Respiratory Capacities

The respiratory system starts from the nose to the lungs in human beings and is different from other organisms. This article explains the volumes and capacities of the respiratory system, which is a vital system of the human body. This system forms inhalation and exhalation of oxygen constantly in the human body to keep the human body alive.

Lungs are the organs of the respiratory system, which include other organs like the nose, nostrils, oesophagus, bronchioles, and alveoli. These organs can hold a certain amount of pressure. Imbalances in air volumes and capacities can affect the respiratory or pulmonary system.

Respiratory volumes and capacities 

Respiratory volume refers to the volume of air present in the lungs during different phases of the respiratory cycle. Generally, it’s six litres for human beings. Lung volume can also be termed respiratory volume. There are four types of volumes in the lung; they all have different average figures for checking the pressure. 

• A spirometer is a device used to calculate the potential pressure one can breathe in one cycle of inhaling and exhaling. 

• Inspiratory reserve volume (IRV), tidal volume (TV), expiratory volume (EV), and residual volume (RV) are the four types of lung volumes. 

• The total of these volumes is called respiratory volume, which indicates the overall health and condition of the lung.

What are the different lung capacities?

Inspiratory capacity

The largest volume of air that can be inhaled after a resting condition is called inspiratory capacity (IC). It is calculated using the sum of inspiratory reserve volume and tidal volume.

Total lung capacities

Total lung capacity is used to determine the overall health of the lung. The addition of different volumes interprets different lung capacities. Lung volume means different pressures present in respiratory functioning, while the term lung capacities focus on the limits of the respiratory system. As lung volumes, there are also four types of lung capacities: total lung capacity, vital capacity, inspiratory and functional residual capacity.

Total lung capacity: The total amount of maximum gas one can inhale during the respiration cycle, including tidal volume, is generally six litres for healthy humans. 

Vital capacity

Vital capacity tests the maximum limits of the lung, the total amount of gas that a human can inhale after a forced exhalation, and vice-versa. Vital capacity also indicates the health of the lung. Imbalance in this capacity means the lung is not in proper health. Lack of vital capacity indicates congested lungs, where the diaphragm doesn’t move correctly, or our lungs don’t expand fully. 

Vital capacity general formula: Vital capacity is generally 4.8 litres for healthy males and 3.1 litres for females.

Functional residual capacity

The overall air left in the lungs after exhalation is termed functional residual capacity. This is 2.4 litres for healthy males and 1.8 litres for healthy females. 

How are the volumes of the lungs measured?

Respiratory volume measurements are necessary for a precise physiological diagnosis, but their role in determining disease severity, functional handicap, disease progression, and treatment response is debatable. Spirometry, body plethysmography, nitrogen washout, and helium dilution are among the techniques that can be used to measure static lung volumes. 

Factors affecting lung volume and capacity

Several factors impact the volume and capacities of the lungs, including the body structure, fitness, nature of their area, etc. The human body has more affinity for oxygen at higher altitudes, which makes the respiration process faster and strengthens the lung capacity and volumes more than the average human body’s volumes and capacities. A person living at moderate or lower altitudes has less affinity towards oxygen, and the respiration process is slower compared to a person living at a higher altitude. Hence, they have less lung capacity. Fitness is also an impactful factor in increasing the body’s volumes and capacities. A fit and healthy body have a higher oxygen diffusion rate towards blood flow than a plump body. The gender of a subject also affects the volumes and capacities of the lungs.

The respiratory volumes are either dynamic or static from a physiological standpoint. Both subtypes are assessed at various degrees of inspiration or expiration, but dynamic lung volumes typically rely on the airflow rate. 

Conclusion 

We read here about respiratory volumes and capacities. We learned their maximum and minimum potential hold, different capacities and pressures, and the results of imbalances. Spirometry can be used to detect, characterise, and quantify the severity of lung disease by measuring the volume of air inhaled and exhaled. Absolute lung volumes, residual volume (RV), functional residual capacity (FRC), and total lung capacity (TLC) are more difficult to measure technically, limiting their usage in clinical practice.