Spirometry is a simple test and considered the gold standard in lung function. An obstructive ventilatory defect is a disproportionate reduction of maximal airflow from the lung in relation to the maximal volume that can be displaced from the lung. It implies airway narrowing and is defined by a reduced FEV1/FVC ratio below the 5th percentile of the predicted value (lower limit of normal, LLN). A restrictive disorder may be suspected when vital capacity (FVC) is reduced and FEV1/FVC is normal. It is definitely proven, however, only by a decrease in TLC below the 5th percentile of predicted value (LLN). The measurement of TLC by body plethysmography is necessary to confirm or exclude a restrictive defect or hyperinflation of the lung when FVC is below the LLN. 2012 a task force of the ERS published new reference values based on 74,187 records from healthy non-smoking males and females from 26 countries. The new reference equations for the 3-95 age range are now available that include appropriate age-dependent mean values and lower limits of normal (LLN). This presentation aims at providing the reader with recommendations dealing with standardization and interpretation of spirometry.
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