(WGN) – He spent nearly four decades designing computerized tomography (CT) machines.

They aid in cancer diagnosis, pinpointing bone injuries and heart and lung ailments, and during the pandemic, they have been critical for COVID-19 patients. But when engineer Bob Senzig became the patient, his work took on a whole new meaning.

Senzig knows the technology of a CT machine inside and out. The engineer who spent 36 years at GE Healthcare gave WGN a peek under the hood of the million-dollar machines, which look deep inside the body.

But last November, he got a different view of the system he helped design. He had to lie flat on his back as his lungs were the subject of an emergency imaging study. The 66-year-old had COVID-19.

“There’s no good explanation as to why I’m still here and 700,000 other people are dead,” he said. “I made the mistake of agreeing to go on vacation and thought, ‘Well I’ll be as safe as I can.’ So I went and had a COVID test, and it was negative. And I thought, ‘I’m good to go.'”

His symptoms surfaced before he even landed.

“And then I got a pounding headache,” he said. “It was so bad.”

Soon, he was having trouble breathing. Senzig went to a local hospital and found his blood-oxygen levels were dangerously low.

“I’m pretty sick,” he said of the time. “I can’t think very well. I’m going into a scanner. I really wondered what CT am I going to see here? And it was a Bright Speed that I helped develop. So it was nice to see that.”

Senzig, whose body of work is lined up at the Waukesha, Wisconsin, manufacturing facility, said he worked on detectors, overall system designs and other specifications.

A CT machine relies on precision and speed.

“The first system I worked on it was 4 seconds per revolution. Now the scanners are .2, .3 seconds, so it’s so quick,” he said.

On his vacation in Mexico, Senzig’s condition spiraled. He reached out to a colleague to help him arrange a medical flight back to the U.S.

“I called him up and said, ‘You got to get me out of Mexico. I’m going to die here,’” he said.

To be transferred safely, Senzig had to be intubated. That’s his last memory before going on a ventilator. 

Thousands of COVID patients have undergone CT scans to help doctors determine damage and a course of action. It’s been a critical tool during the pandemic.  

“My lungs, when I saw them on the CT scanner later, they were just totally engulfed in COVID pneumonia. I don’t know how I was possibly breathing,” he said.

Senzig’s friends and colleagues helped to raise funds for the $25,000 air ambulance ride back to the United States. Senzig was ultimately flown to an Arizona hospital, where his care team attempted to wean him off the ventilator.

“I would be there and in my memory, I would just be (gasping) for breath and thinking to myself, ‘I’m going to die here,’” he said.

After four weeks, he was finally ready to breathe and speak on his own.

“Why does it hit one person more than another?” he said. “And it’s just a gamble that if you get it you might end up in the same position I was in.”

It’s been a year now, and Senzig still has shortness of breath. His most recent scan, taken on another CT he helped design, shows the lingering damage.

“I’ve always felt that healthcare — and that is why I stayed here for 36 years — is so rewarding to work on, something you know is helping people,” he said. “But I didn’t think in the pandemic it would be such a big deal. But it has been.”