You are a PA in a GP practice and you are seeing a 2-year-old boy with his mother. She has reported that her son has been generally unwell over the last couple of days and has now developed a sudden onset of a seal-like barking cough and shortness of breath. She is also worried about this strange noise he is making when he is breathing in. On examination you note that he has a seal-like barking cough with stridor as well as a respiratory rate of 60 with intercostal recessions. He looks exhausted so you ring an ambulance. On waiting for the ambulance to arrive what should you administer as well as supplementary oxygen assuming he is well enough to receive medication?