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

The goal of this clinical trial is to determine if positive pressure during inspiration will improve penetration of aerosolized N-Acetylcysteine (NAC) into airway mucus plugs in the lungs of patients with asthma or Chronic Obstructive Pulmonary Disease (COPD). The main questions it aims to answer are: * Does delivery of aerosolized NAC with positive inspiratory pressure have a greater effect on mucus plug burden in the lungs than delivery of NAC without positive pressure. * Does delivery of aerosolized NAC with positive inspiratory pressure have a greater effect on lung function than delivery of NAC without positive pressure. Participants will be assigned (in a single blind design) to the NAC via jet nebulizer group or the NAC via AeroEclipse-VersaPAP nebulizer group. Participants will each complete 5 treatment visits over the course of 30 days. Each treatment visit will consist of two treatments of a 10% NAC (3 mL) and 2.5 mg albuterol (0.5mL) inhalation solution separated by 4 hours, via the nebulization method specific to their group.

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\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\