A pneumothorax occurs when free air accumulates in the pleural cavity between the visceral and parietal areas, and causes a portion or the complete lung to collapse. Pressure in the pleural space is normally less than that of atmospheric pressure but following a penetration injury, air can enter the cavity from the outside changing the pressure within the lung cavity and causing it to collapse.
Pneumonia is an acute infection of the lung's terminal alveolar spaces and/or the interstitial tissues which results in gas exchange problems. The major challenge is identification of the source of the infection. Pneumonia ranks as the sixth most common cause of death in the United States.
A pulmonary embolus (PE) usually results after a deep vein thrombus partially or totally dislodges from the pelvis, thigh, or calf. The clot then lodges in one or more of the pulmonary arteries and obstructs forward blood flow and oxygen supply to the lung parenchyma.
Chronic obstructive pulmonary disease (COPD) is irreversible condition in which airways become obstructed and resistance to air flow is increased during expiration when airways collapse. COPD is usually further subdivided into other diseases such as bronchitis and emphysema, and actually COPD refers to these simultaneous disease entities.