THE standard oxygen masks worn by some patients produce plumes of droplets that increase the risk of medical staff contracting respiratory diseases such as flu. Such masks might be responsible for some cases of SARS in doctors and nurses during the outbreaks in Asia and Canada last year.
In Toronto, healthcare workers took strict precautions including, in some cases, wearing goggles, masks, gloves and two gowns. Even so, some still caught SARS from patients. Many of the patients required supplementary oxygen, and Robert Fowler of Sunnybrook and Women鈥檚 Health Sciences Centre in Toronto and his colleagues suspected that the oxygen masks may have been part of the problem. They photographed the masks in operation. Their images (above) reveal that plumes of exhaled droplets billow out of the side vents of standard oxygen masks. The plumes can travel about 5 metres (Chest, vol 125, p 1157). 鈥淯ntil doing the study, no one had any idea how far these infectious plumes could travel,鈥� Fowler says.
鈥淚t does offer one plausible explanation,鈥� says Mark Loeb of McMaster University in Hamilton, Canada. A recent study of his showed that just manipulating oxygen masks on patients鈥� faces greatly increased the risk of critical care nurses becoming infected. The plume problem can be eliminated by using modified oxygen masks that filter out droplets, which some members of Fowler鈥檚 team had already helped develop even before the SARS outbreak.
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