Pulse Oximetry and Arterial Oxygen Saturation during Cardiopulmonary Exercise Testing

Introduction/Purpose Peripheral capillary oxygen saturation (SpO2) is used as surrogate for arterial blood oxygen saturation. We studied the degree of discrepancy between SpO2 and arterial oxygen (SaO2) and identified parameters that may explain this difference. Methods We included patients who underwent cardiopulmonary exercise testing (CPET) at Cleveland Clinic. Pulse oximeters with forehead probes measured SpO2 and arterial blood gas (ABG) samples provided the SaO2 both at rest and peak exercise. Results We included 751 patients, 54 ± 16 years old with 53 % of female gender. Bland-Altman analysis revealed a bias of 3.8% with limits of agreement of 0.3 to 7.9% between SpO2 and SaO2 at rest. A total of 174 (23%) patients had SpO2 >= 5% of SaO2, and these individuals were older, current smokers with lower FEV1 and higher PaCO2 and carboxyhemoglobin. At peak exercise (n=631), 75 (12%) SpO2 values were lower than the SaO2 determinations reflecting difficulties in the SpO2 measurement in some patients. The bias between SpO2 and SaO2 was 2.6% with limits of agreement between -2.9 to 8.1%. Values of SpO2 >= 5% of SaO2 (n=78, 12%) were associated with the significant resting variables plus lower heart rate, oxygen consumption and oxygen pulse. In multivariate analyses, carboxyhemoglobin remained significantly associated with the difference between SpO2 and SaO2 both at rest and peak exercise. Conclusion In the present study, pulse oximetry commonly underestimated the SaO2. Increased carboxyhemoglobin levels are independently associated with the difference between SpO2 and SaO2, a finding particularly relevant in smokers. Address for correspondence: Adriano Tonelli MD, 9500 Euclid Avenue A-90, Cleveland, Ohio, 44195. Email: tonella@ccf.org The results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation, and statement that results of the present study do not constitute endorsement by ACSM. Funding Sources: A.R.T. is supported by NIH grant # R01HL130307. Conflict of Interest Statements: Mona Ascha BS: The author has no significant conflicts of interest with any companies or organization whose products or services may be discussed in this article. Anirban Bhattacharyya MD: The author has no significant conflicts of interest with any companies or organization whose products or services may be discussed in this article. Jose A Ramos RT: The author has no significant conflicts of interest with any companies or organization whose products or services may be discussed in this article. Adriano R Tonelli MD, MSc: The author has no significant conflicts of interest with any companies or organization whose products or services may be discussed in this article. Accepted for Publication: 25 April 2018 © 2018 American College of Sports Medicine

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