Field Internship Student Data Acquisition Project. (FISDAP) Airway Practice Exam

What causes air to rush into the lungs during inhalation?

1. Increased external pressure

2. Decreased volume in the lungs

3. Creation of negative pressure in the lungs

4. Closure of the diaphragm

The correct answer is: Creation of negative pressure in the lungs

Air rushes into the lungs during inhalation primarily due to the creation of negative pressure within the thoracic cavity. When the diaphragm contracts and moves downward (along with the intercostal muscles that elevate the rib cage), the volume of the thoracic cavity increases. According to Boyle's Law, as the volume of a container increases, the pressure within that container decreases. This lower pressure inside the lungs compared to atmospheric pressure creates a pressure gradient that causes air to flow into the lungs. This process is fundamental to respiratory physiology, as it relies on the dynamics of pressure changes rather than external pressure increases or lung volume decreases. In fact, during normal inhalation, both external pressure and lung volume work in ways that facilitate this process rather than oppose it. Hence, understanding the role of negative pressure enables a better grasp of respiratory mechanics and is critical for effective airway management.