A threshold loading device for testing of inspiratory muscle performance.

Threshold loading is a method of incrementally loading the inspiratory muscles, which requires development of an adjustable threshold pressure (Pth) before air will flow. In the ideal device, flow is independent of pressure once Pth is exceeded. A "weighted plunger" apparatus is commonly used, but devices described previously perform unreliably at high inspiratory load. We have modified this apparatus using the diaphragm and valve seating from a threshold valve used to deliver positive airway pressure (AMBU 10, AMBU International, Denmark) to yield improved pressure-flow characteristics. With this device, there was a linear relationship between Pth and weight on the plunger (r = 0.998), and flow was largely independent of pressure once Pth was exceeded: pressure developed at an inspiratory flow of 1.3 +/- 0.1 l.s-1 was 13.6 +/- 7.0% below Pth. Our modified weighted plunger apparatus allows consistent and reliable threshold loading of inspiratory muscles, even at high inspiratory loads.

[1]  D. Hillman,et al.  Ventilatory responses to inspiratory threshold loading and role of muscle fatigue in task failure. , 1994, Journal of applied physiology.

[2]  H. Lahrmann,et al.  Inspiratory muscle performance relative to the anaerobic threshold in patients with COPD. , 1993, The European respiratory journal.

[3]  D. Evans,et al.  Measurement of inspiratory muscle performance with incremental threshold loading: a comparison of two techniques. , 1993, Thorax.

[4]  M. Mador,et al.  Effect of respiratory muscle fatigue on breathing pattern during incremental exercise. , 1991, The American review of respiratory disease.

[5]  M. Fairbarn,et al.  The effect of breathing frequency on inspiratory muscle endurance during incremental threshold loading. , 1989, Chest.

[6]  R. Pardy,et al.  Measurement of inspiratory muscle performance with incremental threshold loading. , 2015, The American review of respiratory disease.

[7]  S. Kelsen,et al.  Effect of inspiratory muscle fatigue on perception of effort during loaded breathing. , 1987, Journal of applied physiology.

[8]  T. Clanton,et al.  Effects of breathing pattern on inspiratory muscle endurance in humans. , 1985, Journal of applied physiology.

[9]  T. Clanton,et al.  Inspiratory muscle conditioning using a threshold loading device. , 1985, Chest.

[10]  T. Keens,et al.  Measuring ventilatory muscle endurance in humans as sustainable inspiratory pressure. , 1982, Journal of applied physiology: respiratory, environmental and exercise physiology.

[11]  M. Altose,et al.  Respiratory adjustments to ventilatory loading in chronic obstructive pulmonary disease. Muscular and neural factors. , 1979, American Review of Respiratory Disease.