Respiratory mechanics in kyphoscoliosis.

Kyphoscoliosis is a restrictive respiratory disorder in which total respiratory and lung elastances and lung resistance are increased. Specific airway conductance is increased because of greater lung elastic recoil. Corrective surgical procedures usually result in further immediate increases beyond that related to anaesthesia alone. Despite thoracic deformities, kyphoscoliotics maintain near-normal ventilation through increased central drive, and compensatory mechanisms including force-length and force-velocity properties of contracting inspiratory muscles, the Hering-Breuer reflex, inspiratory duration and airflow. The magnitude of compensation to loading in kyphoscoliotics is proportionately the same as in normal subjects. A recent study has shown that post-inspiratory muscle activity in anaesthetized kyphoscoliotics is proportionate to the magnitude of elastic recoil and intrinsic flow resistance. Expiratory decay may also be influenced by viscoelastic behaviour of thoracic tissues and the transition between their passive and active state.