Airway resistance

Airway resistance or resistance is used to measure the intrabronchial pressure that must be applied to create a flow of 1 litre of air per second in the mouth (when the nose is blocked). The airway resistance is given in kPa/l/s. The upper standard limit of total resistance (Rtot) is 0.35kPa/l/s.

The airway resistance increases as the airways become narrower. It is measured together with the intrathoracic gas volume in body plethysmography. Both measurement parameters are independent of the patient's cooperation and thus represent objectifiable parameters.

An obstruction of the airway acts like a flow obstruction, the free flow of air is hindered. The airway resistance R (= resistance) depends on the pressure required to generate an airflow. If the airway obstruction is massive, considerable pressure must be applied to pump the air out of the lungs.