I claim, the ornamental design for a nasal cannula retainer, as shown and described.
FIG. 1 is a perspective view of a nasal cannula retainer, showing our new design;
FIG. 2 is a front elevation view thereof;
FIG. 3 is a rear elevation view thereof;
FIG. 4 is a left-side elevation view thereof, the right-side elevation view being a mirror image thereof;
FIG. 5 is a top plan view thereof;
FIG. 6 is a bottom plan view thereof; and,
FIG. 7 is a reduced perspective view of the nasal cannula retainer shown in use.
The broken lines showing a nasal cannula and a portion of a frame of eyeglasses in FIG. 7 depict environmental subject matter that forms no part of the claimed design.