The woman was a breast cancer survivor who'd had a double mastectomy, and afterward had gotten breast implants. During a Pilates routine, she was doing a Valsalva maneuver, a breathing technique in which a person takes a deep breath and holds it while bearing down. (In other words, you're going through the motions of exhaling forcibly, but without letting any air escaping through the mouth or nose.)
In this lady's case, enough pressure built to essentially send her right implant through the thin tissue between her ribs and into the space in between the lungs. This left her more perplexed than anything -- where did it go?! Fortunately (and incredibly), she said upon arriving in the the emergency department of the Johns Hopkins Hospital in Baltimore that she wasn't experiencing any chest pain or shortness of breath.