Relationships between spinal deformities and respiratory function in patients with severe motor and intellectual disabilities syndrome

The term severe motor and intellectual disabilities syndrome (SMIDS) refers to describe a heterogeneous group of disorders with severe physical disabilities and profound mental retardation. Many patients with SMIDS have spinal deformities such as spinal rotation and scoliosis. On the other hand, they often have respiratory dysfunction, resulting in high mortality from respiratory failure. Therefore, we hypothesized that spinal abnormalities might affect respiratory dysfunction, and analyzed the correlation between spinal abnormalities (Cobb angles (CA) and spinal rotation scores (SRS)) and respiratory parameters (observed during tidal breathing at static supine posture) in 10 patients with SMIDS (M:F 2:8, age 29.0 ± 7.3 years). The patients inability to make effort in spirometry prevented us from evaluating vital capacity and forced expiratory volume. We measured respiratory rate, tidal volume, and expiratory gas during tidal breathing for 10 minutes. There was no patient with the athethotic type of CP. CA and SRS were found to be correlated with each other (r = 0.81, p < 0.01). CA was inversely correlated with tidal volume (both Vt and Vt/Height; r = -0.69, p < 0.05). Both CA and SRS correlated with respiratory rate (r = 0.67 and 0.69, respectively). Moreover, the slope of the regression lines of the V̇O₂-V̇CO ₂ plots (V-slope) was correlated with CA (r = 0.86, p < 0.01). Contrary to our expectation, none of the respiratory parameters showed significant correlations with BMI. Moreover, we found no relationship between the spinal deformity (CA or SRS) and BMI. These observations suggest that the spinal abnormalities affect respiratory patterns in a restrictive manner and increase the respiratory change rate during tidal breathing in patients with SMIDS.