Poiseuille’s Law describes the flow of a fluid through a cylindrical tube & can be applied to understand airway resistance in the respiratory system.

Airway resistance is a crucial factor in respiratory physiology & Poiseuille’s law helps explain how factors such as the radius of the airways affect the resistance to airflow.

Key points from Poiseuille’s Law:

1. Resistance & Radius:
Airway resistance is inversely proportional to the fourth power of the radius of the airway. This means even a small reduction in the airway radius leads to a large increase in resistance.

2. Viscosity & Length:
Resistance also depends on the viscosity of the air & the length of the airway.

3. Flow Rate:
The law assumes laminar (smooth) flow. In conditions where flow becomes turbulent, such as during rapid breathing, the relationship becomes more complex.

In summary, Poiseuille’s law highlights that small changes in airway diameter can significantly impact breathing by increasing or decreasing airway resistance.