Bypassing lungs may help swine flu pneumonia victims
Patients with acute respiratory stress or pneumonia are typically placed on a ventilator, which assists breathing by forcing air into the lungs under pressure. While ventilation can be lifesaving, it also can damage lung tissues from oxygen toxicity and pressure injury. A new study in the medical journal Lancet has shown that oxygenating blood outside the body with a miniaturized version of a heart-lung machine reduces that damage and can reduce fatalities significantly. The study was not conducted on patients with pandemic H1N1 influenza, but should be directly applicable to them as well. The primary drawback of the approach is the high cost, nearly double that of conventional ventilation.
The technique is called extracorporeal membrane oxygenation, or ECMO for short. In it, blood is run through tiny porous tubes that allow oxygen to filter in and carbon dioxide to escape. The treatment takes stress off the lungs, allowing them time to heal.
Dr. Giles Peek of Glenfield Hospital in Leicester, England, and his colleagues studied 180 adults, ages 18 to 65, with severe breathing problems. They assigned half to consideration for ECMO and half to conventional ventilation. Only three-quarters of those assigned to ECMO actually received it. But 43 of the 68 who received ECMO survived for six months without disability, a total of 63%. In contrast, only 47% of those who were assigned to conventional ventilation survived for the same period without injury.
In a statement, Peek said, "We have already used ECMO during the first wave of the pandemic with good effect, and we are expecting ECMO to prove an invaluable weapon in the fight against the winter resurgence of the infection."
One problem is that most hospitals in Britain -- and the United States -- do not have the machines, which cost nearly $100,000. Although the technology has been around since the 1980s, a 2008 study said that only about 2,000 adult patients in the U.S. had received treatment with it.
One reason hospitals don't like to use it is that blood thinners like heparin must be used to keep clots from forming in the device. That means the patient must be constantly monitored--one therapist for one or two patients 24 hours per day. In contrast, a ventilator technician can monitor as many as 10 patients simultaneously. The average cost of treatment for ECMO patients was about $122,000, compared with an average of about $55,000 for those on ventilators. Six patients needed to be treated for every life saved, Peek said.
-- Thomas H. Maugh II