Tubing internal diameter affects the pressures and oscillation frequencies generated by the therapist-made bubble-positive expiratory pressure device

ABSTRACT

Objectives: To determine the positive expiratory pressures (PEP) and oscillation frequencies generated in the therapist-made-bubble-PEP device using tubing with different internal diameters (IDs). Design: Bench-top experimental study. Therapist-made-bubble-PEP device with a 10 cm column height of water, tubing length of 30 cm with distal end of the tubing resting 3 cm from base of container. Tubing with 2, 4, 5, 7, 8, and 10 mm IDs were tested with flows of 5, 10, 15, 20, and 25 L/min. A pressure transducer measured the pressures and oscillation frequencies. Data were captured with PhysioDAQxs© software and analyzed with Breathalyser© software. Results: Therapist-made-bubble-PEP device with: (1) 2 mm ID tubing with 5 and 10 L/min flows produced mean(SD) PEP of 20.1(0.2) and 41.8(0.5)cmH₂O, respectively, oscillation frequencies of 15-19 Hz; (2) 4 mm ID tubing with 5 and 25 L/min flows produced PEP of 12.5(0.2) and 41.5(0.3)cmH₂O, oscillations of 14–18 Hz; (3) 5 mm ID tubing with 5 and 25 L/min flows produced PEP of 10.9(0.1) and 15.8(0.1)cmH₂O, oscillations of 17–18 Hz; (4) 7 mm ID tubing with 5 and 25 L/min flows produced PEP of 10.7(0.0) and 12.7(0.2)cmH₂O, oscillations of 14–17 Hz; (5) 8 mm ID tubing with 5 and 25 L/min flows produced PEP of 10.5(0.0) and 11.4(0.0)cmH₂O, oscillations of 14–18 Hz; and (6) 10 mm ID tubing with 5 and 25 L/min flows produced PEP of 10.4(0.1) and 10.8(0.2)cmH₂O, oscillations of 13–17 Hz. Conclusions: Therapist-made-bubble-PEP device with tubing of 10 mm ID generated the most stable PEP in relation to water height (10 cm) irrespective of flow compared to tubing with ID of 2, 4, 5, 7, and 8 mm. The oscillation frequencies generated at all flows and tubing IDs were between 13 and 19 Hz.

KEYWORDS:

• Bubble
• device
• positive expiratory pressure
• PEP
• therapist-made

Acknowledgments

Professor Jenny Peat for contributions to statistical analysis; and Biomedical Engineering, Prince of Wales Hospital, for contributions to equipment calibration.

Declaration of interest

The authors report no declarations of interest.