What are the consequences of mucous hypersecretion?  First, mucus plugging means complete occlusion of the airway, with the consequence of atelectasis (seen in the chest x-ray [and ultrasound image^[1]] on the right side of this Figure).  Incomplete occlusion of airways may also occur, with risk of hyperinflation and increased work of breathing.  Due to inhomogeneity of the ventilation/perfusion relationship, there may be worsening hypoxemia.^[6]  According to data from the US Lung Health Study,^[7] cough with phlegm was associated with about 50 mL lower baseline FEV₁.  Sputum itself is a good environment for the growth of bacteria, thereby increasing the bacterial load in the airways, and the risk of exacerbation or infection.  Additionally, hypersecretion leads to decrease in sleep quality, as it has been shown recently with a marked transition to a sitting position during the night in COPD patients and a higher Pittsburgh Sleep Quality Index, 4 versus 3.^[8]

Michael Dreher [Reader: See Dreher, Activity 4, COPD Advanced Patient Management] has talked about the option of noninvasive ventilation (NIV) in advanced hypercapnic COPD patients, but NIV success can be impeded by lots of secretions that cannot be coughed up.  And lastly, an increase in mortality has been reported, with a hazard ratio of 1.27 according to data from the US Lung Health Study.^[7]