Blood Flow VelocityRegional Blood FlowUltrasonography, Doppler, TranscranialCerebrovascular CirculationMiddle Cerebral ArteryEthanolBlood PressureUltrasonography, DopplerOphthalmic ArteryCerebral ArteriesPulsatile FlowUltrasonography, Doppler, ColorUltrasonography, Doppler, PulsedCoronary CirculationVascular ResistanceHemodynamicsLaser-Doppler FlowmetryHypocapniaArea Under CurveCiliary ArteriesTime FactorsEchocardiography, DopplerRetinal ArteryEchoencephalographyRheologyUmbilical ArteriesHyperventilationMicrocirculationCarbon DioxideDiastoleBlood GlucoseUltrasonography, PrenatalAnterior Cerebral ArteryHeart RateHyperemiaUltrasonographyModels, CardiovascularArteriesReference ValuesSystoleIntracranial PressureHeart Rate, FetalCoronary VesselsCeliac ArteryHomeostasisVasodilationGestational AgeAcetazolamideVasodilator AgentsDogsPregnancyDoppler EffectOxygenMesenteric Artery, SuperiorBrainEchocardiography, Doppler, ColorFetal Growth RetardationReproducibility of ResultsCarotid Artery, InternalProspective StudiesCircle of WillisPlacental CirculationCollateral CirculationHemorheologyTilt-Table TestFetal HeartEchocardiographyPosterior Cerebral ArteryVasomotor SystemSplanchnic CirculationHypotension, OrthostaticHypercapniaFlow CytometryBlood ViscosityPulmonary CirculationPostureBlood Circulation TimeBlood VolumeOxygen ConsumptionPartial PressurePapaverineEchocardiography, Doppler, PulsedCardiac OutputRetinal VesselsUterusEchocardiography, TransesophagealVasoconstrictionAdenosineRenal CirculationCarotid ArteriesMitral ValveAnalysis of VarianceInfant, NewbornVentricular Function, LeftFetusMicrospheresSensitivity and SpecificityOrthostatic IntoleranceInfant, PrematureHematocrit