A 10-year-old boy with known asthma presents with an acute exacerbation. He is able to talk in full sentences, his respiratory rate is 30/min, heart rate 110/min, and oxygen saturation is 93% on air. His PEFR is 65% of his best. According to BTS/SIGN asthma guidelines for children, what is the immediate management for this moderate acute asthma attack?