I claim the ornamental design for a ventilator, as shown and described.
The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.
FIG. 1 is a perspective view of an embodiment of a ventilator;
FIG. 2 is a front view thereof; and,
FIG. 3 is a front view thereof, moved to a compressed position.
The features show in broken lines represent portions of the ventilator which form no part of the claimed design.