{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,30]],"date-time":"2026-09-30T04:16:35Z","timestamp":1790741795268,"version":"4.1.0"},"reference-count":50,"publisher":"Ovid Technologies (Wolters Kluwer Health)","issue":"1","content-domain":{"domain":["www.ahajournals.org"],"crossmark-restriction":true},"short-container-title":["JAHA"],"published-print":{"date-parts":[[2022,1,4]]},"abstract":"<jats:sec xml:lang=\"en\">\n            <jats:title>Background<\/jats:title>\n            <jats:p xml:lang=\"en\">Cerebrovascular autoregulation (CA) regulates cerebral vascular tone to maintain near\u2010constant cerebral blood flow during fluctuations in cerebral perfusion pressure (CPP). Preclinical and clinical research has challenged the classic triphasic pressure\u2010flow relationship, leaving the normal pressure\u2010flow relationship unclear.<\/jats:p>\n          <\/jats:sec>\n          <jats:sec xml:lang=\"en\">\n            <jats:title>Methods and Results<\/jats:title>\n            <jats:p xml:lang=\"en\">\n              We used in vivo imaging of the hemodynamic response in pial arterioles to study CA in a porcine closed cranial window model during nonpharmacological blood pressure manipulation. Red blood cell flux was determined in 52 pial arterioles during 10 hypotension and 10 hypertension experiments to describe the pressure\u2010flow relationship. We found a quadriphasic pressure\u2010flow relationship with 4 distinct physiological phases. Smaller arterioles demonstrated greater vasodilation during low CPP when compared with large arterioles (\n              <jats:italic>P<\/jats:italic>\n              &lt;0.01), whereas vasoconstrictive capacity during high CPP was not significantly different between arterioles (\n              <jats:italic>P<\/jats:italic>\n              &gt;0.9). The upper limit of CA was defined by 2 breakpoints. Increases in CPP lead to a point of maximal vasoconstriction of the smallest pial arterioles (upper limit of autoregulation [ULA] 1). Beyond ULA1, only larger arterioles maintain a limited additional vasoconstrictive capacity, extending the buffer for high CPP. Beyond ULA2, vasoconstrictive capacity is exhausted, and all pial arterioles passively dilate. There was substantial intersubject variability, with ranges of 29.2, 47.3, and 50.9\u00a0mm\u00a0Hg for the lower limit, ULA1, and ULA2, respectively.\n            <\/jats:p>\n          <\/jats:sec>\n          <jats:sec xml:lang=\"en\">\n            <jats:title>Conclusions<\/jats:title>\n            <jats:p xml:lang=\"en\">We provide new insights into the quadriphasic physiology of CA, differentiating between truly active CA and an extended capacity to buffer increased CPP with progressive failure of CA. In this experimental model, the limits of CA widely varied between subjects.<\/jats:p>\n          <\/jats:sec>","DOI":"10.1161\/jaha.121.022943","type":"journal-article","created":{"date-parts":[[2021,12,22]],"date-time":"2021-12-22T11:55:18Z","timestamp":1640174118000},"update-policy":"https:\/\/doi.org\/10.1161\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":45,"title":["Differential Hemodynamic Response of Pial Arterioles Contributes to a Quadriphasic Cerebral Autoregulation Physiology"],"prefix":"10.1161","volume":"11","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-5595-4440","authenticated-orcid":false,"given":"Samuel P.","family":"Klein","sequence":"first","affiliation":[{"name":"Department of Neurosurgery University Hospitals Leuven Leuven Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Veerle","family":"De Sloovere","sequence":"additional","affiliation":[{"name":"Department of Anesthesiology University Hospitals Leuven Leuven Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Geert","family":"Meyfroidt","sequence":"additional","affiliation":[{"name":"Department of Intensive Care Medicine University Hospitals Leuven Leuven Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7458-0648","authenticated-orcid":false,"given":"Bart","family":"Depreitere","sequence":"additional","affiliation":[{"name":"Department of Neurosurgery University Hospitals Leuven Leuven Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"276","reference":[{"key":"e_1_3_2_2_2","doi-asserted-by":"publisher","DOI":"10.1007\/s10571-006-9008-1"},{"key":"e_1_3_2_3_2","doi-asserted-by":"publisher","DOI":"10.1161\/STROKEAHA.110.594168"},{"key":"e_1_3_2_4_2","first-page":"1233","article-title":"Association between cerebrovascular reactivity monitoring and mortality is preserved when adjusting for baseline admission characteristics in adult traumatic brain injury: a center\u2010TBI study","volume":"1241","author":"Zeiler FA","year":"2019","unstructured":"Zeiler FA, Ercole A, Beqiri E, Cabeleira M, Thelin EP, Stocchetti N, Steyerberg EW, Maas AIR, Menon DK, Czosnyka M, et al. 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