The pandemic interefered with the progresion of study activity.

Acute exacerbation of COPD usually presents with more sputum production leading to worsening airflow obstruction. Often patients complain of sensation of sputum (phlegm) stuck in throat, which leads to worsening cough and respiratory distress. In an acute exacerbation setting high flow nasal cannula (HFNC), which is a modality that provides humidified and warm oxygenated air at flow of upto 60L/min, has shown to reduce blood carbon dioxide level and respiratory rate. However, studies investigating other effects of HFNC in this setting are lacking. To investigators' knowledge, this is the first study investigating effects of HFNC on sputum clearance in COPD patients.

The purpose of the study is to determine the effects of HFNC on sputum clearance in acute exacerbation of COPD. Primary objective of the study is to determine whether HFNC improves clearability and wettability of sputum produced during acute exacerbation of COPD. Secondary objectives of the study include subjective assessment of cough severity as well as need for escalation of care after HFNC use versus conventional flow nasal oxygen (CFNO) use.

Chronic obstructive pulmonary disease (COPD) is a major cause of morbidity and the 4th leading cause of mortality in the world. Acute exacerbation of COPD usually presents with more sputum production leading to worsening airflow obstruction. During an exacerbation, high flow nasal cannula (HFNC) has shown to reduce blood carbon dioxide level and respiratory rate. However, studies investigating other effects of HFNC in this setting are lacking. To investigators' knowledge, this is the first study investigating effects of HFNC on sputum clearance in COPD patients.

Patients with a diagnosis of acute exacerbation of COPD who are receiving oxygen therapy via conventional nasal cannula or are on room air will be randomized into high flow nasal cannula (HFNC) or conventional flow nasal oxygen (CFNO) group for 24 hours. HFNC group will receive heated (approximately 37 ⁰C) and humidified (100% relative humidity) oxygenated gas delivered at high flow at 50L/min. CFNO group will receive ambient temperate and non-humidified oxygenated gas delivered at flow of up to 8L/min (standard care). Sputum sample will be collected at time = 0 hours (baseline), 4 +/- 1 hours, 8 +/- 2 hours and 24 +/- 2 hours. Visual analogue score (VAS) regarding cough severity and Breathlessness, Cough and Sputum Scale (BCSS) regarding cough frequency and ease will be obtained at time = 0 and 24 hours.

Primary outcomes of the study are the difference in clearability and wettability of sputum sample. Clearability is measured by the distance sputum sample travels in an artificial trachea after a simulated cough. The longer the displacement, the more the clearability. Wetability is measured by determining the contact angle the sputum sample makes on a glass surface. The smaller the contact angle, the more the wettability. Secondary outcomes include subjective assessment of cough using VAS and BCSS scales, as well as need for escalation of care.

Inclusion Criteria:

1. Age ≥ 18 years old
2. Known COPD or high probability of the disease according to treating physician based on clinical history, physical examination and chest imaging.
3. Hospital admission for acute exacerbation of COPD defined by 2018 GOLD report as acute worsening of respiratory symptoms (more than baseline cough, sputum purulence or volume, dyspnea or wheeze) that result in additional therapy.
4. Presence of one or more of following: increase in sputum production, change in sputum color or difficulty in expectorating sputum.

Exclusion Criteria:

1. Inability to obtain informed consent from the patient or legally authorized representative.
2. Inability of the subject to cooperate with protocol.
3. Presence of idiopathic bronchiectasis or cystic fibrosis.
4. Patients with poor short term prognosis not expected to survive the hospitalization.
5. Massive hemoptysis.
6. Patients presenting with coma (Glasgow coma scale <10) or circulatory shock.
7. Respiratory failure requiring non-invasive ventilation (NIV) or endotracheal intubation.
8. Severely impaired cough, impaired swallowing or chronic aspiration due to neuromuscular disorder.
9. Facial deformity or injury leading to difficulty in wearing high flow nasal cannula appropriately.
10. Enrollment in other investigative protocols with apparent overlap.
11. Prisoners

Currently there is no plan to share IPD.