A split night sleep test is done when severe Obstructive Sleep Apnea is found during the first few hours of the sleep test. When it is clear that severe apnea is present, treatment with continuous positive airway pressure (CPAP) will be started halfway through the night of the test. Thus, the first half of the night is used to establish the diagnosis of obstructive sleep apnea while the second half is used to determine how much pressure will be needed to treat the apnea.
The pressure test performed during the second half of the night is called a Positive Airway Pressure Sleep Study (PAP PSG), or more commonly a CPAP Titration. A CPAP titration study is performed to measure the effect of breathing air at a slightly higher pressure. During this stage of the test, the sleep technician monitors your measurements for obstructive apnea and gradually increases the amount of pressure required to control the obstructions.
A person with severe sleep disordered breathing problems might be able to be diagnosed and have treatment assessed in one night. However, realize that you may still have significant sleep apnea even though you did not have a split night study.