Technical-Surgical Interventions for Sleep Apnea

Edwin M. Valladares

LEARNING OBJECTIVES

On completion of this chapter, the reader should be able to:

1. Explain technical-surgical therapy for obstructive sleep apnea by way of hypoglossal nerve stimulation.
2. Identify the anatomy of the airway associated with obstructive sleep apnea.
3. Identify upper airway collapse as shown by drug-induced sleep endoscopy.
4. Explain technical-surgical therapy for central sleep apnea by way of phrenic nerve stimulation.
5. Identify the role of the sleep technologist in technical-surgical interventions.

INTRODUCTION

Continuous positive airway pressure (CPAP) has been the first-line intervention for treating patients with moderate-to-severe sleep apnea since 1981 (1). With approximately 29% to 83% of adult patients unable to meet minimum CPAP therapy adherence criteria (4 hours or more per night for 70% of nights), alternatives to traditional pressure mask-based therapies have long been sought (2, 3, 4). As a result, surgical interventions have been developed, but they can’t be used without selecting the correct patient for optimal benefit (5). Thus, sleep medicine is moving toward personalized interventions for optimal therapy. Technical-surgical interventions are one such example. I call these therapies technical-surgical interventions because they involve a surgical implantation of a device and technical therapy management.

With the advent of new Food and Drug Administration (FDA)-approved implantable stimulators for treating sleep-disordered breathing in a fraction of non-compliant PAP therapy patients, the landscape of sleep medicine and sleep technology is changing to narrow the gap between compliant and noncompliant patients (6, 7). The Inspire upper airway stimulation (UAS) therapy for treating obstructive sleep apnea (OSA) and the remedē ® System for treating central sleep apnea (CSA) are providing new tools for sleep physicians, thus elevating the expertise of sleep technologists and paving the way for personalized medicine.

TECHNICAL-SURGICAL INTERVENTION FOR OSA

In 2014, the FDA approved the Inspire UAS therapy for the treatment of OSA. This therapy provides a feasible option for treating a subset of patients with OSA (7). Although these devices will not be appropriate for all of the PAP-intolerant patients, careful selection criteria make the Inspire UAS therapy a viable option for a small but growing percentage of patients. As of November 2016, Inspire Medical, Inc. had reportedly implanted approximately 1,000 patients (8).

The Inspire UAS therapy is for patients with moderate-to-severe OSA (apnea-hypopnea index [AHI] 15 to 65 per hour) who have not been able to tolerate CPAP therapy and do not have concentric collapse of the upper airway. The Inspire UAS therapy stimulates the hypoglossal nerve during inspiration and moves the tongue base forward to open the upper airway. The UAS therapy stimulates on the basis of signaling from the sensing lead’s breathing information. The patient uses
an external wireless remote to turn the therapy “on,” “off,” “pause,” and to control stimulation intensity across a limited programmed range (9).

Inspire UAS Therapy: Components, Function, and Indications

The Inspire UAS therapy is composed of a neurostimulator with 1-stimulating lead to provide coordinated tongue protrusion and 1-monitoring sensing lead. The stimulator lead is connected to the hypoglossal nerve (XII), specifically on the medial-XII branch, and the sensing lead is connected to the upper border of the underlying rib in the fourth intercostal region to gate the hypoglossal nerve stimulation to inspiration. The device is accessed through an electronic tablet and interrogation component (see Fig. 53-1) (10). The estimated battery life of the neurostimulator is 10.9 years (11).

The criteria for being implanted are as follows: (1) have tried CPAP and failed, (2) have drug-induced sleep endoscopy (DISE) to rule out concentric collapse at the palate, (3) have an AHI 15 to 65 per hour, and (4) have a body mass index less than 32 kg per m². These criteria narrow the therapy to a subset of noncompliant PAP therapy patients. Contraindications for implanting the Inspire UAS therapy are as follows: central + mixed apneas greater than 25% of total AHI, any anatomic finding that would compromise the performance of the therapy (e.g., concentric collapse), any condition or procedure that has compromised the neurologic control of the upper airway, patients who are unable or do not have the necessary assistance to operate the sleep remote, pregnancy or plan to become pregnant, implantable device that may unintentionally interact with the Inspire system, and patients requiring magnetic resonance imaging (MRI) other than the specified MR conditional labeling (Inspire system implant manual) (11).

Figure 53-1 Inspire upper airway stimulation therapy components for treatment of obstructive sleep apnea. (Image courtesy of Inspire Medical Systems, Inc. and Edwin M. Valladares, MS, RPSGT, Manager, USC Sleep Disorders Center, Keck Medical Center of USC, University of Southern California.)

Airway evaluation through DISE has become a good predictor of success for UAS therapy (12). DISE is conducted in an operating room where sleep is induced using a sedative, such as Propofol, to mimic airway collapse during sleep and characterize the airway collapse using a fiber-optic laryngoscope. The sedative is used to the lowest dose, which elicits loss of consciousness as measured by loss of response to normal conversational voice stimulation, while monitoring vital signs. Because this is a procedure conducted in an operating room, a team of nurses assists with monitoring the patient’s vitals (13). It has been shown that patients with concentric collapse of the palate do not do well with UAS therapy, as opposed to other types of collapse, thereby suggesting that tongue protrusion from UAS is insufficient to overcome airway obstruction in concentric collapse (see Figs. 53-2 and 53-3) (12). Figure 53-3 demonstrates examples of (a) an open airway, (b) lateral wall collapse, and (c) concentric collapse.

Inspire UAS Therapy: Patient Process

A trained otolaryngologist implants the Inspire UAS therapy and is subsequently followed at the sleep clinic by a sleep physician. The patient meets with a trained sleep physician and a trained sleep technologist to activate the device 1 month postimplant. This is the visit when the patient feels the stimulation for the first time
and two major parameters are established. The first parameter is the sensing threshold. The sensing threshold is the lowest voltage at which the patient “senses” an impulse from the device. The second parameter is the functional threshold, which is the voltage where the patient’s hypoglossal nerve is stimulated enough to protrude the tongue past the lower teeth. The patient is then sent home with a range of “functional threshold + 10 tenths of a voltage” (e.g., 2.1 to 3.0 V). The patient is asked to try to increase the voltage by 0.1 V every three to four nights to become acclimated to the therapy. A month after this activation visit, the patient comes into the sleep lab to be formally titrated by a trained sleep technologist (9, 11). The Inspire UAS therapy has a
stimulation range from 0.1 to 5.0 V. Settings for each patient can vary, given differences in upper airway physiology (11, 14).

Figure 53-2 Anatomy of the upper airway. (Image courtesy of Krishna Nayak, PhD, Professor, Ming Hsieh Department of Electrical Engineering, Viterbi School of Engineering, University of Southern California.)

Figure 53-3 Images of the palate during drug-induced sleep endoscopy. A: No collapse, (B) lateral wall collapse, and (C) concentric collapse. (Images courtesy of Eric J. Kezirian, MD, MPH, USC Caruso Department of Otolaryngology—Head & Neck Surgery, Keck School of Medicine of USC; with permission from Valladares, E. M., & Hammond, T. C. (2018). Novel therapies for sleep apnea—The implants have arrived! The Neurodiagnostic Journal. Copyright © ASET—The Neurodiagnostic Society, www.aset.org. Reprinted by permission of Taylor & Francis Ltd, http://www.tandfonline.com, on behalf of ASET—The Neurodiagnostic Society.)

Inspire UAS therapy titration has an immediate effect on the upper airway when compared with CPAP titration. This immediate effect is due to the change in the physical upper airway evoked by hypoglossal nerve stimulation, as opposed to a more gradual effect from a CPAP setting increase (15). Although supine sleep during a titration is always ideal to eliminate respiratory events as a worst-case scenario, most of the emphasis during an Inspire titration is in identifying the optimal voltage when the patient is sleeping in a comfortable position because the patient has not been able to use CPAP (9). This may result in the patient being sent home with lateral sleep settings. However, stimulation can be raised at a later time once the patient acclimates to the therapy and shows the need for supine titration. Once the patient is sent home with a range of voltages, the patient meets with the sleep physician to further discuss settings, expectations, and follow-up (11).

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