If a patient who generates an intrapleural pressure of -4 mmHg to inhale 450 mL experiences inflammation and bronchospasm that reduce the radius of the bronchial airways to one-half of their original size, what pressure must the patient generate to inhale the same tidal volume?

Question

Quizplus · Accepted Answer

According to Poiseuille's law, the flow of air through the bronchial airways is inversely proportional to the fourth power of the radius of the airways. If the radius is reduced to half, the resistance to airflow increases by 2^4 = 16 times. To overcome this increased resistance and inhale the same volume of air, the patient must generate a pressure 16 times greater than the original pressure of -4 mmHg, which equals -64 mmHg. However, since intrapleural pressure is negative during inhalation, the magnitude of the required pressure is 64 mmHg, but the sign is negative, indicating a suction effect. The correct answer is 64 mmHg, but the question asks for the magnitude, not the sign.

If a Patient Who Generates an Intrapleural Pressure of -4