COPD

I've already written quite a bit on COPD here, here and here, but there's still a little bit more that I haven't said yet, so bear with me!

Also, there's no nice summary that might help me pin down what hasn't been covered before. Me no like.

Defence Mechanisms

The lung has several defence mechanisms to prevent bad stuff from happening. Nasal hair and mucus serve as physical barriers. The respiratory tract also has immune system cells, immunoglobulins and so forth. If part of the lung is damaged, neighbouring progenitor cells can divide and differentiate to replace them, but if large parts of the lung are damaged, scarring can result. Cells that may divide and replace dead cells include basal cells in the bronchioles, Clara cells further down, and type II alveolar cells (which can replace type I alveolar cells).

Chronic Bronchitis and Emphysema

The two main types of COPD are chronic bronchitis and emphysema. They are quite distinct, but are grouped together for historical reasons.

Chronic Bronchitis

Chronic bronchitis is defined as sputum production for most days for 3 consecutive months for 2 consecutive years.

Chronic bronchitis can be caused by smoking. Cigarette smoke can activate macrophages and neutrophils, which in turn can activate proteases and oxidants, which can cause a lot of damage. Oxidative stress may upregulate goblet cells, leading to mucus hypersecretion.

Emphysema

Emphysema is defined as distal air-space enlargement of the terminal bronchioles due to the alveolar walls breaking down, as explained here.

Emphysema can also be caused by smoking. As mentioned above, cigarette smoke ultimately causes the release of many proteases and oxidants. Additionally, epithelial cells can be harmed, leading to fibrosis.

Diagnosis

Diagnosis of COPD can be done via tests of FEV1, such as flow-volume plots and spirometry. COPD does have many different phenotypes, however, so sometimes many different indices are used in order to more specifically define a particular patient's brand of COPD.

Prognosis

Not all patients with COPD decline. Genetic factors may affect the progression of the disease. Predictive factors include age, BMI and number of previous hospitalisations.