The importance of lung mechanics

Being able to breathe without any apparent difficulty is something that healthy people take for granted, and most of us generally go about our daily lives without giving it a second thought. But breathing is not always easy. A number of common lung diseases can make breathing difficult and uncomfortable. Sometimes these diseases can even make it impossible to breathe at all without the assistance of a machine or another person, a condition known as respiratory failure. There are a variety of factors that can lead to respiratory insufficiency or failure, but among the most important are those that involve a compromise in the mechanical properties of the lungs.

Breathing is essentially a mechanical process in which the muscles of the thorax and abdomen, working together under the control of the brain, produce the pressures required to expand the lung so that air is sucked into it from the environment. These pressures must be sufficient to overcome the tendencies of the lung and chest wall tissues to recoil, much like blowing up a balloon. Pressure is also required to drive air along the pulmonary airways, a system of branching conduits that begins at the mouth and ends deep in the lungs at the point where air and blood are close enough to exchange oxygen and carbon dioxide. The mechanical properties of the lungs thus determine how muscular pressures, airway flows, and lung volumes are related.