Oxygen saturation instability in suspected covid-19 patients; contrasting effects of reduced V A /Q and shunt
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Abstract
Patients in the UK at risk of Covid-19 pneumonia, but not needing immediate hospital attention, are to be given pulse oximeters to identify a fall in oxygen saturation (SaO2 or SpO2) at home. A recent finding in Covid-19 pneumonia is a dominant reduction in ventilation to perfused alveoli (V A /Q). A mathematical model of gas exchange was used to predict the effect of shunt or reduced V A /Q on SaO2 stability inferred from the slope of the PIO2 vs SaO2 curve as it intersected the line representing ambient PIO2. A ±1 kPa variation in PIO2 predicted a 1.5% and 8% change in SpO2 with 15% shunt and 0.4 V A /Q respectively. As a consistency check, two patients with pre-existing lung disease and 12 hour continuous SpO2 monitoring breathing air had gas exchange impairment analysed in terms of shunt and reduced V A /Q. The patient with 16% shunt and normal V A /Q had a stable but reduced SpO2 (circa 93±1%) throughout the 12 hr period. The patient with a V A /Q reduced to 0.48 had SpO2 ranging from 75-95% during the same period. SpO2 monitoring in suspected covid-19 patients should focus on SpO2 varying >5% in 30 minutes. Such instability in at risk patients is not diagnostic of Covid-19 pneumonia but this may be suspected from a dominant reduction in V A /Q if episodic hypoxaemia has progressed from a stable SpO2.
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SciScore for 10.1101/2020.12.17.20248126: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
Institutional Review Board Statement not detected. Randomization not detected. Blinding not detected. Power Analysis not detected. Sex as a biological variable not detected. Table 2: Resources
No key resources detected.
Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).
Results from LimitationRecognizer: An explicit section about the limitations of the techniques employed in this study was not found. We encourage authors to address study limitations.Results from TrialIdentifier: No clinical trial numbers were referenced.
Results from Barzooka: We did not find any issues relating to the usage of bar …
SciScore for 10.1101/2020.12.17.20248126: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
Institutional Review Board Statement not detected. Randomization not detected. Blinding not detected. Power Analysis not detected. Sex as a biological variable not detected. Table 2: Resources
No key resources detected.
Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).
Results from LimitationRecognizer: An explicit section about the limitations of the techniques employed in this study was not found. We encourage authors to address study limitations.Results from TrialIdentifier: No clinical trial numbers were referenced.
Results from Barzooka: We did not find any issues relating to the usage of bar graphs.
Results from JetFighter: We did not find any issues relating to colormaps.
Results from rtransparent:- Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
- Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
- No protocol registration statement was detected.
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