Sleep Study

Backgound

There are multiple diagnostic tests to evaluate sleep disorders. Common tests include polysomnograph (PSG), home sleep apnea test (HSAT), multiple sleep latency test (MSLT), oximetry, and actigraphy. PSG, also known as an “in-lab sleep study or sleep test,” is derived from the Greek roots “poly,” meaning many, “somno,” meaning sleep, and “graphy,” meaning to write, and refers to testing performed on patients while they sleep. HSAT, often referred to as “home sleep test” (HST), is an unattended study that is not performed in a sleep center and typically done at home. PSG with MSLT consists of a PSG followed by a daytime nap study performed in a sleep testing center. Overnight oximetry is a measure of continuous pulse oximetry that is worn when asleep. Oximetry is derived from the Greek roots, “oxys,” from “sharp, acid” and is a shortened form of the word oxygen, and “metry,” to measure. Actigraphy is a measure of movement and is derived from Latin “activus,” “a doing,” and “graphy,” from the Greek for writing or recording.

Therapeutic testing modalities are also performed for the treatment of sleep disorders known as “titration studies.” They evaluate different therapies for effectiveness. Continuous positive airway pressure (CPAP), bilevel positive airway pressure (PAP), adaptive servoventilation (ASV), and volume-assured pressure support (AVAPS/iVAPS) are examples of such modalities.

Diagnostic and therapeutic PSG, known as a “split study,” is an attended test during which the first portion is a diagnostic PSG. If the findings fulfill criteria for sleep-disordered breathing, the remainder of the test is a titration study. Home testing including automatic PAP titration is an option for evaluating PAP therapy.

How to Use It

Sleep testing is used when there is a complaint about sleep quality or abnormal behaviors. Often- times there is an effect on daytime function, including excessive daytime sleepiness, cognitive disturbance, and headaches. It can be part of evaluation of comorbid conditions such as cardiac arrhythmias, uncontrolled hypertension, and seizures.

PSG is used to diagnose many disorders, including sleep-disordered breathing, abnormal behaviors either during non-rapid eye movement (NREM) sleep (known as parasomnias) or during rapid eye movement (REM) sleep (known as REM behavior disorders), periodic limb movements (PLMs), and nocturnal seizures. Sleep-disordered breathing includes obstructive sleep apnea (OSA), nocturnal hypoxemia or hypoventilation, central sleep apnea (CSA), and Hunter-Cheyne-Stokes respiration (HCSR).

HSTs may also be used to diagnose sleep-disordered breathing, including OSA, CSA/HCSR, and nocturnal hypoxemia; however, they are limited to patients that do not have significant cardio­pulmonary or neuromuscular disease in which additional monitoring is required.

PSG with MSLT consists of an overnight PSG followed by a daytime nap study to evaluate for the presence of central disorders of hypersomnia, including type 1 and 2 narcolepsy and idiopathic hypersomnia.

Oximetry is a measure of continuous pulse oximetry that is worn when asleep. This is done to determine the presence of nocturnal hypoxemia related to pulmonary disease. Actigraphy is a measure of movement and position. It is worn continuously over 7–14 days and evaluates sleep-wake patterns for the diagnosis of insufficient sleep syndrome and circadian rhythm disorders.