The use of in-line nebulizers placed in certain locations may lead to aerosol deposits forming over time on the ventilator flow sensor. Should this occur, there is a possibility of inaccurate flow measurements affecting therapy.

http://www.fda.gov/safety/recalls-market-withdrawals-safety-alerts/philips-respironics-issues-additional-usage-instructions-trilogy-evo-ventilators-related-use-line