Pressures and oscillation frequencies generated by bubble-positive expiratory pressure devices

Abstract

BACKGROUND: 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). METHODS: 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 Breath-alyser 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. RESULTS: Flows of 5–25 L/min produced the following mean = SD PEP and oscillation frequencies (Hz): the Bubble-PEP-3cm produced PEP of 10.4 = 0.14 to 10.8 = 0.24 cm H2O, oscillations between 13 and 17 Hz; the Bubble-PEP-0cm produced PEP of 10.9 = 0.01 to 12.9 = 0.08 cm H2O, oscillations between 12 and 14 Hz; the AguaPEP produced PEP from 9.7 = 0.02 to 11.5 = 0.02 cm H2O, oscillations between 11 and 17 Hz; the Hydrapep produced PEP of 9.6 = 0.35 to 10.7 = 0.39 cm H2O, oscillations between 14 and 17 Hz; and the Therabubble produced PEP from 8.6 = 0.01 to 12.8 = 0.03 cm H2O, oscillations between 14 and 17 Hz. CONCLUSIONS: Bubble-PEP-3cm maintained the most stable pressure throughout the range of flows tested. All devices investigated produced similar oscillation frequencies.