ABSTRACT
Variable airway obstruction, typical symptoms, bronchial hyper-responsive-
ness, and airway inflammation form the current definition of asthma and international guidelines place central attention of the treatment of inflam-
mation in this condition (1). Although currently the assessment of disease
severity and progression is based on clinical symptoms and lung function
tests, it is widely agreed that monitoring the nature, extent, and intensity
of inflammation has central importance. Currently, available options to
monitor the inflammatory processes and their response to therapy are lim-
ited. Symptoms and their perception vary widely between individuals and
do not reflect accurately the extent of airway inflammation. Lung function measurements are used in most centers to monitor disease activity; how-
ever, it has been recognized that changes in lung function tests are not clo-
sely related to the degree of inflammation and intensive inflammatory
processes may well precede changes in lung function (2,3). On the other
hand, a recently published study demonstrated that when markers of inflam-
mation (sputum eosinophils and exhaled nitric oxide) are used to guide
asthma treatment instead of traditional methods (lung function), better control and lower exacerbation rate could be achieved (4). Therefore, there is a
growing need to include an ‘‘inflammometer’’ into our tests for monitoring
asthma. The ‘‘gold standard’’ to obtain samples directly from the airways is
bronchoscopy. However, this technique is limited because it is invasive. Its
use is limited in small children and also in severely ill patients, and it cannot
be repeated often. Therefore, the routine clinical use of bronchoscopy for
monitoring airway inflammation/oxidative stress is limited. Sputum induc-
tion is another way of obtaining samples from the lower airways; however, it requires an inhalation of a hypertonic salt solution, which may provoke
bronchoconstriction in asthmatic patients. Furthermore, it cannot be
repeated too often, as the procedure by itself induces inflammatory changes
in the airways. Along these lines, the least invasive technique is the collec-
tion of exhaled breath samples. Several mediators are present in the exhaled
breath (Table 1) (5). Some of them, including nitric oxide (NO) and carbon
monoxide (CO) can be measured in the gas phase, while others such as
hydrogen peroxide, adenosine, and prostaglandins can be determined in the cooled exhalate called ‘‘exhaled breath condensate.’’
