title: Comparison between end-tidal CO₂ and respiration volume per time for detecting BOLD signal fluctuations during paced hyperventilation.
abstract: Respiratory motion and capnometry monitoring were performed during blood oxygen level-dependent (BOLD) functional magnetic resonance imaging (fMRI) of the brain while a series of paced hyperventilation tasks were performed that caused significant hypocapnia. Respiration volume per time (RVT) and end-tidal carbon dioxide (ETCO(2)) were determined and compared for their ability to explain BOLD contrast changes in the data. A 35% decrease in ETCO(2) was observed along with corresponding changes in RVT. A best-fit ETCO(2) response function, with an average initial peak delay time of 12 s, was empirically determined. ETCO(2) data convolved with this response function was more strongly and prevalently correlated to BOLD signal changes than RVT data convolved with the corresponding respiration response function. The results suggest that ETCO(2) better models BOLD signal fluctuations in fMRI experiments with significant transient hypocapnia. This is due to hysteresis in the ETCO(2) response when moving from hypocapnia to normocapnia, compared to moving from normocapnia to hypocapnia.
authors: Department of Anesthesiology, The Ohio State University Medical Center, Columbus, OH 43210, USA.
authors: Keith M
authors: KM
authors: Vogt
authors: James W
authors: JW
authors: Ibinson
authors: Petra
authors: P
authors: Schmalbrock
authors: Robert H
authors: RH
authors: Small
mesh_terms: D000328:Adult; D001931:Brain Mapping / Q000379:methods; D002245:Carbon Dioxide / Q000737:chemistry*; D002560:Cerebrovascular Circulation; D005260:Female; D006801:Humans; D006985:Hyperventilation / Q000503:physiopathology*; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008833:Microcirculation; D008875:Middle Aged; D010100:Oxygen / Q000737:chemistry; D012815:Signal Processing, Computer-Assisted; D012984:Software; D013997:Time Factors
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen