Design and function of a new conical positive expiratory pressure device to be used during exercise

Abstract

BACKGROUND: A flow-dependent conical positive expiratory pressure (PEP) resistor incorporated into a oronasal mask was developed, which might reduce dyspnea and dynamic hyperinflation and increase exercise endurance for patients with COPD. We reported here the flow-pressure relationships and the safety and suitability of the device when used by healthy young and older subjects. METHODS: The flow-pressure relationships were determined for a range of resistors with different orifice diameters and cone lengths. A 1-cm conical-PEP device with a 6-or 7-mm orifice was used during a cycle exercise test (60% heart rate reserve) in 15 young (mean = SD, 24.3 = 3.9 y) and 12 older (mean = SD, 64.4 = 3.5 y) adults. Cardiopulmonary function and dyspnea were monitored for up to 10 min of exercise. RESULTS: For a given flow, pressure decreased as the cone length and orifice size increased. A 1-cm cone with a 6 mm orifice generated pressures of 5.24 = 0.17 cm H2 O and 18.29 = 0.34 cm H2 O at flows of 0.5 and 0.9 L/s, while for a 7 mm orifice, pressures were 4.88 = 0.13 cm H2 O and 19.14 = 0.10 cm H2 O at flows of 0.5 and 1.1 L/s, such as might occur during exercise. The choice of orifice size for a subject depended on his or her estimated expiratory flow; larger flows required the larger orifice to generate an expiratory pressure of between 5 and 20 cm H2 O. Breathing with the conical-PEP device did not affect exercise time, dyspnea, minute ventilation, heart rate, or blood pressure. The SpO2 was slightly lower and PETCO2 was somewhat higher than during control exercise, but the differences were not significant. There were no adverse physiological consequences. CONCLUSIONS: A conical-PEP device of 1-cm length with an orifice of 6 or 7 mm generates effective expiratory pressure for most subjects during exercise. There were no adverse effects in healthy young and older subjects, and the device is suitable for trials with patients with COPD. (ClinicalTrials.gov registration NCT 02788370.) Key words: pressure-flow relationship; PEP device; exercise; cardiopulmonary function; randomized trial; physiotherapy. [Respir Care 2018;63(8):966 –980. © 2018 Daedalus Enterprises].