The ornamental design for a frame for a respiratorymask, as shown and described.
FIG. 1 is a front perspective view of a frame for a respiratory mask according to my design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a top view thereof;
FIG. 5 is a bottom view thereof;
FIG. 6 is a right side view thereof with the left side view being a mirror image thereof; and,
FIG. 7 is a rear perspective view thereof.
Where included, broken lines showing environment or structure are for illustrative purposes only and form no part of the claimed design. Where included, dotted lines represent the border between claimed and non-claimed subject matter and form no part of the claimed design.