Overnight Rostral Fluid Shift in the Pathogenesis of Obstructive Sleep Apnea in Spinal Cord Injured Patients

Detailed Summary

Obstructive Sleep Apnea (OSA), a common disorder resulting from repetitive pharyngeal collapse during sleep, is multifactorial. Usually, OSA is considered primarily a problem of upper airway anatomy, with the craniofacial structure or neck fat decreasing the size of the pharyngeal airway lumen. Obesity, male sex and genetics are well established pathogenic factors. In the last decade rostral fluid displacement (fluid shift) to explain the pathogenesis of upper airway collapsibility has been increasingly studied. Individuals living with spinal cord injury are at increased risk for OSA, with a prevalence that is three- to fourfold higher than the general population. Individual with acute tetraplegia and undiagnosed or untreated OSA may participate less in rehabilitation due to sleepiness and fatigue and therefore be less engaged in activities that improve quality of life and maintain functioning over time. Intermittent hypoxia, sleep fragmentation and alterations of the autonomous nervous system induced by OSA are thought to delay or limit recovery and in the long term, increase cardio- and cerebrovascular morbi-mortality. Redolfi et al have shown that overnight change in leg fluid volume correlated strongly with the Apnea Hypopnea index (AHI) and the time spent sitting. In SCI patients two mechanisms may underline fluid shift importance in the pathogenesis of OSA: first, time spent sitting is obviously increased in patients with no walking abilities (prolonged sitting position in wheelchair). Secondly, motor deficit lead to the loss of skeletal muscle pumping activity which could promote leg fluid accumulation during the day. In our knowledge, no study has specifically assessed the impact of rostral fluid displacement on upper airway collapsibility among patients with spinal cord injury. Better comprehension of upper airway collapsibility determinants in patients with spinal cord injury is mandatory to identify new therapeutic targets (diuretics, contention…) especially since CPAP, the first line treatment for severe OSA, continue to pose adherence issues in SCI patients. In the future, phenotyping OSA patients, especially those with SCI, will improve personalized management. The main objective is to find if there is a correlation between the apnea-hypopnea index (AHI) and rostral fluid shift overnight, in non-obese spinal cord injured patients. The secondary aim is to find if there is a correlation between AHI and: * Neck circumference * Neck volume * Time spent sitting down

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