Ultrasonic nebulizer: atomizes the liquid using the principle of ultrasound.The nebulizer of the ultrasonic atomizer is not selective for the mist particles, so most of the produced drug particles can only be deposited in the upper respiratory tract of the mouth, throat, etc., and because of the small amount of deposition of the lungs, the lower respiratory tract diseases cannot be effectively treated. At the same time, due to the large amount of fog particles generated by the ultrasonic atomizer, the atomization is fast, causing the patient to inhale too much water vapor, so that the respiratory tract is humidified, and the dry thick secretions of the bronchial tubes in the respiratory tract originally absorb the water and then expand, thereby increasing the respiratory tract. Resistance may cause hypoxia, and the ultrasonic atomizer will cause the liquid to hang on the inner wall of the cavity, which is not effective for lower respiratory diseases, and requires a large amount of drugs, resulting in waste.