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THE PULSE-OX FALLACY IN PATIENTS WITH COVID-19

      TOPIC: Respiratory Care
      TYPE: Medical Student/Resident Case Reports
      INTRODUCTION: Oxygen therapy remains the mainstay of treatment for COVID-19 patients. Decision to start, titrate, and escalate oxygen therapy is primarily determined by information from pulse oximetry (pulse-ox) that peripherally measures the patient's oxygen saturation (SpO2). Given the convenience and ability to monitor oxygen saturation without exposure is what makes pulse-ox the backbone of oxygen titration. Early in the course it was discovered that many patients' pulse-ox saturation (SpO2) would not correlate with clinical findings or with invasive measurements of arterial blood gas saturation (SaO2). These patients were dubbed as "happy hypoxic's," given their SpO2 indicating hypoxemia without clinical or SaO2 correlation. We present 3 cases in our medical ICU (MICU) of patients on varying oxygen therapies that showed persistent hypoxia on pulse-ox but would not show clinical or ABG correlation. This is an important phenomenon as pulse-ox has become heavily relied on during the pandemic resulting in potentially unnecessary escalation of care.
      CASE PRESENTATION: Patient 1 is a 48-year-old Hispanic female with diabetes that was admitted to the MICU for hypoxemia and placed on BIPAP, FiO2 of 40% EPAP of 8 and IPAP of 14. Patient 2 is a 53-year-old European male with hypertension admitted to the MICU for hypoxemia and placed on HFNC 60L 80% FiO2. Patient 3 is a 32-year-old African American female with no history admitted to the MICU for hypoxemia and placed on 15L non-rebreather. Figure 1 shows the SaO2 and SpO2 for all three patients plotted over the course of 15 to 19 hospital days depending on their MICU stay. All 3 patients have significant discrepancies with their pulse-ox saturation (SpO2) compared with arterial blood gas (SaO2).
      DISCUSSION: Peripheral pulse oximetry has become a pillar in our daily decisions regarding oxygen delivery to our patients. During the pandemic many clinicians were relying on the data from pulse-ox to determine next course of action on these patients. In the MICU we were able to compare the data from pulse-ox and ABG to show that in multiple patients there were discrepancies between the two. This is a critical finding because the sole reliance on a SpO2 reading to determine if a patient should be escalated in care or remain in the hospital due to high oxygen demands can have detrimental consequences. One theory is that COVID-19's prothrombotic state can cause peripheral microthrombi formations skewing peripheral pulse-ox data. It is vital the physician rely on clinical data to supplement the SpO2 and if required obtain arterial SaO2 readings.
      CONCLUSIONS: Clinicians should be aware that COVID-19 patients may present with inaccurate pulse-ox data resulting in misinformed decisions such as prolonged hospital stay, or worse, unnecessary advancement in oxygen therapies. Further large prospective studies will be needed to determine the accuracy of SpO2 in COVID-19.
      REFERENCE #1: Dhont, S., Derom, E., Van Braeckel, E. et al. The pathophysiology of 'happy' hypoxemia in COVID-19. Respir Res 21, 198 (2020). https://doi.org/10.1186/s12931-020-01462-5
      REFERENCE #2: Wu Z, McGoogan JM. Characteristics of and Important Lessons From the Coronavirus Disease 2019 (COVID-19) Outbreak in China: Summary of a Report of 72 314 Cases From the Chinese Center for Disease Control and Prevention. JAMA. 2020;323(13):1239–1242. doi:10.1001/jama.2020.2648
      REFERENCE #3: Tobin MJ, Laghi F, Jubran A. Why COVID-19 Silent Hypoxemia Is Baffling to Physicians. Am J Respir Crit Care Med. 2020 Aug 1;202(3):356-360. doi: 10.1164/rccm.202006-2157CP. PMID: 32539537; PMCID: PMC7397783.
      DISCLOSURES: No relevant relationships by Krunal Patel, source=Web Response