National Heart Blood and Lung Institute / US Dept. of Health

What Are Sleep Studies?

Sleep studies allow doctors to measure how much and how well you sleep. They also help show whether you have sleep problems and how severe they are.

Sleep studies are important because untreated sleep disorders can increase your risk of high blood pressure, heart attack, stroke, and other medical conditions. Sleep disorders also have been linked to an increased risk of injury due to falls and car accidents.

People usually aren't aware of their breathing and movements while sleeping. They may never think to talk to their doctors about sleep- and health-related issues that may be linked to sleep problems.

Doctors can diagnose and treat sleep disorders. Talk with your doctor if you snore regularly or feel very tired while at work or school most days of the week.

You also may want to talk with your doctor if you often have trouble falling or staying asleep, or if you wake up too early and aren't able to go back to sleep. These are common signs of a sleep disorder.

Doctors can diagnose some sleep disorders by asking questions about your sleep schedule and habits and by getting information from sleep partners or parents. To diagnose other sleep disorders, doctors also use the results from sleep studies and other medical tests.

Sleep studies can help doctors diagnose:

  • Sleep-related breathing disorders (such as Sleep Apnea)
  • Sleep-related seizure disorders
  • Narcolepsy

You can find more information on sleep and sleep disorders in the National Heart, Lung, and Blood Institute's "Your Guide to Healthy Sleep."

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Periodic, Profound Peripheral Vasoconstriction — A New Marker of obstructive Sleep Apnea

Schnall RP, Shlitner A, Sheffy J, Kedar R, Lavie P. SLEEP 1999; 22(7):939-46.

ABSTRACT: We report a novel approach to the determination of sleep apnea based on measuring the peripheral circulatory responses in a primary condition of disordered breathing. The apparatus is a finger plethysmograph coupled to a constant volume, variable pressure, pneumatic system. The plethysmograph's tip (measurement site) is composed of two parallel opposing longitudinal half thimbles, which is attached to a contiguous annular cuff. Each compartment consists of an internal membrane surrounded by an outer rigid wall. These provide a uniform pressure field and impart a two-point locking action preventing axial and longitudinal motion of the finger. Subdiastolic pressure is applied to prevent venous pooling, engorgement, and stasis, to inhibit retrograde venous shock wave propagation and partially unload arterial wall tension. The annular cuff extends the effective boundary of the pressure field beyond the measuring site.

In 42 patients with Obstructive Sleep Apnea Syndrome (OSAS) profound, transient vasoconstriction and tachycardia usually of a periodic nature, were clearly seen with each apneic event, possibly related to transient arousal. Good agreement was found between standard total apnea-hypopnea scoring, 129.522.4 (Mean SEM), and transient vasoconstriction and tachycardia events, 121.219.4 (R=.92, p<.0001).

We conclude that the fingertip exemplifies the scope of peripheral vascular responsiveness due to its high density of alpha sympathetic innervation, and its high degree of blood flow rate ability. Given that elevated peripheral resistance and tightly linked transient heart rate elevation is a consistent part of the hemodynamic response to arousal and OSAS, we believe that pulsatile finger blood flow patterns can be clearly diagnostic of OSAS and other sleep-disordered breathing conditions.

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Peripheral Vasoconstriction during REM sleep detected by a novel plethysmographic method

Lavie P, Schnall RP, Sheffy J, Shlitner A.. Nature Medicine 2000; 6(6):606.

ABSTRACT: In this Letter to the Editor, Lavie et al, introduce the readers to a new plethysmographic technique to measure peripheral arterial tone (PAT). They report that REM sleep in humans is associated with considerable peripheral vasoconstriction. The apparatus that they use is essentially a plethysmograph that, unlike models available, is able to envelop the finger up to and beyond its tip with a uniform pressure field. In their study of 26 cohorts, it was found that REM sleep was associated with considerable attenuation of the PAT signal.

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The effect of upper airway obstruction and arousal on Peripheral Arterial Tonometry in Obstructive Sleep Apnea

O’Donnell CP, Allan L, Atkinson P, Schwartz AR.Am J Respir Crit Care Med 2002; 166(7):965-71.

ABSTRACT: We evaluated the effects of airflow limitation and arousal on digital vascular tone in 10 patients with obstructive sleep apnea (OSA) using the recently developed, noninvasive technique of peripheral arterial tonometry (PAT). Subjects were maintained at a therapeutic level of continuous positive airway pressure, and nasal pressure was acutely dropped for three to five breaths during non rapid eye movement sleep over 1.3 cmH2O, leading to increasing airway obstruction and decreasing levels of inspiratory airflow. In the absence of a detectable electro-encephalographic (EEG) arousal, severe reductions of inspiratory airflow to below 200 ml/second caused significant decreases in PAT amplitude (1.000 _ 0.007 to 0.869 _ 0.007 arbitrary units; p 0.001), whereas mild airflow limitation (_ 200 ml/second) had no effect (1.000_0.009 to 1.011_0.007 arbitrary units). The presence of an EEG arousal accentuated the response to airflow obstruction, such that the PAT amplitude decreased more (p _ 0.001) in the presence of arousal (1.000 _ 0.007 to 0.767 _ 0.010 arbitrary units) than in the absence of arousal (1.000 _ 0.007 to 0.923 _ 0.007 arbitrary units). We conclude that airflow obstruction in patients with OSA causes an acute digital vasoconstriction that is accentuated in the presence of an EEG arousal.

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Obstructive Apneic Events Induce Alpha-receptor Mediated Digital Vasoconstriction.

Zou D, Grote L, Eder ND, Peker Y, Hedenr J. SLEEP 2004; 27(3):485-489.

Study Objective: To characterize the role of alpha-receptors in autonomic control of digital skin blood flow change in response to obstructive apnea-hypopnea events.

Design: Experimental intervention study.

Setting: Sleep laboratory in a university hospital.

Patients: Eight male patients with severe obstructive sleep apnea (OSA).

Interventions: Patients received four cumulative dosage steps of phentolamine (0.066, 0.2, 2 and 5[n=3] ?g/min/100ml forearm tissue) via brachial artery infusion during nonrapid eye movement sleep (stage 1 and 2).

Measurements and Results: The pulse amplitude determined with peripheral arterial tonometry (PAT) was periodically attenuated during the immediate post apnea-hypopnea period coinciding with arousal. PAT ratio (smallest pulse amplitude post apnea divided by largest pulse amplitude during apnea), was determined as a measure of digital vasoconstriction. We found that, compared with baseline, PAT ratio dose-dependently increased during phentolamine (0.2, 2 and 5 ?g) infusion by 11.21.7%, 24.42.1% and 30.94.1%, respectively (P<0.001). Systemic blood pressure and heart rate were largely unaffected by the pharmacological intervention.

Conclusion: OSA related alteration of the pulse amplitude includes a constriction of digital skin vasculature that to a large extent is mediated via sympathoadrenergic ?-receptors.

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Detecting REM sleep from the finger: automatic REM sleep algorithm based on Peripheral Arterial Tone (PAT) and actigraphy

Herscovici S, Peer A, Papyan S, Lavie p.. Physiol Meas 2007; 28(2): 129-140.

ABSTRACT: Scoring of REM sleep based on polysomnographic recordings is a laborious and time-consuming process. The growing number of ambulatory devices designed for cost-effective home-based diagnostic sleep recordings necessitates the development of a reliable automatic REM sleep detection algorithm that is not based on the traditional electroencephalographic, electrooccolographic and electromyographic recordings trio. This paper presents an automatic

REM detection algorithm based on the peripheral arterial tone (PAT) signal and actigraphy which are recorded with an ambulatory wrist-worn device (Watch-PAT100). The PAT signal is a measure of the pulsatile volume changes at the finger tip reflecting sympathetic tone variations. The algorithm was developed using a training set of 30 patients recorded simultaneously with polysomnography and Watch-PAT100. Sleep records were divided into

5 min intervals and two time series were constructed from the PAT amplitudes and PAT-derived inter-pulse periods in each interval. A prediction function based on 16 features extracted from the above time series that determines the likelihood of detecting a REM epoch was developed. The coefficients of the prediction function were determined using a genetic algorithm (GA) optimizing process tuned to maximize a price function depending on the sensitivity, specificity and agreement of the algorithm in comparison with the gold standard of polysomnographic manual scoring. Based on a separate validation set of 30 patients overall sensitivity, specificity and agreement of the automatic algorithm to identify standard 30 s epochs of REM sleep were 78%, 92%, 89%, respectively. Deploying this REM detection algorithm in a wrist worn device could be very useful for unattended ambulatory sleep monitoring. The innovative method of optimization using a genetic algorithm has been proven to yield robust results in the validation set.

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