Pulmonary volume/ Respiratory volume is the quantity of air which human lungs can hold or expel under different conditions.
i. Tidal Volume (TV)
- The volume of air inspired or expired during normal respiration.
- TV - 500 ml approx.
ii. Inspiratory Reserve Volume (IRV)
- The additional volume of air, a person can inspire above TV, by a forcible inspiration.
- IRV - 2500 - 3000 ml
iii. Expiratory Reserve Volume (ERV)
- The additional volume of air, a person can expire above TV, by a forcible expiration.
- ERV - 1000 - 1100 ml
iv. Residual Volume (RV)
- The volume of air remaining in the lungs even after a forcible expiration
- RV - 1100 - 1200 ml
v. Minute Respiratory Volume (MRV)
- The volume of air entering the respiratory tract in a minute.
- It is TV × Respiratory rate
=500 ml × (12 to 16/min)
=6000 - 8000 ml/min
vi. Dead Space Volume (DSV)
- The volume of inhaled air that remains in the conducting airways and does not take part in gaseous exchange.
- It is 1/3rd the value of tidal volume
- 150 ml approx.
vii. Minute Alveolar Ventilation
- The volume of air reaching alveoli for exchange in a minute.
- It is (TV - DSV) × Respiratory rate
= (500ml - 150ml) × (12 to 16/min)
= 350 ml × (12 to 16/min)
= 4200 - 5600 ml/min
|Tidal Volume (TV)||500 ml|
|Inspiratory Reserve Volume (IRV)||2500 - 3000 ml|
|Expiratory Reserve Volume (ERV)||1000 - 1100 ml|
|Residual Volume (RV)||1100 - 1200 ml|
|Minute Respiratory Volume (MRV)||6000 -8000 ml/min|
|Dead Space Volume (DSV)||150 ml|
Respiratory Capacities are Sum of two or more respiratory volumes
i. Inspiratory Capacity (IC)
ii. Expiratory Capacity (EC)
iii. Functional Residual Capacity (FRC)
iv. Vital Capacity (VC)
v. Total Lung Capacity (TLC)
|Inspiratory Capacity (IC)||TV + IRV = 3000 - 3500 ml|
|Expiratory Capacity (EC)||TV + ERV = 1500 - 1600 ml|
|Functional Residual Capacity (FRC)||ERV + RV = 2500 ml|
|Vital Capacity (VC)||IRV + ERV + TV = 3500 - 4500 ml|
|Total Lung Capacity (TLC)||RV + IRV+ ERV + TV = 5800 ml|
Q1. Why do athletes have more vital capacity?
- Athletes have more vital capacity because their oxygen requirement is more as they do strenuous activities.
- Due to strenuous exercise, muscle development occurs which helps in lungs extension, thus vital capacity increases.
Q2. Why is residual volume important?
- Residual volume is volume of air remaining in the lungs even after a forcible expiration
- Residual volume is important because the air that remains in the lungs after forceful exhalation prevents lungs from collapsing.
Q3. What is the difference between residual volume and functional residual capacity?
- Residual volume (RV) is the volume of air remaining in the lungs even after a forcible expiration
- Functional residual volume (FRC) is the volume of air that remains in the lungs after a normal expiration.
- It includes expiratory reserve volume and residual volume
- FRC = ERV + RV
Q4. What causes dead space?
The volume of inhaled air that remains in the conducting airways and does not take part in gaseous exchange leads to dead space formation.
Q5. What is the significance of vital capacity?
- Vital capacity is the maximum volume of air a person can breathe in and out after forced expiration and inspiration respectively.
- This helps to remove deoxygenated blood from the body and allows to inhale fresh air.
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