The following guidelines should be applied to services performed in conjunction with sleep related conditions:

Diagnostic Evaluation of Sleep-Related Disorders

Sleep studies (95805-95807) and polysomnography (95808-95811) refer to the continuous and simultaneous monitoring and recording of various physiological and pathophysiological parameters of sleep for six or more hours with physician review, interpretation and report.

Polysomnography (95808-95811)

Polysomnography is distinguished from other sleep studies by the inclusion of sleep staging which is defined to include a 1 to 4 lead electroencephalogram (EEG), electro-oculogram (EOG), and submental electromyogram (EMG). Additional parameters that can be measured during sleep may include:

ECG
Airflow
Ventilation and respirator effort
Gas exchange by oximetry, transcutaneous monitoring, or end tidal gas analysis
Extremity muscle activity, motor activity-movement
Extended EEG monitoring
Penile tumescence
Gastroesophageal reflux
Continuous blood pressure monitoring
Snoring
Body positions; etc.

An EEG, EOG, EMG, EKG, and oximetry are the most common parameters of sleep measured during a polysomnogram (95808-95811). Therefore, separate payment should not be made for these parameters when reported with a polysomnogram on the same day by the same provider.

Payment may be allowed for polysomnographies for the following diagnoses:

Sleep Apnea: 327.00, 327.01, 327.09, 327.10-327.14, 327.19, 327.20-327.29, 770.81, 770.82, 780.51, 780.53, 780.57

Narcolepsy or hypersomnia: 307.43-307.44, 327.10-327.19, 327.29, 327.51, 327.59, 347.00, 347.01, 347.10, 347.11, 780.53-780.54, 780.58

Myoclonus or restless leg syndrome: 333.2, 333.99

The following conditions are subject to medical review:

Insomnia: 307.41-307.42, 327.00, 327.01, 327.09, 327.8, 780.50, 780.51-780.52 (payable only when the physician suspects sleep apnea)
Sleepwalking: 307.46 (payable only when the physician suspects nocturnal epilepsy)
Night Terrors: 307.46 (payable only when the physician suspects nocturnal epilepsy)
Enuresis: 788.36, 788.38 (payable only when the physician suspects nocturnal epilepsy)

When warranted by the patient's symptoms, payment may be made for polysomnograms performed to "rule out" the conditions/diagnoses specified in the preceding guidelines. It will be necessary for the provider to submit medical records and/or additional documentation to determine coverage in these situations.

Sleep Studies and Polysomnograms

• Sleep studies and polysomnograms performed on the same day:  For a study to be reported as polysomnography (95808, 95810, 95811), sleep must be recorded and staged. A sleep study which includes 3 or more parameters of sleep other than sleep staging (95807) is not a polysomnogram. When a polysomnogram (95808, 95810, 95811) and a sleep study (95807) are performed on the same day, the charges should be combined with the appropriate polysomnography code.

Attended sleep studies(95807) and attended polysomnograms (95808-95811):  Attended sleep studies and attended polysomnograms performed on standard equipment are eligible for payment when performed in the following locations:

• In-hospital (tests performed on patients who are admitted as overnight bed patients in a hospital)
• Outpatient (including locations owned or controlled by a hospital)
• Office (including sleep labs or sleep clinics)
  
  NOTE:  Office place of service should only be reported when all technical costs (technicians, equipment, and office overhead) associated with the polysomnograms are the responsibility of the billing physician.

Unattended sleep studies (95806, G0400) and unattended portable polysomnograms (G0398, G0399) performed in the patient’s home are eligible for the diagnosis of obstructive sleep apnea (327.00, 327.01, 327.09, 327.10-327.14, 327.19, 327.20-327.29, 770.81, 770.82, 780.51, 780.53, 780.57). 

Unattended sleep studies (95806, G0400) and unattended portable polysomnograms (G0398, G0399) performed in the patient’s home must be interpreted by a physician who is either :

1. A diplomat of the American Board of Sleep Medicine (ABSM); or,
2. Diplomat in Sleep Medicine by a member board of the American Board of Medical Specialties (ABMS); or,
3. An active staff member of a sleep center or laboratory accredited by the American Academy of Sleep Medicine (AASM) or The Joint Commission (formerly the Joint Commission on Accreditation of Healthcare Organizations – JCAHO).

Pediatric pneumogram (94772):  Sleep studies and polysomnography (95805-95811) should not be reported when the service provided is a pediatric pneumogram. A pediatric pneumogram (94772) provides 12- to 24-hour continuous recording of an infant's respiratory pattern. The parameters measured may include heart and respiratory rate, oxygen saturation, and/or nasal airflow. A pediatric pneumogram (94772) should not be reported when the service provided is an infant apnea monitor with event recording. See Medical Policy Bulletin E-3 for guidelines on infant apnea monitoring (E0618, E0619).

Multiple sleep latency testing (95805):  Multiple sleep latency testing (MSLT) consists of physiological measurements of sleep during a series of 20 minute naps at two-hour intervals performed four to five times in an eight-hour period. MSLT is generally performed for the diagnosis of narcolepsy.

Actigraphy (95803):  The term actigraphy refers to methods using miniaturized computerized wristwatch-like devices to monitor and collect data generated by movement.  Actigraphy is based on the principle that there is reduced movement during sleep and increased movement during wake.  Actigraphy has been investigated in the evaluation of sleep disorders, including insomnia, sleep related disorders (including obstructive sleep apnea), restless leg syndrome and periodic limb movement disorder.  The scientific evidence supporting the validity of the use of actigraphy is either inconclusive or conflicting.  The role of actigraphy in clinical management is not clear.  Therefore, actigraphy (95803) is considered investigational as a technique to record and analyze body movement, including but not limited to its use to evaluate sleep disorders.  A participating, preferred, or network provider can bill the member for the denied service.

Date Last Reviewed:  07/2009

Other Miscellaneous Services
Services other than the polysomnography which are performed in conjunction with sleep related-conditions (e.g., medical examinations and evaluations, consultations, pathology and laboratory tests, etc.) are to be handled routinely.

NOTE: See Medical Policy Bulletin E-25 for guidelines on the pulse oximetry device.

Treatment for Sleep-Related Disorders

Snoring
Medically necessary services performed for the diagnosis or direct treatment of the member's disease, illness, or injury are contractually covered. Socially disruptive snoring is not a disease, illness, or injury. Therefore, treatment solely for the correction of socially disruptive snoring is noncovered.

Obstructive Sleep Apnea (OSA)
Obstructive sleep apnea is a syndrome that results from blockage of the airway, usually when the soft tissue in the rear of the throat collapses and closes during sleep. OSA is associated with loud snoring, observed apneas during sleep, and sleep fragmentation. OSA can cause excessive daytime sleepiness, cognitive and personality problems, high blood pressure and other cardiovascular disease. Predisposing risk factors include being male, overweight, a smoker, and over the age of 40. However, OSA can strike anyone at any age, even children. Adenotonsillar hypertrophy, retrognathia, hypothyroidism, nasal obstruction, evening alcohol consumption, and the use of sedatives are also risk factors for OSA. The severity of the apnea is a guide for treatment. However, due to the multifactorial nature of this disorder, each patient should be evaluated individually and their treatment planned accordingly.

• Behavior Modification - Behavior modification includes alteration of sleep position, avoidance of alcohol and sedative medication and weight-reduction programs. Avoidance of alcohol and sedative medication does not treat the OSA, it only prevents exacerbation of the existing condition. Weight reduction is potentially therapeutic, but permanent loss of significant excess body weight by behavioral means alone is rarely successful.
• Drug Therapy - Drug Therapy for OSA is of limited clinical value.
• Nasal Continuous Positive Airway Pressure (nCPAP) - nCPAP is considered the first-line treatment for most patients with OSA. Non-compliance with nCPAP is the major limitation to its effectiveness.

  NOTE: See Medical Policy Bulletin E-20 for guidelines on nCPAP.

• Intra-Oral appliances - Intra-oral appliances that affect pharyngeal mechanics by altering the relative position of the upper and lower jaws and tongue are effective in diminishing apnea in some patients.

  When a benefit, intra-oral appliances (E0485, E0486) are eligible for the treatment of diagnosed obstructive sleep apnea (327.00, 327.01, 327.09, 327.10-327.14, 327.19, 327.20-327.29, 770.81, 770.82, 780.51, 780.53, 780.57) for patients who have failed nCPAP.

  There are many different types of appliances that basically fit into one of two categories, tongue retaining appliances, and mandibular repositioning appliances. Payment may be made for one appliance. Additional appliances should be denied as not medically necessary. However, replacement of the appliance is covered in case of loss or irreparable damage or wear when required because of a change in the patient's condition.  It will be necessary for the provider to submit medical records and/or additional documentation to determine coverage in this situation.

When selecting patients for surgical treatment of OSA, the level(s) of obstruction need to be identified in order to determine the appropriate procedure(s) to perform. The levels of obstruction may include one or a combination of the following regions of the upper airway: nasal, nasopharynx, oropharynx, hypopharynx. The staged approach to surgical treatment based on the level(s) of obstruction is generally accepted as the standard of care. However, for select patients with multilevel obstruction as noted on presurgical examination, more than one surgical procedure may be required, either combined or staged. There are no universally accepted “stages” of surgical treatment. The staged approach is individualized based upon each patient and their symptoms, in addition to their physical findings. For most patients, the staged approach is acceptable if the patient is advised at the onset of treatment about the likelihood of success of each procedure and that multiple operations may be necessary.

The following surgical procedures (combined or staged) are available for the treatment of OSA. (This is not an all-inclusive list.)

Septoplasty (30520)
Turbinectomy (30130, 30140)
Polypectomy (31237)
Adenoidectomy (42830-42836)
Tonsillectomy (42820-42826)
Uvulopalatopharyngoplasty (UPPP) or palatopharyngoplasty (PPP) (42145)
* Laser-assisted uvulopalatoplasty (LAUP) (S2080)
* Laser-assisted tonsillectomy or laser ablation of the tonsils (LAT) (42999)
* Radiofrequency reduction of the soft palate and/or tongue base (Somnoplasty) (41530)
Partial glossectomies (41120, 41130)
Inferior sagittal mandibular osteotomy (21121-21123) and genioglossal advancement (21299)
Hyoid myotomy and suspension (21685)
Maxillomandibular osteotomy and advancement (21141-21147, 21195, 21196, 21199)
Tracheostomy (31600)
*Palatal stiffening procedures (e.g., CAPSO)
*Atrial overdrive pacing
*Tongue base suspension, permanent suture technique, e.g., Repose™  System (41512)

The following guidelines apply to LAUP, LAT, Somnoplasty, palatal stiffening, atrial overdrive pacing, and tongue base suspension procedures performed for the treatment of obstructive sleep apnea.

Laser-assisted uvulopalatoplasty (LAUP)(S2080) is a procedure performed with a carbon dioxide laser to progressively enlarge the oropharyngeal air space by trimming and reshaping the uvula, free edge of the soft palate, and pharyngeal pillars. LAUP is performed sequentially over several outpatient settings under local anesthesia. LAUP is a distinct procedure and does not refer to the use of the laser as a tool in performing UPPP. LAUP is covered for patients with obstructive sleep apnea, documented by polysomnography, who require a palatal procedure. Payment will be made for LAUP on a per session basis.

Laser ablation of the tonsils or laser-assisted tonsillectomy (LAT)(42999) may be performed in conjunction with LAUP for the treatment of obstructive sleep apnea. The laser is also used as a surgical tool in an otherwise standard tonsillectomy and to vaporize the surface of the tonsils (i.e., cryptolysis or subtotal tonsillectomy). LAT performed with LAUP for the treatment of documented obstructive sleep apnea is a covered procedure. Payment will be made for both LAUP (S2080) and LAT (42999) subject to multiple surgery guidelines on a per session basis. LAT (42999) is also covered when the laser is used as a surgical tool for a standard tonsillectomy and to vaporize the surface of the tonsils (i.e., cryptolysis or subtotal tonsillectomy).

Radiofrequency ablation of the soft palate and/or tongue base (e.g., Somnoplasty) (41530) is a minimally invasive, outpatient procedure which reduces and tightens excess tissue in the upper airway. Typically more than one procedure is necessary to achieve optimal results. Radiofrequency ablation of the soft palate and tongue base for the treatment of obstructive sleep apnea is experimental/investigational and not covered. A participating, preferred, or network provider can bill the member for the denied service. Studies have been non-randomized and non-controlled. Somnoplasty is still being performed in a clinical trial setting with no long-term outcomes available. (See Medical Policy Bulletin S-136 for guidelines on radiofrequency ablation of the nasal turbinates for nasal obstruction.)

Date Last Reviewed:  6/2009

Palatal stiffening procedures include a cautery-assisted palatal stiffening operation (CAPSO) and insertion of palatal implants.  The CAPSO procedure uses cautery to induce a midline palatal scar designed to stiffen the soft palate to eliminate excessive snoring.  The implanted device is a cylindrical-shaped segment of braided polyester filaments that is permanently implanted submucosally in the soft palate. 

Palatal stiffening procedures, including but not limited to, the cautery-assisted palatal stiffening operation, are considered experimental/investigational as a treatment for upper airway resistance syndrome or OSA and are not covered.  A participating, preferred, or network provider can bill the member for the denied service.  There are minimal published data regarding the cautery-assisted palatal stiffening operation (CAPSO) and palatal implants.

Date Last Reviewed:  09/2007

The use of atrial overdrive pacing by means of an implantable cardiac pacemaker has been evaluated as a treatment for obstructive sleep apnea patients and in certain patients with some degree of heart failure.  Atrial overdrive pacing consists of pacing at a rate higher than the mean nocturnal sinus rate.  Proponents of this treatment theorize that atrial overdrive pacing will improve vagal tone and increase upper airway muscle activity in patients with obstructive sleep apnea (OSA)

Atrial overdrive pacing is considered experimental/investigational for the treatment of obstructive sleep apnea.  There is insufficient evidence to demonstrate the safety and efficacy of atrial overdrive pacing in the treatment of OSA.  A participating, preferred, or network provider may bill the member for the denied procedure.

Date Last Reviewed: 09/2008

Tongue base suspension, permanent suture technique, e.g., the Repose™  System (41512) represents a surgical kit designed to treat obstructive sleep apnea (OSA).  The Repose™ System bone screws are primarily used in tongue suspension procedures intended to keep the tongue from falling back over the airway during sleep.  The Repose™ System involves titanium screws inserted into the posterior aspect of the mandible at the floor of the mouth.  A loop of suture is passed through the tongue base and attached to the mandibular bone screw.  The procedure achieves a suspension or hammock of the tongue base making it less likely for the base of the tongue to prolapse during sleep.

Tongue base suspension (41512) performed for the treatment of OSA is considered experimental/investigational.  Preliminary short-term studies of surgery targeted to alleviate tongue base collapse in sleep disorder breathing have shown subjective improvements in snoring and statistically significant decreases in mean RDI.  However, the reported rates of success have been inconsistent among studies, and larger controlled studies with long-term follow-up are necessary to determine whether the tongue base suspension is safe and effective.  A participating, preferred, or network provider may bill the member for the denied service.

NOTE:

LAUP, LAT, Somnoplasty, palatal stiffening, atrial overdrive pacing, and tongue base suspension procedures performed solely for the treatment of socially disruptive snoring should be denied as contractually noncovered. See guidelines under snoring.

NOTE:

This policy is designed to address medical guidelines that are appropriate for the majority of individuals with a particular disease, illness, or condition. Each person's unique clinical circumstances may warrant individual consideration, based on review of applicable medical records.

Services that do not meet the medical necessity criteria on this policy will be considered not medically necessary.  A participating, preferred or network provider cannot bill the member for the denied service unless the provider has given advance written notice, informing the member that the service may be deemed not medically necessary and providing an estimate of the cost.  The member must agree in writing to assume financial responsibility, in advance of receiving the service.  The signed agreement should be maintained in the provider's records.

This medical policy may not apply to FEP.  Medical policy is not an authorization, certification, explanation of benefits or a contract.  Benefits are determined by the Federal Employee Program.

Managed Care

When a PCP must refer a member to a dentist for an intra-oral appliance, every effort should be made to refer the member to a Blue Shield participating dentist.

PRN References

08/1993, Polysomnograms, reporting
03/1994, Laser-assisted palatopharyngoplasty, reporting of 1
10/1995, Laser-assisted palatopharyngoplasty, codes and reimbursement for
08/1994, Sleep studies and polysomnograms, reporting of
02/1998, Coverage dropped for laser-assisted uvulopalatoplasty, laser ablation of the tonsils
04/1998, Coverage of sleep studies and polysomnograms outlined
08/1998, Reporting guidelines for polysomnograms clarified
10/1999, Coverage for intra-oral appliances for the treatment of obstructive sleep apnea outlined 10/1999, Reporting polysomnograms, pneumograms, and infant apnea monitors clarified
08/2000, Radiofrequency ablation of the soft palate and/or tongue base not covered
12/2000, Laser-assisted uvulopalatoplasty (LAUP) approved for treatment of obstructive sleep apnea
06/2006, Palatal stiffening procedures not covered
10/2006, Coverage for unattended portable comprehensive polysomnograms and home sleep studies outlined
04/2007, Cardiac (atrial) pacing for the treatment of obstructive sleep apnea not covered
08/2007, Polysomnogram performed on portable equipment considered investigational
12/2008, Coverage extended for unattended home sleep studies and portable polysomnograms to diagnose obstructive sleep apnea
10/2009, Coverage expanded for the use of the laser to vaporize the surface of the tonsils (i.e., cryptolysis or subtotal tonsillectomy)

Practice Parameters for the Treatment of Obstructive Sleep Apnea in Adults: The Efficacy of Surgical Modifications of the Upper Airway, American Sleep Disorders Association and Sleep Research Society, Sleep, Volume 19, No. 2, 1996

Laser-Assisted Uvulopalatoplasty for the Treatment of Mild, Moderate, and Severe Obstructive Sleep Apnea, Laryngoscope, Volume 109, No. 1, 1999

Short-Term Objective and Long-Term Subjective Results of Laser-Assisted Uvulopalatoplasty for Obstructive Sleep Apnea, Laryngoscope, Volume 109, No. 3, 1999

Efficacy of Laser-Assisted Uvulopalatoplasty in Obstructive Sleep Apnea, Otolaryngology - Head and Neck Surgery, Volume 119, No. 6, 1998

A Multi-Institutional Study of Radiofrequency Volumetric Tissue Reduction for OSAS, Otolaryngology - Head and Neck Surgery, Volume 125, No. 4, 10/2001

Combined Temperature-Controlled Radiofrequency Tongue Reduction and UPPP in Apnea Surgery, ENT - Ear, Nose & Throat Journal, Volume 8, No. 9, 09/2001

Complications of Radiofrequency Ablation in the Treatment of Sleep-Disordered Breathing Otolaryngology - Head and Neck Surgery, Volume 125, No. 5, 11/2001

Comparison Postoperative Pain Between Laser-Assisted Uvulopalatoplasty (LAUP), Uvulopalatopharyngoplasty (UPPP), and Radiofrequency Volumetric Tissue Reduction of the Palate (RFVTR), Otolaryngology - Head and Neck Surgery, Volume 122, No. 3, 03/2000

National Blue Cross Blue Shield Association Medical Policy 7.01.101, Minimally Invasive Surgery for Snoring, Obstructive Sleep Apnea Syndrome/Upper Airway Resistance Syndrome, 06:2007

National Blue Cross Blue Shield Association Medical Policy 2.01.18, Diagnosis and Medical Management of Obstructive Sleep Apnea Syndrome, 3:2006

Portable Monitoring in the Diagnosis of the Obstructive Sleep Apnea Syndrome - Seminars in Respiratory and Critical Care medicine, Volume 26, No. 1, 2005

Description and Validation of the Apnea Risk Evaluation System, a Novel Method to Diagnose Sleep Apnea-Hypopnea in the Home - Chest, Volume 128, No. 4, 10/2005

Evaluation of the Accuracy of SNAP Technology Sleep Sonography in Detecting Obstructive Sleep Apnea in Adults Compared to Standard Polysomnography - Chest, Volume 125, 03/2004

Comparison of the NovaSom QSG, A New Sleep Apnea Home-Diagnostic System, and Polysomnography - Sleep Medicine, Volume 4, 2003

Home Diagnosis of Sleep Apnea: A Systematic Review of the Literature, An Evidence Review Cosponsored by the American Academy of Sleep Medicine, the American College of Chest Physicians, and the American Thoracic Society - Chest, Volume 124, No. 4, 2003

A Pilot Study of Inexpensive Sleep-Assessment Devices, Behav Sleep Med, Volume 2, No. 1, 2004

Actigraphy – Respir Care Clin N Am, Volume 12, No. 1, 03/2006

Evaluation of the Insomnia Patient, Sleep Medicine Clinics, Volume 1, No. 3, 09/2006

Sleep and Sleep Disorders in Children and Adolescents, Psychiatric Clinics of North America, Volume 29, No. 4, 12/2006

Obstructive Sleep Apnea: A Palatable Treatment Option, Issues Emerg Health Technol, Volume 97, No. 1-4, 01/2007

Palatal Stiffening After Failed Uvulopalatopharyngoplasty With the Pillar Implant System, Laryngoscope, Vol 116, No. 11, 11/2007

Palatal Implants: A New Approach for the Treatment of Obstructive Sleep Apnea, Otolaryngol Head Neck Surg, Volume 135, No. 4, 10/2006

Soft Palate Implants for the Treatment of Mild to Moderate Obstructive Sleep Apnea, Otolaryngol Head Neck Surg, Volume 134, No. 4, 04/2006

U.S. Deparatment of Health and Human Services, Centers for Medicare and Medicaid Services (CMS). Decision memo for Continuous Positive Airway Pressure (CPAP) Therapy for Obstructive Sleep Apnea (OSA) (CAG-0093R2). Medicare Coverage Database. Baltimore, MD: CMS; March 13, 2008

Trikalinos TA, IpS, Raman G, et al. Home Diagnosis of Obstructive Sleep Apnea-Hypopnea Syndrome. Technology Assessment. Prepared for AHRQ by the Tufts-New England Medical Center Evidence-Based Practice Center. Rockville, MD: Agency for Healthcare Research and Quality (AHRQ); August 8, 2007

Collop NA, Anderson WM, Boehlecke B, et al, Clinical Guidelines for the Use of Unattended Portable Monitors in the Diagnosis of OSA in Adult Patients. Portable Monitoring Task Force of the American Academy of Sleep Medicine, J Clin Sleep Med. 2007;3(7):737-47

Ayappa I, Validation of a Self-Applied Unattended Monitor for Sleep Disordered Breathing, J Clin Sleep Med.  2008;4(1):26-37

Ahmed M, Patel N, Rosen I, Portable Monitors in the Diagnosis of Obstructive Sleep Apnea, Chest. 2007;132(5):1672-7

Ghegan M, et al, Laboratory Versus Portable Sleep Studies: A Meta-Analysis, The Laryngoscope. 2006;116(11):859-64

Pang KP et al, A Comparison of Polysomnography and the Sleep Strip in the Diagnosis of OSA, Otolaryngol Head Neck Surg. 2006;135(2);265-8

American Heart Association and American College of Cardiology Foundation Scientific Statement, Sleep Apnea and Cardiovascular Disease, J Am Coll Cardiol. 2008; 52:686-717

American College of Cardiology and American Heart Association Task Force on Practice Guidelines, 2008 Guidelines for Device-Based Therapy of Cardiac Rhythm Abnormalities, J Am Coll Cardiol. 20080; 51:1-62

Kapa S et al, Obstructive Sleep Apnea and Arrhythmias, Sleep Medicine Clinics. December 2007; 2(4):1-7

Shalaby A et al, Analysis of Interaction of Acute Atrial Overdrive Pacing with Sleep-Related Breathing Disorder, J Am Coll Cardiol. February 2007; 99(4):1-10

Krahn et al, Physiologic Pacing in Patients with Obstructive Sleep Apnea, J Am Coll Cardiol. 2006; 47:379-383

Melzer C et al, Nocturnal Overdrive Pacing for the Treatment of Sleep Apnea Syndrome, Sleep. 2006; 29(9):1197-1202

Simantirakis E et al, Cardiac Pacing in Sleep Apnoea: Diagnostic and Therapuetic Implications, Europace. 2006; 8(11)984-987

Won C, Li K, Guilleminault C. Surgical Treatment of Obstructive Sleep Apnea: Upper Airway and Maxillomandibular Surgery. Proc Am Thorac Soc. 2008; 5(2): 193-9

Farrar J, Ryan J, Oliver E et al. Radiofrequency Ablation for the Treatment of Obstructive Sleep Apnea: A Meta-Analysis. Laryngoscope 2008; 118: 1878-83

Silvertsen B et al, A Comparison of Actigraphy and Polysomnography in Older Adults Treated for Chronic Primary Insomnia, Sleep.  2006; 29(10):1353-8

Garcia-Diaz et al, Respiratory Polygraphy with Actigraphy During Sleep, Sleep 2007: 30(10):1362-1369

Sitnick et al, The Use of Actigraphy to Study Sleep Disorders in Preschoolers: Some Concerns About Detection of Nighttime Awakenings, Sleep. 2008; 31(3):395-401