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SpO₂ and Pulse Rate Data: A Comparison of Current Technologies during Sustained Shivering in Post-Operative Patients

Kelley Dixon, Austin Broussard, Mellisa Roskosky and Michael Shuler

Pulse oximetry is a noninvasive method of measuring the oxygen saturation (SpO2) of the arterial blood and is considered standard-of-care in post-operative settings. Patient motion or low perfusion can present challenges in obtaining accurate readings. Postoperative shivering occurs in anywhere from 5-65% of patients who have received general anesthesia and can manifest as continuous tremors and/or sporadic muscle movements.

Objective: Compare the effect of post-operative shivering on functioning capabilities of two commercially available pulse oximeters.

Methods: Two additional pulse oximeter sensors (Nonin 7500 Pulse Oximeter with 8000AA Sensor and Masimo Rad-8 with Rainbow DCI SC-200 Adult Reusable Sensor) were added to 40 shivering patients who met eligibility criteria. Shivering episodes were documented by recording the start and stop times for each episode as it occurred. Dropout rates for each device were calculated by dividing the amount of time that each instrument displayed no SpO2 or pulse rate value by the total time of the test. A 2-sample T-test was performed to compare dropout times of the devices and dropout rates were compared using a z-test for 2 proportions.

Results: Drops in signal occurred in fourteen subjects. The Masimo sensor dropped 21 times, for an average of 40 seconds per drop and Nonin's dropped 16 times averaging 29 seconds per drop. Nonin's dropout rate of 0.108 was less than that of Masimo's at 0.149, however this difference was not found to be statistically significant (p=0.87).

Conclusion: The incidence of shivering was very low among patients in this particular study setting (0.1%) For 5 different subjects, both sensors experienced drops during identical time intervals indicating that motion artifact may impact readings regardless of specific technology. Clinically significant shivering varied in duration among subjects therefore individual shiver rates varied as well. This preliminary analysis shows no significant difference between Nonin and Masimo sensors.