Combined index of heart rate variability and oximetry in screening for the sleep apnoea/ hypopnoea
It has been acknowledged that even amongst sleep physicians the distinction between severe obstructive sleep apnoea, hypopnoea
and obesity hypoventilation syndromes is confused (27).
Apnoea and hypopnoea
were scored as recommended by the American Academy of Sleep Medicine (13).
At the beginning of the study, both groups had a mean apnoea hypopnoea
index (AHI) of 37 apnoeas per hour.
The frequency of apnoea or hypopnoea
is used to assess the severity of this condition.
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syndrome and narcolepsy
was defined as a discernible reduction in respiratory airflow during a preceding period of normal breathing for [greater than or equal to] 10 sec accompanied by a decrease of 4 per cent or more in oxyhaemoglobin saturation during sleep.
was defined as a reduction in amplitude of the primary airflow trace of at least 50% of the preceding amplitude and accompanied in <30 s by oxygen desaturation of 4% (12).
In this issue Chou and colleagues (7) report on a Taiwanese referral-based study demonstrating that unlike the apnoea hypopnoea
index; the oxygen desaturation index defined as the frequency of 4 per cent oxygen desaturation episodes per hour of sleep was significantly associated with hypercholesterolaemia (>200 mg/dl) and hypertriglyceridaemia (>150 mg/dl) even after taking into account confounding factors such as obesity as defined by body mass index.
was defined as 50% or greater reduction of airflow or equivalent associated with an arousal or desaturation of more than 3%.
The definition of hypopnoea
was a 50 per cent or greater reduction in airflow for a minimum of 10 seconds, associated with an equal to or greater more than a 4 per cent drop in Sp[O.
A few periods of apnoea or hypopnoea
may arise during REM sleep.