The effect of angle and oscillation on mucous simulant speed in flexible tubes.

BACKGROUND AND PURPOSE: The aim of this study was to investigate, in a tube model, how the speed of a mucous simulant was influenced by angle and different types of oscillations. METHOD: Using a repeated-measures study design, the primary outcome measure was the mucous simulant speed calculated from the time taken for the mucous simulant to travel a distance of 10 cm. Ultrasonic gel diluted to a viscosity (113 Poise), approximating human sputum, was introduced into a flexible tube similar in diameter to the human adult trachea. The tube was subjected to discrete angles of 0 degrees and 30 degrees, 60 degrees and 90 degrees downward. Symmetrical oscillation was applied in both the transverse and longitudinal directions with frequencies of 5, 15 and 25 Hz at amplitudes of 1 mm and 2 mm peak-to-peak using a commercially available oscillator. Asymmetrical oscillation was applied using repeated cycles of slow acceleration and fast deceleration in the longitudinal direction at 0 degrees and 30 degrees downward and up a 5 degrees incline using a custom-built apparatus. RESULTS: Each 30 degrees angle increment of the tube from 0 degrees to 90 degrees significantly increased mucous simulant speed (p<0.001). Symmetrical oscillation did not provide an advantage over angle in terms of mucous simulant speed; however, asymmetrical oscillation increased mucous simulant speed beyond that caused by angle for all angles tested (p<0.001) and was able to drive mucous simulant up a small incline (5 degrees) in this tube model. It was found that certain types of longitudinal oscillation elongated the mucous simulant. CONCLUSIONS: The present study supports the use of gravity to assist in secretion clearance. Asymmetrical oscillation is a novel technique which warrants further investigation.

Feedback withdrawal and changing compliance during manual hyperinflation.

BACKGROUND AND PURPOSE: The performance of manual hyperinflation by physiotherapists can be improved by the availability of a pressure manometer. The present study aimed to test whether these benefits could be maintained when the manometer is withdrawn and whether the availability of a manometer affects the pressures delivered under changing respiratory compliances. METHOD: Manual hyperinflation breaths were delivered to a test lung by student physiotherapists, with a target peak airway pressure of 30 cm H2O under control, feedback and feedback-withdrawal conditions. The breaths were delivered for three trials under each testing condition at each of three respiratory compliance settings. RESULTS: The availability of augmented feedback increased the accuracy and reduced the variability of performance; however, these improvements were not maintained when feedback was withdrawn. Changing respiratory compliance significantly affected the accuracy and variability during the control and withdrawal conditions, but the availability of a manometer negated these differences. CONCLUSIONS: The availability of a pressure manometer negates the influence of respiratory compliance on the achievement of target peak airway pressures during manual hyperinflation in the laboratory environment, however these benefits are not retained when feedback is withdrawn. Therefore, it is recommended that a pressure manometer should be routinely available during manual hyperinflation in clinical practice to optimize treatment safety and effectiveness.