Pulmonary Function Testing (PFT) is an essential component of assessment of a lung disease. While chest X-ray (CXR) and Chest CT scan largely tell about the structural abnormalities or defects in the lungs, the PFT inform about the normal or abnormal function of the lungs and the respiratory system. The main function of the Respiratory system is to maintain the normal blood gases – oxygen (O2) and carbon-di-dioxide (CO2). 

Oxygen is the essence of life. It is important to maintain a normal oxygen level in the blood and body tissues. It is important to remember that normal oxygen level does not always mean that the lung function is normal. 

There are many steps involved to achieve normal lung function: 
1. Ventilation – Amount of air inhaled and exhaled by the lungs – measured by various parameters of lung volumes, capacities, air-flow, airway-resistance and obstruction, etc.
2. Distribution – The air we breathe should be evenly distributed in the lungs.
3. Diffusion – Exchange of gases (O2 and CO2) in the lungs at the level of alveolo-capillary membrane. It involves intake of O2 and release of CO2.
4. Transport of O2 to the tissues
5. Tissue oxygenation – uptake of O2 and release of CO2.

Most of these steps are required to be assessed separately for an effective assessment of diagnosis of a disease and its response to treatment or progression.

Commonly, we perform the following tests:
1. Spirometry
2. Forced Oscillometry
3. FeNO (Fraction of exhaled CO2)
4. Diffusion Capacity (DLCO)
5. Oximetry and Blood gas assessment

Respiratory function tests require good expertise of technician and cooperation of patient. All these tests are available in the Respiratory Laboratory of your best chest clinic.