Abstract #3672

Comparison Between End-Tidal CO2 and Tidal Volume Changes Calculated from the Respiratory Motion Tracing Used for Correction of Respiratory Fluctuations in a Functional MRI Experiment with Normal Breathing and Hyperventilation

Keith Michael Vogt¹, James W. Ibinson², Robert H. Small¹, Petra Schmalbrock³

¹Anesthesiology, The Ohio State University, Columbus, OH, USA; ²Anesthesiology, University of Pittsburgh Medical Center, Pittsburgh, PA, USA; ³Radiology, The Ohio State University, Columbus, OH, USA

Functional MRI data was acquired during normal ventilation and paced hyperventilation that caused a 35% decrease in end-tidal CO₂ (ETCO₂). Respiratory motion and expired CO₂ data were collected and respiratory volume over time (RVT) and ETCO₂ values were calculated. Although negatively correlated, the RVT and ETCO₂ timecourses did not strictly mirror each other. RVT and ETCO₂ values were convolved with appropriate response functions and regressed against each voxel timecourse. The ETCO₂ regressor was more strongly and diffusely correlated to the FMRI data, suggesting that ETCO₂ monitoring may be warranted in studies with large changes in respiration.