Validation of airflow perturbation device resistance measurements in excised sheep lungs

The airflow perturbation device (APD) is a recently redesigned instrument to measure resistance in the respiratory system. The APD is small and easy to use, gives rapid resistance measurements, and can easily separate inhalation from exhalation components. It also possesses some operational characteristics similar to forced oscillation (FO). Excised sheep lungs within a respiratory chamber were used to determine the effective resistance domain of the APD. Retrograde catheters were installed in the airways, alveolar capsules were used to measure alveolar pressures, and chamber pressure was used as pleural pressure. FO measurements were made to compare with the APD. The APD was found to give a resistance measurement about 1.7 to 1.9 times airway resistance. FO gave a resistance measurement 1.4 times airway resistance. Resistance values differed depending on analysis procedure and frequency of oscillation. Both devices were found to produce oscillations beyond the pleural surface of the lungs. It was concluded that the APD and FO measure similar respiratory resistances.