Tony Passarelli was used to having a bit of breathing trouble.The 52-year-old's asthma often flares up in the spring, but this past March, something felt different. He started wheezing, and several rounds of antibiotics didn't solve whatever was ailing him.Later that month, his wife of more than 25 years, Linda, fell ill as well. Then she tested positive for the virus behind COVID-19. While she isolated in a room at the couple's Bolton, Ont., home, Tony took a turn for the worse, and his wheezing became a cough that just wouldn't quit. He headed to the nearest emergency department — Headwaters Health Care Centre in Orangeville — on March 29."They just said I had pneumonia," Tony said, "and that they were going to keep me."That's the last thing he remembers.What happened next, according to the soft-spoken father of three, was a weeks-long ordeal with COVID-19.After passing out in the hospital, he wound up intubated in an intensive care unit, was transferred to Etobicoke General Hospital in Toronto, suffered round after round of fevers and infections, then became so ill that doctors thought there was nothing more they could do to keep him alive."There's nothing else left," Linda recalled being told by one of the ICU physicians in early April.Then came a sliver of hope.Tony qualified for an ECMO treatment — or extracorporeal membrane oxygenation — which could be his last chance at survival.'High level' of demandRoughly 40 Canadian hospitals have access to at least one ECMO machine, representing just three per cent of all hospital sites across Canada — though it's unclear how many machines in total the country has access to.Offered at only a handful of Ontario hospital sites, with the bulk of the machines at Toronto General Hospital, it's a form of life support that uses a pump to circulate blood through a machine that replaces the work of someone's lungs and, in some cases, their heart.The machine removes carbon dioxide, then sends oxygen-filled blood back into the bloodstream, giving damaged lungs a chance to rest and recover.Patients who qualify for the treatment are usually under 65 and have few pre-existing health conditions, ensuring they have the best shot at surviving.Linda credits the device with saving her husband's life, and she's not alone. In the pandemic's first wave in Ontario, 34 COVID-19 patients were given this potentially life-saving treatment, and more than half survived.Now, as coronavirus infections are surging to record-breaking levels, there's concern that demand is quickly rising again for ECMO — this time as Toronto General juggles both COVID-19 cases and other patients requiring the last-resort approach that's in limited supply, including those hospitalized for lung transplants."It's a pretty high level," said Dr. Marcelo Cypel, surgical director for the University Health Network's extracorporeal life support program, which includes the ECMO treatment at the network's Toronto General site.In just the last two weeks, Cypel said, at least a dozen COVID-19 patients have been hooked up to ECMO machines. At the time of his interview with CBC News on Tuesday, nine of the hospital's 11 intensive care admissions were being given the treatment, using nearly a third of the hospital's 30 ECMO machines — a supply that was increased this year to brace for the earlier influx of COVID-19 patients."We are working at our full ICU capacity right now already," Cypel said. "And that's a concern, because we continue to receive referrals every day."ECMO team 'may have to slow down'While the first coronavirus wave saw the cancellation of thousands of elective surgeries and other procedures to make room for COVID-19 patients, Cypel said in the second wave, his team is handling another influx of the sickest of those patients, as well as anyone needing ECMO for other reasons.But he worries that may not be sustainable much longer.If recent provincial lockdowns for Toronto and Peel Region don't put a dent in case growth and ICU admissions, Cypel said, the ECMO team "may have to slow down," which could affect patients waiting for other crucial hospital services such as transplants.That's a situation Renee Alkass finds alarming, since she once had the treatment herself for a non-COVID medical issue.In 2017, long before the COVID-19 pandemic, the University of Guelph student developed an ear infection that spiralled into acute respiratory distress syndrome (ARDS). After struggling to breathe, Alkass was hospitalized, and doctors discovered that both of her lungs were filled with fluid.She wound up being sent to Toronto General and was on ECMO for 18 days during her stay."I can't even fathom to understand what everyone must be feeling," said the 21-year-old, who has since recovered from ARDS and was eventually diagnosed with a rare autoimmune disorder."And I do hope that there's a light at the end of all this and things start looking up from here, and there isn't such a stretch or this need."When asked if the province has any plans to address the recent demand for ECMO at Toronto General, provincial officials didn't outline any.Instead, a spokesperson told CBC News the decision to use it is a clinical one, with the Ministry of Health providing dedicated funding to the hospital for patients who require the treatment."The hospital can expense the ministry for costs related to treating patients with COVID-19 ... if it is above and beyond their funding allocation," the ministry said in a statement."So, it's not expected that the needs of patients with COVID-19 will impact the use of the therapy for other patients."1 in 10 ICU beds have COVID-19 patientsBut Anthony Dale, president and CEO of the Ontario Hospital Association, said the pressure on the ECMO program is just one example of the impact from rising numbers of COVID-19 hospitalizations and ICU admissions.Roughly one in every 10 intensive care beds in Ontario is now occupied by someone infected with the virus, he recently noted."What people simply have to appreciate is that critical care is the most complex care that you can access in an Ontario hospital, and it's located in only certain hospitals," Dale said. "And it's totally dependent on having access to the right kinds of health professionals with the right kind of technology."Both Dale and Cypel say the key to lowering demand for limited treatments like ECMO is simply reducing the amount of community spread of COVID-19."I don't want people to only see how serious this is when the province's hospitals are facing an even more destabilizing crisis," Dale said."Right now I know it's hidden from you. But I assure you that right now hospitals, especially in major urban centres, are bracing for serious impact over the next two to four weeks."'We're so blessed that he was picked'When Tony Passarelli finally woke up at Toronto General, months before the second surge of COVID-19 cases, he had no idea a machine had helped him get to that point."I just remember one of the nurses there saying, 'Do you know where you are? Do you know what day it is?' Groggily I said, 'I'm in the hospital, but day-wise, no,'" he recalled. "She said the date — which I don't remember — and she says, 'You've been here three weeks.'"Tony soon learned more alarming details: His entire family in Bolton, northwest of Toronto, including his three children and mother, all wound up having confirmed or likely infections of the virus.And he found out there was a long recovery ahead. Tony's motor skills weren't working, and he couldn't eat or drink on his own. He was transferred back to Etobicoke General and discharged in early May, and he now uses an oxygen machine to help him breathe.But he's alive, Linda said, and that's enough."Our family's a family right now because of the ECMO," she added.What scares the couple now? The realization that there's high demand for only a limited number of machines across the entire province."The fact that there are so few, and there's such a demand ... that is incredibly scary," Linda said."We're regular people; we're so blessed that he was picked and he's here today."