二级头呼吸器 èrjítóuhūxīqì regulator; demand valve Origin Definitions Defs Strokes Stroke Words Sentences Sents 二级头 二級頭 èrjítóu second stage the second stage of a scuba regulator that reduces air pressure and provides it through a mouthpiece; used in diving呼吸器 hūxīqì respirator ventilator or artificial breathing apparatus used in hospitals; rebreather