Beyond CPAP: modifying upper airway output for the treatment of OSA

Obstructive Sleep Apnea (OSA) is exceedingly common but often under-treated. Continuous positive airway pressure (CPAP) has long been considered the gold standard of OSA therapy. Limitations to CPAP therapy include adherence and availability. The 2021 global CPAP shortage highlighted the need to tailor patient treatments beyond CPAP alone. Common CPAP alternative approaches include positional therapy, mandibular advancement devices, and upper airway surgery. Upper airway training consists of a variety of therapies, including exercise regimens, external neuromuscular electrical stimulation, and woodwind instruments. More invasive approaches include hypoglossal nerve stimulation devices. This review will focus on the approaches for modifying upper airway muscle behavior as a therapeutic modality in OSA

Dilation of the oropharynx via selective stimulation of the hypoglossal nerve

Obstructive sleep apnea (OSA) is caused by the retraction of the tongue to occlude the upper airway (UAW). Electrical stimulation of the tongue protrudor and retractor muscle has been demonstrated as an effective technique to alleviate UAW obstructions and is considered to be a potential treatment for OSA. Recent studies have shown that selective stimulation of the hypoglossal nerve (HG) to activate tongue muscles using a single implantable device presents an attractive approach for treating OSA. In this study, the functional outcome of selective hypoglossal nerve stimulation with a multi-contact peripheral nerve electrode was studied by imaging the airway in anesthetized beagles. A pulse train of varying amplitude was applied through each one of the tripolar contact sets of the nerve electrode while the pharyngeal images were acquired via a video grabber into a computer. For the open mouth positions, the tongue activation patterns were also viewed and videotaped with a digital camcorder through the mouth. The percent dilation of the pharyngeal opening for each contact was calculated. The images show that stimulations delivered through the electrode contacts placed around the HG nerve trunk can generate several different activation patterns of the tongue muscles. Some of these patterns translate into a substantial increase in the oropharyngeal size, while others do not have any effect on the pharynx. The activation patterns vary as a function of the head position and the lower jaw. These results suggest that selective nerve stimulation can be a useful technique to maximize the effects of HG nerve stimulation in removing the obstructions in sleep apnea patients

The effects of mild hypoxia on hypoglossal motoneurones in neonates

The patency of the upper airway is dependent on the activity of the genioglossus muscle, the main protrusor muscle of the tongue. The force generated by this muscle opposes the negative intraluminal pressure produced by the contraction of the diaphragm during inspiration. Recent studies suggest that there is an immaturity in genioglossus muscle control in neonates and obstructive apnoea may occur when the activity of this muscle is reduced or absent without a corresponding decrease in the activity of the diaphragm. However, little is known of the processes mediating and influencing the activity of the hypoglossal nerve, the motor nerve of the genioglossus muscle, at this stage in development. In newborn babies, central apnoea (when there is no inspiratory effort) is usually followed by obstructive apnoea (when although there is inspiratory effort there is no inspiratory flow). It is therefore possible that hypoxia which develops during central apnoea, inhibits the activity of the genioglossus muscle and as a consequence the airway becomes obstructed. The aim of this study was therefore to determine whether hypoglossal motoneurones are inhibited during hypoxia in neonates. This study has investigated the effect of mild levels of hypoxaemia (PaO2 47.2 ± 3.8mmHg) on the activity of hypoglossal motoneurones in anaesthetized neonatal kittens (27 days old). The results showed that the majority of hypoglossal motoneurones increased in discharge frequency during hypoxia but for a substantial proportion the increase was only transient. Furthermore, some motoneurones showed a decrease in discharge frequency. Intracellular recordings showed that during similar levels of hypoxia, although a large proportion of the motoneurones were depolarized, at least some of these repolarized despite the continuing hypoxia. In addition, some hypoglossal motoneurones were hyperpolarized. This is the clearest evidence that inhibitory mechanisms, in addition to excitatory mechanisms, mediate the effects of hypoxia on hypoglossal output in neonates. Furthermore, the results suggest that hypoxia has an effect on the hypoglossal motoneurones independently of, or in addition to, its effect through respiratory rhythm. In some preliminary studies, the transmembrane input resistance increased during the hyperpolarization in response to hypoxia. One possibility is that the inhibition is mediated by the removal of an excitatory input. If the inhibition found in this study occurs in human babies it may be a compounding factor in apnoeas of the newborn

Die Therapie schlafbezogener Atmungsstörungen mit Hilfe eines den Unterkiefer protrudierenden Schienensystems

50 Patienten wurden mit einem herausnehmbaren unterkiefervorverlagernden Schienensystem im Zeitraum der Jahre 2000 bis 2002 behandelt. Die schlafmedizinisch-diagnostischen Untersuchungen vor Therapiebeginn erfolgten bei 25 Patienten ambulant und bei den anderen 25 Patienten stationär. Es wurden schlafmedizinischen Parameter zur Diagnosestellung herangezogen. Hälftig bestanden bei diesen Patienten die schlafmedizinische Diagnosen einer Rhonchopathie (reine Schnarcher, ohne internistische Besonderheiten) und einer leicht bis mittelgradigen obstruktiven Schlafapnoe. Bei 23 Patienten mit einer Rhonchopathie wurde das Funktionsprinzip der Unterkiefervorverlagerung durch den Wilcoxon-Test bei der Veränderung der schlafmedizinischen Parameter Entsättigungsindex, Schnarchindex, Anzahl der Entsättigungen und niederste Entsättigung bestätigt. Bei zwei (8%) der 25 Patienten veränderten sich die Parameter nicht positiv, so dass die Schienentherapie abgebrochen wurde. Bei 20 Patienten mit leicht- bis mittelgradiger Schlafapnoe bestätigte der Wilcoxon-Test die Signifikanz der Veränderungen bei den polysomnographischen Werten AHI , REM und Schlafeffizienz. Die Signifkanzschranke wurde bei dem somnologischem Wert Tiefschlaf nicht erreicht. Obgleich bei 13 Patienten die Schienentherapie aus unterschiedlichen Gründen innerhalb der zwei Untersuchungsjahre abgebrochen werden musste, wurde die Behandlung bei den 37 verbliebenen Patienten (74%) als erfolgreich und zufriedenstellend eingeschätzt