The Science Journal of the American Association for Respiratory Care

2006 OPEN FORUM Abstracts

MUCUS SHIFTS ACCORDING TO EXPIRATORY/INSPIRATORY FLOW RATIO. 

Marcia Volpe RPT, Alexander Adams FAARC, RRT, John Marini MD, Healthpartners/Regions Hospital, St. Paul , Minnesota and Sao Paulo , Brazil .


Background: Mucus retention and immobility in ventilated patients is a serious, rarely-studied clinical problem. An established method does not exist for evaluating factors that affect mucus movement within airways. Simply measuring the leading edge of mucus movement in an airway simulation circuit may not reflect the overall influence of factors such as ventilator settings, mucus viscosity or lung impedance. In this study we studied whether expiratory/inspiratory flow relationships would impact net mucus movement.  

Methods: A clear tubing circuitry was assembled for imaging of mucus movement by a 12 mega pixel camera ( Olympus ). A software program, Sigmascan, analyzed net mucus movement relative to the injection point. One ml of mucus stimulant mixed with green dye was injected into the circuitry.  A Test Lung (Michigan Instruments, compliance = 0.02) was ventilated via the circuitry at VT =300 ml, f =15/min and inspiratory flow set to establish expiratory/inspiratory flow ratios of 1.8, 1.4, and 0.9.

Results:
The center of mucus mass moved away from the lungs (positive mm in figure) when expiratory flow exceeded inspiratory flow at ratios of 1.8 and 1.4. At a greater inspiratory flow (ratio of 0.9), mucus moved toward the lungs (negative mm in figure).

Conclusions:
We describe a method for assessing factors that may affect mucus movement within airways. Mucus movement was influenced by the ratio of expiratory/inspiratory airflows. The affect of ventilator settings on airflow profiles and, subsequently, mucus movement should be considered in managing ventilatory support.


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