Introduction: Impairments caused by the chronic disorder of the respiratory system generally result
from irreversible loss of pulmonary functional capacity (ventilatory impairment, gas
exchange impairment, or a combination of both). The most common symptom attributable
to these disorders is dyspnea on exertion. Cough, wheezing, sputum production, hemoptysis,
and chest pain may also occur, but need not be present. However, since these symptoms
are common to many other diseases, evaluation of impairments of the respiratory system
requires a history, physical examination, and chest roentgenogram to establish the
diagnosis of a chronic respiratory disorder. Pulmonary function testing is required
to provide a basis for assessing the impairment, once the diagnosis is established
by appropriate clinical findings.
Alteration of ventilatory function may be due primarily to chronic obstructive pulmonary
disease (emphysema, chronic bronchitis, chronic asthmatic bronchitis) or restrictive
disorders with primary loss of lung volume (pulmonary resection, thoracoplasty, chest
cage deformity as seen in kyphoscoliosis), or infiltrative interstitial disorders
(diffuse fibrosis). Impairment of gas exchange without significant airway obstruction
may be produced by interstitial disorders (diffuse fibrosis). Primary disease of pulmonary
circulation may produce pulmonary vascular hypertension and, eventually, heart failure.
Whatever the mechanism, any chronic progressive pulmonary disorder may result in cor
pulmonale or heart failure. Chronic infection caused, most frequently by mycobacterial
or mycotic organisms, may produce extensive lung destruction resulting in marked loss
of pulmonary functional capacity. Some disorders such as bronchiectasis and asthma
may be characterized by acute, intermittent illnesses of such frequency and intensity
that they produce a marked impairment apart from intercurrent functional loss, which
may be mild.
Most chronic pulmonary disorders may be adequately evaluated on the basis of history,
physical examination, chest roentgenogram, and ventilatory function tests. Direct
assessment of gas exchange by exercise arterial blood gas determination or diffusing
capacity is required only in specific relatively rare circumstances, depending on
the clinical features and specific diagnosis.