Pulmonary Function Test

It is not a single test but a group of tests, each measuring a different aspect of how your lungs are working. Together, they tell us three essential things: how much air your lungs can hold, how fast air moves in and out, and how efficiently oxygen crosses from your air sacs into the bloodstream.

The tests we perform most often include:

• Spirometry
  the most common; measures how much air you exhale and how quickly; the starting point for diagnosing asthma and COPD
• Lung Volume Testing
  measures total lung capacity, helping identify restrictive conditions like pulmonary fibrosis
• Diffusion Capacity Test (DLCO)
  assesses how well oxygen transfers across the alveolar membrane into the blood; critical for evaluating emphysema and interstitial lung disease
• Body Plethysmography
  performed inside a small sealed chamber; gives precise measurements of lung volumes and airway resistance
• Methacholine Challenge Test
  used specifically when asthma is suspected but spirometry results are normal; involves inhaling a controlled dose of methacholine to detect airway hyperresponsiveness

Several clinical situations call for this investigation. The most common ones we encounter in practice are:

• Unexplained breathlessness
• Chronic cough lasting more than 8 weeks
• Monitoring of known asthma or COPD
• Pre-operative lung assessment before thoracic or major abdominal surgery
• Occupational exposure history
• Follow-up after tuberculosis

Not every patient with these symptoms needs a PFT immediately, but if they are persistent or unexplained, the test is usually warranted:

• Shortness of breath on exertion that is getting progressively worse
• Wheezing - a high-pitched whistling sound while breathing
• Chest tightness, particularly in the morning or after exposure to dust or cold air
• Chronic cough, dry or productive
• Frequent respiratory infections that take longer than usual to resolve
• Fatigue that seems disproportionate to your activity level

This is where PFT proves its value most clearly. It helps us categorize lung disease into two broad patterns, obstructive and restrictive, each pointing toward a different set of diagnoses:

• Asthma
  variable airflow obstruction, often partially reversible after a bronchodilator
• Chronic Obstructive Pulmonary Disease (COPD)
  progressive, largely irreversible airflow limitation; typically in smokers or those with heavy biomass fuel exposure
• Pulmonary Fibrosis
  a restrictive pattern with reduced total lung capacity and impaired diffusion
• Emphysema
  loss of alveolar tissue, reflected in a significantly reduced DLCO
• Interstitial Lung Disease
  various forms, all showing restriction on PFT
• Bronchiectasis
  obstructive or mixed pattern, confirmed with CT but tracked with PFT

The preparation is simple, but following these steps matters - poor preparation genuinely affects the accuracy:

• Avoid smoking for at least 24 hours before the test
• Do not perform strenuous exercise for a minimum of 30 minutes beforehand
• Inform your doctor about all inhalers and bronchodilator medications
• Avoid a heavy meal immediately before; a light snack is generally fine
• Wear loose, comfortable clothing - tight clothing around the chest and abdomen restricts deep breathing
• Bring a list of your current medications and a brief history of your symptoms

The procedure is entirely non-invasive. For spirometry, the most commonly performed component, you will be seated comfortably and asked to seal your lips firmly around a mouthpiece. You take the deepest breath you can, then blow out as hard and as fast as possible until your lungs feel empty. This is usually repeated three times to ensure reproducibility. After the baseline reading, a bronchodilator inhaler may be administered and the test repeated 15 minutes later. This post-bronchodilator response is extremely useful in diagnosing asthma.

Body plethysmography, if required, involves sitting inside a small transparent cabin roughly the size of a telephone booth and breathing normally. It is not claustrophobic for most patients, and the session lasts only a few minutes. The entire PFT session, depending on which tests are ordered, typically takes between 30 and 60 minutes.

Results are reported by a pulmonologist and compared against predicted values based on your age, sex, height, and ethnicity. The PFT is one of the most informative, low-risk investigations available in respiratory medicine. It is painless, takes under an hour, and gives us objective data that simply cannot be obtained from a clinical examination alone. If your doctor has recommended one, it is because the answers it provides will make a genuine difference to how your condition is understood and managed.

UMC Hospitals offers the most advanced pulmonary function testing in Navi Mumbai. They are performed by trained respiratory technologists using calibrated, internationally accredited equipment, with results interpreted by experienced pulmonologists. We offer the complete range of pulmonary function assessments under one roof, with minimal wait times and quick reporting for most tests. Accurate diagnosis begins with a reliable test, and that is precisely what we ensure.