Flow (Q) in the respiratory system can be calculated by which formula?

• A. Pressure difference divided by volume
• B. Change in pressure divided by compliance
• C. Change in pressure divided by resistance
• D. Volume divided by resistance

Answer: (C)

The correct formula for calculating flow (Q) in the respiratory system is the change in pressure divided by resistance. This relationship comes from fundamental principles related to fluid dynamics and how air moves through the respiratory system.

In this context, the flow of air can be thought of as representing the volume of air that moves in and out of the lungs over time. According to Ohm's law, which is also applicable to the flow of fluids, flow is directly proportional to the pressure difference driving the flow and inversely proportional to the resistance against that flow. Thus, when there is a change in pressure in the airways, it causes a corresponding flow of air that can be calculated by taking the pressure difference and dividing it by the resistance encountered by the airflow.

Resistance in the respiratory system includes factors like airway diameter and length, which can affect how easily air passes through. Understanding this concept is crucial for evaluating respiratory function and determining how factors such as bronchoconstriction or airway obstruction can alter airflow during breathing.