Imposed Power of Breathing Associated With Use of an Impedance Threshold Device.

摘要

To measure the imposed power of breathing (imposed work of breathing per minute) associated with spontaneous breathing through an active impedance threshold device and a sham impedance threshold device. DESIGN: Prospective randomized blinded protocol. SETTING: University medical center. PATIENTS: Nineteen healthy, normotensive volunteers (10 males, 9 females, age range 20 56 y, mean + or - SD weight 54.8 + or - 7.7 kg for females, 84 + or - 8 kg for males). METHODS: The volunteers completed 2 trials of breathing through a face mask fitted with an active impedance threshold device set to open at -7cmH 2 O pressure, or with a sham impedance threshold device, which was identical to the active device except that it did not contain an inspiratory threshold pressure valve diaphragm. Spontaneous breathing frequency (f), tidal volume (VT), exhaled minute ventilation, inspiratory pressure, and inspiratory time were measured with a respiratory monitor, and the data were directed to a laptop computer for real-time calculation of the imposed power of breathing. RESULTS: There were no significant differences in heart rate, respiratory rate, tidal volume, and minute ventilation, with and without inspiratory impedance. For the sham and active impedance threshold device groups, respectively, the mean SD imposed power of breathing values were 0.92 + or - 0.63 J/min and 8.18 + or - 4.52 J/min (p less than 0.001), the mean + or - SD inspiratory times were 1.98 + or - 0.86 s and 2.97 + or - 1.1s(p = 0.001), and the mean + or - SD inspiratory airway/mouth pressures were -1.1 + or - 0.6 cm H2O and 11.7 + or - 2.4 cm H2O (p less than 0.001). CONCLUSIONS: Breathing through an active impedance threshold device requires significantly more power than breathing through a sham device.