The desaturation response time of finger pulse oximeters during mild hypothermia*

Abstract

SummaryPulse oximeters may delay displaying the correct oxygen saturation during the onset of hypoxia. We investigated the desaturation response times of pulse oximeter sensors (forehead, ear and finger) during vasoconstriction due to mild hypothermia and vasodilation caused by glyceryl trinitrate. Ten healthy male volunteers were given three hypoxic challenges of 3 min duration under differing experimental conditions. Mild hypothermia increased the mean response time of finger oximeters from 130 to 215 s. Glyceryl trinitrate partly offset this effect by reducing the response time from 215 to 187 s. In contrast, the response times of the forehead and ear oximeters were unaffected by mild hypothermia, but the difference between head and finger oximeters was highly significant (p < 0.0001). The results suggest that the head oximeters provide a better monitoring site for pulse oximeters during mild hypothermia.

Reliable monitoring of oxygen saturation via pulse oximetry: Which site to choose?

“…peripheral blood vessels in the fingers as compared to those supplying the forehead and ear [18]. This is in agreement with previous studies which highlighted the earlobe to be the most reliable site for SpO 2 measurement regardless the change of temperature [19][20].…”

The Dewey monitor: Pulse oximetry can independently detect hypoxia in a rebreather diver

“…posure to cold causes a significant delay in detection of hypoxemia of up to four minutes in finger oximeters [10]. This delay prohibits the utility of a finger oximeter as a hypoxia detection device for any diver in cold water, as it is longer than the measured possible warning times.…”

“…The "warning time" that the device could provide to a diver was defined as the time between the predetermined alarm level (typically SpO 2 =95%) and the time when the SpO 2 was projected to reach 80%. The data used were from the forehead oximeter because of the practical issues of building a warning device for diver use, including use of hands during working dives and circulatory delays in cold water [10]. The finger oximeter was used primarily as an additional safety measure and the resulting data were not used for analysis.…”

“…It should be noted that pulse oximetry measures the blood oxygen saturation only at the site where the oximeter is located. Thus, when a person is cold and extremity blood flow is reduced, if the sensor is conventionally located on a fingertip there can be a marked delay in detection of hypoxemia [10].…”

Physiologic Considerations in Detection of Hypoxemia during Vasoconstriction: Radial Artery Compared to Various Pulse Oximeter Sensor Sites

“…In their study they cooled core temperature by first having the subject lie on a cooling blanket (normothermic vasoconstriction) and compared paired SaO 2 and SpO 2 values [7]. The second condition was the addition of cold saline (4°C) by intravenous infusion and administration of nitroglycerin, a vasodilator (hypothermic vasodilation).…”