Validation of Respiratory Resistance Measurements Available to Purchase

The airflow perturbation device (APD) has been developed as a portable, easy to use, and rapid-response instrument for noninvasively measuring respiratory resistance in humans. However, the APD has limited data validating it against established techniques; moreover, a method does not exist to standardize resistance measurement outputs between APD units. This study proposes a system that simulates the normal range of human breathing to validate the APD with the clinically accepted impulse oscillometry technique. Two respiratory resistance ranges were tested. The validation system consisted of a sinusoidal flow generator with ten standardized resistance configurations that were shown to represent a total range of resistances from 0.7000–9.4475 cmH₂O·L⁻¹·s⁻¹. Impulse oscillometry (IOS) measurements and APD measurements of the calibration system were recorded and compared at a constant volumetric flow rate of 0.150 L·s⁻¹. Both IOS and the APD consistently failed to estimate nominal resistance accurately. However, a strong second-order relationship was observed between APD measurements and IOS measurements (R² = 0.997). Because of their comparability to IOS measurements, APD measurements are shown to be valid representations of respiratory resistance in a standard pneumatic model.