Lung Volumes / Respiratory Volumes.

 

Introduction.

  • Lung volumes are also known as respiratory volumes

  • It refers to the volume of gas in the lungs at a given time during the respiratory cycle.

  • Lung volumes measurement is done to check functionality of the lungs. 

  • These volumes vary, depending on the depth of respiration, ethnicity, gender, age, body composition and in certain respiratory diseases

  • A number of the lung volumes can be measured by Spirometry and plethysmography.

  • Following are important lung volumes,

    • Tidal Volume.

    • Inspiratory Reserve Volume.

    • Expiratory Reserve Volume.

    • Residual Volume.

  • Tidal Volume:

    • The amount of air that moves in and out of lungs during normal breathing is called “Tidal Volume”.

    • Normal Value: 500 ml.

  • Inspiratory Reserve Volume:

    • The maximum amount of air that can be inhaled after normal inhalation is called Inspiratory Reserve Volume.

    • Normal Value: 2100 to 3200 ml.

  • Expiratory Reserve Volume:

    • The maximum amount of air that can be exhaled after normal exhalation is called the Expiratory Reserve Volume.

    • Normal Value: 1000to 1200 ml.

  • Residual Volume:

    • The amount of air remaining in lungs after a forceful expiration is called Residual volume.

    • Normal Value: 1200 ml.

    • This volume is necessary to keep lungs open and to prevent lung collapse.

Lung Capacities / Respiratory Capacities:

  • Following are important lung capacities,

    • Inspiratory capacity (IC).

    • Functional residual capacity (FRC).

    • Vital capacity (VC).

    • Total lung capacity (TLC).

  • Inspiratory capacity (IC):

    •  Total amount of air that can be inspired after a tidal expiration.

    • Hence it is “Tidal Volume + Inspiratory Reserve Volume”.

  • Functional residual capacity (FRC):

    • Amount of air remaining in the lungs after a tidal expiration.

    • It is “Residual Volume + Expiratory Reserve Volume”.

  • Vital capacity (VC):

    • It is the total amount of exchangeable air.

    • It is “Tidal volume + Inspiratory Reserve Volume + Expiratory Reserve Volume).

    • Normal value is 4800 ml. (excluding residual volume 1200ml).

  • Total lung capacity (TLC):

    • It is the sum of all lung capacities.

    • It is 6000ml.

Commonly Asked Questions.

  1. Write in short about Respiratory Volumes and Lung Capacities.

  2. Define the following terms,

    1. Tidal Volume.

    2. Inspiratory Reserve Volume.

    3. Expiratory Reserve Volume.

    4. Residual Volume.

  3. Define the following terms,

    1. Inspiratory capacity (IC).

    2. Functional residual capacity (FRC).

    3. Vital capacity (VC).

    4. Total lung capacity (TLC).

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