Correlation of Tracheal Cross-sectional Area with Parameters of Pulmonary Function Test in COPD

Abstract

Background : Maximal expiratory flow rate is determined by the size of airway, elastic recoil pressure and the collapsibility of airway in the lung. The obstruction of expiratory flow is one of the major functional impairments of emphysema, which represents COPD. Nevertheless, expiratory narrowing of upper airway may be recruited as a mechanism for minimizing airway collapse, and maintaining lung volume and hyperinflation by an endogenous positive end-expiratory pressure in patients with airflow obstruction. We investigated the physiologic role of trachea in respiration in emphysema. Method : We included 20 patients diagnosed as emphysema by radiologic and physiologic criteria from January to August in 1997 at Seoul Municipal Boramae Hospital. Chest roentgenogram, high resolution computed tomography(HRCT), and pulmonary function tests including arterial blood gas analysis and body plethysmography were taken from each patient. Cross-sectional area of trachea was measured according to the respiratory cycle on the level of aortic arch by HRCT and calibrated with body surface area. We compared this corrected area with such parameters of pulmonary function tests as , , airway resistance, lung compliance and so on. Results : Expiratory cross-sectional area of trachea had significant correlation with (r=-0.61, p (r=0.6, p0.05 with , r=0.26, p>0.05 with , and r=0.44, p>0.05 with minute ventilation). Minute ventilation had significant correlation with tidal volume (r=0.45, p0.05). Cross-sectional area of trachea had no significant correlation with other parameters of pulmonary function including , FVC, /FVC, peak expiratory flow, residual volume, diffusing capacity, airway resistance, and lung compliance, whether the area was expiratory or inspiratory. Conclusion : Cross-sectional area of trachea narrowed during expiration in emphysema, and its expiratory area had significant correlation with , , and minute ventilation.