Residualvolum

Residualvolum is a term used to denote the volume of gas remaining in the lungs after a maximal expiratory effort. In English this concept is commonly called residual volume (RV); in several languages the compound form (for example German Residualvolumen) or variant spellings such as residualvolum may appear in clinical and physiological texts. Residualvolum cannot be expelled voluntarily and contributes to the maintenance of alveolar inflation between breaths.

Measurement of residualvolum is performed indirectly because the air cannot be exhaled; common techniques include body plethysmography, gas dilution methods (helium or nitrogen washout), and imaging-based estimates. Residualvolum is a component of other standard lung volumes and capacities: functional residual capacity (FRC = expiratory reserve volume + RV) and total lung capacity (TLC = vital capacity + RV).

Physiological and clinical significance arises from its role in preventing atelectasis and in gas exchange stability. Normal values vary with age, sex, and body size and typically fall in the range of about 1.0–1.5 liters in adults, with lower values in smaller individuals. Elevated residualvolum is characteristic of obstructive lung diseases (air trapping in chronic obstructive pulmonary disease and emphysema), whereas restrictive disorders may show normal or reduced RV depending on pathology. Understanding residualvolum is important for interpreting pulmonary function tests, planning ventilation strategies, and diagnosing respiratory conditions.