Bronchitis, ChronicBronchitisPulmonary EmphysemaEmphysemaInfectious bronchitis virusSubcutaneous EmphysemaChronic DiseaseMediastinal EmphysemaSmokingPulmonary Disease, Chronic ObstructivePulmonary Heart DiseaseSputumLung Diseases, ObstructiveRespiratory Function TestsForced Expiratory VolumeRespiratory Tract DiseasesLungExpectorantsSpirometryVital CapacityCoughAsthmaCoal MiningTextile IndustryPancreatic ElastaseAirway ObstructionPneumoconiosisBronchiDustFossil FuelsIpratropiumSmokeBronchiectasisalpha 1-Antitrypsin DeficiencyOccupational DiseasesByssinosisLung DiseasesAtropine DerivativesMucociliary ClearanceCefuroximeWeldingAgricultural Workers' DiseasesMucusOccupational ExposureRespiration DisordersRespiratory Tract InfectionsHaemophilus influenzaeMass Chest X-RayAcute DiseaseHeptachlorCoronaviridaeBronchoalveolar Lavage FluidBronchodilator AgentsCoronavirus InfectionsPrevalenceWaste ProductsForced Expiratory Flow RatesPneumoniaBronchoscopyPneumonectomyAlbuterolTomography, X-Ray ComputedFarmer's LungAir PollutionAza CompoundsDyspneaAir Pollutants, Occupationalalpha 1-AntitrypsinRespiratory SoundsSulfur DioxideMatrix Metalloproteinase 12MetallurgyLung Volume MeasurementsTobacco Smoke PollutionRisk FactorsMiningAnti-Infective AgentsTotal Lung CapacityBronchiolitisAnti-Bacterial AgentsYang DeficiencyPulmonary AlveoliLebanonAirway ResistanceIntermittent Positive-Pressure BreathingCross-Sectional StudiesGuaifenesinMethacholine CompoundsAmbroxolSeverity of Illness IndexRespiratory MucosaEstoniaAerosolsOccupationsFluoroquinolonesHaemophilus InfectionsOxygen Inhalation TherapyAge FactorsBacterial InfectionsDouble-Blind Method