Hi bob.coger.sr, and thanks for your question.
Actually, ventilators and oxygen concentrators are two distinctly different pieces of equipment.
Ventilators are considered to be 'life support' machines, and actually provide mechanical ventilatory support for patients who can no longer breathe on their own.
Oxygen concentrators, on the other hand, can provide a supplemental oxygen source for patients who require oxygen therapy. They are generally used with simple oxygen devices like nasal cannulas or oxygen masks. Generally speaking, they can take the place of oxygen cylinders.
I hope this brief reply provided the information you were looking for.
All the best,
Leon (site moderator COPD.net)