By Dr. Todd
Ordering Sleep Studies & Understanding Results
Candidates for sleep study complain of: Daytime somulence in inappropriate situations (work, stoplights, while talking to someone) Despite adequate hours of sleep, day or night Difficulty falling asleep, awakenings multiple times a night Restless sleep Perspiration (not hot flashes) at night Awakening in AM feeling fatigued Difficulty breathing at night, loud snoring, gasping or stopping breathing Physical findings: Obesity or body mass index >26, control obesity Thick neck, large tongue or tonsils Mouth breathing, nasal obstruction especially at night Hypertension, right heart failure, pulmonary hypertension, left ventricular hypertrophy
No single finding is guaranteed to be due to sleep apnea alone but more likely with more than one findings from the list above.
Before ordering a sleep study, the physician should check the patient’s TSH & T4 to rule out hypothyroidism. The patient should not drink alcohol or caffeine prior to a sleep study. They should not take sleeping pills unless this is always done at home.
A sleep study done in a sleep lab can be used to diagnose sleep apnea, fit patient with CPAP (continuous positive air pressure), titrate CPAP for patient or evaluate function of CPAP or all of the above in a single night. Please see attached form.
Sleep studies can also diagnose central apnea, abnormal sleep cycles, hypoxemia, restless leg syndrome and cardiac arrhythmias. These are just a few.
Understanding the results: The results of the study are summarized in a report generated by a sleep specialist. Below is a list of terms and their relevance.
Sleep efficiency: time slept out of total study time, given as percent
AHI (apnea hypopnea index) The number of times the patient stopped breathing (apnea or took less than ½ of a breath (hypopnea) per hour. 0-5 normal, 5-15 mild sleep apnea, 15-30 moderate, >30 severe sleep apnea Sleep Stages: I & II: light sleep, III & IV: deep sleep, REM: dream sleep, restorative, need 20% of sleep to be REM to feel rested EKG changes: arrhythmias & dysarrhythmias Leg movements: known as restless leg syndrome causes sleep fragmentation & recommendations for CPAP, MSLTs or other treatments Fragmented Sleep: multiple awakenings for a variety of reasons (restless legs, apneas, hypoxemias, arrhythmias, snoring arousals) & result in the patient not reaching deep sleep or REM sleep.