To the trach, oxygen lpm flow is affected at >12ft of tubing? Is there a journal/reference for this?

No. There was a study by dl cullen that showed no affect on oxygen flow up to 100ft. Twenty feet or lesa of oxygen tubing should not affect your liter flow. I have many patients on 30 feet of tubing with and without trach in the home setting. Also trach decreases oral dead space (unoxygenated area of the mouth) ensuring good flow rates.