Evaluation of Pressure Generated by Resistors From Different Positive Expiratory Pressure Devices

Abstract

001). There were no significant differences between any of the resistors when testing sizes of 4.5 and 5.0 mm at either flow. The Mini-PEP and adapter resistors gave the highest pressures. CONCLUSIONS: Pressures generated by the different proprietary resistor components of 4 commercial PEP devices were not comparable, even though the diameter of the resistors is reported to be the same. The pressures generated were significantly different, particularly when using small-diameter resistors at a high flow. Therefore, the resistors may not be interchangeable. This is important information for clinicians, particularly when considering PEP for patients who do not tolerate higher pressures.

Design and Function of a New Conical Positive Expiratory Pressure Device to Be Used During Exercise

“…The pressures we reported here were primarily generated by the resistor, although the length of tubing before the resistor (Fig. 2) may have contributed a pressure of up to 1 cm H 2 O at the highest flows, consistent with the observations of Mestriner et al 6 The important factor that determined pressure was the size of the orifice, and, as is shown in Figure 4A, the pressure was related to the square of the flow and inversely to the square of the orifice diameter in much the same way as described by Fagevik Olsén et al, 20 although that study was concerned with relatively small orifices (1.5 to 5 mm diameter) and very low flows (0.17-0.30 L/s). The pressure-flow relationship was also influenced by incorporating the resistor into a cone shape, which reduced the pressure for a given flow, with the reduction being proportional to the length of the cone (Fig.…”

“…C-PEP ϭ conical positive expiratory pressure MAP ϭ mean arterial pressure T E ϭ expiratory time T total ϭ breathing cycle time P ETCO2 ϭ partial pressure of end-tidal carbon dioxide IC ϭ inspiratory capacity SVC ϭ slow vital capacity RPB ϭ rate of perceived breathlessness IQR ϭ interquartile range requirements, for instance, if the resistor is to be fitted into a mask or other breathing aid. Most flow-dependent PEP devices have been used in postsurgical rehabilitation, where expiratory flows are low, and, in a recent evaluation of PEP devices, Fagevik Olsén et al 20 tested a range of resistors with holes of 2, 3, and 4 mm, which, at flows of 10 and 18 L/min, gave clinically useful pressures. However, resistors of this size would give impossibly high pressures at flows encountered during exercise, even with patients with COPD.…”

“…These investigators also commented that there was very little consistency because resistors with apparently similar size holes give different pressures in different devices. 20 We took 20 cm H 2 O to be the upper limit for use during exercise, partly because this was approximately the maximum that can be tolerated but also because PEP of 5-20 cm H 2 O is commonly used in physiotherapy. 21 A PEP of 10 -20 cm H 2 O for airway clearance has been suggested in the AARC clinical practice guideline.…”

Technical Aspects of Devices and Equipment for Positive Expiratory Pressure With and Without Oscillation

“…We identified 2 studies in which resistors were tested. 16,21 Both included various resistors with different designs, and the differences were reported to affect the pressure generated. 16,21 In one of the studies, valves or conical resistors with inner diameters of 5-7 mm were tested with flows of 0.2-1.5 L/min.…”

“…16,21 Both included various resistors with different designs, and the differences were reported to affect the pressure generated. 16,21 In one of the studies, valves or conical resistors with inner diameters of 5-7 mm were tested with flows of 0.2-1.5 L/min. 21 For a given flow, pressure decreased as the inner diameter of the orifice increased; the pressure also decreased as the length of the resistor decreased.…”