Not many patients return voluntarily to intensive care units where they endured pain and nightmares, but Ben O'Donnell stopped by the University of Minnesota Medical Center on Friday to thank those who saved him from one of the state's first and most shocking COVID-19 cases.

The 40-year-old presented his finisher medal from the Ironman Tulsa triathlon on May 22 to caregivers who treated his COVID-19 in March 2020 — a pick-me-up for a critical care team that didn't expect to be battling the pandemic 20 months later.

"All of you were with me the entire 140.6 miles," O'Donnell told doctors, nurses and others on the fourth floor ECMO unit where he was treated. "Every step, you were with me, because without you, I wouldn't be here. My daughter wouldn't have a father. My wife would be alone."

O'Donnell's COVID-19 battle was jarring because it was the first instance of a young Minnesotan — and an athlete at that — who was placed on a ventilator and extracorporeal membrane oxygenation (ECMO) to maintain oxygen intake while his lungs fought the disease.

Caregivers recalled being shocked by the severity of his lung damage, which exacerbated their anxieties about their own safety as they treated patients amid an unknown pandemic with limited protective supplies.

"Everything that could go wrong went wrong. A lot of bad things happened," said Andy Gladstein, an ICU nurse, who recalled how O'Donnell nearly died when his breathing tube filled with "thick, black junk" unlike anything Gladstein had ever seen. "I didn't know if he was going to survive or not. I didn't know if I was going to survive or not."

O'Donnell was hospitalized for a month and had kidney problems and internal bleeding in addition to lung damage — all before treatment protocols for COVID-19 had been clearly established. He later received counseling to deal with the trauma of the experience. Because of the medications and semiconscious state he was in at the hospital, O'Donnell at one point hallucinated that he was a victim of human trafficking and needed to escape.

He has channeled his COVID-19 recovery story into hope for others, noting that he still encounters "brain fog" that forces him to take mental timeouts and numbness in one leg. He spoke to a congressional subcommittee in Chicago this week about ways to overcome vaccine hesitancy, suggesting that advocates "attack the decisionmaking process but not the decision" that people make.

ESPN is preparing a documentary on O'Donnell, who had previously completed an Ironman in Madison, Wis., and finished the Tulsa race after his COVID-19 recovery. O'Donnell was proud to be faster in his post-COVID race, even with a 30-minute delay to change a blown tire.

Caregivers said it was a morale boost to see O'Donnell. Many celebrated when COVID-19 vaccine became available last winter and hoped that the pandemic would soon end. Gaps in vaccination coverage and the emergence of a fast-spreading delta variant of the virus contributed to a renewed surge this fall.

Minnesota reported a 2021 record of 1,245 COVID-19 hospitalizations on Thursday and new data showing that unvaccinated people are taking up most of the beds.

On Friday, the U Medical Center was treating 47 COVID-19 patients. One was on ECMO in O'Donnell's same room. Thirty patients were unvaccinated, including 15 of 18 receiving intensive care.

"You show up every day and do your best," said Breeanna Long, an ECMO coordinator who was part of O'Donnell's treatment team. "He reminds you that it's worth doing it still. Even if we lose tomorrow on someone who is presently here, the wins are worth it."