You are doing a clinical on the medical-surgical floor of a local hospital when mr. b arrives from the emergency room. mr. b is a 32-year-old who was thrown off his bicycle in an accident; he has three fractured ribs and a punctured lung. in the er, they inserted a chest tube to drain air and fluid out of his pleural cavity, allowing his lungs to re-expand. he had one dose of demerol 3 hours ago for pain and a second dose just before transfer, according to the telephone report from the er nurse.