{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,27]],"date-time":"2026-09-27T03:28:16Z","timestamp":1790479696548,"version":"4.1.0"},"reference-count":55,"publisher":"American Physiological Society","issue":"3","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Journal of Applied Physiology"],"published-print":{"date-parts":[[2007,3]]},"abstract":"<jats:p> Clinical transcranial Doppler assessment of cerebral vasomotor reactivity (CVMR) uses linear regression of cerebral blood flow velocity (CBFV) vs. end-tidal CO<jats:sub>2<\/jats:sub> (Pet<jats:sub>CO<jats:sub>2<\/jats:sub><\/jats:sub>) under steady-state conditions. However, the cerebral blood flow (CBF)-Pet<jats:sub>CO<jats:sub>2<\/jats:sub><\/jats:sub> relationship is nonlinear, even for moderate changes in CO<jats:sub>2<\/jats:sub>. Moreover, CBF is increased by increases in arterial blood pressure (ABP) during hypercapnia. We used a modified rebreathing protocol to estimate CVMR during transient breath-by-breath changes in CBFV and Pet<jats:sub>CO<jats:sub>2<\/jats:sub><\/jats:sub>. Ten healthy subjects (6 men) performed 15 s of hyperventilation followed by 5 min of rebreathing, with supplemental O<jats:sub>2<\/jats:sub> to maintain arterial oxygen saturation constant. To minimize effects of changes in ABP on CVMR estimation, cerebrovascular conductance index (CVCi) was calculated. CBFV-Pet<jats:sub>CO<jats:sub>2<\/jats:sub><\/jats:sub> and CVCi-Pet<jats:sub>CO<jats:sub>2<\/jats:sub><\/jats:sub> relationships were quantified by both linear and nonlinear logistic regression. In three subjects, muscle sympathetic nerve activity was recorded. From hyperventilation to rebreathing, robust changes occurred in Pet<jats:sub>CO<jats:sub>2<\/jats:sub><\/jats:sub> (20\u201361 Torr), CBFV (\u221244 to +104% of baseline), CVCi (\u221239 to +64%), and ABP (\u221219 to +23%) (all P &lt; 0.01). Muscle sympathetic nerve activity increased by 446% during hypercapnia. The linear regression slope of CVCi vs. Pet<jats:sub>CO<jats:sub>2<\/jats:sub><\/jats:sub> was less steep than that of CBFV (3 vs. 5%\/Torr; P = 0.01). Logistic regression of CBF-Pet<jats:sub>CO<jats:sub>2<\/jats:sub><\/jats:sub> ( r<jats:sup>2<\/jats:sup> = 0.97) and CVCi-Pet<jats:sub>CO<jats:sub>2<\/jats:sub><\/jats:sub> ( r<jats:sup>2<\/jats:sup> = 0.93) was superior to linear regression ( r<jats:sup>2<\/jats:sup> = 0.91, r<jats:sup>2<\/jats:sup> = 0.85; P = 0.01). CVMR was maximal (6\u20138%\/Torr) for Pet<jats:sub>CO<jats:sub>2<\/jats:sub><\/jats:sub> of 40\u201350 Torr. In conclusion, CBFV and CVCi responses to transient changes in Pet<jats:sub>CO<jats:sub>2<\/jats:sub><\/jats:sub> can be described by a nonlinear logistic function, indicating that CVMR estimation varies within the range from hypocapnia to hypercapnia. Furthermore, quantification of the CVCi-Pet<jats:sub>CO<jats:sub>2<\/jats:sub><\/jats:sub> relationship may minimize the effects of changes in ABP on the estimation of CVMR. The method developed provides insight into CVMR under transient breath-by-breath changes in CO<jats:sub>2<\/jats:sub>. <\/jats:p>","DOI":"10.1152\/japplphysiol.00906.2006","type":"journal-article","created":{"date-parts":[[2006,11,17]],"date-time":"2006-11-17T01:45:49Z","timestamp":1163727949000},"page":"870-877","source":"Crossref","is-referenced-by-count":146,"title":["Transcranial Doppler estimation of cerebral blood flow and cerebrovascular conductance during modified rebreathing"],"prefix":"10.1152","volume":"102","author":[{"given":"Jurgen A. H. 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