. >> alfonsi: we got a sense of that when we met krystal totten. with patients who need ecmo, a machine that oxygenates blood outside the body, and is used when lungs are too weak to do the job. last september, a fellow nurse and friend, becky fulks, became one of her patients, when fulks became sick with covid. >> krystal totten: i remember just, like, you know, just breaking down, because seeing somebody at their worst point, you know, not knowing if they're going to live or die is, you know, is very-- is very hard. >> alfonsi: fulks is a heart and lung nurse. she was vaccinated, and working through the pandemic. she was in bad shape when you saw her? >> totten: oh, she-- yeah. so, for a patient to need to go on ecmo, it's a last-ditch effort. it's a maximum form of life support. >> alfonsi: last month, becky fulks began to improve. she was taken off the ecmo machine, but still has a tracheostomy tube. it's unclear if the 49-year-old mother of two will ever get back to nursing. what does becky's story tell us about all the nurses? >> totten: it's