difference of ≥ 5% compared to the same sensors placed on the finger 4.
• In patients admitted to the intensive care unit for coronary artery bypass surgery, the forehead probe had higher agreement with SaO2 compared to earlobe probes, but lower correlation with SaO2 compared to finger probes 5.

Comparison with Other Monitoring Sites

• Forehead pulse oximetry has been compared with finger, toe, and earlobe probes in terms of accuracy and reliability.
• The highest correlation with SaO2 was found with finger probes, while the highest agreement with SaO2 was found with forehead probes 5.
• Earlobe probes were found to have higher accuracy due to lesser mean difference, more limited confidence level, and higher agreement ratio with SaO2 5.

Clinical Applications

• Pulse oximetry, including forehead pulse oximetry, is a widely used and reliable noninvasive technique that provides useful information about blood oxygenation in individuals 6.
• It can guide oxygen therapy, reduce the occurrence of hypoxemia, and decrease the frequency of admissions to the intensive care unit, as well as arterial blood gas sampling 6.
• New multiwaveform sensors and advanced signal processing techniques can differentiate between different types of hemoglobin and may be useful for continuous measurement of total hemoglobin, as well as for detecting and providing information on blood loss and cardiac output 6.