What is residual air? Write its function.
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Answer:
The residual volume functions to keep the alveoli open even after maximum expiration. In healthy lungs, the air that makes up the residual volume allows for continual gas exchange to occur between breaths. The oxygen-depleted residual air is then mixed with newly inhaled air to improve gas exchange at the alveoli.
Residual volume (RV) is the volume of air that remains in the lungs after maximum forceful expiration. In other words, it is the volume of air that cannot be expelled from the lungs. This volume remains unchanged regardless of the lung volume at which expiration was started. Reference values for residual volume are considered to be 1 to 1.2 L, but these values are dependent on many factors including age, gender, height, weight, and physical activity levels.
The residual volume is an important component of the total lung capacity (TLC) and the functional residual capacity (FRC). TLC is the total volume of the lungs at maximal inspiration. FRC is the amount of air remaining in the lungs after a normal, physiologic expiration (Figure 1A). The TLC, FRC, and RV are absolute lung volumes and cannot be measured directly with spirometry. Instead, they must be calculated using techniques such as gas dilution or body plethysmography. Measuring the residual volume can give an indication of lung physiology and pathology