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Reduced Cerebrovascular Oxygenation in Individuals with Post-Acute COVID-19 Syndrome PACS “long COVID”, 2023, Adingupu et al.

Discussion in 'Long Covid research' started by SNT Gatchaman, Oct 17, 2023.

  1. SNT Gatchaman

    SNT Gatchaman Senior Member (Voting Rights)

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    Reduced Cerebrovascular Oxygenation in Individuals with Post-Acute COVID-19 Syndrome PACS “long COVID”
    Adingupu, Damilola D.; Soroush, A.; Hansen, A.; Twomey, R.; Dunn, J. F.

    There is evidence that hypoxia occurs in the brain of some individuals who contracted the COVID-19 disease. Furthermore, it has been widely reported that about 13% of individuals who contracted the COVID-19 disease report persistent symptoms after the acute infection stage (>2 months post-acute infection). This is termed post-acute COVID-19 syndrome (PACS) or (“long COVID”).

    In this study, we aimed to determine if hypoxia measured non-invasively with frequency domain near-infrared spectroscopy (fdNIRS) occurs in asymptomatic and symptomatic individuals with post-acute COVID-19 disease. We show that 26% of our symptomatic group, measured on average 9.6 months post-acute COVID-19 disease, were hypoxic and 12% of the asymptomatic group, measured on average 2.5 months post-acute infection, were hypoxic.

    Our study indicates that fdNIRS measure of hypoxia in the brain may be a useful tool to identify individuals that are likely to respond to treatments targeted at reducing inflammation and improving oxygenation.

    Link | Paywall (Conference paper: International Society on Oxygen Transport to Tissue)
     
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  2. Hutan

    Hutan Moderator Staff Member

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    26% in the symptomatic group isn't exactly overwhelming, although I'd be quite happy believing that the hypoxia is something that comes and goes, depending on the demands placed on the body or specifically on the brain. I'd also be willing to believe that there are groups under the broad category of Long Covid for whom hypoxia is a significant symptom.

    But having 12% of the asymptomatic group being similarly hypoxic seems like quite a problem to the hypothesis that brain hypoxia is a feature of (a type of) Long covid. I wonder how the authors explain this phenomenon of hypoxia but no symptoms.

    Does the mean time after acute infection of only 2.5 months for the asymptomatic people mean that maybe some people were measured quite soon after the acute infection? So, maybe they still had the effects of the acute disease, but were feeling relatively good compared to having the infection? That doesn't sound like a very good explanation to me. But why else would apparently healthy people appear to have hypoxia? Are there problems in the reliability of the measurement approach?

    This article gives a bit of background on the technique:
    Frequency-domain vs continuous-wave near-infrared spectroscopy devices: a comparison of clinically viable monitors in controlled hypoxia 2017
     
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  3. Hutan

    Hutan Moderator Staff Member

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    If I'm understanding correctly the 2017 paper linked above, the technique is ok for identifying changes in brain oxygenation in a person. But, it's not good for saying 'this person clearly has a problem with brain oxygenation and this person doesn't'; it's not good for comparing between people. Perhaps things have improved since 2017. But it is sounding as though the technology may not be good enough for this purpose it has been put to.

    I wonder if a measurement of the change in oxygenation when oxygen intake is restricted might be more useful? As in, the healthy oxygenated brain will show a big decrease, but a brain that is already rather de-oxygenated might not show much of a change.

    I really want to know if there are differences in brain oxygenation. It feels as though there should be and it would help us know what is going on. I think ME/CFS is a lot like operating at high altitude.

    I assume the measurements were done with the participants supine. I wonder what would happen with the participant upright.
     
  4. SNT Gatchaman

    SNT Gatchaman Senior Member (Voting Rights)

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    I can't access this paper, so can only go on the above summary. I would like to read it though. I had the same question: how the measurements were taken: lying, sitting, standing? When I did this test, looking at frontal lobe saturations I had a 10% drop from lying to standing within a minute.

    We know that many people report full recovery from acute covid, only to develop LC 2 or 3 months down the line. Perhaps the 12% in the "asymptomatic" group are "not yet symptomatic".

    Alternatively, the Perth (/Imperial/Addenbrooke's) pheno-metabolomics team have been indicating that post Covid, there are major metabolic changes, which may be affecting cardiovascular performance even at a subclinical/asymptomatic level. Eg even back in 2020: Integrative Modeling of Quantitative Plasma Lipoprotein, Metabolic, and Amino Acid Data Reveals a Multiorgan Pathological Signature of SARS-CoV-2 Infection (2020, Journal of Proteome Research) —

     
    Last edited: Oct 18, 2023
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  5. Hutan

    Hutan Moderator Staff Member

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    That sounds like quite a lot. In that 2017 paper, oxygen saturations dropped 15% from baseline when the participants had oxygen restriction similar to being 5000 m above sea level. That's just a bit less than the altitude where supplementary oxygen is typically used (and that's after a careful acclimatisation process to the lower oxygen levels, conducted over days).

    For sure there is something weird going on with blood supply. Yesterday my son was doing a trick where he held his arm up and it would immediately blanch white, and then turn grey, as if it was dead. It was as if there was a tap and the blood was gushing out of the arm into the body. Then he would lower the arm and it would rapidly turn bright red. If that is happening in an arm, it would not be at all surprising that oxygen supply is not right in the brain either.
     

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