Which of the following is a feature of Acute severe asthma: (A) Heart rate of 110 beats / min, (B) Pa O2 of 70 mmHg, (C) Peak expiratory flow rate of < 40 %, (D) All of the above
Answer is C. Features of Acute Severe Asthma

Heart rate > 120 beats / min
Pa O2 of < 60 mmHg
Peak expiratory flow rate of < 40 %