# Brain-Body Interaction of Breath-by-Breath O2-CO2 Exchange Ratio withResting State Cerebral Hemodynamic Fluctuations

> **NIH NIH R21** · MASSACHUSETTS GENERAL HOSPITAL · 2020 · $210,000

## Abstract

7. Project Summary/Abstract (No more than 30 lines)
The origin of the low frequencies (below 0.05Hz) resting state cerebral hemodynamic fluctuations (CHF) in
default mode network (DMN) and other resting state networks (RSNs) remains unknown. We hypothesized
that CHF at low frequencies correlated with fluctuations in resting systemic metabolism obtained from
respiratory gas exchange measurements (O2 uptake, CO2 release and their ratio) in spontaneous breathing.
We introduced a new brain-body interaction showing a strong correlation between CHF and breath-by-breath
O2-CO2 exchange ratio (bER) which is a ratio of O2 uptake to CO2 release. With transcranial Doppler
sonography and functional magnetic resonance imaging, bER was shown to be better than O2 uptake which in
turn was far better than CO2 release in correlation with CHF. The superiority of O2 uptake over that of CO2
release indicates that O2 uptake and CO2 release are not redundant in their correlation with CHF. The
coherence of bER with CHF was shown to be significant at the frequency range between 0.03Hz and 0.008Hz
with the coherence getting stronger and stronger at lower and lower frequencies. Brain regions with strong
bER-CHF coupling overlapped many areas of the default mode network (DMN), suggesting a potential
association between oscillations of resting systemic metabolism characterized by bER and the rhythm of
background brain activities characterized by DMN. We propose to study 60 normal individuals to increase our
neuroimaging data base to improve our understanding on the role of bER-CHF coupling, a brain-body
interaction between systemic metabolism and resting state brain activities, especially those at DMN. Such a
data base will not only support more research on the basic mechanism of DMN and other cerebral resting state
oscillations but also provide opportunities for future clinical research which images brain markers for conditions
that modulate respiratory gas exchange for diagnostic as well as therapeutic purposes.

## Key facts

- **NIH application ID:** 9954850
- **Project number:** 1R21AT010955-01
- **Recipient organization:** MASSACHUSETTS GENERAL HOSPITAL
- **Principal Investigator:** KENNETH K KWONG
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $210,000
- **Award type:** 1
- **Project period:** 2020-07-01 → 2022-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9954850

## Citation

> US National Institutes of Health, RePORTER application 9954850, Brain-Body Interaction of Breath-by-Breath O2-CO2 Exchange Ratio withResting State Cerebral Hemodynamic Fluctuations (1R21AT010955-01). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/9954850. Licensed CC0.

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