Lung Volumes and capacities

• Lung volumes and capacities are measurements that reflect the mechanics of breathing, and the volumes of air associated with different phases of the respiratory cycle.
• These measurements are crucial for assessing respiratory health and function.
• There are four primary lung volumes and four lung capacities, which are combinations of different volumes.

Lung Volumes:

1. Tidal Volume (TV)

   • Definition: The volume of air inhaled or exhaled during normal, quiet breathing.
   • Average Value: Approximately 500 mL in healthy adults.

2. Inspiratory Reserve Volume (IRV)

   • Definition: The additional volume of air that can be forcefully inhaled after a normal tidal inhalation.
   • Average Value: Around 1900-3300 mL in healthy adults.

3. Expiratory Reserve Volume (ERV)

   • Definition: The extra volume of air that can be forcefully exhaled after a normal tidal exhalation.
   • Average Value: Approximately 700-1000 mL in healthy adults.

4. Residual Volume (RV)

   • Definition: The volume of air remaining in the lungs after a maximal forced exhalation. This air cannot be expelled and helps maintain lung function.
   • Average Value: Typically, 1000-1200 mL in healthy adults.

Lung Capacities:

1. Inspiratory Capacity (IC)

   • Definition: The total volume of air that can be inhaled after a normal tidal exhalation.
   • Formula: IC = TV + IRV

2. Functional Residual Capacity (FRC)

   • Definition: The volume of air remaining in the lungs after a normal tidal exhalation.
   • Formula: FRC = ERV + RV

3. Vital Capacity (VC)

   • Definition: The maximum volume of air that can be exhaled after a maximal inhalation.
   • Formula: VC = TV + IRV + ERV

4. Total Lung Capacity (TLC)

   • Definition: The total volume of air that the lungs can hold after a maximal inhalation.
   • Formula: TLC = TV + IRV + ERV + RV

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