Pressures and Oscillation Frequencies Generated by Bubble-Positive Expiratory Pressure Devices.

Positive expiratory pressure (PEP) devices are used to assist with airway clearance. Little is known about the therapist-made or commercially available bubble-PEP devices. The aim of this study was to determine the end-expiratory pressures (cm H2O) and oscillation frequencies (Hz) generated when a range of flows were applied to the therapist-made bubble-PEP devices (Bubble-PEP-3cm and Bubble-PEP-0cm) and commercial bubble-PEP devices (AguaPEP, Hydrapep, and Therabubble).

This was a bench-top experimental study using a compressed air source, flow rotameter (flows of 5, 10, 15, 20, and 25 L/min), and pressure transducer. Data were collected using a data acquisition device with PhysioDAQxs software and analyzed with Breathalyser software to determine the pressures and oscillation frequencies generated by 5 bubble-PEP devices. Each flow was constant for a 30-s measurement period, and measurements were repeated in triplicate. The 5 devices were: a therapist-made Bubble-PEP-3cm device (filled with 13 cm of water, tubing resting 3 cm from the base of the container); the therapist-made Bubble-PEP-0cm (filled with 10 cm of water, tubing resting at the base of the container); and the AguaPEP, Hydrapep, and Therabubble devices with water to the 10 cm mark on the containers.

Bubble-PEP-3cm maintained the most stable pressure throughout the range of flows tested. All devices investigated produced similar oscillation frequencies.