Given that ventilation is not a consequence-free process, one might imagine that the process of being ventilated for an unnaturally long time might result in some significant lifestyle changes.
There is a study reporting on the association between duration of ventilation and mortality. Prolonged ventilation (when defined as a ventilation time of more than 21 days) seems to be associated with a 1-year mortality of 52%. Quality of life of the survivors is also poor. However, of those surviving after 3 years roughly 99% report a return to baseline function (which probably means they were good quality protoplasm).
Othr complications of prolonged ventilation include the following:
Most of this information comes from only two textbooks. With "Basic Assessment and Support in Intensive Care" by Gomersall et al (was well as whatever I picked up during the BASIC course) as a foundation, I built using the humongous and canonical "Principles and Practice of Mechanical Ventilation" by Tobins et al – the 1442 page 2nd edition.
A good starting point for long term airway device complications is here:
R.D. Sue, I. Susanto Long-term complications of artificial airways Clin Chest Med 24 (2003) 457–471
Powers et al., Prolonged mechanical ventilation alters diaphragmatic structure and function. Crit Care Med. 2009 October; 37(10 Suppl): S347–S353.
Scheinhorn DJ et al, Post-ICU mechanical ventilation at 23 long-term care hospitals: a multicenter outcomes study. Chest. 2007;131(1):85