Flow is inversely proportional to which of the following in the airways?

• A. Pressure gradient
• B. Volume
• C. Resistance
• D. Compliance

Answer: (C)

Flow in the airways is inversely proportional to resistance. This relationship is described by Poiseuille's law, which states that the rate of flow through a tube (in this case, the airways) is dependent on the pressure difference across the tube and is inversely related to the resistance offered by the tube.

When resistance increases due to factors such as airway constriction or obstruction, flow decreases because more pressure is required to maintain the same flow rate. Conversely, if the resistance in the airways decreases, flow will increase for the same pressure gradient.

Understanding this relationship is crucial in areas such as respiratory physiology and the management of conditions like asthma or chronic obstructive pulmonary disease (COPD), where airway resistance can significantly impact airflow and gas exchange efficiency.

The other factors listed do have important roles in ventilation mechanics but do not have the direct inverse relationship with flow as resistance does. The pressure gradient, for instance, is directly related to flow; as the pressure gradient increases, flow typically increases as well. Volume plays a part in respiratory mechanics, especially concerning tidal volume and total lung capacity but does not directly influence flow independent of pressure and resistance. Compliance relates to the change in volume in response to a change in pressure and thus also