Normally the intrapleural pressure is about −4 mm Hg.When the lungs are fully expanded this pressure may be as great as −9 mm Hg.
The lungs are divided into lobes, the left lung having two (the left upper lobe and the left lower lobe) and the right having three (the right upper lobe, the right middle lobe, and the right lower lobe); these are further subdivided into bronchopulmonary segments, of which there are about 20.
During inhalation the pressure becomes slightly negative (−3 mm Hg) in relation to atmospheric pressure.
During exhalation the intra-alveolar pressure rises to approximately 3 mm Hg.
may be prescribed to assist in drainage of exudate from lungs and bronchioles. If the abscess becomes chronic, surgery may be necessary and usually involves removal of the portion of the lung containing the cancer malignant growths of the lung.
Although the exact cause of lung cancer is not known, inhaled carcinogens are known to be important predisposing causes.
Under normal conditions, however, the intrapleural pressure fluctuates between −4 and −6 mm Hg.