title: Characteristics of the ventilatory load with different ventilatory training devices.
abstract: BACKGROUND
  The characteristics of the load on the ventilatory muscles during breathing with different ventilatory muscle training devices have not been quantified, which may profoundly affect the nature of the training stimulus and the clinical outcome of the ventilatory muscle training.
  
  
  METHODS
  In four normal males, we continuously measured mouth pressure, esophageal pressure, tidal volume, breathing frequency (fb), minute ventilation (VE), inspiratory time, duty cycle, tension time index (TTI), and total respiratory work (WTOT) during 10 seconds' maximum ventilatory maneuvers. Maximum breathing was performed at 3 fb's (20, 60 and 88 breaths/min) with each of 3 different inspiratory loading devices: 1) Isocapnic hyperpnea (H) with an orifice of 2 (H2) and 1 (H1) cm; 2) Resistive breathing through a Pflex using 3 orifices of diameter 0.54 cm (P1), 0.40 cm (P3) and 0.22 cm (P5); 3) A threshold loading device (T) set at 10 (T10) and 25% (T25) of the previously measured maximum inspiratory mouth pressure.
  
  
  RESULTS
  Pflex could provide higher TTI and lower VE, compared with the other 2 devices, at the breathing frequencies of 60 and 88 breaths/min (p < 0.05). Pflex with smaller orifices (P3 and P5) could exaggerate this difference (p < 0.01). WTOT increased significantly as fb increased from 20 to 88 with H1, H2, T10, T25 and P1 (p < 0.02), but not with P3 and P5. VE showed a better correlation with WTOT than TTI did (p < 0.001, r = 0.863 vs p > 0.1, r = -0.365).
  
  
  CONCLUSIONS
  High flow, high WTOT and low tension loads were provided by H2, H1, T10 and T25 devices whereas low flow, low WTOT and high tension loads were provided by P5 and P3. P1 provided intermediate flow and tension load.
authors.affiliation: Department of Respiratory Therapy, Veterans General Hospital-Taipei, Taiwan, R.O.C.
authors.forename: T C
authors.initials: TC
authors.lastname: Lien
authors.forename: M J
authors.initials: MJ
authors.lastname: Belman
mesh_terms: D000328:Adult; D005081:Exercise Therapy / Q000295:instrumentation*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012044:Regression Analysis; D012119:Respiration; D012129:Respiratory Function Tests; D012132:Respiratory Muscles / Q000502:physiology*