Bench Study Simulations: Matching Patient Effort to Four Different Oscillating Positive Expiratory Pressure for Airway Clearance Devices

Abstract

Background:

Positive expiratory pressure (PEP) and Oscillating PEP (OPEP) devices (those that incorporate flow interruptions during active exhalation), are airway clearance therapy (ACT) tools used to assist with the removal of secretions from the lungs. During PEP/OPEP therapy, the patient exhales against a fixed-orifice or oscillation mechanism generating pressures ranging from 10 to 20 cm H₂O. The AARC Clinical Practice Guidelines for PEP/OPEP instruct patients to sustain exhalation actively, but not forcefully, for 3-4 s creating a pressure above baseline of 10 to 20 cm H₂O. We sought to evaluate the characteristics of currently available OPEP devices, and determine the required flow and prerequisite lung volume necessary to generate and sustain the therapeutic pressure.

Methods:

Four different OPEP devices were studied: Acapella DH, (Smiths Medical), Aerobika (Monaghan Medical Corporation), VibraPEP (Curaplex), and vPEP (D. R. Burton Healthcare) to determine flow requirements to achieve and sustain a pressure of 15 cm H₂O. Flow was directed through a TSI flow meter and pressures were measured using a Cecomp pressure gauge. Voltage readings were acquired and exported to an Excel spreadsheet that provided the following calculations; average pressure, average pressure amplitude, average flow and frequency. Device results were compared to the ability of a patient to sustain sufficient pressures/flows.

Results:

Average pressures (cm H₂O): Aerobika: 14.08, Acapella: 14.25, VibraPEP: 14.62, and vPEP: 13.18. Average flow (L/min): Aerobika: 41.9, Acapella: 38.8, VibraPEP: 25.7, and vPEP: 55.3 Calculated exhaled volume (mL) required to sustain pressure for 3.5 s: Aerobika: 2,442, Acapella: 2,265, VibraPEP: 1,498, and vPEP: 3,224. Literature review reveals a mean exhaled tidal volume during OPEP is 33.5 mL/kg, yielding an exhaled volume for a healthy 57 kg patient of 1,909.5 mL.

Conclusions:

When choosing an OPEP device for ACT, one must take into consideration the patient's ability to match flow requirement of the device with individual patient physical characteristics to successfully meet the therapeutic objective. Patients that cannot achieve the required flow for 3-4 s may hyperventilate or fail to maintain the prescribed pressures.