Test yourself in 60 seconds

A 67-year-old male with a history of COPD presents to the emergency department with increased shortness of breath and wheezing. He has been using his albuterol inhaler more frequently but reports no relief. On examination, he is tachypneic, using accessory muscles, and has a respiratory rate of 28 breaths/min. A peak flow measurement shows 50% of his personal best. Which of the following is the most appropriate immediate management?