Instruct: Identify the main category of Biorxiv papers based on the titles and abstracts
Query: Protocol-Dependence of Middle Cerebral Artery Dilation to Modest Hypercapnia There is a need for improved understanding of how different cerebrovascular reactivity (CVR) protocols affect vascular cross-sectional area (CSA) when measures of vascular CSA are not feasible. In human participants, we delivered ~{+/-}4mmHg end-tidal partial pressure of CO2 (PETCO2) relative to baseline through controlled delivery, and measured changes in middle cerebral artery (MCA) cross-sectional area (CSA; magnetic resonance imaging (7 Tesla MRI)), blood velocity (transcranial Doppler and Phase contrast MRI), and calculated CVR based on steady-state versus a ramp protocol during two protocols: a 3-minute steady-state (+4mmHg PETCO2) and a ramp (delta of -3 to +4mmHg of PETCO2). We observed that 1) the MCA did not dilate during the ramp protocol, but did dilate during steady-state hypercapnia, and 2) MCA blood velocity CVR was similar between ramp and steady-state hypercapnia protocols, although calculated MCA blood flow CVR was greater during steady-state hypercapnia than during ramp, the discrepancy due to MCA CSA changes during steady-state hypercapnia. Due to the ability to achieve similar levels of MCA blood velocity CVR as steady-state hypercapnia, the lack of change in MCA cross-sectional area, and the minimal expected change in blood pressure, we propose that a ramp model, across a delta of ~-3 to +4mmHg PETCO2, may provide one alternative approach to collecting CVR measures in young adults with TCD when CSA measures are not feasible.
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The categories of this paper are: developmental
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The categories of this paper are: scientific
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The categories of this paper are: and
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The categories of this paper are: epidemiology
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The categories of this paper are: education
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The categories of this paper are: evolutionary
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The categories of this paper are: systems
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The categories of this paper are: cell
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The categories of this paper are: biophysics
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The categories of this paper are: paleontology
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The categories of this paper are: toxicology
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The categories of this paper are: synthetic
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The categories of this paper are: microbiology
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The categories of this paper are: pathology
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The categories of this paper are: molecular
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The categories of this paper are: immunology