A 23 year old girl presented with perioral paresthesia and carpopedal spasm 20 minutes after a huge argument with her boyfriend. What is the next step for this patient?

The key is C. Rebreathing into a paper bag. [hyperventilation causes CO2 washout and respiratory alkalosis. An increase in pH, alkalosis, promotes increased protein binding, which decreases free calcium levels and this low calcium causes perioral persthesia and carpopedal spasm. If you continue breathing and rebreathing in paper bag it will allow CO2 concentration to rise in paper bag and as you rebreath this again and again you will regain some washed out CO2 and thus relief to this alkalosis].