Advances in Blood Oxygen Measurement

Advances in sensing technology, computational analysis and wireless communication are being used to create next-generation methods of measuring blood oxygen more comfortably for patients, and more accurately and in real time for clinicians. Frost & Sullivan has researched the latest commercially available blood oxygen measuring technologies as well as emerging technologies in this space.

According to the World Health Organization, chronic obstructive pulmonary disease (COPD) claims the lives of more than 3 million people globally each year—approximately 6 percent of all deaths. Everyone requires adequate oxygen, but it is a more acute need for COPD patients. For this reason, measuring blood oxygen level is important for the COPD population.

Masimo Corporation (Irvine, Calif.)

Masimo engineers designed their Oxygen Reserve Index (ORi) and RPVi (a multi-wavelength version of the pleth variability index) to non-invasively measure oxygen saturation with less instrumentation and at a lower cost. Masimo combined ORi’s ability to obtain better insight about a patient’s oxygen reserve in the moderate hyperoxic range with pulse oximetry to give clinicians an earlier warning of imminent desaturation that would have harmed a patient.

The ORi and RPVi technology is worn on the patient’s finger so that the dual technologies can accurately determine changes in fluid volume. Masimo integrates its sensors with audible and tactile feedback to ensure proper connection, and directions are printed on both sides of the sensors to facilitate use.

The technology can give clinicians greater insights into the oxygenation status of patients receiving supplemental oxygen, and the blood oxygen measurement of anesthetized patients and patients in surgery or in an intensive care unit.

King’s College London and the University of Oxford

There is general medical agreement that arterial blood oxygen levels remain constant during breathing. However, no technology had been capable of measuring the breathing rate or the stability of breathing. King’s College scientists collaborated with their Oxford colleagues to develop a fiber-optic sensor that can measure fluctuations in arterial blood oxygen levels during breathing, contradicting the belief that the levels are constant.

The researchers inserted their fiber optic oxygen sensor into the carotid artery of pigs without a lung injury to measure the arterial partial pressure of oxygen, or PaO₂. The sensor resists clotting and was able to measure the rapid variations in PaO₂. The team observed that the PaO₂ levels increased when the subjects inhaled and decreased when they exhaled. Using computer tomography analysis, changes in the breathing rate were mapped to variations in lung volume.

The inventors hope the sensor will be able to efficiently monitor the respiratory behavior of patients suffering from breathing-related problems. It may also find uses in athletics and defense.

Fitbit (San Francisco, Calif.)

Known for its wearable, wireless fitness trackers that monitor the number of steps walked, heart rate and sleep quality, Fitbit has added blood oxygen sensing to its Ionic wearable introduced in 2017. Like other Fitbit trackers, Ionic is worn on the wrist and incorporates an SpO₂ sensor. SpO₂ refers to peripheral capillary oxygen saturation, or the percentage of oxygenated hemoglobin compared to the total amount of hemoglobin in the blood.

SpO₂ sensors emit red and infrared light that is absorbed by the bloodstream and reflected back to the sensor. Because oxygenated and non-oxygenated hemoglobin have very different light absorption patterns, the sensor can analyze the percentage of oxygenated hemoglobin.

Fitbit is marketing SpO₂ sensing as a way to generate new types of health alerts, such as warnings of sleep apnea that can deprive people of oxygen.

Withings, part of Nokia (Issy-les-Moulineaux, France)

Similar to the Fitbit Ionic is the SpO₂ sensor incorporated into the Pulse O₂ wearable tracker introduced by Withings, which Finnish corporation Nokia acquired in 2016. The Pulse O₂, which today is called the Pulse Ox, uses the same oxygen sensing principle that the Fitbit wearable does, but instead of taking blood oxygen measurements passively, users have to press their fingertip against the sensor for readings that will be downloaded to their smartphone via an app.

Eindhoven University of Technology (Eindhoven, Netherlands)

A limitation of SpO₂ measurement is the need for the patient to remain still in order to obtain the most accurate results. This is due to the small amplitudes of the common ratio-of-ratios measurement principle that SpO₂ sensors employ.

Researchers at Eindhoven have developed a new principle to take more accurate SpO₂ measurements even when the patient is moving. The team inverted the principle of robust pulse-extraction that is usually employed by searching for the signature providing the best pulse quality. They then used the optimal signature to map an SpO₂ reading.

The scientists achieved clinically relevant SpO₂ levels ranging from 80 to 100 percent accuracy, outperforming the ratio-of-ratios methods currently used. For example, the new principle’s margin of error during head movements was approximately 2 percent, compared with a benchmark margin of error of 24 percent for head movements during conventional SpO₂ measurement

The Road Ahead

As seen in the King’s College/Oxford and Eindhoven University examples, considerable research is being devoted to improving on existing blood oxygen measurement technologies. The potential for better blood oxygen measurement to improve and even save the lives of COPD patients is attracting government funding, such as for the U.S. National Institutes of Health’s National Heart, Lung, and Blood Institute study on the long-term effects of oxygen therapy on patients with low blood oxygen levels.

Frost & Sullivan expects that private firms, academic institutions and research laboratories will continue to drive improvements in measuring the vital relationship between oxygen and blood.