Levels of end-tidal carbon dioxide are low despite normal respiratory rate in individuals with Long COVID, 2021, Wood, Putrino et al

To the Editor,

Debilitating symptoms including fatigue, post-exertional malaise, brain fog, weakness, headache and dizziness can persist for over six months in individuals with Long COVID 1,2 (also referred to post-acute COVID-19 syndrome, post-COVID condition or post-acute sequelae of COVID-19) with many still experiencing these symptoms for 12 months after acute Coronavirus Disease 2019 (COVID-19) infection.1,2 Long COVID can occur despite less severe initial infection or hospitalization, and in the absence of obvious organ damage.1,2 Low end-tidal carbon dioxide (ETCO2) in an alert, spontaneously breathing individual can result from hyperventilation, and has also been documented in patients with postural tachycardia syndrome, with or without hyperventilation.3 Of note, some of the symptoms attributed to Long COVID are also observed during hyperventilation and subsequent hypocapnia.4 While there is potential for hypocapnia to be observed post COVID-19 infection in the presence of more severe sequelae such as microthrombi, pulmonary embolism and lung fibrosis,5 data are presented from a cohort of patients with Long COVID who were mostly absent of severe sequelae following infection.

Open access, https://iopscience.iop.org/article/10.1088/1752-7163/ac3c18

 

I am not sure of the biology, but are things like hypocapnia causing effects or are a consequence of low oxygen availability in the cell? That would be equivalent to the aerobic system not working properly so the symptoms would be similar in ME to what is found with these things.