Respiratory mechanics in acute quadriplegia: Lung and chest wall compliance and dimensional changes during respiratory maneuvers

We measured lung and chest wall compliance as well as rib cage and abdominal dimensions in the supine position in five acute C_4-7 quadriplegics. Studies were performed serially from 1 to 12 months after injury. Results were compared with those of control groups of chronic (> 1 yr after injury) quadriplegics and normal volunteers. We found that lung compliance was lower in acute and chronic quadriplegics (0.129 ± 0.023 and 0.176 ± 0.043 L/mm Hg, respectively) than in normal subjects (0.278 ± 0.086 L/mm Hg) and that these changes apparently occurred within 1 month of injury. Specific lung compliance appeared to be reduced to a lesser degree, suggesting that the changes in lung compliance were partly due to reduced lung volumes and partly to altered mechanical properties of the lung. During respiratory maneuvers, abdomen and rib cage dimensional changes demonstrated rib cage distortion. This distortion was less severe in chronic than in acute quadriplegics. The improvement in chest wall stability was likely due to increased strength of cervical accessory muscles of respiration and improved coupling of the various rib cage elements in chronic quadriplegics.