A 4-month-old previously well infant presents to the emergency department in winter with a 2-day history of coryza, cough and difficulty feeding. On examination, he has mild subcostal recession, respiratory rate 48 breaths/min, oxygen saturation 93% on room air and widespread crackles and wheeze. He is afebrile and hydrated. According to the Royal Children's Hospital bronchiolitis guideline, what is the mainstay of management?