Certified Transport Registered Nurse Certification Practice Exam

In respiratory physiology, what does Boyle's Law relate to?

1. Pressure and volume

2. Temperature and volume

3. Dissolved gas concentration

4. Gas diffusion rates

The correct answer is: Pressure and volume

Boyle's Law establishes a fundamental principle in respiratory physiology by describing the relationship between pressure and volume of a gas at constant temperature. According to this law, when the volume of a gas increases, the pressure decreases, and conversely, when the volume decreases, the pressure increases, given that temperature remains consistent. This relationship is critical in understanding how the lungs function during inhalation and exhalation. During inhalation, the diaphragm contracts, increasing the volume of the thoracic cavity, which causes a drop in intra-thoracic pressure compared to atmospheric pressure. As a result, air flows into the lungs. During exhalation, the diaphragm relaxes, decreasing the volume of the thoracic cavity, which raises the pressure and forces air out of the lungs. The other options, while relevant to aspects of gas behavior and respiratory function, do not capture the specific relationship that Boyle's Law emphasizes in relation to pressure and volume in gases. Temperature and volume pertain to Charles's Law, dissolved gas concentration is governed by Henry's Law, and gas diffusion rates are associated with Dalton's Law and Fick's Law, each of which addresses different physical principles. Understanding Boyle's Law is foundational for grasping essential mechanisms of respiratory mechanics and gas