Ear oximetry during combined hypoxia and exercise

Abstract

Ear oximetry is widely used to detect arterial O2 desaturation during exercise in patients with cardiopulmonary disease. Although oximeters have been evaluated for accuracy, response time, and the influence of skin pigmentation, tests of their reliability have not been reported during strenuous exercise. Accordingly, we compared arterial O2 saturation (Sao2) measurements obtained by Hewlett-Packard (HP, model 47201A) and Biox II oximeters with those determined directly from arterial blood in six healthy volunteers during progressive exercise while rebreathing hypoxic gas mixtures. The relationship between the HP oximeter value and blood Sao2 was described by the equation: HP = 0.93 (Sao2) + 5.37 and for the Biox II: Biox = 0.55 (Sao2) + 38.97. With these equations, at a blood Sao2 value of 90%, the underestimation by both oximeters was less than 2%. At a blood value of 70%, the HP oximeter overestimated blood Sao2 by 0.7%, whereas the Biox II showed an overestimation of 10.7%. Below blood Sao2 of 83%, the Biox II tended to overestimate blood Sao2 by an amount greater than the error of the instrument, whereas the HP estimations were within the error of the instrument over all levels of blood Sao2 studied. We conclude that the HP oximeter provides valid estimates of Sao2 during exercise but that the Biox II oximeter, although reflecting qualitative changes in oxygenation that occur during exercise, does not provide accurate records of the degree of desaturation.

Accuracy of pulse oximetry during intense exercise under severe hypoxic conditions

“…The SEE obtained in this study (1.8) was lower than that obtained with the Hewlett-Packard (4.1) and Biox II (5.4) evaluated by Smyth et al (1986). The discrepancy between these two studies could be due to the dierent protocols used.…”

“…The accuracy of dierent oximeters during normoxic exercise (Breuer et al 1990;Norton et al 1992) or hypoxic exercise (Smyth et al 1986;Martin et al 1992) has been evaluated. While some authors have shown that pulse oximeters provide a valid predictor of percentage saturation of haemoglobin with oxygen (%HbO 2 ; Powers et al 1989;Barthe le my et al 1990;Breuer et al 1990;Martin et al 1992), other authors (Smyth et al 1986;Norton et al 1992) suggest that pulse oximetry has serious limitations during exercise. The dierences in oximeters used (Barthe le my et al 1990) and in the intensity of exercise (Norton et al 1992) may explain these discrepancies.…”

Impairment of 3000-m Run Time at Altitude Is Influenced by Arterial Oxyhemoglobin Saturation

“…The oximeter was calibrated using an internal protocol before each test according to the manufacturer's instructions. This instrument has been reported to be accurate across a wide range of SaO2, with arterial SaO2 values >75% underestimated by <2% (31 ). The "older" HP 47201A oximeter is unique because it uses eight wavelengths covering the range from 650 to 1050 nm and 18 molar extinction coefficients to detennine oxy-and deoxyhemoglobin concentrations, whereas most modem oximeters use only two or three wavelengths.…”

Comparison of invasive and noninvasive saturation monitoring in prescribing oxygen during exercise in COPD patients

“…The reliability of oximetry during exercise has been questioned [14,15] when Sp,O 2 values below 90% are recorded [15,16], and particularly when evidence of hypoxia exists in connection with exercise [17]. On the other hand, several studies have demonstrated that oximetry provides accurate measures of arterial oxygen saturation (Sa,O 2 ) in subjects breathing hypoxic gas mixtures [18,19], as well as in normal subjects [20], pulmonary patients [21], and trained athletes [22] during exercise.…”