Emphysema – images.md gas constant for air

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Emphysema is a lung disease, which together with chronic bronchitis, is referred to as Chronic Obstructive Pulmonary Disease (COPD). These diseases are characterized by the flow of air in the lungs being obstructed. A major cause of emphysema is smoking but it can be caused by other diseases. In Emphysema the alveoli (the tiny air sacs at the end of airways where gaseous exchange takes place) break down and form much larger sacs. The broken alveoli cause air to get trapped inside the lungs. In severe cases, sections of the lungs can totally collapse causing a pneumothorax, this occurs when air or gas are present in the cavity between the lungs and chest causing the lung to collapse. Imaging in emphysema plays an important part in diagnosis and high resolution computed tomography (HRCT) is especially effective in this process. Emphysema is generally classified into three types according to the area of the lung affected:- centrilobular (or centriacinar), panlobular (or panacinar) and paraseptal. Centrilobular is the most common type of emphysema and is associated with smoking and dust inhalation, (2) it usually involves the upper zones of each lobe and is mainly localized to the proximal respiratory bronchioles.

High Resolution CT scan of the chest shows centrilobular areas of areas of focal lucenies (darker areas) with no discernible walls in most of the cases. There is a white dot in the centre or periphery of the radiolucencies that indicates the central bronchovascular bundle, as indicated by the purple arrows. Findings Centrilobular Emphysema.

CT scan of a 49 year old male patient who presented with severe breathlessness and recurrent chest infections. This scan is characteristic of Pan-lobular Emphysema demonstrating basal predominance. Evident is severe destruction of the basal segments of the lungs with widespread tracheal diverticulae (diverticulae are sacs or pouches thought to be acquired due to prolonged pressure due to a chronic cough) that extend into the lower bronchial tree – associated with severe emphysema. Findings Pan-Lobular (or panacinar) Emphysema with Alpha-1-Antitrypsin deficiency confirmed after the scan.

Panlobular emphysema is mainly situated in the lower lobes and has a uniform distribution across parts of the secondary pulmonary lobule. The secondary pulmonary lobule represent specific structures of the lung which includes the pulmonary artery and arterioles, bronchi and bronchioles, pulmonary veins and lymphatics within the interlobular septae. One of the causes of Panlobular (or panacinar) emphysema is a rare, inherited condition whereby the protein ‘Alpha-1 Antitrypsin’ is deficient (3). This protein protects the elasticity of the lungs and prevents white blood cells from damaging normal lung tissue. Patients with this deficiency develop emphysema at a much younger age and if patients smoke as well the emphysema progresses much quicker and is more severe.

CT scan of a patient, with known centrilobular emphysema, being investigated for potential pulmonary embolus. The CT image shows paraseptal emphysema with a background of centrilobular emphysema. In this case, the alveolar sacs and ducts at the periphery of the lung are affected. The areas of emphysema are commonly surrounded by interlobular septa. Interlobular septa is ‘the connective tissue between secondary pulmonary lobules, usually containing a vein and lymphatics; seen radiographically when thickened as a Kerley B or septal line’. (4)