The Effects of Positive Airway Pressure on the Mucolytic Effects of NAC (TEAM)

Inclusion Criteria: Asthma Group: 1. Male or female between the ages of 18 to 85 at Visit 1 2. Written informed consent obtained from subject and ability for subject to comply with the requirements of the study. 3. Able to perform reproducible spirometry according to American Thoracic Society (ATS) criteria 4. Clinical history of asthma per patient report or medical record 5. Asthma requiring treatment with inhaled corticosteroids (ICS) or biologic therapy for 3 months or greater 6. Computed Tomography (CT) mucus score ≥ 3 (done as part of screening) 7. There is no lower threshold on Forced Expiratory Volume in the first second (FEV1), which means the study will attempt to enroll all patients regardless of asthma severity. However, eligible participants will need to demonstrate ability to tolerate study treatment reflected by a post-treatment FEV1 ≥ 80% of pre- treatment, pre-bronchodilator FEV1. Participants who have a \>20% drop in FEV1 after receiving any study treatment will be excluded from the study. 8. For participants with known mucus plugging on CT: no limit on FEV1; For participants with unknown mucus plugging: FEV1\<70% predicted COPD Group: 1. Males or females between the ages 18 to 85 at the time of visit 1. 2. Written informed consent obtained from subject and ability for subject to comply with the requirements of the study. 3. History of COPD per patient report or medical record and confirmed by an FEV1/FVC ratio of under 70%. 4. Current or former smoker with a history of at least 10 pack-years of smoking. 5. CT mucus score ≥ 3 6. There is no lower threshold on FEV1, which means the study will attempt to enroll all patients regardless of COPD severity. However, eligible participants will need to demonstrate ability to tolerate study treatment reflected by a post-treatment FEV1 ≥ 80% of pre- treatment, pre-bronchodilator FEV1. Participants who have a \>20% drop in FEV1 after receiving any study treatment will be excluded from the study. 7. For participants with known mucus plugging on CT: no limit on FEV1; For participants with unknown mucus plugging: FEV1\<50% predicted Exclusion Criteria: 1. A history of medical disease, which in the opinion of the investigator may put the subject at extra risk from study-related procedures or because the disease may influence the results of the study. 2. Currently pregnant 3. URI in past 10 days