Comparing the Performance Characteristics of Different Positive Expiratory Pressure Devices.

BACKGROUND: Positive expiratory pressure (PEP) devices are widely used in clinical settings, yet the performance characteristics of these devices remain relatively unknown. This study compared the performance characteristics of 6 airway clearance devices by varying resistance and flow. METHODS: Mean PEP, peak PEP, oscillation frequency, and amplitude PEP of the Flutter, Pari PEP S, Acapella Choice, Acapella DM, Acapella DH, and Aerobika devices were obtained across flows of 5, 10, 15, 20, 25 and 30 L/min and at low, medium, and high resistance using an experimental apparatus custom-built for this bench study. RESULTS: Performance characteristics of the devices differed across flows and resistance settings (device × flow/resistance interaction; P < .001). At a fixed resistance, increasing flows increased mean PEP produced by the Acapella Choice, Acapella DH, Aerobika, and Pari PEP S. Increasing flow resulted in minimal change in mean PEP produced by the Flutter and Acapella DM. Increasing flow increased peak PEP and amplitude PEP produced by all devices except the Acapella DH and Acapella Choice. Increasing flow maintained or increased oscillation frequency for all devices except the Flutter. At a fixed flow, increasing resistance increased mean PEP produced by all devices except the Acapella Choice. Increasing resistance increased peak PEP produced by the Acapella DM, Aerobika, and Pari PEP S but resulted in minimal change in peak PEP for the Flutter and Acapella Choice. Increasing resistance either maintained or increased oscillation frequency for all devices. Amplitude PEP was either maintained or increased during oscillations when increasing resistance for all devices except the Flutter. CONCLUSIONS: PEP devices produced small but statistically significant variations in performance characteristics across a range of flows and resistance settings. There appear to be flow-dependent and non-flow-dependent devices. Varying flow or resistance typically maintained or increased the production of mean, peak, and amplitude PEP and oscillation frequency.

Design and construction of a novel low-cost device to provide feedback on manually applied forces.

STUDY DESIGN: Design and evaluation, technical note. OBJECTIVES: To describe the design of a simple, low-cost device for providing feedback of manually applied forces to the cervical spine, and to assess the device against specific design criteria. BACKGROUND: The forces applied during manual therapy may vary by as much as 500% between practitioners. But consistency can be improved in students when they are provided with contemporaneous feedback. The current methods of providing feedback, however, are expensive, complex, and/or preclude their performance in a clinically relevant manner. METHODS: The design of the device was assessed in accordance of the following criteria: (1) ease of use, (2) low cost, (3) minimal interference with technique, (4) ability to provide feedback with suitable accuracy at forces up to 50 N, and (5) no requirement of specialized skills to construct. RESULTS: A device is described that interfaces with standard computers through the sound card and measures force, using thin, low-cost, force-sensing resistors. Evaluated against the design criteria, the device (1) is easy to set-up and use, (2) can be produced for under $30 US dollars, (3) creates minimal interference with performance of a variety of techniques, (4) has limits of agreement from -3.8 to 4.2 N for forces of 5 to 45 N and repeatability coefficients of ± 2.0 N or 12%, and (5) can be constructed without specialized skills or knowledge. CONCLUSION: A device is described that fulfills most of the design criteria for providing feedback on forces for physical therapy students and may have applications in other fields.