She started hyper-ventilating from anxiety and had to sit down to rest.

hyper-ventilating 是动词 hyperventilate 的现在分词形式。hyperventilate 由前缀 hyper-（表示"过度"）和词根 ventilate（"通风、呼吸"）组成，字面意思是"过度呼吸"，指由于紧张或焦虑导致的呼吸过快过深的状态。