Respiratory Disturbance Index
Encyclopedia
The respiratory disturbance index (RDI) — or respiratory distress Index — is an formula used in reporting polysomnography
(sleep study) findings. Like the apnea-hypopnea index
(AHI), it reports on respiratory events during sleep, but unlike the AHI, it also includes respiratory-effort related arousals (RERAs). RERAs are arousals from sleep
that do not technically meet the definitions of apnea
s or hypopneas, but do disrupt sleep. They are abrupt transitions from a deeper stage of sleep to a shallower.
A RERA is characterized by increasing respiratory effort for 10 seconds or more leading to an arousal from sleep, but one that does not fulfill the criteria for a hypopnea or apnea. The gold standard
for measuring RERAs is esophageal manometry, as recommended by the American Academy of Sleep Medicine
(AASM). However, esophageal manometry is uncomfortable for patients and impractical to use in most sleep centers.
Some research studies have found that a high RDI was significantly correlated
with excessive daytime sleepiness
, and that this correlation was stronger than that for the frequency of oxygen saturation
decreases below 85%, but other studies have found only a weak correlation.
Polysomnography
Polysomnography , also known as a sleep study, is a multi-parametric test used in the study of sleep and as a diagnostic tool in sleep medicine. The test result is called a polysomnogram, also abbreviated PSG...
(sleep study) findings. Like the apnea-hypopnea index
Apnea-hypopnea index
The apnea-hypopnea index is an index of sleep apnea severity that combines apneas and hypopneas. The apneas must last for at least 10 seconds and are associated with a decrease in blood oxygenation...
(AHI), it reports on respiratory events during sleep, but unlike the AHI, it also includes respiratory-effort related arousals (RERAs). RERAs are arousals from sleep
Sleep
Sleep is a naturally recurring state characterized by reduced or absent consciousness, relatively suspended sensory activity, and inactivity of nearly all voluntary muscles. It is distinguished from quiet wakefulness by a decreased ability to react to stimuli, and is more easily reversible than...
that do not technically meet the definitions of apnea
Apnea
Apnea, apnoea, or apnœa is a term for suspension of external breathing. During apnea there is no movement of the muscles of respiration and the volume of the lungs initially remains unchanged...
s or hypopneas, but do disrupt sleep. They are abrupt transitions from a deeper stage of sleep to a shallower.
A RERA is characterized by increasing respiratory effort for 10 seconds or more leading to an arousal from sleep, but one that does not fulfill the criteria for a hypopnea or apnea. The gold standard
Gold standard
The gold standard is a monetary system in which the standard economic unit of account is a fixed mass of gold. There are distinct kinds of gold standard...
for measuring RERAs is esophageal manometry, as recommended by the American Academy of Sleep Medicine
American Academy of Sleep Medicine
The American Academy of Sleep Medicine is a United States professional society for the medical subspecialty of sleep medicine. It was established in 1975. The AASM is the only professional society that is dedicated exclusively to the medical subspecialty of sleep medicine...
(AASM). However, esophageal manometry is uncomfortable for patients and impractical to use in most sleep centers.
Some research studies have found that a high RDI was significantly correlated
Correlation
In statistics, dependence refers to any statistical relationship between two random variables or two sets of data. Correlation refers to any of a broad class of statistical relationships involving dependence....
with excessive daytime sleepiness
Excessive daytime sleepiness
Excessive daytime sleepiness is characterized by persistent sleepiness, and often a general lack of energy, even after apparently adequate night time sleep...
, and that this correlation was stronger than that for the frequency of oxygen saturation
Oxygen saturation
Oxygen saturation or dissolved oxygen is a relative measure of the amount of oxygen that is dissolved or carried in a given medium. It can be measured with a dissolved oxygen probe such as an oxygen sensor or an optode in liquid media, usually water.It has particular significance in medicine and...
decreases below 85%, but other studies have found only a weak correlation.