Lung DiseasesPulmonary Disease, Chronic ObstructiveChronic DiseaseLungRisk FactorsLung Diseases, ObstructiveForced Expiratory VolumeSpirometryRespiratory Function TestsBronchodilator AgentsDyspneaVital CapacityPulmonary EmphysemaScopolamine DerivativesSmokingAdministration, InhalationOxygen Inhalation TherapySputumExercise ToleranceSeverity of Illness IndexEmphysemaCholinergic AntagonistsRespiratory MusclesRespiratory System AgentsIpratropiumAlbuterolAsthmaSmokeRespiratory InsufficiencyBronchiAdrenal Cortex HormonesBronchitis, ChronicAdrenergic beta-2 Receptor AgonistsQuality of LifePulmonary MedicineTreatment OutcomeInspiratory CapacityExpectorantsPneumoniaRespiratory MucosaCase-Control Studiesalpha 1-Antitrypsin DeficiencyRespiratory TherapyNebulizers and VaporizersBronchitisBronchoalveolar Lavage FluidInhalationProspective StudiesHospitalizationBronchiectasisBlood Gas AnalysisTime FactorsBreathing ExercisesExercise TestOxygenPositive-Pressure RespirationWork of BreathingRespiration, ArtificialHypercapniaBronchoscopyRespiratory MechanicsRetrospective StudiesDisease ProgressionQuestionnaires