Sleep Study
Polysomnography (PSG) is a sleep study that records several changes in your physical body as you sleep. The breakdown of term is as follows: “Poly” which means “many”, “somn” which means “sleep” and “graphy” which means “writing or to record.” So putting each part together, poly-somno-graphy means we record many things in sleep. The polysomnography records a lot of information of your body during sleep. For example it records an EEG, which shows your brain wave activity. We use the EEG to identify the different levels of sleep as well as waking states. It also records an EOG, which shows your eye activity. We use this to identify REM states, as well as slow moving eye movements during drowsy state. The polysomnogaphy also records airflow, as in the change in temperature and/or change in pressure from your nasal channels. In addition to that it we set chest and abdomen belts to indicate effort to breath, an EMG to monitor chin and leg muscle activity, and finally an Oximeter, which allows us to record oxygen saturation and pulse. PSG (Polysomnogram) is the most helpful tool for identifying disorders of sleep fragmentation.
The above graph has a hypnogram of normal sleep. A hypnogram is a graph that shows the stages of sleep over time. The hypnogram below is abnormal, however there can be several factors causing abnormal sleep. 
With this hypnogram, part of the abnormality is trouble with sleep onset. Which can be caused by many factors. Some of them include: – Insomnia: Primary or Comorbid – Circadian Rhythm Disorder – RLS (restless leg syndrome) – Environmental Sleep Disorder If we take a close look at the hypnogram, we can identify instances of sleep fragmentation as well as shown below by the arrows.
Sleep fragmentation can be caused by different disorders. Some disorders that may contribute to sleep fragmentation include: – OSA (obstructive sleep apnea) – PLMD (periodic limb movement disorder) – Narcolepsy – Environmental Sleep Disorders – Medical Disorders – Pregnancy Disorders that cause sleep fragmentation may result in feelings of non-refreshing sleep. The main symptoms are daytime sleepiness, fatigue, memory disturbances, or neurobehavioral symptoms. There are disorders that result in difficulty re-initiating sleep. This results in decreased sleep time. This is also viewed as sleep maintenance insomnia. See the blue arrow below to see how this person had trouble falling back asleep between 5 and 6. Note: Terminal insomnia is when return to sleep is not able to be obtained.
