Pulmonary Disease, Chronic ObstructiveLung Diseases, ObstructiveForced Expiratory VolumeSpirometryLungBronchodilator AgentsRespiratory Function TestsDyspneaVital CapacityPulmonary EmphysemaScopolamine DerivativesSmokingAdministration, InhalationOxygen Inhalation TherapyExercise ToleranceSeverity of Illness IndexSputumLung DiseasesEmphysemaCholinergic AntagonistsIpratropiumRespiratory MusclesAlbuterolSleep Apnea, ObstructiveSmokeAdrenal Cortex HormonesAsthmaRespiratory InsufficiencyBronchitis, ChronicAdrenergic beta-2 Receptor AgonistsBronchiQuality of LifePulmonary MedicineRespiratory System AgentsInspiratory CapacityTreatment OutcomeCase-Control StudiesExpectorantsRisk FactorsRespiratory TherapyRespiratory MucosaBronchitisNebulizers and Vaporizersalpha 1-Antitrypsin DeficiencyPneumoniaPositive-Pressure RespirationInhalationProspective StudiesLung Volume MeasurementsHypercapniaLung NeoplasmsOxygenBronchoalveolar Lavage FluidRespiratory MechanicsBreathing ExercisesBlood Gas AnalysisExercise TestHospitalizationWork of BreathingRespiration, ArtificialQuestionnairesTime FactorsAirway ObstructionDisease ProgressionNoninvasive VentilationHome Care Services, Hospital-BasedTotal Lung CapacityMetered Dose InhalersHeliumPulmonary Gas ExchangeRetrospective StudiesPhosphodiesterase 4 InhibitorsComorbidityDouble-Blind MethodChronic DiseaseCross-Sectional StudiesExhalationBronchoscopyExercise TherapyAirway ResistancePrevalenceEthanolaminesAcute DiseasePulmonary VentilationDiaphragmRespiratory SystemLung TransplantationInflammationCohort StudiesBiological MarkersGlycopyrrolateRespirationCarbon DioxideGlucocorticoidsCoughJaundice, ObstructiveAnti-Inflammatory AgentsAnoxiaStatistics, NonparametricPositive-Pressure Respiration, Intrinsic