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This Article Full Text Full Text (PDF) All Versions of this Article: 578/1/359    most recent jphysiol.2006.119925v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Pena, J. P. Articles by Longo, L. D. Search for Related Content PubMed PubMed Citation Articles by Pena, J. P. Articles by Longo, L. D. Related Collections Integrative

Jorge Pereyra Pea¹, Takuji Tomimatsu¹, Douglas P. Hatran¹, Lisa L. McGill¹ and Lawrence D. Longo¹

¹ Center for Perinatal Biology, Departments of Physiology, Obstetrics and Gynecology, School of Medicine, Loma Linda University, Loma Linda, CA 92350, USA

For the fetus, although the roles of arterial blood gases are recognized to be critical in the regulation of cerebral blood flow (CBF) and cerebral oxygenation, the relation of CBF, cortical tissue P_O2 (tP_O2), sagittal sinus P_O2, and related indices of cerebral oxygenation to arterial blood gases are not well defined. This is particularly true for that fetus subjected to long-term hypoxia (LTH). In an effort to elucidate these interrelations, we tested the hypothesis that in the fetus acclimatized to high altitude, cerebral oxygenation is not compromised relative to that at low altitude. By use of a laser Doppler flowmeter with a fluorescent O₂ probe, in near-term fetal sheep at low altitude (n = 8) and those acclimatized to high altitude hypoxia (3801 m for 90 ± 5 days; n = 6), we measured laser Doppler CBF (LD-CBF), tP_O2, and related variables in response to 40 min superimposed hypoxia. At both altitudes, fetal LD-CBF, cerebral O₂ delivery, tP_O2, and several other variables including sagittal sinus P_O2, correlated highly with arterial P_O2 (P_a,O2). In response to superimposed hypoxia (P_a,O2 = 11 ± 1 Torr), LD-CBF was significantly blunted at high altitude, as compared with that at low altitude. In the two altitude groups fetal cerebral oxygenation was similar under both control conditions and with superimposed hypoxia, cortical tP_O2 decreasing from 8 ± 1 and 6 ± 1 Torr, respectively, to 2 ± 1 Torr. Also, for these conditions sagittal sinus P_O2 and [HbO₂] values were similar. In response to superimposed hypoxia, cerebral metabolic rate for O₂ decreased 50% in each group (P < 0.05). For both the fetus at low altitude and that acclimatized to high altitude LTH, we present the first dose–response data on the relation of LD-CBF, cortical tP_O2, and sagittal sinus blood gas values to P_a,O2. In addition, despite differences in several variables, the fetus at high altitude showed evidence of successful acclimatization, supporting the hypothesis that such fetuses demonstrate no compromise in cerebral oxygenation.

(Received 24 August 2006; accepted after revision 21 October 2006; first published online 26 October 2006)
Corresponding author L. D. Longo: Center for Perinatal Biology, Loma Linda University, School of Medicine, Loma Linda, CA 92350, USA. Email: llongo{at}llu.edu

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