[Mechanical ventilation during MRI in children. Anesthetic constraints].

Early use of magnetic resonance imaging (MRI) excluded patients needing mechanical ventilation. However magnetic resonance imaging is an innocuous investigation and affords important elements to the diagnosis of many pathologies. Improvement of anaesthetic equipment have led to enlarge MRI applications considerably. Ventilations situated outside the MRI room required very long tubing, to 9-11 m. Although the ferromagnetic charge of presently used ventilators is greatly reduced, it is still necessary to keep them at some distance from the patient, with tubing of about 3 m, even in children. Therefore the compressible gas volumes are larger than the usual ones. For a tube length of 3 m, about 2-3 ml.kg-1 should be added to the standard tidal volume (10 ml.kg-1), so as to obtain safe normoventilation.