Valsalva ManeuverSinus of ValsalvaAutonomic Nervous SystemAutonomic Nervous System DiseasesHeart Septal Defects, AtrialPelvic FloorEmbolism, ParadoxicalPure Autonomic FailurePostureBlood PressureUltrasonography, Doppler, TranscranialHypotension, OrthostaticHeadache Disorders, PrimaryHeart RateSupine PositionForamen Ovale, PatentBaroreflexMaximal Voluntary VentilationPneumocephalusButylscopolammonium BromideUterine ProlapseKinetocardiographyHypovolemiaAortic AneurysmPatient PositioningEchocardiography, TransesophagealVaricoceleTilt-Table TestPerineumRespirationCentral Venous PressureThoraxReflexHemodynamicsBlood Flow VelocityHead-Down TiltCoronary Vessel AnomaliesHemostasis, SurgicalMicroscopy, Acoustic