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RESEARCH LETTER
Year : 2020  |  Volume : 37  |  Issue : 6  |  Page : 553-554  

Falsely low values of oxygen saturation measured by pulse oximetry in patients with coronavirus disease 2019


1 Department of Chest Diseases, University of Health Sciences, Istanbul Gaziosmanpasa Research and Training Hospital, Istanbul, Turkey
2 Department of Infectious Diseases, University of Health Sciences, Istanbul Gaziosmanpasa Research and Training Hospital, Istanbul, Turkey
3 Department of Rheumatology, University of Health Sciences, Istanbul Gaziosmanpasa Research and Training Hospital, Istanbul, Turkey

Date of Submission18-May-2020
Date of Acceptance19-May-2020
Date of Web Publication30-Oct-2020

Correspondence Address:
Celal Satici
Department of Chest Diseases, University of Health Sciences, Istanbul Gaziosmanpasa Research and Training Hospital, Istanbul
Turkey
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/lungindia.lungindia_392_20

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How to cite this article:
Satici C, Demirkol MA, Alkan M, Esatoglu SN. Falsely low values of oxygen saturation measured by pulse oximetry in patients with coronavirus disease 2019. Lung India 2020;37:553-4

How to cite this URL:
Satici C, Demirkol MA, Alkan M, Esatoglu SN. Falsely low values of oxygen saturation measured by pulse oximetry in patients with coronavirus disease 2019. Lung India [serial online] 2020 [cited 2020 Nov 28];37:553-4. Available from: https://www.lungindia.com/text.asp?2020/37/6/553/299659



Sir,

Digital pulse oximetry is a rapid noninvasive test and is used to estimate arterial oxygen saturation. However, falsely low readings are common due to a range of causes including motion artifact, hypotension, nail polish, darker skin pigmentation, and venous pulsations. We recently encountered a number of patients with coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) with falsely low oxygen saturation detected by digital pulse oximetry.

Following the first confirmed COVID-19 case on March 11 in Turkey, our hospital started to serve as a coronavirus pandemic hospital on April 1, 2020. Three hundred and forty-five patients were hospitalized to Istanbul University of Health Sciences Gaziosmanpasa Research and Training Hospital between April 1, 2020, and April 14, 2020. Among these, we identified 17 patients who had a discordance of oxygen saturation measured by digital pulse oximetry and arterial blood gas analysis. This study was approved by our institutional ethics committee (Approvement protocol number: 58/06.05.2020).

The mean (standard deviation [SD]) age was 65.7 ± 17.0 years, and 10 of 17 patients (58.8%) were men. Nine of these 17 patients had fever. Hypotension and tachycardia were not observed in all the patients. Laboratory parameters showed elevated aspartate transaminase (median: 46 U/L, interquartile range [IQR]: 34–58), ferritin (median: 447 ng/mL, IQR: 237–1119), D-dimer (median: 1062 ng/mL, IQR: 774–1387), C-reactive protein (mean ± SD: 141.4 ± 103.1 mg/L), fibrinogen levels (mean ± SD: 382.6 ± 72.0 mg/dL), and low lymphocyte count (mean ± SD: 790 ± 409 cells/μL). The findings of oxygen saturation levels measured by pulse oximetry and arterial blood gas analysis are shown in [Table 1]. Repeated measurements of oxygen saturation by different pulse oximetry devices were still falsely low in all the patients. Hypertension and chronic ischemic heart disease were the most common comorbidities. In addition, one of them was diagnosed with acute pulmonary thromboembolism. Eleven patients were treated by therapeutic dose enoxaparin, whereas 6 were treated by prophylactic dose enoxaparin. Among the 17 patients, 8 (47%) remained hospitalized at the final study follow-up date, 7 (41.1%) were discharged alive, and the remaining 2 (11.9%) were transferred to the intensive care unit.
Table 1: Findings of oxygen saturation measured by pulse oximeter and arterial blood gas

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The relationship between inflammation due to viral infection and hypercoagulation has already been known.[1] Similarly, extensive intravascular microthrombosis was observed in autopsy series including four deceased cases with COVID-19.[2] Endothelial cell involvement has been suggested a possible reason for impaired microcirculatory function in different vascular beds.[3],[4] Ciceri et al. have recently proposed a new hypothesis called “microvascular COVID-19 lung vessels obstructive thromboinflammatory syndrome (MicroCLOTS).”[5] This hypothesis was based on the following findings. First, SARS-CoV-2 enters into endothelial cell through the receptor angiotensin-converting enzyme 2. Second, replication of the virus causes release of pro-inflammatory cytokines and activation of macrophages and the complement cascade in endothelial cells. Activation of complement cascade triggers further immune response, tissue injury, and microvascular thrombosis. Third, the progression of endothelial damage with microvascular thrombosis can spread locally in the lung and potentially extends to the microvascular bed of several organs. In our case series, all of the patients were hemodynamically stable and had no clinical sign of hypoperfusion. In addition, none of the patients had anemia, hypothermia, nail polish, pigmented skin, dyshemoglobinemia, and hyperbilirubinemia that may cause misconceptions in reporting oxygen saturation. Although inappropriate placement of pulse oximeter probe may be a limitation of our observation, repeated measurements by different pulse oximetry devices were consistent. We suggest that discordance between pulse oximeter and arterial blood gas analysis may also indicate widespread microvascular thrombosis, not limited to the lung, and may further support MicroCLOTS hypothesis. Moreover, oxygen saturation is an essential monitoring tool in the management of COVID-19. Some patients may experience silent hypoxemia,[6] and there is an ongoing discussion whether pulse oximetry screening at home could provide an early warning system for COVID-19 pneumonia. However, arterial blood gas analysis seems to be more appropriate to assess arterial oxygen saturation.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
   References Top

1.
Smeeth L, Cook C, Thomas S, Hall AJ, Hubbard R, Vallance P. Risk of deep vein thrombosis and pulmonary embolism after acute infection in a community setting. Lancet 2006;367:1075-9.  Back to cited text no. 1
    
2.
Fox SE, Akmatbekov A, Harbert JL, Guang Li, Brown JQ, Heide RS. Pulmonary and Cardiac Pathology in Covid-19: TheFirst Autopsy Series from New Orleans. medRxiv 2020.2004.2006.20050575; 2020.  Back to cited text no. 2
    
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Varga Z, Flammer AJ, Steiger P, Haberecker M, Andermatt R, Zinkernagel AS, et al. Endothelial cell infection and endotheliitis in COVID-19. Lancet 2020;395:1417-8.  Back to cited text no. 3
    
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Sardu C, Gambardella J, Morelli MB, Wang X, Marfella R, Santulli G. Hypertension, thrombosis, kidney failure, and diabetes: Is COVID-19 an endothelial disease? A comprehensive evaluation of clinical and basic evidence. J Clin Med 2020;9:E1417.  Back to cited text no. 4
    
5.
Ciceri F, Beretta L, Scandroglio AM, Colombo S, Landoni G, Ruggeri A, et al. Microvascular COVID-19 lung vessels obstructive thromboinflammatory syndrome (MicroCLOTS): An atypical acute respiratory distress syndrome working hypothesis. Crit Care Resusc 2020; (Ahead of print).  Back to cited text no. 5
    
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Xie J, Tong Z, Guan X, Du B, Qiu H, Slutsky AS. Critical care crisis and some recommendations during the COVID-19 epidemic in China. Intensive Care Med 2020;46:837-40.  Back to cited text no. 6
    



 
 
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