Adaptation of the Threshold IMT® with double spring load allows higher inspiratory pressure for muscle training

Abstract

We aimed to evaluate the functionality of an adapted inspiratory muscle training device designed to allow pressures higher than 41 cmH(2)O that can be precisely controlled. The adaptation was made in a commercially available Threshold IMT device, and the opening pressures and linearity of load were evaluated in an experimental setting. The original IMT Threshold device was modified by inserting a second spring load juxtaposed to the original spring and then the modified device was coupled to a system designed to assess the range of opening pressures. Linear regression was used to test the correlation between the visual pressure scale of the original device and the opening pressure load obtained from the adapted device. For the modified device, we found a range of load from 13.9 +/- 0.7 to 85.6 +/- 0.7 cmH(2)O. Linear regression analysis of our data found an excellent relation between the modified device's opening pressure and the preset opening pressure marked on the visual scale in the original device, y = -1.275 + 2.08x, r(2) = 0.99 and P = 0.0001. The Threshold IMT adaptation proposed here is simple, affordable, precise, safe and allows for a high degree of reproducibility. It also achieves pressures higher than 41 cmH(2)O that can be used when training inspiratory muscles.