Original ContributionsDelays in the detection of hypoxemia due to site of pulse oximetry probe placement
Introduction
The use of pulse oximetry to detect hypoxemia is now well established as a standard of care in anesthesia and critical care practice, and in numerous other settings where sedatives and analgesics are administered. The accuracy of pulse oximetry has been reviewed in detail by numerous authors and has been found to be acceptable.1, 2, 3, 4 However, a number of studies also have verified the inaccuracies of pulse oximetry in settings associated with decreased cardiac output, increased or decreased systemic vascular resistance, hypothermia, elevated or dependent limb position, venous engorgement, and regional anesthesia.5, 6, 7, 8, 9, 10, 11, 12
To date, no studies have specifically evaluated pulse oximetry at the toe compared with other more commonly used sites in adults, or determined if any significant differences in the time to detect hypoxemia exist among them. Because, in certain circumstances, the toe is used as a site for peripheral pulse oximetry monitoring, we felt it would be useful to determine if such monitoring could result in any delays in the time to detect hypoxemia compared with more usual monitoring sites.
Section snippets
Materials and methods
University of Utah Institutional Review Board approval and volunteer consent were obtained. Subjects were healthy volunteers, aged 18 to 44 years, not taking any regular medication, and free of chronic pulmonary or other significant medical problems. On routine prestudy screening, a positive urine pregnancy test resulted in a volunteer’s exclusion from the study. Following establishment of informed consent, all subjects enrolled in the study underwent a practice breathing session to experience
Results
Thirteen volunteers underwent a total of 36 hypoxic breathing challenges. Figure 3 depicts the data for the differences in time to detect hypoxemia between probe sites following each acute hypoxic challenge.
One-sample t-tests revealed statistically significant delays to hypoxemia detection between the indicated probe sites for combined hypoxia trials (Table 1). This is represented graphically for one subject and one hypoxic challenge in Figure 4.
Paired t-tests for differences between ear–hand
Discussion
Clinicians are frequently concerned with the critical nature of respiratory and hypoxic events in patients.13, 14 In the clinical setting, it is unclear which degree of hypoxemia can be tolerated. It is known that significant hypoxia can cause serious complications within minutes of its onset. The rapid detection of hypoxemia is therefore critical. Although widely accepted as a standard of care and considered a great advance, the application of pulse oximetry as a method for detecting hypoxemia
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