Guide to Understanding Sleep Study Results From Advanced Sleep Medicine Services, Inc. Visit Us Online at www.sleepdr.com Indexes/Benchmarks Used to Measure Sleep Quality Term Apnea/Hypopnea Index Respiratory Disturbance Index Arousal Index (AI) PLM Index Latency to Sleep Onset (LTSO) Latency to REM Onset (LTRO) Sleep Efficiency Oxygen Saturation (SaO2) Definition Your average number of combined apneas and hypopneas per hour. This number is used to determine the severity of a person’s sleep apnea. Your combined number of apneas, hypopneas, and RERAs per hour of sleep Average number of partial awakenings or breaks in sleep continuity per hour The number of significant leg movements (PLMS) per hour of sleep. LTSO is measured from Lights out or when the patient first attempts to initiate sleep, not just getting into or going to bed The time it takes a patient to fall into REM sleep after sleep onset. E.g., LTSO=20 minutes. REM seen at the 90th minute of recording. LTRO=70 minutes The patient’s total sleep time (TST) over the patient’s total time in bed (TIB) Typical Measurement < 5: normal sleep 5-15: indicates mild sleep apnea 15-29: indicates moderate sleep apnea >30: severe sleep apnea Physicians who use this scale typically follow the same guidelines that are used for the apnea/hypopnea index As low as 5 can be problematic and cause daytime sleepiness Over 15 is significant 10-20 minutes is typical About 90 minutes is typical Should be over 90% Normal saturation is above or around 95% A measure of how much oxygen is Between 95% and 90%: mild in the blood, expressed as the desaturation percentage of oxygen capacity that Between 89% and 80%: moderate is actually found in the blood desaturation Less than 80%: severe desaturation ©2015 Advanced Sleep Medicine Services, Inc. Indexes/Benchmarks Used to Measure Sleep Quality Events During Sleep Term Apnea Hypopnea Respiratory Effort Related Arousal (RERA) Arousal Periodic Limb Movements of Sleep (PLMS) Definition A cessation of airflow lasting at least ten seconds A significant reduction in airflow; it is characterized by at least a 4% oxygen desaturation or an arousal An event that causes a break in sleep or brief awakening or a decrease in oxygen saturation, without qualifying as an apnea or hypopnea. Brief period of disruption of the brainwaves accompanied by a shift from a deeper to a lighter stage of sleep. Patients may not be aware of these events. The PLMS is the total number of significant leg movements that occur during sleep, as part of a sequence of at least 4 motions. Underlying problem The number of apneas and hypopneas that a patient experiences, sometimes combined with the number of RERAs, is the main metric used to determine if he/she has sleep apnea. Arousals can be caused by the respiratory events above, though “spontaneous” arousals have no directly attributable causes. Arousals cause daytime sleepiness. Can be indicative of movementrelated sleep disorders. Other Significant Terms Term Definition Sleep Stages: N1, N2, N3, REM The sleep test keeps track of which stage of sleep the patient occupies throughout the night. It will usually report how many times a patient entered a particular sleep stage and how long the patient spent in that stage. PAP Pressure If you participated in a split-night or titration study*, the sleep technician will have tested what PAP pressure was required to eliminate your apnea events. Typical Measurement Humans typically experience around 3 sleep cycles per night of about 90 minutes in which they move through the stages in the given order. Adults usually spend about half their time in N2 sleep, about 20% in REM sleep, and about 30% in N1 and N3. This pressure is often expressed in the report in cm of water. *For more information on different sleep studies, see our Guide to Sleep Study Types and Codes. ©2015 Advanced Sleep Medicine Services, Inc. Events During Sleep/Other Significant Terms
