A year ago, 42-year-old runner Victor Carlos never thought he'd be excited just to see the starting line. But that was before he almost died.
In fact, the father of two girls didn't breathe for a month; a machine pushed oxygen through his body.
Now he's training for another marathon.
It all began in December with a bad bout of the flu that led to an acute bacterial infection. By the time he checked into the hospital, Carlos was barely hanging on.
"We walked into the triage, and his oxygen level was only 57%, and everybody turned a corner," Carlos' wife, Brenda Voglewede, told CNN. Healthy blood oxygen levels are higher than 95%.
Carlos was in deep trouble. He had developed acute respiratory distress syndrome, also known as ARDS. It was slowly killing Carlos by attacking his lungs.
"Not only that, but he had multiple organ failure related to the infection. So his kidneys were not working. His liver was not working. And his bone marrow was failing as well," said Dr. Ashok Babu, a cardiothoracic surgeon at the University of Colorado Hospital.
Babu had no time to spare. He knew trying to force air into Carlos' lungs would do more harm than good. But without oxygen, Carlos' organs would soon shut down. Babu had one shot: a procedure called extracorporeal membrane oxygenation, or ECMO.
With this treatment, doctors turn down the patient's respirator, then insert a special tube through the heart. A pump draws blood from the body, flushes it through an oxygenation machine that removes the carbon dioxide and delivers oxygen back to the heart. It functions as an external lung, without the patient taking a single breath.
"So (oxygenated blood) could pass through the lungs, and the lungs didn't have to do anything to it because it was already processed," Babu said. "And what we see on the X-ray is the lungs basically collapse down to nothing. ... They are just resting. We support the patient until the lungs can heal on their own."
Carlos' family was told he had a 40% to 50% chance of survival.
"Dr. Babu initially said he thought he'd be on ECMO for a week," Voglewede recalled. "Then the week turned into two weeks. And then he's just like, 'Well, sometimes you just have to wait these things out.' "
Babu said, "Two weeks into it we were all pretty worried that we had this young guy whose lungs just didn't seem to be coming back. At the time, he was the patient we had had on ECMO the longest in the history of our program."
Two weeks became four. Carlos didn't take a single breath for a month.
Then a breakthrough came.
"Somewhat miraculously, his lungs just started to open up on their own," Babu said.
By that time, Carlos was a shadow of his former self. He had lost more than 30 pounds.
"You can imagine, before going into the hospital you are this active person. Then you go in, they put you under, and when you wake ... you can't sit up, you can't move your arms up and you look at your legs, and they're just not there anymore," Carlos said. "Then you realize it's far worse than you ever expected it to be."
Still, he was determined to make a full recovery. Seven weeks after entering the hospital, Carlos got to go home.
"I started out just walking a block and then pushing that out the following day to a block and a half, or two. Then it was like walking to school with the girls," he said.
Remarkably, just six months later, Carlos is running.
"My goal at the time was to be able to jog nonstop for three miles. And I didn't think that was going to happen until November. That happened in May," he said.
Once he was able to cover three miles, the distance he usually started out at to train for a marathon, "that's when I knew it was just a matter of time."
Carlos has set his sights on completing the Denver Rock 'N Roll Marathon on October 20. He's already covered the 26.2 miles in a training run.
Carlos isn't running for time. He's running just because he can.