Tetraplegic obstructive sleep apnoea patients dilate the airway similarly to able-bodied obstructive sleep apnoea patients

Context/objective: Obstructive sleep apnoea (OSA) develops soon after cervical spinal cord injury (SCI) at rates higher than the general population, but the mechanisms are not understood. This study aimed to determine whether OSA in SCI is associated with altered pharyngeal muscle dilatory mechanics during quiet breathing, as has been observed in the non-SCI injured with obstructive sleep apnoea. Design: Cross sectional imaging study. Setting: Medical research institute. Participants: Eight cervical SCI patients with OSA were recruited and compared to 13 able-bodied OSA patients and 12 able-bodied healthy controls of similar age and BMI. Interventions and outcome measures: 3T MRI scans of upper airway anatomy and tagged-MRI to characterize airway muscle motion during quiet breathing were collected for analysis. Results: Considerable variation in the patterns of inspiratory airway muscle motion was observed in the SCI group, with some participants exhibiting large inspiratory airway dilatory motions, and others exhibiting counterproductive narrowing during inspiration. These patterns were not dissimilar to those observed in the able-bodied OSA participants. The increase in airway cross-sectional area of able-bodied control participants was proportional to increase in BMI, and a similar, but not significant, relationship was present in all groups. Conclusion: Despite the limited sample size, these data suggest that SCI OSA patients have heterogeneous pharyngeal dilator muscle responses to the negative pressures occurring during inspiration but, as a group, appear to be more similar to able-bodied OSA patients than healthy controls of similar age and BMI. This may reflect altered pharyngeal pressure reflex responses in at least some people with SCI.