[名词解释] 呼吸困难

下述药物对闭塞性细支气管炎伴机化性肺炎疗效肯定的是（） ["泼尼松","先锋霉素","甲氨蝶呤","胺碘酮","博来霉素"] 下列哪项是心肌梗死的“损伤型”心电图改变（） ["R波电压降低","异常Q波","T波直立高耸","S-T段抬高","T波呈对称性"] "三凹征" 某人心电图上R-R间期为0.75s，其心率为（） ["40次/分","60次/分","80次/分","100次/分","120次/分"] 发绀 呼吸困难