If the diaphragm muscle is paralyzed, how limited is the breathing effort?

If the diaphragm muscle is paralyzed, breathing is significantly affected because the diaphragm is the primary muscle responsible for inhalation. When the diaphragm cannot function, the lungs cannot expand effectively, leading to a reduced ability to take in air. Although other muscles can assist in breathing, such as the intercostal muscles and accessory muscles of respiration, they are not as efficient in creating the negative pressure required for inhalation as the diaphragm is.

The correct choice indicates that breathing effort is reduced to about one-third of normal capacity, suggesting that while the individual may still be able to breathe to some extent, it would require increased effort from auxiliary muscles, leading to shallow and labored breathing. Understanding the functional role of the diaphragm is critical, as it highlights the significant impact of its paralysis on respiratory mechanics.