The Science Journal of the American Association for Respiratory Care
Background: Chest physical therapy (chest PT) techniques are commonly performed to enhance secretion clearance. However, the effect of these techniques in lung mechanics have not been studied We have already reported the change in lung mechanics during chest PT techniques, Respir Care 42:1087, 1997 and 1 also have reported that chest wall percussion and vibration techniques were ineffective, and squeezing techniques were more effective than chest wall percussion in critically ill patients. The purpose of this study was to evaluate the change in lung mechanics using the model lung during application of the chest PT techniques. The theory behind squeezing technique is to improve regional ventilation, expiratory flow and expiratory pressure to enhance mucus movement. Method: We measured alveolar pressure (Palv), expiratory flow and tidal volume (VT) using by Respiratory Monitor OMR-8101 (Nipon Koden Inc. Japan) and Dual Adult TTL (Michigan Instruments Inc. USA) during application of the chest PT techniques. We compared with squeezing, springing and forced expiratory compression (FEC) in spontaneous breathing, volume control ventilation (VCV), pressure support ventilation (PSV) and pressure control ventilation (PCV). Each techniques in each ventilatory mode were applied in normal lung mechanics (CST 50, RAW 5), stiff lung mechanics (CST 10, RAW 5) and high airway resistant lung mechanics (CST 50, RAW 50). Results: 1) Spontaneous breathing in normal lung mechanics have expiratory flow 0.8L/sec, Pal v 8cmH2O, and VT 520ml. when squeezing was applied, spontaneous breathing changed to expiratory flow 1.3L/sec, Palv 12cmH2O, and VT 800ml. 2) When squeezing was applied in high resistant lung, especially, Palv increased. 3) The changes of expiratory flow, VT and Palv were small at squeezing in stiff lung. 4) VT increased at only the first squeezing in VCV, But VT did not change during application from the second squeezing. Expiratory flow and Palv also did not increase. 5) Expiratory flow, VT and Palv increased at every one time squeezing in VCV. 6) Expiratory flow, VT and Palv increased during application of squeezing at PCV and PSV.
Conclusions: Squeezing technique is effective in normal and high resistive lung mechanics and this technique is also effective in spontaneous breathing, PCV, PSV and CPAP mode in mechanically ventilated patients.