Coordination of mucociliary transport in human trachea and intrapulmonary airways

A wide range of both mucus velocities in the trachea and rates of bronchial mucociliary clearance have been measured in humans. To investigate the coordination of mucociliary transport in the intrapulmonary and extrapulmonary airways, simultaneous measurements of tracheal mucus velocity and lung clearance were made in 22 healthy nonsmoking adults. Each subject inhaled several breaths of an iron oxide aerosol tagged with 99mTc. Measurements of retained activity in the right lung were made for 2.25 h with a pair of 5 x 2 in. NaI (T1) detectors. Tracheal mucociliary transport rates (TMTR) were measured with a probe containing six vertically aligned rectangular NaI (T1) detectors. The mean TMTR was 5.1 +/- 2.9 mm/min. The mean time for the first bolus to be detected on the multidetector probe (large airway transit time, LATT) was 52 +/- 24 min. At this time the percent cleared (Bi) was 24 +/- 15% and the rate of clearance (Bi) was 0.64 +/- 0.35%/min. The mean percent cleared within a 2-h interval (B120) was 51 +/- 22%. The TMTR was closely correlated with Bi and Bi with B120. The TMTR was also correlated to B120, but not closely correlated with LATT. It is suggesting that coordination of mucus transport throughout the airways of the lung represents the nonchallenged state and is responsible for the maintenance of normal bronchial toilet.