California Sleep Institute


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Our History & Staff

Our Physicians

Dr. Hester - Dr Jerry Hester is Board Certified in Otolaryngology-Head and Neck Surgery. After completing medical school at the University of Texas, Dr. Hester received his specialty training in head and neck surgery at Stanford University Hospital. Learn more about Dr. Hester

Dr. Schendel - We are pleased and honored to announce that Dr. Steve Schendel is joining our Center for Facial and Airway Reconstructive Surgery. He is an internationally recognized surgeon, researcher and teacher in pediatric and adult craniofacial reconstruction, plastic and maxillofacial surgery.
Learn more about Dr. Schendel

The Sleep Institute Founders

  • Dr. Nelson B. Powell (retired)
  • Dr. Robert W. Riley

Dr. Nelson Powell and Dr. Robert Riley began to develop methods and surgical procedures for OSAS in early 1983. Very few physicians at the time believed in the significance of OSAS. At the time very few options were available for the treatment of OSAS. Tracheotomy was very successful with nearly 100% cure rates but patients did not readily accept it. The UPPP procedure was developed to treat snoring but used in some cases of OSAS without a cure being found. Drs. Nelson Powell and Robert Riley came to believe that the tongue base, not previously identified as a potential area of obstruction, was at least partially responsible for failures of the UPPP procedure.

Below is a timeline of their efforts presented from 1983 to the present.

Cephalometric Analysis

In 1983 we made note of the fact that in isolated treatments of OSAS using the UPPP procedure, with or without nasal construction, there was little to no improvement in the patients. This is when we had the thought that the tongue could be an obstruction. This idea had not yet been approached. We settled on using a simple dental radiographic study (cephalometric film) to assess the soft tissues and bony anatomy of the face and neck. We found marked abnormalities of the upper airway in this study of patients with OSAS. This analysis showed narrowing in the posterior airway space (PAS) accompanied with a low position of the hyoid bone. This new adaptation of the cepalometric film allowed us to evaluate this portion of the airway in a non-invasive manner both before and after treatment.

There are several important landmarks used that had not been previously described by others in our field. We have used these measurements for over 20 years to assess the anatomical configuration of the airway. About ten years ago we combined cephalometrics with fiber-optic technology using a tiny fiber-optic scope to give us a three dimensional view of the upper airway to confirm the two dimensional data from the cephalometrics. We consider this approach a necessary step for any patient with OSAS who is considering surgery.

  • Riley R, Guilleminault C, Herran J, Powell N: Cephalometric analysis and flow-volume loops in obstructive sleep apnea patients. Sleep 1983;6:303-311
  • Guilleminault C, Riley R, Powell N: Obstructive sleep apnea and abnormal cephalometric measurements. Chest 1984;86:793-794
  • Riley R, Guilleminault C, Powell N, Simmons FB: Palatopharyngoplasty failure, cephalometric roentgenograms, and obstructive sleep apnea. Otolaryngol Head and Neck Surg 1985;93:240-244

First Mandibular Osteotomy with Objective Data

Cephaolmetrics helped identify a patient with OSAS who had a small jaw and a large tongue. The PAS was seriously compromised as the tongue was markedly collapsed. The symptoms and polysomnogram showed severe OSAS. The patient refused tracheotomy. The first step was to treat his severe mandibular deficiency. This patient was our first case report of a mandibular advancement. Several other surgeons had previously reported on mandibular advancement for OSAS but objective data was not presented. This index case was to be the beginning of skeletal surgery for OSAS.

  • Powell N, Guilleminault C, Riley R: Mandibular advancement and obstructive sleep apnea syndrome. Bull. Europ.Physiopath (Clinical Respiratory Physiology) 1983;19:607-610

First Mandibular Osteotomy and Hyoid Advancement for OSAS

  • Riley R, Guilleminault C, Powell N, Derman S: Mandibular Osteotomy and hyoid bone advancement for obstructive sleep apnea: A case report. Sleep 1984;7:79-82

First Inferior Sagittal Mandibular Osteotomy (Geioglossus Advancement-Hyoid)

  • Riley R, Powell N, Guilleminault C: Inferior sagittal osteotomy of the mandible with hyoid myotomy-suspension: A new procedure for obstructive sleep apnea. Otolaryngol Head and Neck Surg 1986;94:589-593

First Objective Report of Bi-Maxillary Advancement for OSAS

  • Riley R, Powell N, Guilleminault C, Nino-Murcia G: Maxillary, mandibular and hyoid advancement: An alternative to tracheostomy in obstructive sleep apnea syndrome. Otolaryngol Head and Neck Surg 1986;94:584-588

First Reported Use of CPAP Postoperatively to Protect the Airway

  • Powell N, Riley R, Guilleminault C, Nino-Murcia G: Obstructive sleep apnea, continuous positive airway pressure and surgery. Otolaryngol Head and Neck Surg, 1988;99:362-369

First Objective Comparison of Nasal CPAP and Maxillofacial Surgery for OSAS

  • Riley R, Powell N, Guilleminault C: Maxillofacial surgery and nasal CPAP: a comparison of treatment for obstructive sleep apnea syndrome. Chest, 1990;98:1421-1425

Largest Outcomes Study of Powell and Riley’s Phased Surgical Protocol

  • Riley R, Powell N, Guilleminault C: Obstructive sleep apnea syndrome: a review of 306 consecutively treated surgical patients. Otolaryngol Head Neck Surg, 1993;108:117-125

Reversible Uvulopalatal Flap an Alternative to Traditional UPPP First Reported in 1996

  • Powell N, Riley R, Guilleminault C, Troell R: A reversible uvulopalatal flap for snoring and sleep apnea syndrome. Sleep 1996;19(7):593-599

Temperature Controlled Radiofrequency for OSAS (TCRF)

In 1995 we were looking for an upper airway soft tissue treatment modality that would be minimally invasive, safe and could be done without hospitalization. Radiofrequency technology had not been previously used on soft tissues but was used in many other fields of medicine and surgery. There were no reports on the cellular changes associated with RF treatments thus we set out to examine this issue before using RF to shrink human soft tissues in the airway.

We started this investigation hoping RF could treat the tongue base thus possibly bypassing the need for the more aggressive skeletal jaw surgery. We used a four stage investigational protocol to treat not only the tongue but also the nose and palate regions of the upper airway using RF. The original work was done at our center with Drs. Nelson Powell and Robert Riley as the primary investigators. The technique is now used in many countries. After we were well into our investigations a company was formed to manufacture and sell the products developed as part of this investigation. We declined to own a part of the company, believing it was more important to remain objective and independent.

First Powell and Riley Investigation of TCRF Include: Tongue, Palate and Turbinates


  • Powell N, Riley R, Guilleminault C, Troell R, Blumen M: Radiofrequency volumetric reduction of the tongue: a porcine pilot study for the treatment of obstructive sleep apnea syndrome. Chest 1997;111:1348-1355
  • Powell N, Riley R, Guilleminault C: Radiofrequency tongue base reduction in sleep disordered-breathing-a pilot study. Otolaryngol Head Neck Surg 1999;120:656-664


  • Powell N, Riley R, Troell R, Li K, Blumen M, Guilleminault C: Radiofrequency volumetric tissue reduction of the palate in subjects with sleep-disordered breathing. Chest 1998;113:1163-1174


  • Li K, Powell N, Riley R, Troell R: Radiofrequency volumetric tissue reduction for treatment of turbinate hypertrophy-a pilot study. Otolaryngol Head Neck Surg 1998;119(6):569-573

For additional articles, see PubMed: Or type “radiofrequency treatments for sleep apnea” in your browser.

First Report of New Surgical Technique to Treat Nasal Alar Collapse

A bilateral nasal alar collapse is common in patients with OSAS. To correct this, cartilage is placed along the internal portion of the alar rim of the nasal opening thereby limiting such collapses.

Medical Investigations in OSAS by Powell and Riley

The majority of patients with OSAS complain about Excessive Daytime Sleepiness (EDS). We felt it was important to better understand the relationship between EDS and quality of life of the patients.

  • Powell NB. Driving Drowsy: Time for personal accountability. Int J Sleep. Wakefulness-Prim Care 2007, 1(2): 66-9
  • Powell NB, Schechtman KB, Riley RW, Guilleminalut c, Chiang RP, Weaver EM. Sleepy Driver Near-Misses May Predict Accident Risks. Sleep , Mar 1;30(3):331-42, 2007
  • Powell N, Schechtman K, Riley R, Li K, Guilleminault C. Sleepy Driving: Accidents and Injury. Otolaryngology Head and Neck Surgery. Otolaryngology Head and Neck Surg 2002; 126:217-27
  • Powell NB, Schechtman KB, Riley RW, Li K, Troell R, Guilleminault C: The road to danger: the comparative risks of driving while sleepy. Laryngoscope 2001;111:887-893
  • Powell N, Riley R, Schechtman K, Blumen M, Dinges D, Guillleminault C: A comparative model: Reaction time performance in sleep-disordered breathing versus alcohol impaired controls. Laryngoscope 1999;109:1648-1654