Elevated cerebral oxygen extraction in patients with post-COVID conditions, 2024, Liu et al.

Elevated cerebral oxygen extraction in patients with post-COVID conditions
Peiying Liu; Thomas Ernst; Huajun Liang; Dengrong Jiang; Eric Cunningham; Meghann Ryan; Hanzhang Lu; Shyamasundaran Kottilil; Linda Chang

OBJECTIVES
Dysfunction of cerebral microcirculation due to SARS-CoV-2 infection has been postulated to be a plausible mechanism for the neurological symptoms of post-COVID-19 conditions (neuro-PCC), affecting oxygen homeostasis in the brain. In this study, we aimed to investigate the balance between cerebral oxygen delivery and consumption, measured by oxygen extraction fraction (OEF), in patients with neuro-PCC.

METHODS
25 participants with neuro-PCC (8 previously hospitalized and 17 not hospitalized) and 59 age-matched healthy controls were studied. Global OEF was quantified using TRUST MRI and compared across the three groups. Associations between OEF and neurobehavioral measures were also evaluated in participants with neuro-PCC.

RESULTS
OEF was significantly different (one-way ANCOVA-p=0.046) among the three groups, after accounting for age and sex. On post-hoc analyses, previously hospitalized neuro-PCC participants had significantly higher OEF (42.40 ± 5.40 %) than both uninfected controls (37.70 ± 5.09 %, p=0.032) and neuro-PCC participants without hospitalization (37.02 ± 5.05 %, p=0.015). Within the participants with neuro-PCC, OEF was significantly associated with locomotor function assessed with the 4-m walk gait speed score (β=−0.03, r=0.34, p=0.003).

CONCLUSIONS
Participants with neuro-PCC had altered cerebral OEF, which is also associated with slower locomotion. OEF is a promising marker for studying neuro-PCC.

Link | PDF (NeuroImmune Pharmacology and Therapeutics) [Open Access]

 

Yes, they'd be lying supine, quietly in the scanner at most listening to a background audio track. For this type of study I would expect there to be no audio playing as it could be a confounder when attempting to measure brain metabolism. Just background scanner noise can have effects though, see fMRI-acoustic noise alters brain activation during working memory tasks (2005, NeuroImage). So as long as the same protocol was used in all groups that's probably the best we can do.

[10] is Quantitative evaluation of oxygenation in venous vessels using T2-Relaxation-Under-Spin-Tagging MRI (2008, Magnetic Resonance in Medicine)

13 and 14 include this paper's lead author.

[13] is Calibration and validation of TRUST MRI for the estimation of cerebral blood oxygenation (2012, Magnetic Resonance in Medicine)

[14] is Test–retest reproducibility of a rapid method to measure brain oxygen metabolism (2013, Magnetic Resonance in Medicine)

 

And measuring blood flow at rest and during activity in an upright MRI scanner might really show us something.