Ventilation-Perfusion RatioPerfusion ImagingTechnetium Tc 99m Aggregated AlbuminMyocardial Perfusion ImagingPerfusionPulmonary EmbolismVentilationTomography, Emission-Computed, Single-PhotonRespiration, ArtificialPulmonary VentilationPulmonary CirculationLungExercise TestHigh-Frequency VentilationTomography, X-Ray ComputedRadiopharmaceuticalsPulmonary ArteryTidal VolumeIntermittent Positive-Pressure VentilationPositive-Pressure RespirationSensitivity and SpecificityHigh-Frequency Jet VentilationNoninvasive VentilationRespirationVentilator WeaningPredictive Value of TestsRespiratory MechanicsPulmonary Gas ExchangeVentilators, MechanicalCarbon DioxideOxygenIntubation, IntratrachealHypercapniaRespiratory Distress Syndrome, AdultBlood Gas AnalysisPartial PressureVentilator-Induced Lung InjuryWork of BreathingLung ComplianceTime FactorsTracheostomyChemotherapy, Cancer, Regional PerfusionHeliumOne-Lung VentilationAir PressureCoronary CirculationRespiratory Function TestsIntensive Care UnitsCerebrovascular CirculationLaryngeal MasksMaximal Voluntary VentilationAnoxiaVentilators, Negative-PressureLung Volume MeasurementsRespiratory Distress Syndrome, NewbornMasksRegional Blood FlowProspective StudiesKryptonHemodynamicsIntensive CareOxygen ConsumptionProne PositionKrypton RadioisotopesPressureTreatment OutcomeRespiratory Dead SpaceMagnetic Resonance ImagingAirway ResistanceOrganotechnetium CompoundsContrast MediaTracheotomyTechnetium Tc 99m SestamibiLung InjuryDiaphragmHypoventilationXenon RadioisotopesReproducibility of ResultsRespiratory RateRespiratory Physiological PhenomenaApneaPulmonary AtelectasisFluorocarbonsEquipment DesignRetrospective StudiesInfant, NewbornOxygen Inhalation TherapyNitrogen RadioisotopesHyperventilationIntermittent Positive-Pressure BreathingAirway ObstructionLung DiseasesAcute Lung InjuryPulmonary EdemaCritical IllnessBlood PressureRespiratory MusclesHeartDogsImage Processing, Computer-Assisted