We all have two lungs to exchange oxygen from the air into our blood and carbon dioxide that is generated by all our cells back into the air. Just like how a car cannot run without petrol, oxygen is needed for every second of our bodily functions. There is no reserve in our bodies for oxygen; a lack of oxygen for more than five minutes can lead to permanent, irreversible damage to our brains. A common adage says “We are what we eat.” We put food into our bodies thrice to six times a day but we breathe 22,000 times a day and put in 11,000 liters of air into our lungs. More correctly, we are what/if we breathe!
Our lungs are about 100 m2 big or about half the size of a tennis court if spread-out. This development has occurred to ensure that the vital function of oxygen and carbon dioxide exchange continues with a large safety margin. We use only 8-10% of this immense lung capacity at rest. This also means that early disease of the lungs will not be apparent because of the large reserve. The only way to diagnose early abnormalities is to exercise our lungs as the resting function will be abnormal only when 50% of the lungs are damaged. Pulmonary function tests are like ECG for the heart, except that they are seldom performed!
Our lungs consist of branching tubes leading to thin balloon-like structures (alveoli) that expand due to contraction of breathing muscles and expel air out themselves by recoil. Blood from the heart passes very close to the alveoli and matching of blood flow to air delivery (ventilation-perfusion matching) is important for oxygen to be exchanged. Testing of the lungs is thus complex, unlike testing for kidney or liver tests and does not involve a single simple blood test. It involves testing the airways leading to the air-sacs, the air-exchanging air-sacs themselves (alveoli), the blood vessels adjacent to the alveolus, matching of blood flow and air-delivery and finally, the neuromuscular apparatus expanding the air-sacs. The last part also makes testing of the respiratory system subject to good effort, just like any muscle testing. This is why a good PFT technologist, a good lab with overlapping holistic tests and a pulmonologist attuned to these complexities are crucial while doing and interpreting pulmonary function testing. Thus, it is now clear that a CT scan per se cannot clarify several of these above components like the airways, blood vessels and flow-matching and neuromuscular strength. Assessment of lung status requires integration of exposure, symptoms, imaging by CT and physiologic assessment by spirometry, a type of pulmonary function testing. Unlike CT which has radiation exposure, spirometry is non-invasive and can be repeated without any concern over time. Spirometry also quantifies lung disease unlike CT, which is semi-quantitative at best.
The tests required during pulmonary function testing, therefore, are based on what is suspected to be abnormal during examination by a pulmonologist and may be one of the below:
Respiratory Function and Age
Most adults seldom obtain a baseline lung function at 20-30 years which is their peak function; everyone loses lung function annually after that and both the peak and rate of decline influence respiratory health at later age. Patients who have low peak lung function due to childhood exposures and respiratory disease can have chronic lung disease even with normal rate of lung function loss in their mid-40s. Patients with normal peak lung function have chronic lung disease in adulthood due to adult exposures (tobacco smoking, passive smoking, indoor biomass fuel exposure, outdoor air pollution, occupational exposures, pet exposures and major infection like COVID-19, respiratory viral pneumonias and tuberculosis). Chronic lung disease is a silent epidemic and is the 2nd MOST COMMON cause of death in India, accounting for over a million deaths a year. Besides respiratory symptoms and lung failure, low lung function has been shown to be an independent predictor of all-cause mortality.
Who Needs Pulmonary Function Testing?
- Any asymptomatic person after 30 years doing an annual master health check-up.
- Anyone with childhood major or frequent respiratory infections.
- Children from pre-term births.
- Anyone with treated tuberculosis of the lungs.
- Exposure to environmental substances, including tobacco smoke.
- For risk-stratification of lungs before undergoing any major surgical procedure under anesthesia.
- To help with disability claims.
- To determine a plan for specific circumstances (e.g., fitness to fly, drug bronchoprovocation for aspirin, etc.).
- Anyone with cough, sputum, breathlessness, chest pain, wheezing and snoring needs to see their pulmonologist and obtain good pulmonary function testing.
- Anyone with ANY diagnosed respiratory illness.
Pulmonary Function Tests (PFTs) are an important tool in the investigation, diagnosis, management, risk stratification and follow-up for response during the treatment of suspected or already diagnosed respiratory disease. These tests provide vital information regarding modifications to the treatment protocols including inhalers, oral medications, injections, surgical and other interventions. While the tests themselves are most important, the correct interpretation of the results is vital to ensure that the prescribed treatments are the most effective. This requires the kind of detailed expert knowledge of respiratory physiology that is available at the Kauvery Lung Centre. We have holistic testing that is tailored to each individual. Asking for the right tests is important; doing the tests as per standard criteria is crucial. This is because these tests are effort-dependent and values obtained must be interpreted in concordance with the quality of the tests. Kauvery Lung Clinic is proud of the quality of its testing and feedback provided by our experienced technicians that help in the interpretation of lung function testing.
