The normal airway resistance range is which of the following?

• A. 1.5-3.0 cm H2O/L/s
• B. 0.6-2.4 cm H2O/L/s
• C. 0.1-0.4 cm H2O/L/s
• D. 3.0-6.0 cm H2O/L/s

Answer: (B)

Airway resistance is the pressure required to drive a given amount of air through the conducting airways. It follows the pressure–flow relationship Raw = ΔP / V′, so the pressure drop across the airways for a given flow tells you how open or obstructed the airways are. In a healthy adult, the normal range is about 0.6 to 2.4 cm H2O per L per second. Values within this range reflect typical airway caliber and low impedance. If resistance climbs higher, you’d see more pressure needed for the same flow, which points to bronchospasm, secretions, edema, or a circuit issue. Lower values (like 0.1–0.4) are not typical for the human airway, while very high ranges (3.0–6.0) indicate notable obstruction or malfunction in the system.