Thanks...The ventilator is hooked to a trach with in-line suction and the cough assist machine is by Respironics which says you can attach this to the vent tubing, using both at the same time, but there is no demonstration or picture in the manual or on-line.
You can call or email their website for more information. There are alot of devices out there and whoever told you this might have been confused. The device can be connected using some existing pieces of the vent circuit but is not designed to be used with the vent inline. Some reps are just sales people and don't ever realize airway tubes such as trachs are 15 mm for universal fitting of most devices.
Other devices such as the MetaNeb and IPV can be used with a ventilator but have valves or a pressure relief manifold and specific instructions to prevent over pressuring the lungs.
I appreciate your feedback, and agree...how would all the different pressures balance themselves out?...let alone inside a person's lung with fragile tissue? I spoke to the person who told me this could be done, and made the same suggestion.