Respiratory motor function in seated and supine positions in individuals with chronic spinal cord injury

This case-controlled clinical study was undertaken to investigate to what extent pulmonary function in individuals with chronic spinal cord injury (SCI) is affected by posture. Forced vital capacity (FVC), forced expiratory volume in one second (FEV₁), maximal inspiratory pressure (PI_max) and maximal expiratory pressure (PE_max) were obtained from 27 individuals with chronic motor-complete (n=13, complete group) and motor-incomplete (n=14, incomplete group) C₂-T₁₂ SCI in both seated and supine positions. Seated-to-supine changes in spirometrical (FVC and FEV₁) and airway pressure (PI_max and PE_max) outcome measures had different dynamics when compared in complete and incomplete groups. Patients with motor-complete SCI had tendency to increase spirometrical outcomes in supine position showing significant increase in FVC (p=.007), whereas patients in incomplete group exhibited decrease in these values with significant decreases in FEV₁ (p=.002). At the same time, the airway pressure values were decreased in supine position in both groups with significant decrease in PE_max (p=.031) in complete group and significant decrease in PI_max (p=.042) in incomplete group. In addition, seated-to-supine percent change of PI_max was strongly correlated with neurological level of motor-complete SCI (ρ=-.77, p=.002). These results indicate that postural effects on respiratory performance in patients with SCI can depend on severity and neurological level of SCI, and that these effects differ depending on respiratory tasks. Further studies with adequate sample size are needed to investigate these effects in clinically specific groups and to study the mechanisms of such effects on specific respiratory outcome measures.