Nurse Open Heart, scrub nurse at Ponyville General Hospital from the My Little Pony: Friendship is Magic episode, "Where the Apple Lies", dressed in a dark blue EquestriTech surgical gown, light-blue EquestriTech surgical gloves, a light-blue EquestriTech surgical tail cover which covered her tail, a light blue EquestriTech surgical cap which covered her ears and the most of her hair except for the back and her horn, and is breathing in her white EquestriTech EMFFN95-M/L-W flatfold-style disposable particulate surgical respirator mask over her nose and mouth, to protect her lungs from any harmful airbourne particles and nasty germs. Open Heart's mask also keeps her muzzle warm.
Nurse Open Heart's cap and respirator mask colors are the exact colors as the cap and surgical mask she wore in the My Little Pony: Friendship is Magic episode, "Where the Apple Lies", during Granny Smith's "Apple Blight" presentation operating room scene in a Goof Troop episode, "To Heir is Human"-esque finale of that episode.