A pulmonologist uses a range of tests to evaluate how well your lungs work, identify the cause of symptoms like chronic cough or shortness of breath, and monitor known lung conditions over time. The specific tests depend on your symptoms and medical history, but most visits start with breathing tests and imaging before moving to more specialized procedures if needed.
Spirometry and Pulmonary Function Tests
Spirometry is the most common test you’ll encounter. You breathe into a mouthpiece as hard and fast as you can, and the device measures two key numbers: how much air your lungs can hold (forced vital capacity, or FVC) and how much air you can push out in the first second (FEV1). The ratio between these two numbers tells your pulmonologist whether your airways are narrowed. A ratio below 0.70 signals an obstructive pattern, which is the hallmark of conditions like asthma and COPD.
A second component, called a diffusion test, checks how efficiently oxygen crosses from your lungs into your bloodstream. You’ll inhale a tiny, harmless amount of carbon monoxide and then exhale it. The amount your lungs absorb reveals whether the air sacs are damaged or the blood vessels around them aren’t working properly. Low results paired with normal spirometry can point to early interstitial lung disease, pulmonary vascular problems, or emphysema. High results sometimes show up with asthma or obesity.
These tests require some preparation. You’ll need to stop using short-acting inhalers like albuterol at least 6 hours beforehand. Short-acting anticholinergic inhalers require a 12-hour pause, long-acting inhalers need 24 hours, and ultra-long-acting agents like tiotropium require 36 hours. Your pulmonologist’s office should give you specific instructions, but it helps to know this before scheduling.
Chest X-rays and CT Scans
A standard chest X-ray is often the first imaging test ordered. It gives a broad look at the lungs, heart, and surrounding structures and can reveal infections, fluid buildup, or large masses. It’s quick, inexpensive, and widely available, which makes it a useful starting point.
When more detail is needed, a high-resolution CT scan (HRCT) provides cross-sectional images that are far more sensitive at detecting subtle changes in lung tissue. HRCT can pick up early scarring, small nodules, and patterns of inflammation that a standard X-ray would miss entirely. For conditions like interstitial lung disease, early-stage occupational lung damage, or unexplained findings on an X-ray, CT is the preferred tool.
Arterial Blood Gas Test
An arterial blood gas (ABG) test gives a detailed snapshot of how well your lungs exchange oxygen and carbon dioxide. Unlike a standard blood draw from a vein, the sample comes from an artery, usually at the wrist, because arterial blood reflects what your lungs are actually delivering to the body.
The test measures oxygen pressure in your blood, carbon dioxide levels, blood acidity (pH), and bicarbonate concentration. Together, these values tell your pulmonologist whether your lungs are getting enough oxygen into your bloodstream and clearing carbon dioxide out efficiently. A simpler alternative, pulse oximetry (the clip placed on your fingertip), only measures oxygen saturation. It’s useful for quick checks, but when carbon dioxide levels or blood acidity are also a concern, an ABG provides the full picture.
Six-Minute Walk Test
This test measures your functional exercise capacity in a way that mimics everyday activity. You walk along a flat corridor at your own pace for six minutes, covering as much distance as you can. You’re allowed to slow down or stop and rest against a wall if needed, but the clock keeps running. Before you start, a technician records your heart rate, blood pressure, oxygen saturation, and your self-rated level of breathlessness and fatigue. These same measurements are taken again at the end.
The total distance you cover, combined with any drops in oxygen saturation during exertion, helps your pulmonologist gauge how much your lung condition is affecting daily life. It’s particularly useful for tracking disease progression in COPD, pulmonary fibrosis, and pulmonary hypertension, and for evaluating whether treatments are making a real difference.
Sleep Studies
If your pulmonologist suspects a sleep-related breathing disorder like obstructive sleep apnea, they may order a polysomnography, or overnight sleep study. You spend the night in a sleep lab while sensors record your brain waves, eye movements, heart rate, breathing pattern, blood oxygen levels, body position, chest and abdominal movement, limb movements, and snoring. Brain wave and eye movement data help classify your sleep stages, which reveals how fragmented your sleep actually is. The combined data shows whether your airway repeatedly collapses during sleep and how severely it affects your oxygen levels.
Bronchoscopy
Bronchoscopy is a more involved procedure where a thin, flexible tube with a camera is guided through your nose or mouth and into your airways. It allows your pulmonologist to visually inspect the inside of your airways and collect tissue samples or fluid for analysis. You’re typically sedated for the procedure.
On the diagnostic side, it’s used to investigate coughing up blood, persistent unexplained cough, suspicious masses seen on imaging, and enlarged lymph nodes near the lungs. It’s also a key tool for staging lung cancer, since tissue samples from lymph nodes can be taken directly through the airway wall. Therapeutically, bronchoscopy can retrieve inhaled foreign objects, place stents to open narrowed airways, remove tumors blocking the airway, and even deliver targeted treatments for severe asthma.
Thoracentesis
When fluid accumulates in the space between your lungs and chest wall, a procedure called thoracentesis drains it. A needle is inserted through your back into the fluid collection, guided by ultrasound. The procedure serves two purposes: relieving the pressure that makes breathing difficult and providing a fluid sample for testing.
The fluid is analyzed for protein levels, cell counts, bacterial cultures, and abnormal cells that could indicate cancer. A key part of the analysis uses criteria that distinguish between fluid caused by a local problem in the lung (like infection or cancer) and fluid caused by a systemic condition (like heart failure or liver disease). That distinction shapes the entire treatment approach.
Blood Tests and Genetic Screening
Pulmonologists order specific blood work depending on the clinical picture. One important test screens for alpha-1 antitrypsin deficiency, a genetic condition that can cause emphysema at an unusually young age. The initial test measures the level of a protective protein in your blood. If it comes back abnormally low, a follow-up genetic test confirms the diagnosis by identifying the specific gene mutation involved. People diagnosed with this deficiency typically undergo additional testing to assess both lung and liver function, since the condition can affect both organs.
Other blood panels may check for markers of inflammation, autoimmune conditions that can involve the lungs, or allergic responses, depending on what your symptoms and imaging suggest.
Methacholine Challenge Test
When asthma is suspected but spirometry results look normal, a methacholine challenge can provoke the airway sensitivity that defines the condition. You inhale increasing concentrations of methacholine, a substance that causes airways to tighten in people with asthma, and spirometry is repeated after each dose. If your airways narrow significantly at a low concentration, the test confirms airway hyperreactivity. Preparation rules are stricter than for standard spirometry: short-acting inhalers must be stopped 6 hours ahead, long-acting ones for 36 hours, and ultra-long-acting agents for 48 hours.