The key difference between tidal volume and vital capacity is that the tidal volume represents the normal volume of air a person can inhale and exhale during one breath at rest while the vital capacity represents the maximum volume of air a person can access with one breath.
Lung volumes and lung capacities can be measured under different physiological states of expiration and inspiration. Also, they are dependent on the amounts of air a person takes in and release out of the lungs. Here, tidal volume is one of the types of static lung volumes. Whereas, vital capacity is a measurement derives from the dynamic lung volumes. A spirometer is a piece of equipment that analyzes these volumes and capacities. In measuring, vital volume refers to the amount of air inhaled and exhaled during normal breathing under resting conditions. The average tidal volume of a human is about 500 ml. But, the vital capacity of the lung refers to the total amount of air that one can exhale after a full inhalation. However, this volume is dependent on many factors such as body mass and height.
CONTENTS
1. Overview and Key Difference
2. What is Tidal Volume
3. What is Vital Capacity
4. Similarities Between Tidal Volume and Vital Capacity
5. Side by Side Comparison – Tidal Volume vs Vital Capacity in Tabular Form
6. Summary
What is Tidal Volume?
Tidal volume measures the volume of air taken into and out of the lungs during normal breathing. The measurement involved regular inhalation and exhalation under resting conditions. Therefore, one should not apply an extra effort or force in the breathing process when measuring the tidal volume. In a healthy male adult, the tidal volume is approximately equal to about 500 ml while in a healthy female adult, it is 400 ml. However, these values may change to fit physiological needs.
Generally, the tidal volume depends on the individual’s body mass. In a normal person, the optimum tidal volume, more precisely, can be 7mL/kg of body mass. However, the tidal volume also increases with rapid exercising and remains at normal levels during resting conditions.
Figure 01: Tidal Volume
Besides, the tidal volume measurements is taken mainly during the mechanical ventilation processes. To add to this, it is important to check for the tidal volume during mechanical ventilation to avoid damages it can cause to the lungs. Hence, when administering a patient to the ventilator, the tidal volume should be deduced first. In the absence of the analysis of tidal volume during mechanical ventilation, the patient may have to face ventilator-induced injuries which would affect the patient lungs. Moreover, tidal volume measurements are also important during the administration of nebulized drugs.
What is Vital Capacity?
Vital capacity is one of the dynamic lung measurements. It is the maximum amount of air which exhales after a maximum inhalation. Therefore, the vital capacity can be calculated as a summation of inspiratory reserve volume, tidal volume, and expiratory reserve volume. Thus, vital capacity cannot be measured under normal resting conditions and breathing patterns. A normal adult’s vital capacity is about 3 – 5 L. Moreover, there are many factors in which the vital capacity depends on such as the age, the sex, the body mass and the height.
Figure 02: Vital Capacity
Similar to the tidal volume, the vital capacity is also measured using the spirometer. But, this measurement is an indirect measurement. The vital capacity is important in the diagnosis of different lung conditions and to assess the behaviour of the lung muscles, their contractibility and their actions.
What are the Similarities Between Tidal Volume and Vital Capacity?
- Tidal Volume and Vital Capacity are two measurements that use to analyze the lung physiology.
- Both are helpful in diagnosing of varied lung conditions.
- Also, spirometer is an equipment that can measure both these parameters.
- Both can be expressed in litres.
- They depend on the body mass and sex.
What is the Difference Between Tidal Volume and Vital Capacity?
Tidal volume and vital capacity are two important parameters useful in analyzing lung conditions. But, the key difference between tidal volume and vital capacity is the conditions for measurements. The tidal volume is measured under normal respiratory cycle while the vital capacity is measured under forced inhalation conditions. Hence, the tidal volume represents the normal volume of air a person can access during a normal one breath while vital capacity represents the maximum volume of air a person can access during a full inhalation. Another difference between tidal volume and vital capacity is that tidal volume is a static measurement while vital capacity is a dynamic measurement.
The below infographic tabulates the difference between tidal volume and vital capacity in more detail.
Summary – Tidal Volume vs Vital Capacity
The lung volumes and capacities are vital in analyzing respiratory physiology. Tidal volume is the amount of air a person expires after a normal inhalation. In contrast, the vital capacity is the amount of air a person expires after a maximum, forced inhalation. The body mass is an important parameter in determining the tidal volume and the vital capacity. The tidal volume is important during mechanical ventilation. In contrast, the vital capacity is important in analyzing the lung physiology and the behaviour of the lung muscles. Hence, this is the difference between tidal volume and vital capacity.
Reference:
1.Hallett, Sasha. “Physiology, Tidal Volume.” Current Neurology and Neuroscience Reports., U.S. National Library of Medicine, 26 Jan. 2018. Available here
2.Lutfi, Mohamed Faisal. “The Physiological Basis and Clinical Significance of Lung Volume Measurements.” Current Neurology and Neuroscience Reports., U.S. National Library of Medicine, 2017. Available here
Image Courtesy:
1.”Lungvolumes”By Vihsadas (CC BY-SA 3.0) via Commons Wikimedia
2.”Vital Capacity”By No machine-readable author provided. (Public Domain) via Commons Wikimedia