Ring-shaped pulse oximeter and its application: measurement of SpO2 and blood pressure during sleep and during flight.

Respiratory and cardiovascular functions show circadian and day-to-day changes. We have developed a wireless ring-shaped pulse oximeter in collaboration with MC Medical Inc. and Advanced Medical Inc. We investigated the accuracy of this pulse oximeter and its application in daily life. Percutaneous arterial oxygen saturation (SpO2) of 47 volunteers was measured simultaneously with the ring-shaped pulse oximeter and a standard pulse oximeter. A total of 103 volunteers underwent measurement of SpO2 for 24 hr, and 11 healthy volunteers underwent measurement of SpO2 and blood pressure (BP) during flight. SpO2 and heart rate (HR) were measured and recorded every 20 sec, cabin barometric pressure and cabin oxygen concentration equivalent to sea level were measured minute-to-minute, and BP was measured every 3 min with a portable BP recorder during each flight. The SpO2 values measured with the ring-shaped pulse oximeter were similar to those measured with the standard method. The mean SpO2 during sleep was significantly lower in the group with high-normal BP or mild hypertension than in the group with normal BP. During flight, the mean change in SpO2 was -2.4 +/- 1.7% during nose-up flight, and 2.1 +/- 2.6% during nose-down flight. There was a significant correlation between change in SpO2 and change in systolic BP during nose-up flight. The wireless ring-shaped pulse oximeter was useful for investigating changes in SpO2 and its effect on BP in daily life during sleep and during air travel.