Uvm graphpad prism 8
The study was conducted in accordance with the Standards for the Reporting of Diagnostic Accuracy studies, and we obtained local institutional review board approval. Our academic ED at the University of Vermont Medical Center in Burlington, Vermont, sees approximately 60,000 patient visits each year. We enrolled a convenience sample of ED patients suspected of having CO toxicity and measured S pCO and HbCO concurrently. We performed a prospective, observational study to determine the diagnostic performance of the S pCO sensor in the ED setting under optimal experimental conditions. We also report diagnostic performance characteristics for this cohort as sensitivity and specificity of a positive test at the ≥ 10% threshold for the detection of true positive, elevated HbCO at levels of both ≥ 10% and ≥ 15%. We compared concurrent S pCO and HbCO measurements with a Bland-Altman plot and report the limits of agreement.
We prospectively compared the experimental measurement of HbCO with S pCO to the criterion standard, which is laboratory measurement of HbCO in the blood sample. We limited the elapsed time between blood collection and S pCO measurement to < 5 min, thereby eliminating the confounding variable of CO washout. To optimize the potential sensitivity of pulse oximetry to detect elevated HbCO, 3 measurements were obtained by trained research technicians.
4 Therefore, it represents a clinically meaningful CO elevation in any patient, regardless of the source of CO exposure. We selected this threshold for elevated HbCO ≥ 10% not because it represents CO toxicity, per se, but because it is above the upper limit for the expected physiological range of smokers, even with recent tobacco use. We also screened a convenience sample of non-acute ED patients in triage for elevated S pCO at a 10% threshold. We identified patients who presented with either report of a CO exposure or clinical symptoms consistent with CO poisoning. We elected to use a multipronged recruitment method to enroll as large a number of true positive (ie, CO-poisoned) patients as possible to determine the performance characteristics of the device for detecting individuals with clinically meaningful CO levels in their blood. 9 We hypothesized that the sensitivity of pulse oximetry for detecting blood HbCO levels ≥ 10% in patients in the ED setting, under optimal conditions and when performed within a short time interval from the blood test, would be improved relative to previous reports. These studies may therefore have failed to adequately assess the utility of pulse oximetry for detecting higher HbCO levels that are more likely to be toxic. Furthermore, the performance of diagnostic tests may vary depending on the magnitude of the abnormal value, and previous studies defined elevated CO at relatively low levels (eg, HbCO > 5%). Limitations of prior studies included times between S pCO measurement and blood draws for laboratory analysis of up to 1 h. Both Roth et al 9 and Sebbane et al, 10 on the other hand, found similar bias but much narrower limits of agreement, prompting them to recommend the technology for screening patients in the ED. 6– 8 Touger et al 8 found a bias of 1.4% but unacceptably wide limits of agreement (−11.6% to 14.4%), leading them to conclude that S pCO could not be used as a substitute for laboratory testing. 5, 7 Two additional studies reported satisfactory accuracy and precision for screening subjects in the ED. 5– 10 Two studies reported relatively wide limitations of agreement with laboratory measurement but concluded that the device has acceptable bias and correlation for screening purposes. The objective of this study was to address the limitations of prior studies and to determine the diagnostic performance of this device in the detection of elevated HbCO under optimal conditions in the ED setting.ĭespite the promise of multi-wavelength pulse-oximetry technology, controversy exists regarding the agreement of the device with standard laboratory testing. The Radical-7 pulse oximeter measures the refraction of 8 wavelengths of light through the nail bed using signal-extraction technology pulse oximetry to noninvasively measure HbCO, methemoglobin (Hbmet), oxyhemoglobin, and pulse rate. 3, 4 However, a noninvasive point-of-care device (Radical-7 Pulse CO-Oximeter, MX board version 7.5.0.3, Masimo, Irvine, California) has been cleared by the FDA for CO measurement via pulse oximetry (S pCO).
3 The standard method of carboxyhemoglobin (HbCO) measurement is arterial or venous blood gas analysis. 1, 2 Diagnosis of CO toxicity is complicated by non-specific symptoms, and misdiagnosis of CO toxicity is believed to be common. Carbon monoxide (CO) exposure causes 40,000 emergency department (ED) visits and 3,000 deaths in the United States each year.