What will happen during laboratory sleep testing?

DEAR DOCTOR K: My doctor thinks I may have sleep apnea, and he wants me to go to a sleep lab to be tested. What will happen during the testing?
DEAR READER: Sleep apnea is a serious health condition in which breathing stops or becomes shallower. In the most common form, obstructive sleep apnea, the tongue or throat tissues temporarily and repeatedly block the flow of air in and out of your lungs. This can happen hundreds of times each night. Laboratory sleep tests are the most reliable way to diagnose this problem.