I am 71, have copd, on oxygen, taking lisinopril and coreg (carvedilol). Pulse was erratic for 1 hour. High 139 low 59. Bp was fine. Why?

Atrial fib? It sounds like you may have had an episode of atrial fibrillation, which is a rapid and irregular heart rhythm. Of it persists, it may increase your risk of a stroke. Talk to your doctor about the need for testing or medication adjustment to help keep your heart regular.
Check with your doc. Probably atrial fibrillation. You want to have a blood thinner to prevent stroke. Check with your doc asap. Very important.