{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,7]],"date-time":"2026-07-07T23:54:24Z","timestamp":1783468464890,"version":"3.55.0"},"reference-count":47,"publisher":"American Physiological Society","issue":"3","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Journal of Applied Physiology"],"published-print":{"date-parts":[[2010,3]]},"abstract":"<jats:p> Dynamic cerebral autoregulation (CA) is the transient response of cerebral blood flow (CBF) to rapid blood pressure changes: it improves in hypocapnia and becomes impaired during hypercapnia. Batch-processing techniques have mostly been used to measure CA, providing a single estimate for an entire recording. A new approach to increase the temporal resolution of dynamic CA parameters was applied to transient hypercapnia and hypocapnia to describe the time-varying properties of dynamic CA during these conditions. Thirty healthy subjects (mean \u00b1 SD: 25 \u00b1 6 yr, 9 men) were recruited. CBF velocity was recorded in both middle cerebral arteries (MCAs) with transcranial Doppler ultrasound. Arterial blood pressure (Finapres), end-tidal CO<jats:sub>2<\/jats:sub> (ET<jats:sub>CO<jats:sub>2<\/jats:sub><\/jats:sub>; infrared capnograph), and a three-lead ECG were also measured at rest and during repeated breath hold and hyperventilation. A moving window autoregressive moving average model provided continuous values of the dynamic CA index [autoregulation index (ARI)] and unconstrained gain. Breath hold led to significant increase in ET<jats:sub>CO<jats:sub>2<\/jats:sub><\/jats:sub> (+5.4 \u00b1 6.1 mmHg), with concomitant increase in CBF velocity in both MCAs. Continuous dynamic CA parameters showed highly significant changes ( P &lt; 0.001), with a temporal pattern reflecting a delayed dynamic response of CA to changes in arterial Pco<jats:sub>2<\/jats:sub> and a maximal reduction in ARI of \u22125.1 \u00b1 2.4 and \u22125.1 \u00b1 2.3 for the right and left MCA, respectively. Hyperventilation led to a marked decrease in ET<jats:sub>CO<jats:sub>2<\/jats:sub><\/jats:sub> (\u22127.2 \u00b1 4.1 mmHg, P &lt; 0.001). Unexpectedly, CA efficiency dropped significantly with the inception of the metronome-controlled hyperventilation, but, after \u223c30 s, the ARI increased gradually to show a maximum change of 5.7 \u00b1 2.9 and 5.3 \u00b1 3.0 for the right and left MCA, respectively ( P &lt; 0.001). These results confirm the potential of continuous estimates of dynamic CA to improve our understanding of human cerebrovascular physiology and represent a promising new approach to improve the sensitivity of clinical applications of dynamic CA modeling. <\/jats:p>","DOI":"10.1152\/japplphysiol.01157.2009","type":"journal-article","created":{"date-parts":[[2009,12,24]],"date-time":"2009-12-24T21:48:04Z","timestamp":1261691284000},"page":"604-613","source":"Crossref","is-referenced-by-count":76,"title":["Continuous estimates of dynamic cerebral autoregulation during transient hypocapnia and hypercapnia"],"prefix":"10.1152","volume":"108","author":[{"given":"N. 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