Allen, a medical doctor with Fletcher Allen Health Care and the University of Vermont department of medicine, has treated patients on ventilation. Bates is a University of Vermont department of medicine researcher interested in lung physiology.
Ventilators are commonly used in hospital intensive care units with a variety of patients, including those with acute lung injury, acute respiratory distress syndrome, pneumonia, septic shock, trauma, aspiration of vomit and chemical inhalation. As a result of these conditions, fluid can build up in the lungs, blocking the alveoli. This causes the body to mount an inflammatory response, which injures the lung's epithelial lining, Bates said. At that point, doctors provide mechanical ventilation in the intensive care unit until the body heals itself.
Bates explains the difficulty of treating the injured lung this way: "Imagine you have two balloons which you fill by pumping in air. Now imagine you have only one balloon, and you must drive the same volume of air into the one balloon as you did into two," Bates explained. The same thing happens in the lungs. When parts of the lungs are no longer working, it places greater pressure on the portions of the lung that are working, with the remaining lung handling the air pressure that two lungs had handled.
Doctors consider tidal volume (the amount of air an individual normally inhales and exhales), deep inflation frequency (the number of deep breaths given) and PEEP (positive end-expiratory pressure), which helps keep lungs from collapsing by preventing the airways from emptying completely. PEEP also helps improve gas exchange within the lungs.
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Contact: Christine Guilfoy
cguilfoy@the-aps.org
301-634-7253
American Physiological Society
25-Jul-2006