A Rational Basis for Percussion-Augmented Mucociliary Clearance

Abstract

We sought objective data to determine the effectiveness of postural drainage and chest percussion in the mobilization of retained respiratory secretions. Our goal was to identify evidence of (1) the level and character of percussion energy transmitted across the thoracic cage, and (2) the effects of a broad range of percussion frequencies on mucociliary transport rate. To observe inertial changes in anesthetized dogs, we determined energy transfer in vivo across the thoracic cage by placing an accelerometer in various bronchi and using a strip-chart recorder to monitor the amounts of energy transferred by both manual and mechanical percussion applied sequentially to each of 11 regions of the chest. In human subjects we used bronchoscopy to visually assess the extent of percussion energy transmission across the thorax. To study mucociliary transport rate changes in vivo, we applied percussion to the chests of dogs whose tracheal lumens had been injected at the level of the carina with radiopaque oily dionosil; this allowed us, through fluoroscopy, to observe changes in mucus flowrates and to observe the general character of mucus flow. To observe percussion's effect on mucociliary transport rates in vitro, we placed human “thick” and “thin” sputum on excised rabbit tracheas and then monitored the effects of various percussion frequen-cies and degrees of incline on the mucociliary transport rate of sputum specimens during and after the application of percussion. Percussion energy transmission across the thoracic cage of the dog occurred with relatively good frequency fidelity but with variable amplitude dampening. When percussion was applied to various regions of the human chest, we observed oscillations of the trachea, carina, and smaller bronchi, with an estimated amplitude of oscillation of 1 to 2 mm. From data obtained in vivo in dogs and human beings we determined that speed of mucus transport and facility of mucus flow were markedly enhanced by percussion energy. From data obtained in vitro we determined that there was a positive relationship between gravity and speed of mucus transport, the greatest increase in mucociliary transport rate occurring at a tracheal incline of -60°, the maximum incline studied. For all inclines and sputum types, the optimal percussion energy frequency range for the transport of mucus was 25-35 Hz, a range usually outside manual capability.