Genioglossus reflex responses to negative upper airway pressure are altered in people with tetraplegia and obstructive sleep apnoea

Abstract

More than 60% of people with tetraplegia have obstructive sleep apnoea (OSA). However, the specific causes are unknown. Genioglossus, the largest upper-airway dilator muscle, is important in maintaining upper-airway patency. Impaired genioglossus muscle function following spinal cord injury may contribute to OSA. This study aimed to determine if genioglossus reflex responses to negative upper-airway pressure are altered in people with OSA and tetraplegia compared to non-neurologically impaired able-bodied individuals with OSA. Genioglossus reflex responses measured via intramuscular electrodes to ∼60 brief (250 ms) pulses of negative upper-airway pressure (∼-15 cmH O at the mask) were compared between 13 participants (2 females) with tetraplegia plus OSA and 9 able-bodied controls (2 females) matched for age and OSA severity. The initial short-latency excitatory reflex response was absent in 6/13 people with tetraplegia and 1/9 controls. Genioglossus reflex inhibition in the absence of excitation was observed in three people with tetraplegia and none of the controls. When the excitatory response was present, it was significantly delayed in the tetraplegia group compared to able-bodied controls: excitation onset latency (mean ± SD) was 32 ± 16 vs. 18 ± 9 ms, P = 0.045; peak excitation latency was 48 ± 17 vs. 33 ± 8 ms, P = 0.038. However, when present, amplitude of the excitation response was not different between groups, 195 ± 26 vs. 219 ± 98% at baseline, P = 0.55. There are major differences in genioglossus reflex morphology and timing in response to rapid changes in airway pressure in people with tetraplegia and OSA. Altered genioglossus function may contribute to the increased risk of OSA in people with tetraplegia. The precise mechanisms mediating these differences are unknown.

Changes in pharyngeal collapsibility and genioglossus reflex responses to negative pressure during the respiratory cycle in obstructive sleep apnoea

“…The delayed reflex latency during expiration in the current study was similar in magnitude to that recently reported in people with OSA and tetraplegia (Wijesuriya et al . ) to negative pressure pulses delivered during early inspiration (excitation onset both 32 ms). In addition, there were two instances of reflex inhibition before excitation during expiration in the current study.…”

“…Recent studies also highlight changes in genioglossus reflex responses to negative pressure pulses in people with tetraplegia and OSA, which may be an important contributor to OSA in many of these individuals (Wijesuriya et al . ). Earlier studies (Woodall et al .…”

“…However, secondary genioglossus reflex suppression varies with sleep stage with more pronounced suppression in non-REM sleep compared to wakefulness and marked suppression during REM sleep when OSA tends to be most severe (Eckert et al 2007). Recent studies also highlight changes in genioglossus reflex responses to negative pressure pulses in people with tetraplegia and OSA, which may be an important contributor to OSA in many of these individuals (Wijesuriya et al 2018). Earlier studies (Woodall et al 1989;Horner et al 1991;Wheatley & White, 1993;Tantucci et al 1998) have shown differences in the genioglossus reflex depending on the timing of the negative pressure with the most robust responses during end expiration and early inspiration.…”

Intermittent hypoxia: friend or foe?

“…As a result, prevalence of obstructive sleep apnoea is greater in patients with spinal cord injury as compared to the general population (Wijesuriya et al . ). Therefore, does intermittent hypoxia provoke greater increase of frequency and duration of apnoeic/hypopnoeic events in patients with spinal cord injury than in subjects without it?…”

How does spinal cord injury lead to obstructive sleep apnoea?

“…The underlying mechanisms may also dynamically change during progression from acute to chronic SCI. A new report in this issue of The Journal of Physiology from Wijesuriya and colleagues sheds new light on this complex physiological question (Wijesuriya et al 2018). The electryomographic activity of an important pharyngeal dilator muscle -the genioglossus (GG) -was studied in two groups of individuals with OSA.…”