Phase 1 evaluation of tubing PEP as an improvised positive expiratory pressure device: pressures generated through oxygen tubing across a range of flow rates and lengths

Introduction: Positive expiratory pressure (PEP) devices are widely used for respiratory therapy. Cost and accessibility of commercial devices can be preclusive, leading to therapists using improvised PEP devices. There are very few studies describing a new improvised PEP device: Tubing PEP. The purpose of this study was to compare pressures generated by different lengths of 4 mm internal diameter hospital-issue oxygen tubing and to estimate if therapeutic PEP could be delivered with tubing PEP.

Methods: 4 mm internal diameter oxygen tubing was cut into lengths of 40, 60, 80, 100, and 120 cm The pressure generated through each length was tested at gas flows of 4 to 11 L/min in 1 L/min increments. Pressure manometer measurements were taken visually three times for each flow rate and the mean of these measures calculated and recorded.

Results: There was a strong positive linear relationship between pressure and flow across lengths of oxygen tubing up to 120 cm with flow rates from 4 to 11 L/min. Regression modelling can estimate pressures generated with physiological flow rates to 20 L/min.

Conclusions: Tubing PEP consisting of 4 mm internal diameter oxygen tubing behaves as a flow-regulated PEP device. It is estimated that ≥60 cm lengths of tubing could provide therapeutic PEP of 10-20 cm H₂O throughout the expected range of physiological flow rates in subjects with respiratory pathology. This requires further confirmatory in-vivo testing. Tubing PEP is a viable, low-cost, readily available, low-risk, waterless, flow-regulated means of administering PEP.