Just when experts are warning about a potential COVID and flu surge going into the winter holidays, Massachusetts’ main airborne medical transport service is warning about a dearth of ICU beds.

Hospital services are hamstrung by COVID-19 and other factors stemming from the pandemic, such as nursing shortages and a greater amount of sicker patients who might have delayed doctors’ appointments.

“In our 36 years, we’ve never seen this high volume of critically ill patients,” said Boston MedFlight CEO Maura Hughes.

Hughes said Boston MedFlight, which provides air and ground transportation for Massachusetts’ critically ill patients, has been inundated — as are local hospitals, even the biggest ones.

“We are taking patients anywhere that there’s an ICU bed. I’d say in the last week, we’ve probably taken a half dozen patients out of state. We’ve taken them to Connecticut, we’ve taken them to New Hampshire.”

But hospitals in other states are also seeking to send their sickest patients anywhere with an open bed.

“We’re getting calls from everywhere, right, anywhere,” said Dr. Jarone Lee, who runs an Intensive Care Unit at Massachusetts General Hospital. “Usually we just get our regional calls from Maine…but we're getting calls from all the way down from Florida asking for beds, because I know that other states are also having ICU bed crunches as well.”

ICUs are fillling up with patients who are far sicker and require a higher level of care than the hospital sees typically, Lee said. It’s a trend that can be seen across the city, the state and the nation.

Part of the problem could be delayed care, Hughes said, caused by patients in the pandemic opting not to go to a regular check-up appointment, or deciding not to get a symptom checked out.

“You have someone who has chest pain and, for some reason, they don't want to go to the doctor — and now they're having a full-blown heart attack,” Hughes said.

Though COVID patients take up a far smaller share of beds in the Northeast than during the surge last winter — Hughes estimated that 10% of their transports are COVID patients — Lee also sees a bottleneck effect that starts with community hospitals. Smaller ICUs are occupied by sicker and longer-staying patients, including COVID patients, he said, whereas one ICU bed might otherwise see several patients rotate in and out in a week.

“If you imagine a hospital that's on a smaller side with a 10-bed ICU, COVID patients...once they are sick enough to need an ICU bed, they stay for a long time,” Lee said. “As these smaller hospital ICUs fill up, they can't keep their normal, sicker patients as well, and they require transfer.”

The well-documented nurses shortage is also taking its toll. Mass General is using travel nurses, who work temporary contracts, to supplement staffing levels, Lee said. But Hughes said that many of the nation’s travel nurses are going to where hospitals need the most support taking care of COVID-19 patients — far away from New England.

“What you're seeing is different parts of the country are getting overloaded at certain periods of time,” she said. “Our health care system has relied on levers to be able to pull...But there's no traveling nurses to be had now. They're all in Texas, they're in California. So these levers that these hospitals were able to pull the past, they just don't have that ability now.”

Going into the flu season, Lee said he hopes anyone who feels sick will stay home to prevent the spread of infection. Even with an additional strain, though, he said hospitals learned with COVID how to increase their capacities in a crisis when it’s needed.

“In many ways, it’s the same as COVID, and just, folks, get vaccinated to protect ourselves from influenza,” Lee said. “Because what we definitely do not want is having an influenza outbreak on top of our current COVID outbreak on top of our current capacity issues.”