2~3mg/(kg·min)下降至1~2mg/(kg·min)
3~4mg/(kg·min)下降至2~3mg/(kg·min)
4~5mg/(kg·min)下降至3~4mg/(kg·min)
5~6mg/(kg·min)下降至4~5mg/(kg·min)
6~7mg/(kg·min)下降至5~6mg/(kg·min)