This invention provides devices and systems and methods therefrom for properly controlling negative pressure applied to oral cavity, facilitating breathing and treating sleep apnea and snoring. The systems comprise a negative pressure control system providing a vacuum source and an oral device comprising a shield situated between lips and front teeth, a tube passing through the shield, and a negative pressure deliverable part connected to the shield or the tube, wherein the negative pressure deliverable part is situated at the space between tongue and upper palate conformable to the contour of the upper palate, whereby the oral device delivers negative pressure through the negative pressure deliverable part to both front and back of the oral cavity to eliminate air space between the tongue and the upper palate.本發明提供適當控制施予在口腔內負壓的裝置、系統及其使用方法，以利於使用者呼吸、治療睡眠呼吸中止症狀及打鼾。該系統包括提供負壓源的一負壓控制系統及一口部裝置。該口部裝置包括一屏障用以設置於一使用者的唇部與前方牙齒之間、一中空管件通過該屏障及一負壓傳送部件連接至該屏障或該中空管件，其中該負壓傳送部件設置於舌頭與上顎之間並且順形於上顎的輪廓，該口部裝置通過該負壓傳送部件傳送負壓至口腔內的前端區域與後端區域，以減少舌頭與上顎之間的空氣空間。
