Understanding Your Sleep Study
At SleepMed, we will provide you with the
full results of your sleep study. Some terms will be
unfamiliar and below is a guide in understanding the
technical words in plain English. Your doctor can
explain these in detail.
1. Sleep Efficiency
The proportion of bed time actually staying asleep.
2. Sleep Latency
The time taken from ‘lights out,’ to the onset of sleep.
3. Sleep Architecture
This is the proportionate and timing of the different
Stage I & Stage II are ‘light sleep’
Stage III & IV = ‘deep’ or ‘slow wave’ sleep’
(usually 20% of sleep time and decreases with age)
REM = ‘dream sleep’ (usually 20% of sleep) .
Normally, a person will go through 3-5 cycles of light
to deep back to light sleep. As the night goes on REM
episodes grow progressively longer, so that slow wave
sleep predominates in the first third of the night and
REM in the last third Sleep disorders often disrupt this
normal pattern leading to a reduced REM and slow wave
sleep, leaving predominantly the lighter stages of
4. AHI (Apnoea-Hypopnoea Index)
Measure of how severe your sleep apnoea is. It is the
average number of abnormal breathing events per hour of
<5 is normal; 5 to 14 is mild; 15 to 29 is moderate;
more than 30 is severe.
No airflow through both the nose and mouth
for more than 10 seconds. It may be obstructive (related
to the throat), central (related to the controllers of
breathing) or mixed (a combination).
A significant reduction in breathing but
not complete cessation. These often result in a drop in
oxygen or cause a disruption in the brain’s sleep
pattern (ie. an arousal).
An abrupt change in the brain activity, often causing
change from ‘deeper’ stage of sleep to a ‘ligher’ one.
Sometimes they lead to awakening as the final outcome.
An Arousal Index >20/hr is abnormal.
8. Oxygen Saturation (SaO2)
A measure of how much
oxygen is available to the body at a given time.
Normally, this is 94-100%.