Polysomnography

From Anvita Health Wiki

Contents 1 Introduction 2 Indications 3 Methods 4 More General Terms 5 References

Introduction

• Comprehensive recording of the biophysiological changes that occur during sleep. It is usually performed at night, when when most people sleep. It is the gold standard for diagnosis of obstructive sleep apnea.

Indications

• excessive daytime sleepiness
• unexplained pulmonary hypertension
• unexplained polycythemia
• disturbances in respiratory control in patients with daytime hypercapnia
• violent sleep-related behaviors or parasomnias
• suspected periodic limb movement disorder
• assessment of optimal CPAP therapy
• assessment of response to therapy
• used to diagnose

• narcolepsy
• restless legs syndrome
• REM behavior disorder
• parasomnias
• sleep apnea

Methods

• (Components of polysomnography)
• electroencephalogram ( EEG) to measure brain activity

• generally consist of 4 exploring electrodes & 2 reference electrodes ( seizure disorder requires more electrodes)
• exploring electrodes are usually attached to the scalp near the central & occipitial portions of the brain
• readout of brain activity scored into different stages of sleep (1, 2, 3, 4, REM, & wakefulness)

• electooculogram ( EOG) to measure eye movements

• 2 electrodes
• one is placed superior & lateral to the outer canthus of the right eye
• one is placed inferior & lateral to the outer canthus of the left eye
• placement of electrodes picks up electropotential difference between the cornea & the retina ( cornea is positively charged relative to the retina)
• detects rapid eye movements

• electromyogram ( EMG) to mease muscle activity ( actigraphy)

• 4 electrodes
• 2 leads placed on chin, 1 above jaw line, 1 below
• 2 leads placed on anterior tibialis of each leg
• measures muscle tension
• monitor excessive leg movements during sleep (see periodic Limb Movement Disorder)

• electrocardiogram ( ECG) to measure heart rhythm

• 2 or 3 leads
• either placed under clavicle on either side, or
• 1 under clavicle, the other 6 inches above the waist on either side

• pulse oximetry to measure arterial blood oxygenation
• nasal & oral airflow

• measured using pressure transducers &/or a thermocouple
• measures rate of respiration
• respiratory effort measured by use of belts that expand & contract
  

• In many cases, polysomnography is replaced by actigraphy.

More General Terms

• clinical procedure

References

1. Manual of Medical Therapeutics, 28th ed, Ewald & McKenzie (eds), Little, Brown & Co, Boston, 1995, pg 257
2. Alessi C In: Intensive Course in Geriatric Medicine & Board Review, Marina Del Ray, CA, Sept 29-Oct 2, 2004
3. National Guideline Clearinghouse Practice parameters for the respiratory indications for polysomnography in children. American Academy of Sleep Medicine ngc-guideline: [1]

polysomnography (PSG)