EFFECTS OF OSCILLATING AIR-FLOW ON THE RHEOLOGICAL PROPERTIES AND CLEARABILITY OF MUCOUS GEL SIMULANTS

This in vitro study addressed the question of clearance-related change s in the physical properties of mucous gel simulants (MGS) subjected t o oscillating air flow. Delineating some of the possible mechanisms of action for the reported beneficial effects of high-frequency chest co mpression (HFCC) therapy constituted the rationale. The rheological va riables measured were spinnability by filancemeter and viscoelasticity (mechanical impedance, G, and loss tangent, tan delta) by magnetic m icrorheometry. Two derivative parameters, mucociliary clearability ind ex (MCI) and cough clearability index (CCI), were computed from the th eological variables, based on relationships established from model stu dies of clearance. Two ranges of air flow oscillation frequencies used previously in animal and clinical studies, i.e., 12-13 Hz or 22-23 Hz , were applied. The measurements were made after application of oscill ating air flow for 15, 30 and 60 minutes, and compared with those at b aseline and negative control. A significant decrease in log G with ad ministration of oscillations was observed (p = 0.06 at 30 minutes, p < 0.01 at 60 minutes, for G measured at 1 rad/s). Spinnability also de creased by 19.3% and 30.7% after 15 minutes; 32.9% and 41.1% after 30 minutes; 36.4% and 50.5% after 60 minutes, for 12 Hz and 22 Hz, respec tively (all significantly different from baseline). There was a positi ve correlation between viscoelasticity and spinnability, and a negativ e correlation between spinnability and CCI, but no correlation between ''mucolytic'' that affected mostly the cough clearability of the mucu s simulant.