A new method for measurement of respiratory resistance

A new method for measuring the resistance of the total respiratory system is presented. The method uses a device comprising a solenoid valve, a multiperforated plate, and a pneumotachograph. The multiperforated plate serves as a constant resistor (Rk) that is used to partially occlude the airway opening, thus rapidly and briefly reducing airflow during natural expiration. If it is assumed that the driving pressure remains constant during the very short period the airway is partially occluded, the respiratory flow immediately preceding the addition of Rk (V) and the flow reduction during partial occlusion (delta V) allow calculation of the resistance of the total respiratory system. The resistance of 14 normal subjects and 18 patients with chronic obstructive pulmonary disease (COPD) was measured with this new method as well as with the body plethysmographic method: 90% of the interrupter values fell within +/- 0.6 cmH2O . l-1.s of the plethysmographic values, and all fell within +/- 0.8 cmH2O . l-1.s.