TLC Full Form

TLC stands for Total Lung Capacity. TLC means the volume of air present in the lungs after complete inspiration. The total capacity of air inspired and expired in a single breath is known as the Tidal Volume. Lung Plethysmography is one of the few lung function tests which is used for the measurement of TLC. Evaluation of lung function helps in determining and diagnosing different types of lung disorders.

Purpose of Determining TLC:

TLC is measured to diagnose different types of lung disorders and differentiates between asthma, COPD (Chronic Obstructive Pulmonary Disorder), and other lung diseases. It is necessary to measure TLC to assess the severity of any lung disorder and evaluate whether the candidate is fit to undergo any lung surgeries. 

Lung Volume:

The lung volumes are divided into two types, static and dynamic.

  1. Dynamic lung volume depends upon the rate of airflow.

  2. The static lung volume is further divided into Tidal, inspiratory reserve, expiratory reserve, residual volume.

Static lung capacities are also divided into 4 types that are, inspiratory, functional residual, vital, and total lung capacities. 

Dynamic lung volumes help in the diagnosis of obstructive lung diseases whereas the static lung volumes help in evaluating both obstructive and ventilatory disorders.

The Capacity of the Healthy Lung:

A normal healthy adult has a lung capacity of 5-6 litres. Normal lung capacity can differ based on age, gender, height, weight, and other body composition. Even the place where an individual is born and stays also accounts for the lung volume. For example, people who are born and brought up at sea level have a lesser lung volume than compared to people belonging to higher altitudes. This happens because at higher altitudes the body’s diffusing capacity increases in order to tolerate more air. Lung volume is also affected during pregnancy because of the growing baby, the fundal height reaches the diaphragm thus reducing the lung capacity.

Types of Lung Disorders:

Lung disorders are broadly classified into 2 types: obstructive and restrictive disorders. Restrictive lung disorders include Distress Syndromes, Pulmonary Fibrosis, Sarcoidosis, Scoliosis, etc. In this type, the volume is decreased.

Obstructive lung disorders include COPD, Asthma, Cystic Fibrosis, etc. In this variety, the volume is sufficient but the flow rates are affected.

Increasing Lung Capacity:

Though many factors are applicable to different lung capacities. An individual can also increase the lung capacity by implementing certain healthy lifestyle habits in their daily life such as performing yoga, exercising frequently, performing breathing exercises. It is noticed that athletes, singers, swimmers have greater lung capacities when compared to normal people who don’t follow healthy lifestyle routines.

Researchers have proved that lung capacity varies in males and females. The males have more lung capacity than females. Males have larger bronchioles and wider airways despite the same age as females. Males have larger anthropometric measurements, therefore, increased lung capacity.

Before the Test:

To get the most accurate result of Total Lung Capacity, the patient undergoing the tests needs to refrain from smoking, alcohol intoxication, and the patient needs to avoid large meals and rapid exercise which might cause the breathing to increase. These things need to be followed at least until 4-5 hours before the tests are conducted.

Procedure to Measure TLC:

There are various methods which are conducted to measure total lung capacity some of which are Spirometry, Lung Plethysmography. 

In Lung Plethysmography, the physician will ask the patient to enter into a clear glass room and the patient is asked to breathe quickly through the mouthpiece of the tube which is attached to the machine used for measuring TLC. The test takes around 2-3 mins after which the patient can carry on with his normal activities.

There are chances that the patient might feel slightly dizzy after the test because of random breathing through the mouthpiece of the machine, and patients who have a phobia of staying in enclosed spaces might feel uncomfortable during and after the test. Hence the physician needs to explain the process clearly before conducting the test.


The normal and abnormal result of the Lung Plethysmography test for the measurement of TLC cannot be considered as the final diagnosis of the lung disease. It is only used as a medium to differentiate between various lung problems whether the patient is suffering from a restrictive variety or an obstructive variety of lung disorder.

FAQ (Frequently Asked Questions)

1. What makes up a Total Lung Capacity?

Ans: Total Lung Capacity is the maximum amount of air inflated into the lungs in one breath which is around 6 litres. The formula used to measure this is (TLC= TV + IRV + ERV + RV)

2. Can Spirometry Increase the Lung Capacity?

Ans: With the use of spirometry, the patient is able to learn how to take slow and deep breaths hence proving it to be helpful to increase lung capacity post-trauma and surgery.