Do I Have Mucus Plugs?

Background Mucus plugs refer to secretions or phlegm stuck inside an airway (breathing tubes) as shown in the figures below. These plugs may be seen on CT scans of the chest. Recent studies have shown that mucus plugs can be important contributors to poor lung health.

Mucus plugs block airflow as shown on left and microscopic view on right.

Several studies have recently identified that airway mucus plugs are associated with adverse (“bad”) outcomes in COPD.

Study Dr. Jin and colleagues from the Seoul National University College of Medicine, Seoul, Republic of Korea, analyzed the impact of mucus plugs on CT scans of the chest on flare-ups (exacerbations) and the decline in lung function (FEV1) over five years in patients with COPD. The study results were published in the March 2025 issue of the journal Archivos de Bronconeumologic (volume 61; pages 138-146). The presence of mucus plugs was graded by the number identrified on the CT scan as 0 (no plugs), 1-2, and 3 or more.

Results Of 623 individuals, 44% had one or more airway mucus plugs. Those with mucus plugs had higher rates of flare-ups (both moderate and severe). In addition, the annual decline (worsening) in FEV1 accelerated (faster) in the mucus plug group. Additional analysis showed higher risks in those with 3 or more mucus plugs compared with 0 plugs.

Summary of findings from study by Jin and colleagues published March 2025 in the journal Archivos de Bronconeumologic (volume 61; pages 138-146).

Conclusions The authors concluded that airway mucus plugs are associated with increased risks of flare-ups and decline in lung function over 5 years.

My Comments In a previous study by Dr. Mettler and colleagues from Brigham and Women’s Hospital in Boston, patients with COPD with mucus plugs had increased risks of both respiratory and cancer deaths (June 15, 2024, issue of the American Journal of Respiratory and Critical Care Medicine, volume 209, pages 1508-1510).

Why are airway mucus plugs associated with “bad” outcomes? One possibility is that the mucus in the airways might allow bacteria to grow - which would increase the risks of bronchitis and pneumonia. A second possibiity is that the mucus plugs reduce the oxygen level due to mismatch between ventilation (air into the lungs) and perfusion (blood flow in the lungs). One possibility for the increase in cancer deaths is “shared inflammation.”

Based on these and other studies, it is important for you to ask your health care professional the following question: “Do I have mucus plugs on my CT scan?” If so, ask your health care professional what can be done to “get rid of” the mucus plugs with the hope to prevent “bad outcomes.”