Don't blow it

日期:2019-03-07 04:01:03 作者:梁丘浯 阅读:

By Philip Cohen BUNGED up with a cold? Use that tissue for wiping only. Every time you blow your nose, you’re just prolonging the misery. Blowing your nose drives virus-laden mucus deep into the sinuses, a new study concludes. Sneezing and coughing don’t do this, although of course they increase the chance of spreading your germs to friends, family and workmates. Our sinuses are usually filled with air. But in about 85 per cent of people with a cold, they contain viscous fluid. Because sinuses themselves do not produce mucus, congested nasal passages are the obvious source of the goo. But it has not been clear how this mucus gets into the sinuses. This medical mystery intrigued Jack Gwaltney and Birgit Winther of the University of Virginia, Charlottesville. And the plot thickened when they examined computerised tomography (CT) scans of the sinuses of patients with a cold and found that the fluid was filled with bubbles. Since the mucus is very viscous, these could not have been created by mixing inside the sinuses. “You’d have to jam your head in a jackhammer to do that,” says Gwaltney. But the mucus could have mixed rapidly with air if it entered the sinuses under high pressure. To try to understand how that might happen, Gwaltney, Winther and their colleagues inserted thin straw-like pressure gauges up one of the nostrils of each of four healthy adult volunteers. The researchers made their subjects sneeze by sticking a cotton swab dabbed with histamine up their noses or asked them to cough or blow their nose. Each nose blow produced a rapid change in pressure. In the space of one second, the pressure shot up to an average of 8800 pascals—about half the pressure of blood in a major artery. “And if you cut an artery, the blood would hit the ceiling,” says Gwaltney. A computer model predicted that this pressure would propel a millilitre of the mucus into the sinuses. Sneezing and coughing, on the other hand, produced only a tenth of the pressure of a nose blow, hardly enough to get mucus moving. To see if these calculations were correct, the researchers placed artificial mucus, made from a sugary gel, up the noses of 10 more subjects and used a CT scanner to follow its journey. After a sneeze or a cough, the liquid stayed in the nasal passages, but a nose blow shot the gel deep into the sinuses. Ronald Turner, a paediatrician and cold specialist at the Medical University of South Carolina in Charleston, says that people with colds rarely get severe sinus infections. Still, Winther argues that nose blowing could increase the duration and discomfort of colds, by allowing germs to hide out and by carrying biochemicals that cause inflammation to the sinuses. She recommends treating a cold early with antihistamines and ibuprofen to suppress the production of mucus. More on these topics: