Types of Lung Volumes and Their Role in Breathing
What is the Respiratory System?
The Respiratory system is one of the important physiological processes of life. The human respiratory system comprises a pair of lungs, trachea, bronchi and bronchioles, alveoli, pharynx, larynx and the nose. The major roles of the respiratory system are breathing, exchange of gases between the external environment and the body fluids, and respiration. Now, there are several parameters based on which we can classify our respiratory system. One such parameter is: respiration and lung volumes.
Respiratory Volumes and Capacities
Respiratory Volumes
Respiratory volume simply connotes the amount of air that our lungs can inhale, absorb or exhale under certain conditions. It can also be regarded as the lung volume definition.
There is an apparatus for the calculation of volumes of air present in the lungs. This apparatus is recognized as a ‘Spirometer’. It also enables us to check other criteria associated with the lungs.
The respiratory volume can be further categorized into:-
Tidal Volume (TV) -> Tidal volume can be best explained as the quantity of air that we breathe in and out of the body at the time of normal breathing. It stands roughly around 500 ml. A normal person takes 12-16 breaths each minute. So, if we calculate the tidal volume in a minute, it stands around 6000-8000 ml per minute.
Inspiratory Reserve Volume (IRV) -> Whenever we inhale air beyond the normal capacity by exerting maximum force, that extra amount of inhaled air is termed as inspiratory reserve volume. It is calculated that the approximate value comes somewhat between 2500 ml to 3000 ml.
Expiratory Reserve Volume (ERV) -> Whenever we exhale air beyond the normal capacity by exerting maximum force, that extra amount of exhaled air is explained as expiratory reserve volume. It is calculated that the overall value comes around 1000 ml-1100 ml.
Residual Volume (RV) -> After releasing the air from the body, some amount of air still remains in the lungs. Thus, the amount of air still remaining in the lungs, subsequent to vigorous/energetic expiration is quoted as Residual volume. The approximate data ranges between 1100 ml-1200 ml.
Human Lung Capacity
From the above discussion, it is clear that there are certain lung volumes and capacities associated with the human respiratory system. Now, what is lung capacity? When two or more respiratory volumes/ lung volumes are combined, the result we get is lung capacity or to be more precise respiratory capacity.
The respiratory capacity can be further categorized into:-
Inspiratory Capacity (IC): Whenever a person inhales air immediately followed by releasing it under usual condition (i.e. not forcibly), the air that is received by the body is designated as inspiratory capacity. Thus, inspiratory capacity is found to be a summation of tidal volume and inspiratory reserve volume.
Expiratory Capacity (EC): Just in an opposite manner, when a person exhales air immediately followed by inhalation under usual condition (i.e. not forcibly), the air that is released out of the body is designated as expiratory capacity. Thus, expiratory capacity is found to be a summation of tidal volume and expiratory reserve volume.
Functional Residual Capacity (FRC): As mentioned earlier, some amount of air still stays in the lungs, even after exhalation of air under ordinary conditions. This amount of air can be mentioned as functional residual capacity. It is basically a combination of expiratory reserve volume and residual volume.
Vital Capacity (VC): The maximum amount of air taken in or released out by someone immediately followed by exhalation and inhalation of air respectively is defined as vital capacity. It is an aggregation of tidal volume, inspiratory reserve volume and expiratory reserve volume.
Total Lung Capacity: Total lung capacity is interpreted as the absolute amount of air remaining in the lungs prior to vigorous inhalation of air. This is a sum total of residual volume, expiratory reserve volume, inspiratory reserve volume and tidal volume. The total lung capacity formula is RV+ERV+TV+IRV. Total lung capacity in ml is around 5800 ml.
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Lung Volumes and Capacities Values
We can express lung volumes and capacities normal values as under:-
Inspiratory capacity = 3000 ml- 3500 ml
Expiratory capacity = 1500 ml- 1600 ml
Functional residual capacity = 2500 ml
Vital capacity = 3500 ml- 4500 ml
Total lung capacity = 5800 ml
Lung Volume vs Lung Capacity
There is a vast difference between Lung volume and lung capacity. The amount of air that the human lung can inhale, perceive or exhale is determined as Lung volume. On the other hand, the assimilation of two or more lung volumes gives us lung capacity.
FAQs on Respiratory and Lung Volumes: Definitions, Types & Importance
1. What are the main respiratory volumes that help us understand how we breathe?
There are four primary respiratory volumes, each measuring a different aspect of air movement in the lungs:
- Tidal Volume (TV): The amount of air you breathe in or out during a normal, relaxed breath. It's usually about 500 mL.
- Inspiratory Reserve Volume (IRV): The extra amount of air you can forcefully inhale after a normal inhalation. This is typically around 2500-3000 mL.
- Expiratory Reserve Volume (ERV): The extra amount of air you can forcefully exhale after a normal exhalation, which is about 1000-1100 mL.
- Residual Volume (RV): The amount of air that always remains in the lungs even after a forceful exhalation, preventing them from collapsing. This volume is about 1100-1200 mL.
2. What is the main difference between lung volumes and lung capacities?
The main difference is that lung volumes are direct measurements of air, while lung capacities are calculated by adding two or more lung volumes together. For example, Tidal Volume (TV) is a single measurement (a volume). In contrast, Vital Capacity (VC) is a calculation (TV + IRV + ERV), making it a capacity that represents the total usable volume of the lungs.
3. How much air do we breathe normally, compared to the total our lungs can hold?
During normal, quiet breathing, you only use a small fraction of your lung's ability. This is called the Tidal Volume (TV) and is about 500 mL. However, the Total Lung Capacity (TLC), which is the maximum amount of air your lungs can hold after a deep breath, is much larger—around 5000 to 6000 mL (5 to 6 litres). This shows we have a large reserve for when we need more oxygen, like during exercise.
4. What does 'Vital Capacity' (VC) really tell us about a person's health?
Vital Capacity (VC) is the maximum amount of air a person can exhale after taking the deepest possible breath. It is a very useful indicator of lung health and function. A higher VC suggests strong respiratory muscles and good lung elasticity. Doctors often measure VC to diagnose and monitor respiratory conditions, as a decrease can signal a problem.
5. Why can't you breathe out all the air from your lungs, no matter how hard you try?
You can't exhale all the air because a certain amount, called the Residual Volume (RV), must always remain. This is crucial for two reasons. Firstly, it prevents the tiny air sacs (alveoli) and the lungs themselves from collapsing. Secondly, it ensures that gas exchange between the lungs and the bloodstream can continue uninterrupted, even between breaths.
6. How do factors like age or regular exercise affect these lung volumes?
Lung volumes and capacities change throughout our lives. Generally, Vital Capacity (VC) tends to decrease with age as the chest wall becomes less flexible and respiratory muscles may weaken. However, activities like regular aerobic exercise can help maintain or even increase a person's vital capacity by strengthening the diaphragm and other respiratory muscles, improving overall lung efficiency.
7. Besides breathing, how is understanding respiratory capacity useful in the real world?
Understanding respiratory capacity is vital in many fields. In medicine, it's used to diagnose conditions like asthma and COPD. For athletes, knowing their vital capacity and training to improve it can enhance endurance and performance. It is also important for singers and musicians who play wind instruments, as it directly impacts their ability to hold notes and control airflow.
