Ventilation-Perfusion RatioPulmonary EmbolismLungKrypton RadioisotopesPulmonary VentilationPulmonary Gas ExchangeLaser-Doppler FlowmetryHindlimbTechnetium Tc 99m Aggregated AlbuminRespiration, ArtificialPerfusion ImagingXenon RadioisotopesIschemiaNoble GasesPerfusionPulmonary CirculationRespirationOxygenCarbon DioxideBlood Gas AnalysisVentilationOne-Lung VentilationTidal VolumePartial PressureThoracic Surgical ProceduresPulmonary ArteryPositive-Pressure RespirationAlligators and CrocodilesRespiratory MechanicsHypoventilationLung Volume MeasurementsIntubation, IntratrachealAdministration, InhalationHeliumRespiratory Function TestsXenonTechnetium Tc 99m PentetateTurtlesHypergravityRana catesbeianaTomographyAnoxiaHigh-Frequency VentilationMetamorphosis, BiologicalLung Diseases