[Stenoses of the upper airways. Lung function, local resistance and load compensation. A review]

In benign laryngotracheal stenosis the amount of respiratory deterioration rather than the crude morphologic appearance will determine whether or not surgical measures such as dilatation or resection should be applied. This review focuses on currently available and newly developed diagnostic tools to assess the functional importance of central airway obstruction. After an outline of upper airway physiology is formulated, spirometric measurements at rest are collected. Among these, Peak Expiratory Flow Rate (PEF) proved to be the simplest and most reliable parameter to monitor an obstructing lesion of the upper airways. A novel technique for fibrobronchoscopic assessment of glottic and tracheal resistance is presented in detail. In contrast to usual tests of total airflow resistance which cannot distinguish between central and peripheral contributions, this test identifies the pressure-flow-relationship created exclusively by the local lesion. In serial stenoses, it indicates which is of higher clinical impact. Patients with upper airway obstruction complain of impaired exercise capacity. They tend to hypoventilate with imminent respiratory muscle fatigue. Therefore, spiroergometry may play a role in defining the point of incomplete compensation of a central load. The decision to operate will depend upon up the degree of physical capacity required to compensate for the stenosis.