Classification of chest wall diseases.

Several disorders of the thoracic cage are known to cause respiratory failure, by means of relatively simple mechanisms, such as the increased work of breathing, which results in alveolar hypoventilation. A variety of pathogenic mechanisms may be considered, as functions of the types of thoracic disorders present. As causes of these additional potential mechanisms, we considered the following: 1) ventilation-perfusion (V/Q) inhomogeneity; 2) inability to cough; 3) malformation or acquired defect of the respiratory centres; and 4) excess blood volume and fluid retention, which aggravate work of breathing and V/Q inhomogeneity. All of these disorders can be grouped into two major categories (which nevertheless have some of the pathophysiology in common): the mechanical syndrome and the neuromuscular or paralytic syndrome. In this paper we discuss chest wall diseases falling into the first category; namely, kyphoscoliosis, fibrothorax, thoracoplasty, ankylosing spondylitis and obesity-hypoventilation. Congenital deformities of the thoracic cage, which do not have important effects on ventilatory apparatus (e.g. pectus excavatum and pectus carinatum), were also considered.