Spirogram Diagram

Table of Contents:

• Spirometry
• Spirogram Diagram
• What is Spirogram?
• Frequently Asked Questions

Spirometry

Spirometry is a method used to measure lung capacities and lung volumes. The instrument used for this purpose is called a spirometer. The subject usually breathes into the mouthpiece of this instrument and the further process is recorded in the form of a graph.

A spirometer is used for only a single breath and cannot be used to measure cycles of respiration. The graphical record that is used for inference is termed a spirogram.

In this article, let us learn about the spirogram with the help of a diagram.

Spirogram Diagram

Check:Lung Volumes and Lung Capacities

What is Spirogram?

Spirogram is the graphical record of lung capacities and lung volumes using a spirometer. In the above diagram, the upward deflection depicts inspiration and the downward deflection depicts expiration.

To determine the lung capacities and volumes, the following 4 parameters are noted:

1. Normal end inspiratory level
2. Normal end expiratory level
3. Maximum inspiratory level
4. Maximum expiratory level

A typical spirogram comprises the following details of lung capacities and volumes –

• TV (tidal volume) – It is the volume of air respired in and out in a normal single respiration. It signifies the depth of breathing. Normal TV is 500 mL (0.5 L)
• IRV (inspiratory reserve volume) is the volume of additional air that could be inhaled forcefully after a normal end-inspiration. Normal value of IRV is 3,300 mL (3.3 L).
• ERV (expiratory reserve volume) is the volume of additional air that could be expired forcefully after a normal-end expiration. Normal ERV value 1,000 mL (1 L).
• RV (residual volume) – It is the volume of air that remains in the lungs even after a forceful expiration. Normally, lungs can’t be completely emptied even after forceful expiration. Some amount of air always remains in the lungs even after the forced exhalation. The normal RV value is 1,200 mL (1.2 L)
• Static lung capacities are the mixture of 2 or more lung volumes. They are of four types – IC, VC, FRC and TLC.
• IC (inspiratory capacity) is the maximum volume of air that is inspired after normal expiration, It is the sum of TV and IRV (3800 mL)
• VC (vital capacity) – It is the maximum volume of air that can be expelled out of the lungs forcefully after a deep inspiration. It is the sum of IRV, ERV and TV (4800 mL). The forced vital capacity (FVC) is the volume of air that could be exhaled rapidly and forcefully after a deep inspiration. It is usually equal to VC unless there is a pulmonary disease.
• FRC (functional residual capacity) – It is the volume of air in the lungs after a passive expiration. It is usually measured with the help of plethysmography, nitrogen washout or helium dilution methods and not spirometry. It is the sum of RV and ERV (2200 mL).
• Finally, the volume of air present in the lungs after a maximal inspiration is TLC (total lung capacity). It includes the sum of all the volumes (6000 mL).

Usually, residual volume of the lungs cannot be measured using spirometry. These can be measured only using helium dilution technique, nitrogen washout technique or plethysmography. All these techniques are used to detect respiratory diseases, diagnose asthma, vocal cord dysfunction etc.

Also Read:Mechanism of Breathing

Keep exploring BYJU’S Biology for more such exciting diagrams.