Measurements of Exhaled Nitric Oxide in Healthy Subjects in Thailand

Inclusion Criteria: * healthy subjects in community Exclusion Criteria: * smoker or past history of smoking * asthma, allergic rhinitis, chronic respiratory disease or other chronic illness * history of wheezing within 12 months before enrollment * history of upper or lower respiratory tract infection within 6 weeks before enrollment * drink ethanol within 48 hours before enrollment * drink caffeine within day before enrollment * during pregnancy * chronic use of any drugs * participate other project within 30 days