[Silent lung zone - application of multi-breath nitrogen washout test (MBNW) in the diagnosis of small airways diseases in children - preliminary report based on literature and own experience].

Small airways are the site of pathological changes often in an early stage in many diseases such as asthma or cystic fibrosis. However this part of the airways is overlooked in conventional respiratory function tests and it is therefore often referred to as "silent lung zone". This paper presents the theoretical background of MBNW multi-breath nitrogen washout in the diagnosis of minor respiratory diseases. The technical issues related to the preparation of pediatric patients for the test. Clinical applications of the MBNW test results are still subject to a number of studies. There is hope for filling the gaps in the small airway function tests. Due to the authors' involvement in the diagnosis and treatment of patients with cystic fibrosis, their own experience in the use of this study was also described. Currently, the method is in the phase of intensive analysis for the early diagnosis of lung disease in cystic fibrosis, when still other functional tests are in normal range or impossible to perform due to patient age. Correlation with medical imaging methods (chest computed tomography) and the severity of structural changes may in future limit the amount of radiology tests. In addition this can reduce the patient's exposure to ionizing radiation. Introduction of lung function tests such a MBW in infants and preschool children with cystic fibrosis and other minor respiratory diseases may modify clinical management and improve prognosis.