Lower Body Negative PressureCentral Venous PressureCardiac OutputBlood PressureHemodynamicsHypovolemiaForearmOrthostatic IntoleranceHead-Down TiltVascular CapacitanceBed RestHeart RateDizzinessVascular ResistancePressoreceptorsHypotension, OrthostaticPulmonary Wedge PressureCardiovascular DeconditioningBaroreflexPressureSympathetic Nervous SystemBlood VolumeGravity SuitsSupine PositionWeightlessness SimulationRegional Blood FlowWeightlessness CountermeasuresStroke VolumeSpace FlightHeart FailureReflexSyncopeNegative-Pressure Wound TherapyPlethysmographyVentilators, Negative-PressureVasoconstrictionArterial PressureTilt-Table TestNorepinephrineBlood Flow VelocityGravitationLegPostureComplianceWeightlessnessVentricular PressureVeinsVasomotor SystemCold TemperatureHypotensionSkin TemperatureAutonomic Nervous SystemRestPelvisHand StrengthCardiovascular Physiological PhenomenaHeartExerciseDiastoleBrachial ArteryTime FactorsMuscle, SkeletalEchocardiography, DopplerVentricular Function, LeftHydrostatic PressureStress, PhysiologicalElectrocardiographyCerebrovascular CirculationMiddle Cerebral ArteryOxygen ConsumptionAir PressureReference ValuesAnalysis of VarianceCardiac CatheterizationEpinephrineVenous PressureMusclesSkinTransducers, PressureVentricular Dysfunction, LeftEchocardiography, Doppler, PulsedHypertensionBlood Pressure DeterminationMitral ValveMyocytes, CardiacAgingSuctionSkin CareAbdominal Wound Closure Techniques