Potential Treatments for Epiglottic Collapse in Obstructive Sleep Apnea: How Modified Drug-Induced Sleep Endoscopy Help?

OBJECTIVE

In patients with obstructive sleep apnea (OSA), epiglottic collapse (EC) constitutes a major factor in the failure of continuous positive airway pressure therapy and uvulopalatopharyngoplasty. This study explored treatments that can improve EC in patients with OSA through drug-induced sleep endoscopy with target-controlled infusion (TCI-DISE).

STUDY DESIGN

Retrospective cohort study.

SETTING

Tertiary center.

METHODS

This study screened 352 OSA patients who underwent TCI-DISE between 2016 and 2022. Fifty-four patients with EC were included in the final analysis. EC severity was assessed multiple times through TCI-DISE with different interventions.

RESULTS

The application of these interventions in patients with anteroposterior epiglottic collapse (apEC) led to a significant decrease in apEC severity from total to partial or no obstruction in 60.0% of patients by head rotation, in 53.6% by mouth closure, in 47.4% who received oral appliances (OA), and in 28.0% who received intermittent negative airway pressure (iNAP). With simultaneous head rotation, apEC severity decreased more significantly from total to partial or no obstruction in 77.8% of patients by mouth closure, in 70.3% who received OA, and in 68.0% who received iNAP. Lateral epiglottic collapse (latEC) severity decreased in 53.8% of patients after OA use and in 61.5% of patients with OA use and head rotation.

CONCLUSION

This study identified head rotation with mouth closure as the most effective treatment for apEC through TCI-DISE. Patients with latEC had higher weight, apnea-hypopnea index, and body mass index compared with patients with apEC. OA use with head rotation appeared more effective in latEC through TCI-DISE.

Endorsement of "European Respiratory Society guideline on non-CPAP therapies for obstructive sleep apnoea" by World Sleep Society

Guidelines for management of sleep disorders from national or regional societies provide recommendations that may be regionally appropriate but may not always be practical or relevant in other parts of the world. A task force of experts from the World Sleep Society's (WSS) International Sleep Medicine Guidelines Committee and Sleep and Breathing Disorders Task Force reviewed the European Respiratory Society's guideline on non-CPAP therapies for obstructive sleep apnea (OSA) with respect to its relevance and applicability to the practice of sleep medicine by sleep specialists in various regions of the world. The task force and the WSS guidelines committee endorsed the European Respiratory Society's guideline with respect to the utilization of bariatric surgery, mandibular advancement devices, positioning devices, myofunctional therapy, hypoglossal neurostimulation, maxilo-mandibular surgery, and carbonic anhydrase inhibitors for the treatment of OSA. The task force and the WSS guidelines committee noted that there is substantial new evidence for the role of soft tissue, upper airway surgery, not included in the guidelines paper.

Upper Airway Surgery or Weight Control? Modified Drug-Induced Sleep Endoscopy for Obstructive Sleep Apnea

OBJECTIVE

To identify the value of head rotation in the supine position and oral appliance (OA) use in drug-induced sleep endoscopy (DISE).

STUDY DESIGN

Eighty-three sleep apnea adults undergoing target-controlled infusion-DISE (TCI-DISE) were recruited from a tertiary academic medical center.

SETTING

During DISE, 4 positions were utilized: supine position (position 1), head rotation (position 2), mandibular advancement using an OA (position 3), and head rotation with an OA (position 4).

METHODS

Polysomnography (PSG) data and anthropometric variables during DISE were analyzed.

RESULTS

Eighty-three patients (65 men and 18 women; mean [standard deviation, SD], 48.5 [11.0] years) who underwent PSG and TCI-DISE were included. The mean (SD) apnea-hypopnea index (AHI) was 35.5 (22.4) events/h. Twenty-three patients had persistent complete concentric velopharyngeal collapse in the supine position, even with concurrent head rotation and OA (position 4). Their mean (SD) AHI was 54.7 (24.6) events/h, significantly higher than that of the 60 patients without such collapse in position 4 (p < .001). Their mean (SD) body mass index (BMI) was 29.0 (4.1) kg/m2 , also significantly higher (p = .005). After adjustment for age, BMI, tonsil size, and tongue position, the degree of velum and tongue base obstruction was significantly associated with sleep apnea severity in positions 2, 3, and 4.

CONCLUSION

We showed the feasibility, safety, and usefulness of using simple edge-to-edge, reusable OA in DISE. Patients who are not responsive to head rotation and OA during TCI-DISE may need upper airway surgery and/or weight control.

Could the use of a new novel bipolar radiofrequency device (Aerin) improve nasal valve collapse? A systematic review and meta-analysis

BACKGROUND

Surgical treatment for nasal obstruction caused by nasal valve collapse requires a significant recovery period and risks of complications, while nasal dilators are uncomfortable. Recently, radiofrequency treatment of lateral walls has been used under local anesthesia as an office base surgery. This work aims to assess the efficacy of a new radiofrequency device, the Vivaer™ System (Aerin Medical, Sunnyvale, CA), to treat nasal obstruction through a systematic review and meta-analysis.

METHODS

Two researchers independently reviewed the literature up to December 2021. Studies on patients seeking treatment for nasal obstruction due to nasal valve collapse were included in the analysis.

RESULTS

Four studies (218 patients) met the inclusion criteria and treated the nasal valve regions bilaterally with the Aerin Medical Vivaer™ System. After the treatment, the NOSE score was reduced at three months postoperatively. Minor adverse events were reported in the included studies, and two showed no complications. None of the studies reported changes in the external appearance of the nose.

CONCLUSION

The radiofrequency treatment using the Vivaer device can be useful for treating nasal valve collapse, improving significantly subjective breathing symptom scores. Further studies on a large scale are needed to confirm these results.

Targeted Hypoglossal Nerve Stimulation for Patients With Obstructive Sleep Apnea: A Randomized Clinical Trial

Importance

Evidence is lacking from randomized clinical trials of hypoglossal nerve stimulation in obstructive sleep apnea (OSA).

Objective

To evaluate the safety and effectiveness of targeted hypoglossal nerve stimulation (THN) of the proximal hypoglossal nerve in patients with OSA.

Design, Setting, and Participants

This randomized clinical trial (THN3) was conducted at 20 centers and included 138 patients with moderate to severe OSA with an apnea-hypopnea index (AHI) of 20 to 65 events per hour and body mass index (calculated as weight in kilograms divided by height in meters squared) of 35 or less. The trial was conducted from May 2015 through June 2018. Data were analyzed from January 2022 through January 2023.

Intervention

Implant with THN system; randomized 2:1 to activation at month 1 (treatment) or month 4 (control). All received 11 months of THN with follow-up at months 12 and 15, respectively.

Main Outcomes and Measures

Primary effectiveness end points comprised AHI and oxygen desaturation index (ODI) responder rates (RRs). Treatment responses at months 4 and 12/15 were defined as a 50% or greater reduction in AHI to 20 or less per hour and an ODI decrease of 25% or greater. Coprimary end points comprised (1) month 4 AHI and ODI RR in the treatment greater than the control group and (2) month 12/15 AHI and ODI RR in the entire cohort exceeding 50%. Secondary end points included sleep apnea severity (AHI and ODI) and patient-reported outcomes (Epworth Sleepiness Scale, Functional Outcomes of Sleep Questionnaire, and EQ-5D visual analog scale).

Results

Among 138 participants, the mean (SD) age was 56 (9) years, and 19 (13.8%) were women. Month 4 THN RRs were substantially greater in those in the treatment vs control group (AHI, 52.3% vs 19.6%; ODI, 62.5% vs 41.3%, respectively) with treatment-control standardized mean differences of 0.725 (95% CI, 0.360-1.163) and 0.434 (95% CI, 0.070-0.843) for AHI and ODI RRs, respectively. Months 12/15 RRs were 42.5% and 60.4% for AHI and ODI, respectively. Improvements in AHI, ODI, Epworth Sleepiness Scale, Functional Outcomes of Sleep Questionnaire, and EQ-5D visual analog scale scores were all clinically meaningful (medium to large effect size). Two serious adverse events and 100 nonserious related adverse events were observed from the implant procedure or study protocol.

Conclusions and Relevance

This randomized clinical trial found that THN demonstrated improvements in sleep apnea, sleepiness, and quality of life in patients with OSAs over an extended AHI and body mass index range without prior knowledge of pharyngeal collapse pattern. Clinically meaningful improvements in AHI and patient-reported responses compared favorably with those of distal hypoglossal nerve stimulation trials, although clinically meaningful differences were not definitive for ODI.

Trial Registration

ClinicalTrials.gov Identifier: NCT02263859.

Design and rationale for the treating Obstructive Sleep Apnea using Targeted Hypoglossal Nerve Stimulation (OSPREY) trial

Obstructive sleep apnea (OSA) affects nearly 1 billion people worldwide, including approximately 35 million US residents. OSA has detrimental cardiovascular and neurocognitive consequences. Positive airway pressure corrects sleep disordered breathing but is not always tolerated or used sufficiently. Oral appliances and surgery provide alternatives in select populations but are variably effective. Hypoglossal nerve stimulation can effectively treat obstructive sleep apnea. Targeted hypoglossal nerve stimulation (THN) is simpler than incumbent technology with no sensor and an easier, proximal electrode implantation. The third clinical study of THN, THN3, was the first randomized, controlled trial of hypoglossal nerve stimulation to demonstrate significant improvement of sleep disordered breathing in OSA. The present investigation reports the design of a novel trial of targeted stimulation to provide additional Level 1 evidence in moderate to severe obstructive apnea. OSPREY is a randomized, parallel-arm, 13-month trial wherein all subjects are implanted, 2/3 are activated at Month 1 ("Treatment") and 1/3 are activated at Month 7 ("Control"). The primary endpoint is the difference in apnea-hypopnea index response rates between Treatment and Control groups at Month 7. Secondary endpoints include quality of life and oximetry metrics. OSPREY follows an adaptive "Goldilocks" design which optimizes the number of subjects with the need for high-confidence results. A maximum of 150 subjects is allowed, at which study power of >95% is predicted. Interim analyses begin once 50 patients are randomized and recur after each 20 additional randomizations to detect early success or futility. OSPREY is a unique, efficient trial that should provide high-confidence confirmation of the safety and efficacy of targeted hypoglossal nerve stimulation for moderate to severe obstructive sleep apnea.

0765 Enhanced Response to Targeted Hypoglossal Nerve Stimulation in Patients with Normal Sleep Efficiency: A THN3 Post-Hoc Analysis

Introduction

THN3 was the first reported parallel-arm, randomized controlled trial of hypoglossal nerve stimulation (HGNS), wherein targeted HGNS (THN) was shown to be safe and efficacious at ameliorating sleep disordered breathing in selected patients with moderate to severe OSA and BMI≤35kg/m2 without screening with drug-induced sleep endoscopy. A secondary THN3 objective was to identify baseline characteristics which enhance therapeutic response.

Methods

Predictors of long-term (Month 12/15) apnea-hypopnea index (AHI) response (reduction ≥50% to ≤20/hr) were identified in stages. Baseline characteristics, including polysomnography parameters, were screened one at a time using univariate logistic regression. Variables significant at α=0.25 were further selected using stepwise multivariate logistic regression. Candidate predictors were then optimized by manual, incremental threshold adjustment to maximize AHI response rate (RR). Optimized predictors were ranked according to the AHI RR and size of the corresponding subpopulation, with a goal of capturing at least 40% of the overall THN3 cohort.

Results

Baseline sleep efficiency (SE) in the normal range (&gt;85%) achieved the highest AHI RR while retaining 42% (58/138) of the THN3 cohort. Similar to the overall study population, subgroup subjects were predominantly middle-aged (age 54±7 years), male (83%), Caucasian (86%) and overweight/obese (BMI 30±3 kg/m2). Short-term (Month 4) AHI RRs in the Treatment and Control groups were 59.5% and 20.0%, respectively, with long-term AHI RR at 50.9%. Median AHI was reduced from 35.1 to 16.0, as compared to 29.3 to 9.0 in the STAR trial of distal HGNS. ODI RRs (reduction ≥25%) for Treatment and Control were respectively 73.0% and 30.0% at Month 4 and 64.9% at Month12/15. Enhanced response carried through to larger point estimates for improvement in secondary variables, including the Epworth Sleepiness Scale and the Functional Outcomes of Sleep Questionnaire, exceeding minimum clinically important differences thresholds of 2-3 and 1.7-2.0, respectively.

Conclusion

Normal SE at Baseline was associated with enhanced AHI and ODI RR as well as patient-reported outcome measures for patients receiving THN therapy, providing results similar to those obtained with distal HGNS. Future studies, including the ongoing OSPREY trial, will be needed to prospectively validate these findings.

Support (If Any)

LivaNova

0761 Adaptability of the Treating Obstructive Sleep Apnea Using Targeted Hypoglossal Nerve Stimulation (OSPREY) Trial

Introduction

With few exceptions, clinical trials of hypoglossal nerve stimulation (HGNS) for obstructive sleep apnea (OSA) are single-arm, open-label studies sometimes followed by short-term, unblinded, randomized withdrawal. By contrast, the THN3 study was a parallel-arm, randomized, controlled trial (RCT) of targeted HGNS (THN) in moderate to severe OSA, and provided higher-level evidence of HGNS safety and efficacy.Despite generating strong evidence, conventional RCTs are risky due to their inherent inflexible designs. We therefore launched a confirmatory THN RCT (OSPREY) with an adaptive, Bayesian “Goldilocks” design that optimize its sample size dynamically, yet achieve high-confidence results.

Methods

Four scenarios were simulated within the OSPREY design framework (randomized 2:1 Treatment:Control) for the primary endpoint of apnea-hypopnea index (AHI) response rate (RR): nominal with results equal to those of THN3 (Treatment AHI RR 52%/Control AHI RR 20%), improved Treatment RR (63%/20%), worsened Treatment RR (41%/20%) and null [Treatment RR=Control RR] (20%/20%). Each scenario was simulated 10 times with 10,000 simulations of each interim analysis. Subject outcomes were determined by randomly drawing from a binomial distribution with the relevant AHI RR.Interim analyses in OSPREY begin at 50 randomized subjects and repeat every 20 additional subjects to the maximum sample size of 150, with opportunities for early success and futility at each milestone to generate high-confidence results from an optimal sample size. OSPREY assesses secondary endpoints including quality of life inventories (Epworth Sleepiness Scale; Functional Outcomes of Sleep Questionnaire; EQ-5D, SF-6D and PROMIS sleep questionnaires) and oximetry metrics (Oxygen Desaturation Index, %sleep time below 90% oxygen saturation). Previous results suggest secondary endpoints will be adequately powered at the final sample size determined by AHI RR.

Results

Simulations produced the following outcomes formatted as [scenario: randomized sample size, overall success rate, probability of early success, mean success probability]: null: 150, 0%, 0%, 2.47%; nominal: 130-150, 100%, 80%, 95.3%; improved: 90-130, 100%, 100%, 98.9%; worsened: 150, 100%, 0%, 68.6%.

Conclusion

OSPREY is uniquely able to adapt to various Treatment/Control response scenarios and should provide high-confidence confirmation of the safety and efficacy of THN therapy in moderate to severe OSA.

Support (If Any)

LivaNova

0766 Group Trajectories Demonstrate Robust Effects of Targeted Hypoglossal Nerve Stimulation in the THN3 Randomized, Controlled Trial

Introduction

THN3 was the first reported parallel-arm, randomized controlled trial (RCT) of hypoglossal nerve stimulation (HGNS), wherein targeted HGNS (THN) was shown to be safe and efficacious at ameliorating sleep disordered breathing in patients with moderate to severe OSA and BMI≤35kg/m2 without screening with drug-induced sleep endoscopy. Unique among reported HGNS trials, separate cohorts of patients receiving early and late THN were followed longitudinally.

Methods

Measurements of apnea-hypopnea index (AHI) were available Pre-enrollment, Baseline (2 nights), Month 4 and Month 12/15. Except for Pre-enrollment, AHI values were calculated by an independent core laboratory from polysomnographic recordings. All subjects with complete data were included for analysis. AHI trajectories were constructed for early and late THN activation (Treatment[T], N=83, Month 1 and Control[C], N=45, Month 4, respectively) by computing median values. Confidence intervals were calculated by bootstrapping each median (N=30,000). Patient-reported outcome measures (PROMs) were treated similarly.

Results

AHI (Median (95% CI)) trajectories demonstrated a consistent pattern of pre-implant alignment (Pre-enrollment T:39.1 (36.0-45.0), C:38.0 (32.0-41.0); Baseline 1 T:36.1 (33.0-39.9), C:31.3 (27.2-38.6); Baseline 2 T:37.0 (34.3-41.0), C:35.2 (32.3-38.2)), divergence at the conclusion of the randomization period (Month 4 T:15.6 (11.9-25.3), C:30.6 (23.7-38.6)) and reconvergence following 11 months of treatment (Month 12/15 T:20.7 (16.0-26.4), C:18.1 (16.3-23.3)). Non-standardized Pre-enrollment AHI was slightly higher than Baseline values. Trajectories were similar for oxygen desaturation index (Baseline 1 T:35.3 (31.9-38.0),C:34.3 (27.5-40.3); Baseline 2 T:37.1 (33.4-39.3),C:36.8 (33.9-38.3); Month 4 T:19.5 (16.2-28.5), C:33.8 (25.4-41.1); Month 12/15 T:19.5 (16.0-25.6), C:19.7 (16.3-26.0)), the Epworth Sleepiness Scale (Baseline T:11.0 (10.0-13.0),C:11.5 (8.5-14.0); Month 4 T:6.0 (5.0-7.0), C:11.5 (8.0-12.5); Month 12/15 T:6.0 (4.0-7.0), C:5.5 (4.5-6.0)), the Functional Outcomes of Sleep Questionnaire (Baseline T:15.3 (14.0-16.5),C:14.7 (13.3-16.6); Month 4 T:18.3 (17.7-18.8), C:16.7 (14.9-17.7); Month 12/15 T:18.8 (18.3-19.3), C:18.5 (17.5-19.5)) and the Snore Outcomes Survey (Baseline T:26.6 (21.9-31.3),C:21.9 (18.8-31.3); Month 4 T:60.9 (56.3-67.9), C:29.7 (23.4-42.9); Month 12/15 T:62.5 (59.4-68.8), C:68.8 (62.5-71.9)).

Conclusion

Group trajectories of sleep-disordered breathing and PROMs further demonstrate the robust effects of THN in patients with moderate to severe OSA and the value of parallel-arm RCTs. Similar results may be expected in the ongoing OSPREY confirmatory trial of THN.

Support (If Any)

LivaNova

Endorsement of: "treatment of adult obstructive sleep apnea with positive airway pressure: an American academy of Sleep Medicine Clinical Practice Guideline" by World Sleep Society

Guidelines for the evaluation and management of sleep disorders from national societies provide recommendations that may be regionally appropriate but may not always be practical or relevant in other parts of the world. A task force of experts from the World Sleep Society's (WSS) International Sleep Medicine Guidelines Committee and Sleep and Breathing Disorders Taskforce reviewed the American Academy of Sleep Medicine's Clinical Practice Guideline on the Treatment of Adult Obstructive Sleep Apnea (OSA) with Positive Airway Pressure with respect to its relevance and applicability to the practice of sleep medicine by sleep specialists in various regions of the world. To improve the evaluation of the guideline, surveys were sent by the senior author and the WSS to approximately 800 sleep doctors around the world to query the availability of OSA treatments in their respective region. The task force and the WSS guidelines committee endorsed the AASM's CPAP guidelines with respect to the indications for PAP therapy, utilization of different PAP modalities, and concurrent strategies to improve outcomes, noting appropriate caveats for universal applicability.

Improving outcomes of hypoglossal nerve stimulation therapy: current practice, future directions and research gaps. Proceedings of the 2019 International Sleep Surgery Society Research Forum

Hypoglossal nerve stimulation (HGNS) has evolved as a novel and effective therapy for patients with moderate-to-severe obstructive sleep apnea (OSA). Despite positive published outcomes of HGNS, there exist uncertainties regarding proper patient selection, surgical technique, and the reporting of outcomes and individual factors that impact therapy effectiveness. According to current guidelines, this therapy is indicated for select patients, and recommendations are based on the Stimulation Therapy for Apnea Reduction (STAR) trial. Ongoing research and physician experiences continuously improve methods to optimize the therapy. An understanding of the way in which airway anatomy, OSA phenotypes, individual health status, psychological conditions and comorbid sleep disorders influence the effectiveness of HGNS is essential to improve outcomes and expand therapy indications. This manuscript presents discussions on current evidence, future directions, and research gaps for HGNS therapy from the 10th International Surgical Sleep Society expert research panel.

Post-Operative Sleep Endoscopy with Target-Controlled Infusion After Palatopharyngoplasty for Obstructive Sleep Apnea: Anatomical and Polysomnographic Outcomes

INTRODUCTION

The findings of drug-induced sleep endoscopy (DISE) are not always correlated with the outcome of upper airway surgery for obstructive sleep apnea (OSA), and whether multilevel surgery is truly required in treating multilevel obstruction identified in preoperative DISE remains an issue. We attempted to compare DISE findings before and after palatopharyngoplasty in patients with OSA because changes in DISE may be beneficial to better understand polysomnographic and anatomical outcomes.

METHODS

This was a prospective cohort study for 34 patients with moderate to severe OSA who underwent palatopharyngoplasty at a tertiary care center from 2016 to 2018. We recorded the patients' demographic characteristics, procedures, and surgical outcomes and compared the preoperative and postoperative DISE staging patterns.

RESULTS

The apnea-hypopnea index (AHI) values of 34 adults improved significantly after surgery (40.6 ± 23.3 versus 25.6 ± 20.6, P < 0.001). The majority of patients, 26/34, had preoperative complete concentric collapse at the velum, and for most (20/26, 77%) there was a change of the collapse pattern into anteroposterior collapse postoperatively. Patients with postoperative velar collapse had higher follow-up AHI values than those who without (27.8 ± 21.9 versus 15.2 ± 7.7, P = 0.023). Patients with preoperative complete tongue base collapse had higher follow-up AHI values than did those with no or partial collapse (40.6 ± 21.0 versus 21.0 ± 18.6, P = 0.017). Patients with postoperative complete tongue base collapse also had higher follow-up AHI values than the others (42.7 ± 22.1 versus 18.5 ± 15.4, P = 0.001).

CONCLUSION

Palatopharyngoplasty could change the collapse pattern at the velum in most patients. Preoperative and postoperative complete tongue base collapse and postoperative velar collapse identified in TCI-DISE were associated with relatively poor outcomes.

Novel Intraoral Negative Airway Pressure in Drug-Induced Sleep Endoscopy with Target-Controlled Infusion

BACKGROUND

In intermittent negative airway pressure (iNAP) therapy, soft tissues are reshaped into a forward-resting position, thus reducing airway obstruction during sleep. This study investigated the effect of iNAP therapy that was administered during drug-induced sleep endoscopy with target-controlled infusion (TCI-DISE) in patients with obstructive sleep apnea (OSA) intolerant of continuous positive airway pressure (CPAP) therapy.

METHODS

This prospective case series study included 92 patients with polysomnography (PSG)-confirmed OSA who underwent TCI-DISE with iNAP from January 2018 to February 2020 at a tertiary referral hospital. Upper airway obstruction was evaluated and scored using the velum, oropharynx, tongue base, and epiglottis (VOTE) classification. Obstruction severity was assessed multiple times with the patient in the supine position with or without lateral rotation of the head and the application of iNAP therapy, respectively.

RESULTS

After the application of iNAP therapy in the supine position, obstruction severity decreased significantly: from complete or partial obstruction to partial or no obstruction in 37, 12, and 36 patients (40.2%, 13%, and 39%, respectively) with velar obstruction, oropharyngeal, and tongue base obstruction, respectively. After simultaneously applying iNAP therapy with head rotation, obstruction severity decreased in 47, 43, and 19 patients (51%, 47%, and 21%, respectively) with velar, tongue base, and epiglottic obstruction, respectively.

CONCLUSION

In TCI-DISE, we found that iNAP therapy relieved velar, oropharyngeal, and tongue base obstruction in the supine position in some patients. Moreover, iNAP therapy can be combined with positional therapy to alleviate velar, tongue base, and epiglottic obstruction in some patients. TCI-DISE can also be used to screen the possible responders for iNAP therapy because it is less time consuming than PSG.

Sleep medicine in otolaryngology units: an international survey

PURPOSE

No study to date has described the overall landscape of sleep disorders management and training in otolaryngology departments of different countries. The aim of our study was to investigate and compare settings, diagnostic and therapeutic approaches and training programmes.

METHODS

An international online survey was developed with the collaboration of the YO-IFOS (Young Otolaryngologists-International Federation of Otorhinolaryngological Societies) to assess the current practice of otolaryngologists in the management of sleep disorders. The survey also included a session dedicated to training.

RESULTS

A total of 126 otolaryngologists completed the survey. The larger part of responses was collected from Central/South America and Europe. The majority of responders from South/Central America (97%) declared to be certified as sleep specialist while 49% of Europeans stated the opposite. Of responders 83% perform a drug-induced sleep endoscopy (DISE) before planning a possible surgical intervention. Soft palate and base of tongue interventions were the most common procedure, respectively performed in 94% and 79% of the cases. Residents were allowed to perform soft palate surgery in 77% of the cases. Upper airway stimulation (26% vs 10%), trans-oral robotic surgery (36% vs 11%) and radiofrequency of the base of the tongue (58% vs 25%) were preferred more frequently by European responders. The highest caseloads of soft palate surgery and bi-maxillary advancement were registered in the academic institutions.

CONCLUSION

Significant concordance and few interesting divergences in diagnosis and treatment of sleep disorders were observed between nationalities and types of institution. Economic resources might have played a significant role in the therapeutic choice. Trainees' lack of exposure to certain interventions and to a sufficient caseload appeared to be the main burden to overcome.

Quality-of-life impact after in-office treatment of nasal valve obstruction with a radiofrequency device: 2-year results from a multicenter, prospective clinical trial

Background

Insufficiency of the nasal valve is increasingly being recognized as a cause of nasal airway obstruction. The condition is associated with many symptoms, including nasal congestion, sleep disturbance, snoring, and an overall decline in quality of life (QoL). An in‐office, minimally invasive radiofrequency treatment of the nasal valve has been associated with improved symptoms of nasal obstruction and patients’ QoL for a 6‐month period in a noncontrolled, prospective, single‐arm study. The purpose of this study was to determine whether the results achieved with radiofrequency treatment at 6 months would be sustained through 24 months.

Methods

Thirty‐nine adult patients from an original cohort of 49 patients with severe to extreme Nasal Obstruction Symptom Evaluation (NOSE) Scale scores and dynamic or static internal nasal valve obstruction as the primary or significant contributor to obstruction were studied. Patients received intranasal bilateral radiofrequency treatment in a clinical study with a follow‐up to 6 months, and were prospectively evaluated at 12, 18, and 24 months at 8 community‐based otolaryngology practices. The patient‐reported NOSE Scale score and 21 QoL questions were assessed.

Results

Clinically significant improvement from baseline in NOSE Scale score change demonstrated at 6 months (mean, 55.9; standard deviation [SD], 23.6; p < 0.0001) was maintained through 24 months (mean, 53.5; SD, 24.6; p < 0.0001). Responders (≥15‐point improvement) consisted of 92.3% of participants at 6 months and 97.2% at 24 months. Responses to the QoL questions also showed improvement in patients’ QoL.

Conclusion

Treatment of the nasal valve with an in‐office, transnasal temperature‐controlled radiofrequency procedure was associated with stable and lasting improvement in symptoms of nasal obstruction and QoL through 24 months in this noncontrolled, single‐arm study.

The faces of sleep apnea in the age of machine learning

Jacobowitz O, MacKay S. The faces of sleep apnea in the age of machine learning. J Clin Sleep Med . 2020;16(4):469–470.

A New Metric for Precision Medicine: PAP and Hypoglossal Neurostimulation

CITATION

Jacobowitz O, Woodson BT. A new metric for precision medicine: PAP and hypoglossal neurostimulation. J Clin Sleep Med. 2019;15(8):1079-1080.

In-office treatment of nasal valve obstruction using a novel, bipolar radiofrequency device

Objectives

To assess the safety and effectiveness of in‐office bipolar radiofrequency treatment of nasal valve obstruction

Study Design

Prospective, nonrandomized, multicenter case series

Methods

Adult patients with a Nasal Obstruction Symptom Evaluation scale (NOSE) score ≥60 were selected. Patients were clinically diagnosed with dynamic or static internal nasal valve obstruction as primary or significant contributor to obstruction and were required to have a positive response to nasal mechanical dilators or lateralization maneuvers. Bilateral radio‐frequency treatment was applied intranasally using a novel device, under local anesthesia in a single session. Safety and tolerance were assessed by event reporting, inspection, and Visual Analogue Scale (VAS) for pain. Efficacy was determined using the NOSE score and patient‐reported satisfaction survey at 26 weeks.

Results

Fifty patients were treated. No device or procedure‐related serious adverse events occurred. Soreness, edema, and crusting resolved by 1 month. The mean baseline NOSE score was 79.9 (SD 10.8, range 60–100), and all had severe or extreme obstruction. At 26 weeks, mean NOSE score was 69% lower at 24.7 (P < .0001) with 95% two‐sided confidence intervals 48.5 to 61.1 for decrease. The decrease in NOSE score did not differ significantly between patients who did or did not have prior nasal surgery. Patient satisfaction mean by survey was 8.2 of 10.

Conclusion

In office treatment of internal nasal valve obstruction using a bipolar radiofrequency device is safe and well‐tolerated. Nasal obstruction, as assessed using the NOSE questionnaire at 26 weeks, was markedly improved with high patient satisfaction.

Level of Evidence

2b, prospective cohort

Drug-Induced Sleep Endoscopy and Surgical Outcomes: A Multicenter Cohort Study

OBJECTIVE

To evaluate the association between findings of blinded reviews of preoperative drug-induced sleep endoscopy (DISE) examinations using the VOTE Classification and obstructive sleep apnea (OSA) surgical outcomes in a large multicenter, international cohort.

METHODS

Retrospective, multi-center cohort study of adults without tonsillar hypertrophy who underwent pharyngeal surgery for OSA. The study included only participants without enlarged tonsils. Four independent reviewers performed blinded review of preoperative DISE videos using the VOTE Classification system and scoring of a primary structure contributing to airway obstruction. DISE findings were examined for an association with surgical outcomes with univariate analyses and multiple regression.

RESULTS

Two hundred seventy-five study participants were included from 14 centers. Mean age was 51.4 ± 11.8 years, and body mass index was 30.1 ± 5.2 kg/m² . There was moderate interrater reliability (kappa = 0.40-0.60) for DISE findings. Oropharyngeal lateral wall-related obstruction was associated with poorer surgical outcomes (adjusted odds ratio (AOR) 0.51; 95% CI 0.27, 0.93). Complete tongue-related obstruction was associated with a lower odds of surgical response in moderate to severe OSA (AOR 0.52; 95% CI 0.28, 0.98), with findings that were similar but not statistically significant in other analyses. Surgical outcomes were not clearly associated with the degree and configuration of velum-related obstruction or the degree of epiglottis-related obstruction. Surgical response was associated with tonsil size and body mass index (inversely).

CONCLUSION

DISE findings concerning the oropharyngeal lateral walls and tongue may be the most important findings of this evaluation technique.

LEVEL OF EVIDENCE

2B Laryngoscope, 129:761-770, 2019.

Does Sleep Endoscopy Staging Pattern Correlate With Outcome of Advanced Palatopharyngoplasty for Moderate to Severe Obstructive Sleep Apnea?

STUDY OBJECTIVES

Although drug-induced sleep endoscopy (DISE) is an accepted method to localize upper airway obstruction, it is not known whether all sites identified by DISE must be treated to achieve sufficient apnea-hypopnea index (AHI) improvement. The aim of this study was to compare outcomes for unilevel (upper) versus multilevel DISE collapse patterns in a patient cohort that only underwent modern palatopharyngoplasty. Our hypothesis was that not all tongue base-level obstructions on DISE must be treated.

METHODS

Thirty-eight patients with mean AHI of 45 events/h underwent DISE followed by palatopharyngoplasty. Outcome was measured by polysomnography or home sleep apnea testing.

RESULTS

Eleven patients (29%) had multilevel, complete tongue base obstruction and nineteen (50%) had no obstruction. These two groups were similar in age, body mass index, and AHI; the complete group had smaller tonsils and higher tongue position. The postoperative success rate and AHI in the group without tongue base obstruction were not significantly different from those of the complete group (68%; 17.4 ± 11.0 versus 73%; 15.4 ± 20.5, P > .99). Seventeen patients (45%) had circumferential collapse of velum. The postoperative AHI was higher for patients with circumferential collapse (23.6 ± 15.8 from 55.3 ± 22.1 versus 10.5 ± 9.94 from 36.4 ± 16.7, P < .0001), but both groups had clinically and statistically significant AHI reductions.

CONCLUSIONS

Patients with multilevel obstruction on DISE, treated with palatopharyngoplasty alone, had similar AHI outcome as those with unilevel obstruction. Multilevel surgery may not be needed in some patients with a multilevel obstruction pattern. Circumferential collapse of velum, however, was associated with a higher residual AHI.

Advances in Oral Appliances for Obstructive Sleep Apnea

Oral appliances that advance the mandible are widely used as alternatives to positive airway pressure (PAP) devices or as primary therapy for obstructive sleep apnea (OSA) in adults. Although PAP is more efficacious at lowering the polysomnographic indices of OSA, the clinical effectiveness of PAP and oral appliances is similar, and patients are more likely to adhere to oral appliance therapy than to PAP treatment. Clinical examination is used to determine the candidacy of oral appliances and to select a particular appliance for a given patient. Endoscopic examination of the pharynx may be used to help assess the potential for efficacy. Otherwise, if available, titration of mandibular protrusion during sleep may be performed prior to appliance production in order to assess efficacy. Once a patient is fitted with a titratable oral appliance, further advancement is usually performed at home to resolve the clinical symptoms and signs of OSA. Clinical follow-up is needed to assess the outcome, side effects, and adherence, as the long-term adherence rate is approximately 50%. Recent advances in oral appliance therapy include the development of embedded temperature sensors for adherence monitoring and the production of thinner, lighter appliances via 3D printing techniques.

Quality measures for the care of adult patients with obstructive sleep apnea

ABSTRACT

Obstructive sleep apnea (OSA) is a prevalent disorder associated with a multitude of adverse outcomes when left untreated. There is significant heterogeneity in the evaluation and management of OSA resulting in variation in cost and outcomes. Thus, the goal for developing these measures was to have a way to evaluate the outcomes and reliability of the processes involved with the standard care approaches used in the diagnosis and management of OSA. The OSA quality care measures presented here focus on both outcomes and processes. The AASM commissioned the Adult OSA Quality Measures Workgroup to develop quality care measures aimed at optimizing care for adult patients with OSA. These quality care measures developed by the Adult OSA Quality Measures Workgroup are an extension of the original Centers for Medicare & Medicaid Services (CMS) approved Physician Quality Reporting System (PQRS) measures group for OSA. The measures are based on the available scientific evidence, focus on public safety, and strive to improve quality of life and cardiovascular outcomes for individual OSA patients. The three outcomes that were selected were as follows: (1) improve disease detection and categorization; (2) improve quality of life; and (3) reduce cardiovascular risk. After selecting these relevant outcomes, a total of ten process measures were chosen that could be applied and assessed for the purpose of accomplishing these outcomes. In the future, the measures described in this document may be reported through the PQRS in addition to, or as a replacement for, the current OSA measures group. The overall objective for the development of these measures is that implementation of these quality measures will result in improved patient outcomes, reduce the public health burden of OSA, and provide a measurable standard for evaluating and managing OSA.

Targeted Stimulation of the Hypoglossal Nerve for Treatment of Obstructive Sleep Apnea

Objectives:

Determine safety and effectiveness of targeted hypoglossal neurostimulation sleep therapy system for obstructive sleep apnea (OSA). Titration with multi-contact electrode and multi-channel pulse generator (IPG) allows stimulation of multiple areas of the proximal hypoglossal nerve permitting identification of optimal tongue position in each patient.

Methods:

A total of 105 adults were screened in this prospective, multicenter, single-arm study. Inclusion criteria were continuous positive airway pressure (CPAP) failure/intolerance, apnea hypopnea index (AHI) > 20, and body mass index (BMI) > 37. 56 patients meeting inclusion/exclusion criteria were surgically implanted with the unilateral hypoglossal nerve stimulator electrode and IPG (aura6000TM System, Imthera Medical, San Diego). Patients were evaluated at 1, 3, 6, and 12 months. Outcomes included AHI, oxygen desaturation index (ODI), Epworth Sleepiness Scale (ESS), Sleep Apnea Quality of Life Index, and EQ-5D quality of life questionnaire.

Results:

Postsurgical transient tongue paresis was observed in 5 out of 56 patients (8.9%); all resolved spontaneously. Four patients withdrew, leaving 52 subjects to complete the study by September 2014. All were male, with mean age of 54.8 ± 10.6 years, and mean BMI of 30.4 ± 3.6. Preliminary data at month 3 showed significant decrease in AHI by 43.7% from 50.5 ± 18.4 to 26.7 ± 19.8 ( P < .001) and significant improvement in ESS from 12.4 ± 4.0 to 9.1 ± 4.5 ( P < .001).

Conclusions:

Surgical implantation of targeted hypoglossal neurostimulation sleep therapy system appears to be a safe and practical treatment option for OSA. Preliminary data shows significant improvement in objective and subjective outcomes. Final safety and effectiveness will be determined.

Hypoglossal Nerve Stimulation Therapy for Obstructive Sleep Apnea

Program Description:

Obstructive sleep apnea (OSA) significantly affects sleep, daytime function, quality of life, public safety, and cardiovascular risk. Although positive pressure remains the primary treatment, suboptimal adherence rates necessitate alternative treatment strategies. Hypoglossal nerve stimulation is a new and emerging treatment option with published prospective clinical trial data. Sleep-boarded otolaryngologists will review the physiology and basic science of upper airway stimulation, demonstrate the current technology and surgical procedure, present safety and efficacy data from recent multicenter clinical trials, and discuss patient selection and cost-effectiveness. A panel will explore future directions and the advantages/disadvantages of this technology as it compares to other sleep apnea treatment options.

Educational Objectives:

(1) Examine the pathophysiology of OSA with a particular focus on the neuromuscular control mechanisms. (2) Interpret the basic science and feasibility studies on hypoglossal nerve stimulation and describe the current technology and surgical procedure. (3) Report the safety, efficacy, and cost-effectiveness data from published prospective multicenter clinical trials.

Surgical reconstruction of the upper airway for obstructive sleep apnea

Positive airway pressure can be effective for OSA treatment but is not effectively used by many patients. Surgical reconstruction of the airway is appropriate for patients who are not otherwise effectively treated or as first-line treatment for patients with focal airway lesions. For surgical planning, examination schemes of the awake patient, as well as sleep endoscopy may be used. Nasal surgery may facilitate treatment using positive airway pressure or oral appliances or to improve quality of life. Pharyngoplasty and tongue base techniques for therapeutic upper airway reconstruction may be performed staged or simultaneously. Current and future approaches are described.

Tongue anatomy and physiology, the scientific basis for a novel targeted neurostimulation system designed for the treatment of obstructive sleep apnea

INTRODUCTION

 Obstructive sleep apnea (OSA) is a chronic condition that affects millions adults. The effective standard treatment is positive airway pressure (PAP). However, approximately half of the patients that are prescribed PAP are unable or unwilling to comply with this therapy. Untreated OSA ultimately leads to very serious comorbidities. An alternative therapy for this patient population, therefore, is desirable. Hypoglossal nerve (HGN) stimulation is under investigation by multiple groups as a possible alternative therapy for OSA.

OBJECTIVE

To understand the underlying mechanisms of actions related to HGN stimulation, and the implication of this knowledge for specifying and designing a neurostimulation system for the treatment of OSA.

RESULTS

 Loss of lingual and pharyngeal tone within a narrow airway is the primary mechanism for OSA. Posterior and anterior tongues are different in their anatomy and physiology. Muscle fibers in the posterior tongue are predominantly fatigue resistant that are responsible for the long sustained tonic activities required for maintaining the tongue's position and preventing its mass from falling into the retroglossal airway. The human tongue is a muscular hydrostat and hence would benefit from a sophisticated HGN stimulation system that is capable of achieving a concerted spatio-temporal interplay of multiple lingual muscles, including retrusors.

CONCLUSION

 Targeted neurostimulation of the proximal HGN presents as a viable system approach that is far more versatile and physiologic and quite different than prior systems.

Palatal and tongue base surgery for surgical treatment of obstructive sleep apnea: a prospective study

OBJECTIVE

To assess the effect of concurrent uvulopalatopharyngoplasty (UPPP) and hypopharyngeal procedures in obstructive sleep apnea (OSA) patients with diffuse airway narrowing.

STUDY DESIGN AND SETTING

Forty-eight patients were treated surgically by a single surgeon in private practice over 2 years. Symptoms, Epworth score, and polysomnographic outcome were assessed preoperatively and postoperatively. The Friedman staging system was applied. UPPP with genioglossus advancement, hyoid suspension, or radiofrequency treatment was carried out.

RESULTS

In 37 patients with complete data, the average apnea-hypopnea index (AHI) was reduced from 46.5 +/- 24.8 to 14.9 +/- 16.8. The Epworth score was reduced from 12.1 +/- 4.9 to 6.7 +/- 3.7. Most patients reported improved sleep quality, alertness, memory, concentration, and mood.

CONCLUSION

Successful outcome, defined by symptom and AHI reduction, was achieved with multilevel surgery for most patients with advanced Friedman stages 2 and 3.

SIGNIFICANCE

Multilevel surgery seems effective in treating severe OSA patients with diffuse airway narrowing.

EBM RATING

C-4.

Prevention of headache after retrosigmoid removal of acoustic tumors

OBJECTIVE

To demonstrate a causal relationship between bone dust and the development of headache after retrosigmoid removal of acoustic neuromas.

STUDY DESIGN

The study design was both retrospective (group I) and prospective (groups 2 and 3).

SETTING

Tertiary Care Referral Center/Outpatient Data Collection.

PATIENTS

Eighty-four consecutive patients underwent surgery at the Mount Sinai Medical Center in New York by the same surgical team.

INTERVENTION

All patients underwent retrosigmoid removal of acoustic neuromas via the following methods: group 1, standard excision; group 2, excision and cranioplasty; group 3, excision, cranioplasty, and residue trapping.

MAIN OUTCOME MEASURE

Presence or absence of postoperative headache.

RESULTS

In all, 43 patients (51%) reported postoperative headache. By groups, headache incidence was 64% for group 1 (43% grade 3-4), 81% for group 2 (37% grade 3-4), and 10% (all grade 1) for group 3. Differences with respect to headache incidence and severity were statically significant between groups 1 and 3, and between groups 2 and 3 (p < 0.001).

CONCLUSIONS

Free circulation of bone dust into the posterior fossa during intradural drilling of the internal auditory canal may be the most important factor in the development of headache after this surgical procedure.

Distinct characteristics of the basal activities of adenylyl cyclases 2 and 6

Regulation of basal activities of adenylyl cyclase (AC) 2 and 6, expressed in Sf9 cells by infection with recombinant baculovirus, was studied. An antipeptide antibody that recognizes AC2 and AC6 with equal sensitivity was used to establish that equivalent levels were expressed. Basal activities of AC2 and AC6 were compared at varying concentrations of Mg2+ or Mn2+ ions; AC2 had 15- and 10-fold greater activity than AC6, respectively. At 20 mM Mg2+, the Km values for ATP were 88 and 39 microM for AC2 and AC6, respectively, whereas their Vmax values were 281 and 11 pmol/mg protein.min. With 100 microM forskolin and either Mg2+ or Mn2+, the difference in activities between AC2 and AC6 was reduced to approximately 2-fold. Forskolin stimulated AC6 greater than 40-fold at 0.5-2 mM Mg2+, whereas AC2 was stimulated 4-6-fold. At 20 mM Mg2+, AC2 was stimulated 2-fold by forskolin, whereas AC6 was stimulated 18-fold. With Mg2+ alone, activities of AC2 and AC6 were not saturable up to 20 mM and yielded curvilinear Hofstee transformations. With forskolin, activities of both AC2 and AC6 were saturable by 10 mM Mg2+ and yielded linear Hofstee transformations. These data indicate that there are substantial differences in the basal enzymatic activities of adenylyl cyclase isoforms, due to differential regulation by Mg2+ ions rather than intrinsic catalytic capabilities. Thus the presence and relative abundance of adenylyl cyclase subtypes could greatly affect the resting cellular cAMP levels with consequent effects on important biological functions, such as differentiation and proliferation.

Phorbol ester-induced stimulation and phosphorylation of adenylyl cyclase 2

Adenylyl cyclase 2 was expressed in Sf9 cells by recombinant baculovirus infection. Phorbol 12-myristate 13-acetate (PMA) treatment of cells expressing adenylyl cyclase 2 (AC2) increased basal activity. This increase was blocked by staurosporine, a protein kinase C inhibitor. PMA treatment increased Vmax without affecting Km. Greatest increase in basal activity was seen at physiologically relevant Mg2+ concentrations. PMA treatment did not alter sensitivity to guanine nucleotide stimulatory factor (Gs) but enhanced stimulation at all concentrations of activated Gs alpha subunit tested. AC2 was tagged at the N terminus with an 8-amino acid epitope. Epitope-tagged AC2 was purified to apparent homogeneity in a single step by using an antiepitope antibody-affinity column. The eluate was resolved by SDS/PAGE. Silver staining of the gel showed a 106-kDa band. The purified protein was recognized by antipeptide antibody against a region common to all mammalian adenylyl cyclases. The epitope-tagged enzyme expressed in Sf9 cells was also stimulated by PMA. When cells were labeled with 32P and treated with PMA, a 3-fold increase in 32P incorporation of purified epitope-tagged AC2 was observed. We conclude that activation of protein kinase C results in phosphorylation and stimulation of AC2, a cell-surface G protein effector enzyme. Thus, covalent modification of cell-surface effectors may provide an independent mode for signal transmission through G protein pathways.

Signal recognition and integration by Gs-stimulated adenylyl cyclases

Six Gs-stimulated adenylyl cyclases have been cloned. Two additional forms have been identified as partial cDNAs. These adenylyl cyclases have distinct functional properties and are differentially regulated by protein kinases. The adenylyl cyclases have distinct patterns of distribution in peripheral tissues and various brain regions. The unique functional characteristics of the members of this effector family may allow each cell type and/or brain region to customize the signal-recognition and integrative properties of its cAMP-generation system by varying the ratios of the various adenylyl cyclases.

Stimulation of specific types of Gs-stimulated adenylyl cyclases by phorbol ester treatment

Regulation of adenylyl cyclases by protein kinase C was studied. Types 1-6 were transiently expressed in 293 cells. The cells were treated with 4 beta-phorbol 12-myristate 13-acetate (PMA), and adenylyl cyclase activity was measured. PMA treatment of untransfected or vector-transfected cells resulted in a 35% (mean) increase in basal and forskolin-stimulated activity. PMA treatment of type 2 enzyme-transfected cells showed a 3-fold increase in basal activity. This stimulation varied with Mg2+ concentration with up to 4.5-fold increases at low Mg2+. PMA treatment resulted in about a 60% increase in fluoride or GTP gamma S (guanosine 5'-O-(thiotriphosphate))-stimulated activity in type 2 enzyme-transfected cells. Expression of the type 1 and 3 enzymes resulted in pronounced Ca2+/calmodulin stimulation, which was significantly increased upon pretreatment with PMA. No effects of PMA treatment were observable on other activities of the type 1 enzyme, whereas all activities of the type 3 enzymes were stimulated. Expressed types 4, 5, and 6 enzymes showed modest (approximately 30%) or no increases in basal and forskolin-stimulated activities upon PMA treatment. These data indicate that specific types of adenylyl cyclases can be functional targets for protein kinase C. The pronounced effects on the basal activity of the type 2 enzyme suggest this adenylyl cyclase could in the appropriate environment be an intracellular signal generator for external signals not routed through the activation of Gs.

Lowered responsiveness of the catalyst of adenylyl cyclase to stimulation by GS in heterologous desensitization: a role for adenosine 3',5'-monophosphate-dependent phosphorylation

Treatment of chick hepatocytes with glucagon results in homologous and heterologous desensitization of the receptor-stimulated adenylyl cyclase. The loci of postreceptor heterologous desensitization was studied. The addition of excess purified GS to glucagon-desensitized hepatocyte membranes did not fully restore fluoride stimulation of adenylyl cyclase, even though the absolute activity was increased at least 2-fold. Treatment of chick hepatocytes with 8-bromo-cAMP resulted in a similar reduction of fluoride stimulation that could not be restored by the addition of purified GS. When membranes from control and glucagon-treated hepatocytes were treated with purified catalytic subunit of protein kinase-A (PKA), fluoride stimulation was lowered in control, but not glucagon-treated, membranes. Treatment of membranes from S49 kin- lymphoma cells with PKA also resulted in decreased fluoride- and forskolin-stimulated adenylyl cyclase activity, but activity stimulated by Mn2+ was not altered. Since previous studies from our laboratory had shown that GS and G(i) are not substrates for protein kinase-A, it appears that the catalyst of adenylyl cyclase is the likely locus of modulation. To determine if both chick hepatocytes and S49 cells contain similar types of adenylyl cyclase that could account for the similar PKA regulatory properties, we used polymerase chain reaction-based techniques to identify GS-stimulated adenylyl cyclases present in these systems. The chick liver contains both type 5 and type 6 adenylyl cyclases, while S49 cells contain the type 6 enzyme. Type 5 and 6 adenylyl cyclases are members of one widely expressed subfamily of mammalian GS-responsive adenylyl cyclases and share a predicted PKA phosphorylation site in the central cytoplasmic loop. This site is not found in other known adenylyl cyclases (types 1-4), although the olfactory-specific type 3 enzyme has a predicted site nearby. These data indicate that one component of hormone-induced desensitization of the adenylyl cyclase system can be at the level of the catalyst, where PKA-mediated phosphorylation could result in lowered responsiveness. The types 5 and 6 adenylyl cyclases are likely candidates for such regulation.