The base of the lung rests of the diaphragm, the tough sheet of tissue separating the chest cavity from the abdomen. Precise anatomical terminology can be used to refer to different parts of the lungs no matter what position the patient is in, and may eliminate confusion when discussing symptoms and procedures. In a healthy patient sitting or standing upright, the pressure at the base of the lung is slightly higher than in other regions.
Each lung also includes a network of lobes and fissures, and is heavily supplied with blood vessels to facilitate gas exchange. The lungs trade carbon dioxide as a waste product from inside the body with oxygen. On the left, the lung has two lobes to make room for the heart, while the right lung includes three. At the base of the lung, the tissue becomes somewhat concave to accommodate the convex curve of the diaphragm, and this shape is more marked in the right lung, where the diaphragm is slightly higher.
When people breathe in, the base of the lung drops to allow the lung to inflate as the negative pressure inside the lungs works to pull in air. As they breathe out, this part of the lung rises and pushes the air out while the pressure rises. The diaphragm plays an important role in this process. Patients with lung disease may struggle to breathe because they can’t maintain appropriate pressure differentials. Fluid deposits can also develop in the lungs or between the lungs and the pleura, the tissues that surround them and provide room to expand.
During a medical examination, care providers want to make sure to reach all the way down to the base of the lung when they listen to the patient’s breathing. The ribs can help with navigation during an examination, and the care provider also listens attentively with a stethoscope to the changing sounds. This ensures complete coverage of the lung to identify any abnormal sounds that might be a cause for concern. Care providers also typically listen to the lungs from the front and back to make sure they don’t miss anything.
In surgical treatment for conditions like lung cancer, one or more lobes may be removed, along with the base of the lung. This can change the way the patient breathes. People with a history of lung disease who have decreased lung function due to scarring or lobectomies may need to undergo regular evaluations to assess their remaining lung health.