A.氧流量1-2L/min B.氧流量2-3L/min C.氧流量3~4L/min D.氧流量5~10L/min E.氧流量10~20L/min
A.30% B.40% C.50% D.60% E.70%
A.10% B.20% C.30% D.50% E.70%