What is most likely to happen if an adult is breathing 45 breaths/min with shallow breaths?

The situation described involves an adult taking 45 breaths per minute with shallow breaths, which is indicative of a rapid but ineffective breathing pattern. In this context, the correct choice highlights that the inhaled air is primarily remaining in the anatomic dead space.

The concept of anatomic dead space refers to the parts of the respiratory system where no gas exchange occurs, such as the trachea and bronchi. When a person breathes rapidly but with shallow breaths, the tidal volume—the amount of air moved in and out of the lungs with each breath—remains low. As a result, a significant portion of the air being inhaled does not reach the alveoli, where gas exchange takes place. Instead, it gets trapped in the conducting airways, failing to participate in oxygenation of the blood or removal of carbon dioxide. This is why shallow breathing at an increased rate leads to most of the inhaled air staying in the dead space, rather than contributing meaningfully to ventilation.

This phenomenon explains why the volume of air reaching the alveoli would not significantly increase; minute alveolar volume would remain low due to the inadequate depth of inhalation. Lungs are less likely to hyperinflate in this scenario, as sufficient volume is not being brought into