What are the limiting factors of invasive ventilation?

Despite ventilator therapy, ALS continues to progress. Invasive ventilation can maintain respiratory function, but motor function continues to decline. At this point, deciding in favor of invasive ventilator therapy presents a challenge.

At the time of decision-making, motor symptoms are less severe than they will be later in the course of the disease, when long-term mechanical ventilation becomes necessary. This presents the challenge of the physician and patient working together to develop a shared understanding of which symptoms and difficulties can be expected as the disease progresses.

If the decision is made to proceed with invasive ventilation, it is important for the patient to imagine what it would be like to be completely paralyzed and to have lost motor autonomy. This includes a state of “being confined,” in which communication with the outside world is achieved through eye movements, other minimal motor functions, or electronic communication systems.

A major limitation of long-term mechanical ventilation is the potential development of eye muscle paralysis, which can progress to a loss of eye movement. This problem affects about half of all patients on long-term mechanical ventilation. The likelihood of developing eye muscle paralysis is increased if a slowing of eye movements is already apparent before the tracheotomy or if the disease is progressing at a very rapid rate.

Eye muscle paralysis makes it difficult or impossible to use eye-controlled communication systems (or to communicate through eye contact). This eliminates an essential means of communication. Eye muscle paralysis is usually accompanied by impaired eyelid function and, consequently, a reduced ability to open the eyes. Eye muscle paralysis thus significantly affects visual acuity.

Because of its significant implications for communication and vision, ALS-related eye muscle paralysis is one of the main limitations of long-term mechanical ventilation.