Interpretation of Polysomnography Presented By Dr. Mohammad Reza Najafi Professor of Neurology, Isfahan University of Medical Sciences

Medications The list of medications is important in the fact that certain medication can suppress stage 3 and stage 4 sleep, and some medications may suppress REM sleep. Each medication may have a different affect on the patient’s sleep stages and fragmentation.

Signs and Symptoms The signs and symptoms portion is completed by the patient and helps in determining the patient’s overall need for the polysomnogram as well as their chief complaint.

Recording Protocol This is the devices and recording instrumentation used on the patient during there nocturnal polysomnogram.

Sleep Architecture The NREM/REM stage and cycle infrastructure of sleep understood from the vantage point of the quantitative relationship of these components to each other.

Time in bed Time in bed is the total number of minutes that a patient spends in bed. This amount varies for different age groups and can also vary on an individual patient basis. This is important because it gives a basic idea as to whether or not the patient is spending enough time attempting to sleep.

Total Sleep Time Total sleep time is the actual amount of sleep time in a sleep period ; equal to total sleep period less movement and awake time. Total sleep time is the total of all REMS and NREMS in a sleep period. This is important because it gives a basic idea as to whether or not the patient is achieving enough sleep for the time they are in bed.

Sleep Efficiency Sleep efficiency is the proportion of sleep in the period potentially filled by sleep, that is, the ratio of total sleep time to time in bed. This is important because it displays the patients overall quality of sleep as it pertains to any sleep disorder they exhibit.

Sleep Latency Sleep latency is the period of time measured from “lights out”, or bedtime, to the commencement of sleep. This is important because it can show the level of sleepiness by how fast the patient gets to sleep or their sleep latency. It can also help to determine insomnia in patients that displays signs of excessive daytime sleepiness but do not achieve sleep in a timely manner.

Wake Percentage Wake percentage is the percentage of wake scored from lights out to the final wake-up. This is important because it will help determine how much any sleep disorder is affecting the patient’s sleep architecture.

Stage 1 Stage 1 is a stage of NREM sleep that ensues directly from the awake state. It’s criteria consists of a low-voltage EEG with slowing to theta frequencies, alpha activity less than 50%,EEG vertex spikes, and slow rolling eye movements. Stage 1 percentage is the total time spent in stage1 sleep from lights out to the final wake-up. Stage 1 generally constitutes about 2-5% of sleep.

Stage 2 Stage 2 is a stage of NREM sleep characterized by the advent of sleep spindles and K complexes against a relatively low-voltage, mixed-frequency EEG background, high-voltage delta waves may compromise up to 20% of stage 2 epochs. Stage 2 percentage is the total time spent in stage 2 from lights out to the final wake-up. Stage 2 generally constitutes 45-55% of sleep.

Stage 3 Stage 3 is a stage of NREM sleep defined by at least 20% but not more than 50% of the period consisting of EEG waves less than 2 Hz and more than 75 uV, it constitutes deep NREM sleep. Stage 3 percentage is the total time spent in stage 3 from lights out to final wake-up. Stage 3 sleep is usually combined with stage 4 sleep and usually constitutes 12-18% of sleep.

Stage 4 Stage 4 is a NREM sleep that consists of the same characteristics a s stage 3 over more than 50% of the epoch. Stage 4 percentage is the total time spent in stage 4 from lights out to final wake-up.

REM Sleep REM sleep consists of low-voltage, fast frequency EEG which may be accompanied by both saw-tooth waves and rapid eye movements. REM percentage is the total time spent in REM sleep from lights out to the final wake-up. REM sleep usually constitutes 20-25% of sleep in 4 to 6 episodes.

REM latency REM latency is the period of time from sleep onset to the first appearance of REM sleep. This is important in showing a short onset of REM sleep, which is a sign of Narcolepsy.

Respiratory Events Respiratory events is the breakdown of the respiratory changes recorded during the entire polysomnogram.

Obstructive Apneas Obstructive apneas are respiratory episodes where there is a complete cessation of airflow lasting greater than 10 seconds and is accompanied by a 4% desaturation or an arousal.

Hypopneas Hypopneas are a respiratory episode where there is partial obstruction of the airway lasting greater than 10 seconds and accompanied by a 4% desaturation or an arousal.

Central Apneas Central Apneas are respiratory episodes where there is no airflow and no effort to breathe lasting greater than 10 seconds.

Mixed Apneas Mixed Apneas are respiratory episodes where there are features of both obstructive and central apneas in the same event.

Total events Total events is the total number of Obstructive apneas, Hypopneas, Central apneas, and mixed apneas from lights out to the final wake-up.

RDI RDI is an abbreviation for Respiratory Disturbance Index. This number is the average number of respiratory events per hour of sleep. Any RDI lower than 5/hr is considered to be within normal limits.

REM RDI REM RDI is the total number of respiratory episodes per hour of REM sleep.

Supine RDI Supine RDI is the number of respiratory episodes per hour of supine sleep. This is important because the patient may have only positional apnea and therefore can be treated with positional therapy.

Oxygen (SaO2) Baseline = the baseline oxygen level for the entire polysomnogram. Low = the lowest oxygen level recorded during the polysomnogram.

Miscellaneous The miscellaneous category is for other important information regarding the patient’s polysomnogram.

Blood pressure Blood pressures are taken both before and after the polysomnogram. The blood pressure before the study is to determine a baseline for this patient. The blood pressure after the polysomnogram is to help determine any hypertensive response to sleep apnea or any other sleep disorder that may be present during the polysomnogram.

Periodic Limb Movements # of PLMS = the total number of periodic limb movements during the polysomnogram. PLMS Index = the average number of PLMS per hour of sleep.

Arousals # of arousals = the total number of arousals recorded during the polysomnogram. Arousal index = the average number of arousals per hour of sleep.

Technical impression The technical impression is the overall breakdown and comments for the entire polysomnogram.

Diagnosis The diagnosis portion is where the diagnosis for this polysomnogram are listed. The diagnosis of Obstructive sleep apnea is based upon the RDI. A mild RDI would range from 5/hr. to 15/hr. A moderate RDI would range from 15/hr. to 30/hr. A severe RDI would be higher than 30/hr. The severity can also be determined by other factors such as oxygen saturation or position. A person with a RDI of 28.2 / hr. with accompanying desaturations below 80% may be considered to have severe OSA. This is also the portion of the study where any Hypoxemia, Periodic Limb Movement Syndrome, Restless Legs Syndrome, Insomnia, Hypertensive response to apnea, etc.. would be noted.

Recommendations This is where any recommendations for treatment would be listed. This can include positional therapy, nasal CPAP, dental appliance, and surgery for treatment of OSAS. This can also include medications for treatment of Periodic Limb Movement Syndrome, as well as Insomnia or any other sleep disorder.