Ventilation-Perfusion RatioHypoventilationObesity Hypoventilation SyndromePulmonary EmbolismKrypton RadioisotopesLaser-Doppler FlowmetryPulmonary Gas ExchangeSleep Apnea, CentralHindlimbTechnetium Tc 99m Aggregated AlbuminPerfusion ImagingIschemiaNoble GasesBlood Gas AnalysisPerfusionPulmonary CirculationRespiration, ArtificialLungCarbon DioxideXenon RadioisotopesPulmonary VentilationPartial PressureOxygenVentilationHypercapniaIntermittent Positive-Pressure VentilationAnoxiaPulmonary ArteryRespiratory MechanicsHypothalamic DiseasesPositive-Pressure RespirationTidal VolumeRespiratory Function TestsRespirationSleep Disorders, IntrinsicNeuromuscular DiseasesAdministration, InhalationHirschsprung DiseaseNoninvasive VentilationHigh-Frequency VentilationHyperventilationHealth Status DisparitiesRespiratory Physiological ProcessesCapnographyRespiratory Insufficiency