the aim of this study are to explore the characteristics of mean airway pressure, oscillatory amplitude and power spectral density (PSD) of oscillatory airway pressure that generate by various loaded and flow rate during expiration and inspiration in healthy subjects and to explore the best loaded and flow rate for airway secretion clearance using the BreatheMAX® device

For inspiratory group, the resistive load 3, 4, 5, 6 and 7 cm H2O were test with three flow rate: 0.2, 0.4, and 0.6 L/sec in each load. In each flow rate, the subjects were instructed to inspire as deeply as possible with steady flow rate for 3 seconds with end-inspiratory pause for 2-3 seconds through the inspiratory circuit and follow by passive exhalation. For expiratory group, the resistive load and flow rate were test similar inspiratory group. In each flow rate, the subjects were instructed to inspire as deeply as possible through the nose with end-inspiratory pause for 2-3 seconds and partially forced exhalation with reach to 1/3 of expiratory reserve volume (ERV) for at least 3 seconds through expiratory circuit

Inclusion Criteria:

• the healthy subjects
• able to breathe against resistive load with the BreatheMAX device
• good conscious and cooperation

Exclusion Criteria:

- fever