By Dr. Dixit Kumar Thakur
If you have ever sat in a lung function laboratory, been asked to breathe into a tube as hard and fast as you can, and then waited anxiously for a report you could not fully understand — this guide is for you. Lung function tests are among the most information-rich investigations available in all of medicine, but they are also among the least explained to patients. Most people leave their spirometry appointment with a printout of numbers and ratios that they cannot interpret — and often, no one has taken the time to explain what those numbers actually mean about their lungs.
At Pulmovista Clinics in Delhi, Dr. Dixit Kumar Thakur is one of Delhi’s most experienced respiratory disease specialists in the interpretation and clinical application of the full spectrum of lung function tests. In this comprehensive guide, I will explain — in plain, accessible language — exactly what each test involves, what it measures, what the results mean, and how they guide diagnosis and treatment decisions at Pulmovista Clinics.
By the end of this guide, you will never look at a lung function report the same way again.
1. Why Lung Function Tests Matter: The Case for Objective Measurement
Before I explain the individual tests, I want to address a question I hear regularly at Pulmovista Clinics: ‘Do I really need all these tests? I know how I feel.’ The answer, in every case, is yes — and here is why.
Symptoms are subjective. Breathlessness, cough, and wheeze are experienced differently by different patients, influenced by pain tolerance, psychological factors, fitness levels, and disease adaptation. A patient who has had gradually worsening COPD over ten years may describe themselves as ‘managing fine’ — because they have unconsciously reduced their activity level to match their declining lung function. Their subjective experience tells us almost nothing about their objective lung capacity.
Lung function tests are objective. They measure, with precision and reproducibility, exactly how much air your lungs can move, how quickly they can move it, how efficiently they transfer oxygen into the blood, and where in the lung the disease is located. This objectivity is what makes them indispensable for:
• Diagnosis: Confirming whether breathlessness is caused by asthma, COPD, pulmonary fibrosis, or another condition — and distinguishing between conditions that present identically on clinical examination.
• Severity assessment: Classifying COPD by GOLD stage, asthma by GINA step, and pulmonary fibrosis by degree of restriction — which directly determines the correct treatment strategy.
• Monitoring disease progression: Serial lung function tests over months and years reveal whether a condition is stable, slowly declining, or accelerating — allowing treatment to be adjusted proactively rather than reactively.
• Assessing treatment response: Confirming that a new inhaler, biologic therapy, or anti-fibrotic drug is producing measurable benefit — not just symptom relief that could be placebo effect.
• Pre-operative assessment: Determining whether a patient’s lung function is adequate to safely undergo surgery — particularly thoracic, cardiac, or major abdominal procedures.
• Detecting subclinical disease: Identifying lung disease before it causes significant symptoms — particularly important for high-risk patients such as smokers, occupational dust exposures, and patients with a family history of lung disease.
| “I have seen patients at Pulmovista who were completely certain their breathing was ‘not that bad’ — until we did spirometry and found an FEV₁ of 38% predicted. I have also seen patients who were convinced they had severe COPD — and turned out to have normal spirometry with dysfunctional breathing syndrome. The tests do not lie. That is why we do them.” — Dr. Dixit Kumar Thakur, Pulmovista Clinics, Delhi |
2. Test 1: Spirometry — The Foundation of All Lung Function Testing
Spirometry is the most fundamental, most widely performed, and most clinically important lung function test. It is the starting point for the diagnosis of virtually every obstructive and many restrictive lung conditions. At Pulmovista Clinics, spirometry is performed on every new respiratory patient — regardless of their presenting complaint.
What Spirometry Measures
Spirometry measures the volume and speed of air movement during a maximal forced breath. The patient takes the deepest possible breath in, then exhales as hard and fast as possible into the spirometer for at least 6 seconds. This produces two key measurements:
| Measurement | What It Means |
| FEV₁ (Forced Expiratory Volume in 1 second) | The amount of air expelled in the first second of a forced exhalation. The single most important number in respiratory medicine. Reflects the calibre of the large and medium airways. |
| FVC (Forced Vital Capacity) | The total amount of air expelled during the entire forced exhalation. Represents the total usable lung volume — reduced in restrictive lung disease. |
| FEV₁/FVC Ratio | The proportion of total lung volume expelled in the first second. The key diagnostic ratio: below 0.70 (70%) = obstructive pattern (COPD, asthma); normal or elevated = restrictive pattern. |
| FEF 25-75% | Flow rate in the middle portion of the exhalation — a sensitive early marker of small airway disease, often abnormal before FEV₁ declines. |
| Peak Expiratory Flow (PEF) | The fastest flow rate achieved at the very start of exhalation. Highly effort-dependent; used primarily for asthma monitoring rather than diagnosis. |
| FVC % Predicted | FVC expressed as a percentage of the expected normal value for a patient’s age, sex, and height. Below 80% suggests restriction — but must be confirmed with TLC measurement. |
Interpreting the Spirometry Pattern: What Dr. Dixit Kumar Thakur Looks for at Pulmovista
| Pattern | FEV₁/FVC Ratio | Conditions Suggested |
| Normal | ≥0.70 and FEV₁ ≥80% predicted | No spirometric abnormality — does not exclude all lung disease (e.g. mild ILD may have normal spirometry early) |
| Obstructive | <0.70 (post-bronchodilator) | COPD, asthma, bronchiectasis, obliterative bronchiolitis, tracheal stenosis |
| Restrictive (suspected) | ≥0.70 but FVC <80% predicted | Pulmonary fibrosis (ILD), pleural disease, chest wall deformity, neuromuscular disease, obesity — requires TLC confirmation |
| Mixed | <0.70 AND FVC <80% predicted | Combined obstruction and restriction — COPD with pulmonary fibrosis, sarcoidosis with airway involvement |
| Non-specific | <0.70 and FEV₁ ≥80% predicted | Early obstruction, small airway disease, poor effort — requires clinical context and further testing |
The Bronchodilator Reversibility Test: Asthma vs. COPD
At Pulmovista Clinics, spirometry is almost always performed with a bronchodilator reversibility test — spirometry before and 15–20 minutes after administering 400mcg of Salbutamol via spacer. The change in FEV₁ after bronchodilator is critical for distinguishing asthma from COPD:
• Significant reversibility (FEV₁ increase ≥200mL AND ≥12%): Strongly suggests asthma — the obstruction reverses significantly with a bronchodilator.
• Incomplete or absent reversibility: Characteristic of COPD — the obstruction is fixed or only partially reversible, reflecting permanent airway and parenchymal damage.
• Important caveat: Reversibility is a spectrum, not a binary — many patients have intermediate responses. Dr. Dixit Kumar Thakur interprets reversibility in the context of the full clinical picture, not as a standalone test.
GOLD Staging: How Spirometry Classifies COPD Severity
| GOLD Stage | Post-Bronchodilator FEV₁ % Predicted |
| GOLD 1 (Mild) | FEV₁ ≥80% — obstruction confirmed but lung function near-normal |
| GOLD 2 (Moderate) | FEV₁ 50–79% — significant obstruction; breathlessness on moderate exertion |
| GOLD 3 (Severe) | FEV₁ 30–49% — severe obstruction; breathlessness on mild exertion; frequent exacerbations |
| GOLD 4 (Very Severe) | FEV₁ <30% — very severe obstruction; breathlessness at rest; may require LTOT |
How to Prepare for Spirometry at Pulmovista Clinics
| ✔ Patient Preparation Instructions for Spirometry at Pulmovista Clinics ✔ Do NOT use short-acting bronchodilators (Salbutamol / Ventolin) for 4–6 hours before the test ✔ Do NOT use long-acting bronchodilators (LABA, LAMA) for 12–24 hours before the test (unless Dr. Thakur specifies otherwise) ✔ Do NOT smoke for at least 4 hours before the test ✔ Do NOT eat a large meal within 2 hours — a full stomach restricts diaphragm movement ✔ Wear loose, comfortable clothing — tight clothing around the chest restricts full inhalation ✔ Bring your inhalers to the appointment so the team can review them ✔ Arrive 10–15 minutes early to rest before testing — exertion immediately before the test affects results |
3. Test 2: Oscillometry (IOS/FOT) — The Test That Detects What Spirometry Misses
Oscillometry — also known as the Impulse Oscillometry System (IOS) or Forced Oscillation Technique (FOT) — is one of the most clinically important advances in lung function testing of the past two decades, and one that remains significantly underutilised across India. At Pulmovista Clinics, Dr. Dixit Kumar Thakur uses oscillometry routinely, particularly for patients in whom spirometry results do not fully explain the clinical picture.
What Is Oscillometry and How Does It Work?
Unlike spirometry — which requires a maximal forced breathing effort — oscillometry is performed during normal, quiet, tidal breathing. The patient simply breathes normally through a mouthpiece while the oscillometry device delivers tiny, imperceptible pressure waves (oscillations) at multiple frequencies into the airway. The pattern of how these pressure waves travel through the lung — and how much resistance and reactance they encounter — is analysed to map the mechanical properties of the entire airway tree, from the largest airways to the smallest peripheral bronchioles.
This is the fundamental advantage of oscillometry over spirometry: it assesses the small airways — the bronchioles less than 2mm in diameter — with a sensitivity that spirometry cannot match. Small airway disease is the earliest site of damage in COPD, asthma, and smoking-related lung disease — often present for years before spirometry detects any abnormality.
Key Oscillometry Parameters — What They Mean
| Parameter | Clinical Meaning |
| R5 (Resistance at 5Hz) | Total airway resistance — reflects both large and small airway resistance combined. Elevated in COPD, asthma, and any condition causing airflow obstruction. |
| R20 (Resistance at 20Hz) | Predominantly large airway resistance — reflects central airway (trachea, main bronchi) resistance. |
| R5-R20 (Frequency Dependence of Resistance) | The difference between total and central resistance — a specific marker of SMALL AIRWAY resistance. Elevated R5-R20 indicates peripheral (small) airway disease — often the first detectable abnormality in early COPD. |
| X5 (Reactance at 5Hz) | Reflects the elastic and inertial properties of the lung periphery. Negative X5 values indicate air trapping and hyperinflation — characteristic of advanced COPD and severe asthma. |
| AX (Reactance Area) | The area under the reactance curve — an integrated measure of small airway dysfunction. Highly sensitive to changes in small airway disease. |
| Fres (Resonance Frequency) | The frequency at which resistance and reactance balance. Elevated in obstructive disease — higher Fres indicates worse obstruction. |
When Dr. Dixit Kumar Thakur Orders Oscillometry at Pulmovista
• Early COPD or pre-COPD detection: Patients with normal or near-normal spirometry but symptoms of breathlessness or significant smoking history — oscillometry frequently detects small airway disease before FEV₁ declines.
• Asthma assessment: Oscillometry quantifies peripheral airway inflammation and air trapping — complementing FeNO and spirometry for a complete asthma phenotype assessment.
• Children and elderly patients: Oscillometry requires only normal tidal breathing — making it the preferred technique for patients who cannot perform the maximal forced effort required by spirometry.
• Monitoring treatment response: Oscillometry detects improvements in small airway function from ICS therapy, SMART therapy, or biologic treatment that may not yet be visible on spirometry.
• Post-COVID lung assessment: Small airway disease is a dominant feature of post-COVID lung syndrome — oscillometry precisely characterises the nature and distribution of persistent post-COVID airways dysfunction.
| “I ordered oscillometry for a 38-year-old patient at Pulmovista who had been told her spirometry was ‘borderline normal.’ Her R5-R20 was markedly elevated and her AX was significantly abnormal. She had early small airway disease that spirometry had completely missed — almost certainly driven by her 15-year smoking history and Delhi’s PM2.5 exposure. We started targeted therapy immediately. Oscillometry found what spirometry could not.” — Dr. Dixit Kumar Thakur, Pulmovista Clinics, Delhi |
4. Test 3: DLCO (Diffusing Capacity) — Measuring Oxygen Transfer Efficiency
The DLCO — Diffusing Capacity of the Lung for Carbon Monoxide — measures how efficiently gas crosses from the air sacs (alveoli) of the lung into the bloodstream. It is, in simple terms, a measure of the health and surface area of the gas-exchange membrane — the thin tissue layer across which oxygen and carbon dioxide are exchanged with every breath.
What Does DLCO Actually Tell Us?
A reduced DLCO tells Dr. Dixit Kumar Thakur at Pulmovista that the lung’s gas exchange capacity is impaired — even when the airways themselves may be relatively unaffected. This distinction is clinically critical:
| DLCO Finding | Clinical Interpretation |
| Normal DLCO with obstruction | Asthma — the alveolar surface is intact; only the airways are narrowed |
| Reduced DLCO with obstruction | COPD with emphysema — alveolar walls have been destroyed; both airways and gas exchange are damaged |
| Reduced DLCO with restriction | Pulmonary fibrosis (ILD) — thickened, scarred alveolar walls impair gas diffusion; this is the hallmark finding in ILD |
| Markedly reduced DLCO with normal or near-normal spirometry | Early ILD; pulmonary vascular disease (pulmonary hypertension); anaemia (DLCO corrected for Hb) |
| Elevated DLCO | Pulmonary haemorrhage; polycythaemia — blood filling alveolar spaces increases CO uptake |
DLCO in Practice at Pulmovista Clinics
Dr. Dixit Kumar Thakur orders DLCO in the following clinical situations:
• Suspected ILD or pulmonary fibrosis: DLCO is the most sensitive early marker of gas exchange impairment in ILD — often reduced before spirometry shows restriction.
• COPD severity assessment: In COPD, DLCO reduction indicates emphysema — a different phenotype with different treatment implications (and a key factor in bronchoscopic lung volume reduction candidacy assessment).
• Dyspnoea disproportionate to spirometry: When a patient is significantly more breathless than their FEV₁ would suggest — reduced DLCO may explain the gap.
• Pre-operative assessment: Before lung resection surgery — DLCO predicts post-operative respiratory reserve.
• Monitoring anti-fibrotic therapy: In IPF patients on nintedanib or pirfenidone — serial DLCO tracks whether the rate of gas exchange decline is being modified by treatment.
5. Test 4: Lung Volumes (Body Plethysmography) — The Complete Picture
Body plethysmography — performed in a sealed, phone-booth-sized airtight box called a body box or plethysmograph — measures the absolute volumes of air within the lungs under all conditions. This is a level of detail that spirometry cannot provide, because spirometry only measures the air that can be moved in and out — not the air that is trapped within the lungs.
Key Lung Volume Measurements at Pulmovista
| Lung Volume | What It Tells Dr. Dixit Kumar Thakur |
| TLC (Total Lung Capacity) | The total volume of air in the lungs at full inhalation. Reduced in restriction (ILD, fibrosis, pleural disease). Normal or increased in obstruction. TLC <80% predicted confirms a restrictive defect. |
| RV (Residual Volume) | The air remaining in the lungs after maximal exhalation — air that can never be expelled. Markedly elevated in emphysema and severe asthma — reflects gas trapping. |
| RV/TLC Ratio | The proportion of the total lung that is permanently trapped air. RV/TLC >40% indicates significant gas trapping — a hallmark of COPD with emphysema and hyperinflation. |
| FRC (Functional Residual Capacity) | The air in the lungs at the end of a normal quiet exhalation. Elevated FRC indicates hyperinflation — the lungs are operating at a higher baseline volume, causing breathlessness and inefficient breathing. |
| IC (Inspiratory Capacity) | The air that can be inhaled from FRC. Reduced IC is one of the best predictors of exercise limitation in COPD — more predictive of breathlessness than FEV₁ alone. |
Body plethysmography is ordered at Pulmovista Clinics when spirometry shows a possible restrictive pattern (reduced FVC), when gas trapping or hyperinflation is suspected in COPD, and when the complete lung volume profile is needed for surgical candidacy assessment or monitoring of ILD progression.
6. Test 5: FeNO (Fractional Exhaled Nitric Oxide) — Measuring Airway Inflammation
FeNO is a unique lung function test in that it does not measure airflow or lung volumes — it measures airway inflammation directly. Specifically, it measures the concentration of nitric oxide in exhaled breath, which is produced by the inflamed bronchial epithelium in proportion to the degree of eosinophilic (allergic) airway inflammation.
How FeNO Is Performed at Pulmovista
The test is remarkably simple. The patient exhales slowly and steadily through a mouthpiece at a constant, controlled flow rate for approximately 10 seconds. The device measures the concentration of nitric oxide in the exhaled air in real time. It is completely non-invasive, requires no forced breathing effort, and takes less than 2 minutes. It is suitable for all ages, including young children.
Interpreting FeNO Results: Dr. Dixit Kumar Thakur’s Clinical Framework
| FeNO Level | Interpretation | Clinical Action at Pulmovista |
| <25 ppb (Low) | Little or no eosinophilic airway inflammation present | Eosinophilic asthma unlikely; consider alternative diagnosis; if on ICS, may indicate need to step down |
| 25–50 ppb (Intermediate) | Possible eosinophilic inflammation — interpret with clinical context | Asthma likely if symptomatic; ICS therapy indicated; repeat after 4 weeks of treatment |
| >50 ppb (High) | Significant eosinophilic airway inflammation — asthma very likely | Strong indication for ICS therapy; high FeNO predicts good response to ICS and to anti-IL-5 biologics |
| >150 ppb (Very High) | Severe type 2 airway inflammation | Urgent consideration of biologic therapy — Dupilumab, Mepolizumab, or Benralizumab; review ICS adherence and inhaler technique |
How Dr. Dixit Kumar Thakur Uses FeNO at Pulmovista Clinics
• Asthma diagnosis: FeNO above 40–50 ppb in a patient with typical asthma symptoms strongly supports the diagnosis — particularly valuable when spirometry is normal.
• ICS dose guidance: Low FeNO in a patient on ICS = inflammation controlled, step-down possible. High FeNO despite ICS = poor adherence, poor technique, or steroid-resistant inflammation.
• Biologic therapy selection: FeNO above 25 ppb is the threshold for Dupilumab eligibility; FeNO is part of the biologic selection algorithm for all severe asthma patients at Pulmovista.
• Monitoring treatment response: Serial FeNO measurement confirms that anti-inflammatory therapy is working — a falling FeNO over weeks indicates effective suppression of airway inflammation.
• Occupational asthma investigation: Serial FeNO at work and away from work can identify occupational allergen exposure as the trigger.
7. Test 6: The 6-Minute Walk Test (6MWT) — Functional Exercise Capacity
The 6-Minute Walk Test is a simple, practical, and enormously informative assessment of functional exercise capacity. The patient walks at their own pace along a measured corridor for 6 minutes, with standardised encouragement at set intervals. The distance covered — the 6MWT distance — reflects the integrated function of the respiratory, cardiovascular, and musculoskeletal systems under real-world walking conditions.
What the 6MWT Tells Dr. Dixit Kumar Thakur at Pulmovista
• Baseline functional capacity: A 6MWT distance below 350 metres in a COPD or ILD patient is associated with significantly increased mortality risk — making it a powerful prognostic tool beyond what spirometry alone can provide.
• Exercise-induced desaturation: Continuous SpO₂ monitoring during the 6MWT identifies patients who desaturate significantly on exertion — even if resting saturation is normal. This determines the need for ambulatory oxygen and influences pulmonary rehabilitation programme design.
• Pulmonary rehabilitation response: A change of 26 metres or more in 6MWT distance after a rehabilitation programme is the minimum clinically important difference — confirming meaningful functional benefit.
• Pre-transplant assessment: 6MWT distance is a key criterion in lung transplant candidacy evaluation — used by Pulmovista Clinics when preparing referral documentation.
• ILD progression monitoring: Serial 6MWT in pulmonary fibrosis patients tracks functional decline alongside DLCO and FVC — a declining 6MWT predicts mortality independently of spirometry.
8. Test 7: Cardiopulmonary Exercise Testing (CPET) — The Gold Standard for Unexplained Breathlessness
Cardiopulmonary Exercise Testing (CPET) is the most comprehensive exercise assessment available — the investigation I reach for at Pulmovista Clinics when a patient has significant breathlessness but standard lung function tests do not provide a clear explanation. CPET simultaneously measures the responses of the respiratory, cardiovascular, and skeletal muscle systems during progressive exercise on a cycle ergometer, providing an integrated picture of exercise physiology that no other test can match.
What CPET Measures and Why It Matters
| CPET Measurement | Clinical Significance |
| VO₂max (Peak Oxygen Uptake) | The maximum rate of oxygen consumption during exercise — the single best measure of overall cardiorespiratory fitness. Reduced in respiratory disease, cardiac disease, deconditioning, and anaemia. |
| Ventilatory Reserve | How much breathing capacity remains unused at peak exercise. Low ventilatory reserve = lungs are the limiting factor. Normal ventilatory reserve = heart, muscles, or motivation is the limit, not the lungs. |
| Breathing Pattern During Exercise | Identifies hyperventilation, inefficient breathing patterns, and dynamic hyperinflation — the primary mechanism of exertional breathlessness in COPD. |
| Oxygen Pulse (VO₂/HR) | Reflects stroke volume — low oxygen pulse suggests cardiac limitation or anaemia as the primary exercise limiter. |
| AT (Anaerobic Threshold) | The exercise intensity at which lactate accumulates — reduced in deconditioning and cardiac disease; normal in pure respiratory limitation. |
| Exercise-induced SpO₂ decline | Documents the severity and pattern of exertional desaturation — more precise than 6MWT oximetry. |
At Pulmovista Clinics, CPET is particularly valuable for: distinguishing respiratory from cardiac causes of breathlessness; evaluating unexplained exercise intolerance in patients with normal resting lung function; pre-operative risk assessment before major surgery; and designing individualised pulmonary rehabilitation exercise prescriptions for complex patients.
9. How a Respiratory Disease Specialist in Delhi Puts It All Together: The Pulmovista Diagnostic Approach
Understanding individual lung function tests is important — but what separates a truly expert respiratory disease specialist in Delhi from a general practitioner ordering a single spirometry is the ability to synthesise results from multiple tests into a coherent clinical picture. At Pulmovista Clinics, Dr. Dixit Kumar Thakur follows a structured, multi-test diagnostic approach that ensures no aspect of a patient’s respiratory function goes unmeasured or unexplained.
The Pulmovista Clinics Lung Function Test Selection Framework
| Clinical Scenario | Tests Ordered at Pulmovista | What We Are Looking For |
| Breathlessness — unknown cause | Spirometry + bronchodilator; FeNO; DLCO; 6MWT with oximetry; oscillometry if spirometry near-normal | Obstruction (asthma/COPD), restriction (ILD), small airway disease, gas exchange impairment, exercise desaturation |
| Suspected or known asthma | Spirometry + bronchodilator reversibility; FeNO; oscillometry; peak flow diary | Confirm obstruction, assess reversibility, quantify inflammation, detect small airway involvement |
| Suspected or known COPD | Spirometry + bronchodilator; lung volumes (plethysmography); DLCO; 6MWT; oscillometry | Confirm obstruction, classify GOLD stage, detect emphysema, quantify hyperinflation and gas trapping |
| Suspected ILD / Pulmonary Fibrosis | Spirometry; DLCO; lung volumes (TLC); 6MWT with oximetry; FeNO (to exclude eosinophilic overlap) | Confirm restriction, quantify gas exchange impairment, assess exercise capacity and desaturation |
| Unexplained breathlessness (normal spirometry) | Oscillometry; FeNO; DLCO; CPET; 6MWT | Small airway disease, eosinophilic inflammation, gas exchange limitation, cardiac limitation, dysfunctional breathing |
| Pre-operative assessment | Spirometry; DLCO; 6MWT; CPET if high-risk procedure | Surgical risk stratification; post-operative respiratory reserve prediction |
| Post-COVID lung assessment | Spirometry; oscillometry; DLCO; FeNO; 6MWT | Small airway disease (most common), gas exchange impairment, persistent inflammation, functional limitation |
| 📋 What Makes Pulmovista Clinics the Right Choice for Lung Function Testing in Delhi 📋 Full range of lung function tests available: Spirometry, Oscillometry (IOS), DLCO, Body Plethysmography, FeNO, 6MWT, CPET 📋 Tests performed by trained, experienced respiratory technicians — quality of performance directly affects result accuracy 📋 All results personally interpreted by Dr. Dixit Kumar Thakur — not outsourced to a report-generating algorithm 📋 Results explained in full during a dedicated results consultation — patients leave understanding their numbers 📋 Serial lung function monitoring — structured follow-up testing to track disease progression and treatment response 📋 Integration with clinical findings, imaging, and biomarker results for a complete diagnostic picture 📋 GINA 2026 and GOLD 2026 compliant interpretation — results mapped to current international diagnostic and treatment frameworks |
Conclusion: Lung Function Tests Are Your Lungs Speaking — Pulmovista Clinics Translates
Spirometry, oscillometry, DLCO, body plethysmography, FeNO, the 6-Minute Walk Test, and CPET — each of these tests tells a different part of the story of your respiratory health. Together, interpreted by an experienced respiratory disease specialist, they provide a complete, objective, and actionable picture of what is happening inside your lungs — and what can be done about it.
At Pulmovista Clinics in Delhi, Dr. Dixit Kumar Thakur offers the most comprehensive lung function testing and interpretation service available in Delhi NCR. Every test is performed to the highest technical standard, interpreted personally by a senior pulmonologist with 13+ years of experience, and explained clearly to every patient. Because understanding your lung function is not just the doctor’s job — it is yours too.
If you have been told your spirometry is abnormal and you do not fully understand what that means, or if you have breathlessness that has not been fully investigated, or if you simply want a thorough, expert assessment of your respiratory health — book your lung function testing consultation at Pulmovista Clinics today.
FAQs-Lung Function Tests and Your Respiratory Disease Specialist in Delhi
- Do I need to stop my inhalers before lung function tests?This depends on which test is being performed and what question is being asked. For a diagnostic spirometry — where the aim is to see your 'true' baseline obstruction — short-acting bronchodilators should be withheld for 4–6 hours and long-acting bronchodilators for 12–24 hours. For a monitoring spirometry — where the aim is to assess your lung function on optimised treatment — taking your inhalers as usual is correct. Dr. Dixit Kumar Thakur at Pulmovista Clinics will give you specific instructions before your appointment based on the clinical question being answered. If in doubt, call the clinic before your appointment.
- My spirometry report shows FEV₁/FVC of 0.68. Does that mean I have COPD?A post-bronchodilator FEV₁/FVC ratio below 0.70 is the GOLD criterion for confirming airflow obstruction consistent with COPD — but a ratio of 0.68 alone does not mean you have COPD without clinical context. At Pulmovista Clinics, Dr. Dixit Kumar Thakur interprets this finding alongside your symptoms, smoking history, age, exposure history, DLCO, and reversibility test. In older adults (above 70), a ratio of 0.65–0.70 may represent normal age-related changes rather than COPD. In a 40-year-old non-smoker, it warrants thorough investigation. Spirometry results require expert interpretation — not just a number comparison to a threshold.
- My FeNO is 62 ppb. What does this mean for my treatment?A FeNO of 62 ppb represents significant eosinophilic airway inflammation. At Pulmovista Clinics, this level of FeNO tells Dr. Dixit Kumar Thakur that: (1) asthma or eosinophilic bronchitis is very likely; (2) inhaled corticosteroid therapy is strongly indicated and should produce a good response; (3) if you are already on ICS and your FeNO remains this high, your inhaler technique or adherence may be suboptimal — or you may need a higher ICS dose; and (4) if your asthma remains uncontrolled despite optimised ICS, a FeNO of 62 ppb meets the threshold for Dupilumab biologic therapy eligibility.
- What is the difference between spirometry and a lung function test?Spirometry is one type of lung function test — specifically, the measurement of airflow during forced breathing. 'Lung function test' is a broader term that encompasses spirometry, oscillometry, DLCO, body plethysmography, FeNO, the 6-Minute Walk Test, and cardiopulmonary exercise testing. When a respiratory disease specialist in Delhi refers to 'lung function tests,' they typically mean a combination of these investigations tailored to the clinical question. At Pulmovista Clinics, Dr. Dixit Kumar Thakur selects the most appropriate combination of lung function tests for each individual patient — not a fixed panel applied to everyone.
- How often should lung function tests be repeated?The frequency of repeat testing depends on the diagnosis and its stability. For stable, mild asthma — annual spirometry and FeNO. For COPD — spirometry every 1–2 years; DLCO and 6MWT annually. For ILD/pulmonary fibrosis — spirometry, DLCO, and 6MWT every 3–6 months, as these conditions can decline rapidly and treatment decisions (initiation or escalation of anti-fibrotic therapy, transplant referral) are triggered by objective functional decline. For patients starting new treatment — repeat lung function tests at 4–8 weeks to confirm response. Dr. Dixit Kumar Thakur schedules all follow-up lung function testing for Pulmovista patients as part of their personalised long-term management plan.