Split Night Sleep Studies

Split Night Sleep Studies


A split night sleep test is an overnight sleep test done in a

sleep testing facility.  It is usually a planned change in

the testing no later than half way through the night. It

occurs when a certain level of Obstructive Sleep Apnea is

found during the first few hours of the sleep test.  On

some tests, the night will be split when severe apnea is

discovered although it was not planned.


The first few hours of the test is performed to observe

and record your usual sleep. Sleeping while wearing the

diagnostic monitors may not feel like normal sleep to

you, but sleep observed while wearing those monitors is

usually representative of your typical sleep. The

diagnostic portion of the study will be stopped when a

certain level of apnea is observed.  You physician usually

determines the level of apnea at which the study will be



For the remaining portion of the test time, treatment

with positive airway pressure will be started and

continued 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 titration or

more commonly a PAP Titration. A PAP titration 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 to determine the pressure required to control

the obstructions.


A person with sleep disordered breathing problems

might be able to be diagnosed and have treatment

assessed in one night when a split night test is

performed. However, realize that you may still have

significant sleep apnea even though you did not have a

split night study.


Sometimes a scheduled split night test does not get split.

This can occur when no apnea is observed, when the

amount of apnea observed does not reach the level

required to meet the criteria, or when there was not

enough time left in the study to complete the titration.


Page Thought –Positive airway pressure treatment is the first treatment considered for apnea because it is the safest most effective therapy for obstructive sleep apnea.

Updated June 2022