When DHD Healthcare was designing its new vibratory Positive Expiratory Pressure (PEP) system for patients suffering respiratory difficulties, it enlisted the help of specialty compounder RTP Co. to develop materials capable of the new system's diverse criteria for rigidity, dimensional stability, repeated autoclaving, and FDA compliance.

The new system, called acapella choice, directs pulsated air to the lungs — agitating mucous and fluids and making them easier to manually dispel. The PEP system also allows the patient, under a physician's guidance, to make dial adjustments in the pulsation frequency, providing optimal effect for those afflicted with COPD, asthma, or cystic fibrosis. In addition, the system can be easily disassembled for regular cleaning via steam autoclaving, boiling, or machine dishwashing.

For the device's internal rocker arm component, material rigidity and dimensional stability are critical requirements, according to Bob Cianfrocco, a plastics engineer at DHD. The rocker arm is the key internal component that positions a pulse-generating magnet. The position of the magnet controls the frequency and ensures that therapy is dispensed as directed. Any excessive creep or elongation could interfere with accurate operation.

That's why the engineering team at DHD turned to RTP 100 Series glass-reinforced polypropylene. The compound has a flexural modulus of 0.8 psi x 106 and a heat deflection temperature of 295°F at 264 psi. It proved capable of maintaining dimensions through repeated autoclaving. In addition, the FDA-compliant ingredients used in the compound satisfied biocompatibility requirements.

In addition, the shell material of the PEP system required precise color both for model identification and to correspond with existing color schemes. DHD was able to achieve the color match it was looking for by using a color concentrate also developed by RTP. "RTP Company was eager to attempt what they knew to be a tough color match; a specific aqua that falls between our existing blue and green is not a big window to hit," says Ken Pelerossi, engineering manager at DHD. "And, they nailed it."