Variability in expiratory flow requirements among oscillatory positive expiratory pressure

Oscillatory positive expiratory pressure (OPEP) devices facilitate secretion clearance by generating positive end expiratory pressure. However, different device designs may produce different levels of expiratory pressure with the same expiratory flow rate. We bench tested four devices to determine the relationship between expiratory flow and expiratory pressure in each.

A bench model was created to test the gas flow rates required by different OPEP devices to generate target expiratory pressure. Four different devices were tested: Acapella^® (DH Green, Smiths Medical), AerobiKa^® (Monaghan Medical Corporation), VibraPEP^® (Curaplex), and vPEP™ (D R Burton Healthcare). Each OPEP device was tested to determine the expiratory flow needed to generate expiratory pressure thresholds considered appropriate for OPEP therapy.

The expiratory flow required to generate the same expiratory pressure thresholds varied considerably among devices. Valved OPEP devices such as the VibraPEP required less flow than mechanical devices such as the vPEP, Aerobika, and Acapella.

In this bench test of OPEP devices, we found considerable variability in expiratory flow requirements needed to generate an expiratory pressure of >10 cm H₂O. Our finding suggests that smaller patients or those with limited expiratory airflow due to diseases such as COPD, obesity, chronic congestive heart failure, and restrictive lung disease may have better results when matched to OPEP devices requiring less expiratory airflow.