Breathing tests can feel confusing when names sound similar, and results matter to your health. You may hear spirometry and PFT used as if they mean the same thing.
We clear up the difference so you know what each test does and why a clinician may choose one over the other. Spirometry measures how much air you move and how fast, while pulmonary function tests (PFTs) include spirometry plus other tests that check lung size and how well oxygen moves into your blood.
You often get spirometry for quick checks like asthma or COPD. We use full PFTs when symptoms need a deeper look or when treatment decisions depend on more detail.
Spirometry measures how much air we move and how fast we move it. Clinicians use it to check lung function, spot breathing problems, and track changes over time with clear numbers.
We perform a spirometry test with a spirometer, a small device that measures airflow. The patient sits upright, wears a nose clip, and seals lips around a mouthpiece.
We ask the patient to inhale fully, then blow out hard and fast until the lungs feel empty. We repeat the effort at least three times to get reliable results.
Short rest breaks help reduce fatigue. A trained staff member coaches each breath to improve accuracy.
The full test usually takes 10 to 15 minutes. We may give a bronchodilator and repeat the test to see how the airways respond, which helps separate asthma from other causes.
Spirometry focuses on airflow and usable lung volume during forced breathing. These values help us tell obstructive from restrictive patterns.
| Measurement | What it Shows | Why It Matters |
| FVC (Forced Vital Capacity) | Total air blown out | Low values suggest restriction |
| FEV₁ | Air blown out in 1 second | Low values suggest obstruction |
| FEV₁/FVC | Airflow ratio | Confirms obstructive lung disease |
| PEF | Fastest blow speed | Tracks day-to-day control |
We compare results to predicted values based on age, sex, height, and race. A low FEV₁ with a low ratio points to obstructive lung disease like COPD or asthma.
A low FVC with a normal ratio suggests restrictive lung disease, such as pulmonary fibrosis.
We use spirometry to diagnose and monitor asthma and COPD. It shows airway narrowing, response to medicine, and changes over time.
Clinicians order spirometry for chronic cough, shortness of breath, or wheeze. We also use it before surgery to assess lung risk and during routine care for smokers.
Spirometry helps track lung function in known diseases. It cannot measure total lung volume or gas exchange, so it does not replace full pulmonary function tests.
Pulmonary function tests, often called PFTs, assess how the lungs move air, hold air, and transfer oxygen. We use these tests to find patterns of lung disease and to track changes over time.
Pulmonary function tests include several related exams done together or on separate days. Each test answers a specific question about lung function.
Common PFTs include:
We choose test types based on symptoms and clinical needs. For example, airflow tests help with asthma and COPD.
Lung volume tests help when restriction or air trapping is suspected. A full pulmonary function test gives a broader view than spirometry alone.
PFTs focus on airflow, lung volumes, and gas exchange. Together, these values show how the lungs work at rest and sometimes with exercise.
| Measurement | What It Shows |
| Airflow | How fast air moves in and out |
| Lung volumes | How much air the lungs hold |
| Total lung capacity | Maximum air in the lungs |
| Gas exchange | Oxygen transfer to blood |
Abnormal results point to obstructive or restrictive patterns. Obstruction limits airflow, while restriction lowers lung volume.
We compare results to reference values and review test quality. Clinical context matters, so we interpret PFTs alongside symptoms and history.
Body plethysmography measures lung volume with high accuracy. The patient sits in a sealed booth called a plethysmograph and breathes through a mouthpiece.
Pressure changes inside the booth allow us to calculate lung volume, including air that spirometry cannot measure. This includes trapped air and total lung capacity.
Body plethysmography helps when airflow tests seem normal, but symptoms persist. We often use this test to assess complex cases.
It clarifies restriction, air trapping, and severe obstruction. The test is noninvasive and takes only a few minutes, but it provides detailed data that standard methods may miss.
We compare spirometry and pulmonary function tests by scope, detail, and clinical use. Both measure lung health, but they answer different questions and serve different settings.
We use both spirometry and pulmonary function testing to measure how well the lungs work. Each test relies on breathing maneuvers and compares results to reference values based on age, sex, height, and race.
The main difference is scope. A spirometry test measures how much air a person blows out and how fast.
It focuses on airflow and basic lung volume. A pulmonary function test (PFT) includes spirometry but adds other tests.
PFTs can measure total lung volume, gas exchange (DLCO), and airway resistance. These added measures help separate obstructive and restrictive patterns.
Spirometry alone cannot assess gas transfer or full lung capacity.
| Feature | Spirometry | Full PFT |
| Airflow | Yes | Yes |
| Lung volumes | Limited | Yes |
| Gas exchange | No | Yes |
| Test setting | Office or bedside | Specialized lab |
We value spirometry for its speed and access. It is easy to perform, low-cost, and useful in many clinics.
The test helps track conditions like asthma and COPD over time. Spirometry has limits.
It cannot measure air left in the lungs or how well oxygen moves into the blood. Poor effort or technique can affect results.
We use full pulmonary function testing when we need more detail. PFTs provide a broad view of lung health and identify complex patterns.
These tests support accurate interpretation but require more time and equipment. PFTs also have limits.
They cost more and often need a dedicated lab. Some patients struggle with longer testing sessions or complex breathing steps.
We choose spirometry when we need quick answers about airflow. It works well for screening, routine follow-up, and medication response.
Primary care and outpatient clinics often use it first. We order a full PFT when spirometry results raise questions.
PFTs help evaluate unexplained shortness of breath or abnormal imaging. They also support the diagnosis of restrictive lung disease or diffusion problems.
We often start with spirometry and expand to pulmonary function testing if needed. This stepwise approach balances efficiency with accuracy.
Beyond spirometry, full pulmonary function tests measure how well gases move across the lungs and how open the airways remain. These tests add detail that airflow numbers alone cannot show and often explain symptoms when spirometry looks normal.
DLCO, also called diffusion capacity, measures how well oxygen moves from the air sacs into the blood. We perform this gas diffusion study by having the patient inhale a small, safe amount of test gas and hold their breath for a short time.
A low DLCO points to problems with gas exchange. Common causes include emphysema, pulmonary fibrosis, and pulmonary vascular disease.
Anemia can also lower DLCO because fewer red blood cells carry gas. We often use DLCO to explain shortness of breath when airflow tests look normal.
It also helps track disease over time.
DLCO is most useful for:
Airway resistance measures how easily air moves through the breathing tubes. We usually assess it with body plethysmography, which detects small airway narrowing that spirometry may miss.
High airway resistance supports diagnoses like asthma or chronic bronchitis. It also helps measure response to bronchodilator treatment.
Fractional exhaled nitric oxide (FeNO) measures nitric oxide levels in exhaled air. High values suggest airway inflammation, most often linked to allergic or eosinophilic asthma.
We use FeNO to guide inhaled steroid treatment and monitor control. It does not replace spirometry or full PFTs but adds useful context.
Key FeNO uses include:
We use spirometry and full pulmonary function tests (PFTs) for different clinical goals. Spirometry often answers focused questions about airflow, while PFTs provide a wider view of lung volume and gas exchange.
The choice depends on symptoms, risk factors, and how much detail we need.
We use spirometry as a first-line test to diagnose many respiratory conditions. It helps identify obstructive lung disease, such as asthma and chronic obstructive pulmonary disease (COPD), including emphysema.
The test measures how much air a person can force out and how fast. We often add a bronchodilator during spirometry.
A clear improvement after medication supports an asthma diagnosis. Limited improvement suggests COPD or another fixed obstruction.
We order full PFTs when spirometry alone does not explain symptoms. PFTs help detect restrictive lung disease, such as pulmonary fibrosis, by measuring total lung volume and gas transfer.
Common diagnostic uses
We rely on spirometry to track changes in known lung disease over time. It shows whether airflow worsens, stays stable, or improves with treatment.
This matters for asthma control and COPD management. We use repeat testing to check the response to inhalers or steroids.
A drop in values may signal poor control, infection, or disease progression. We turn to full PFTs when we need more detail.
PFTs help diagnose pulmonary fibrosis and other restrictive disorders. Changes in lung volume or gas exchange can guide treatment decisions.
Monitoring goals
We often start with spirometry when patients report shortness of breath. It helps rule in or rule out common airflow problems.
Normal results suggest we need a broader evaluation. We order full PFTs when symptoms remain unexplained.
These tests assess lung volume and oxygen transfer, which spirometry cannot fully measure. This helps separate lung causes from heart or muscle problems.
We also use PFTs before surgery or strenuous activity. Clear results help assess risk and guide next steps in care.
Test selection by symptom
| Symptom pattern | Preferred test |
| Wheezing, cough | Spirometry |
| Unclear dyspnea | Full PFTs |
| Suspected restriction | Full PFTs |
We interpret spirometry and pulmonary function testing by looking at measured values, patient limits, and the clinical question. Accurate use depends on correct reference values, awareness of test limits, and choosing the right test for lung health concerns.
We compare test results to reference values based on age, sex, height, and race. These factors affect lung size and airflow, so correct data entry matters.
A poor match can lead to false results. Spirometry focuses on airflow, such as FEV1 and FVC.
Pulmonary function testing adds lung volumes, including RV, and gas transfer. We use percent predicted and lower limits of normal to judge results.
| Factor | Why It Matters |
| Age | Lung function drops over time |
| Height | Taller people have larger lungs |
| Sex | Lung size differs by sex |
| Race | Reference equations vary |
We always check test quality first. Poor effort or leaks can distort lung function results.
Spirometry is safe and quick, but it has limits. It cannot measure lung volumes or gas exchange.
It may miss early disease or mixed patterns. Pulmonary function testing provides more detail, but it takes more time.
Some patients feel short of breath during testing. Rare issues include dizziness or cough.
Results depend on patient effort. Pain, fatigue, or poor understanding can lower values.
We also avoid testing during recent surgery, chest pain, or active infection. Advanced tests, like a cardiopulmonary exercise test, assess exercise limits.
These tests need special staff and equipment. We reserve them for complex cases, not routine screening.
We choose spirometry for common symptoms like cough, wheeze, or shortness of breath. It works well for asthma and COPD checks.
We use full pulmonary function testing when spirometry looks abnormal or unclear. It helps separate obstruction from restriction.
It also measures lung volumes and RV to assess air trapping.
We consider patient history and exam findings first. Suspected interstitial disease, neuromuscular weakness, or unexplained low oxygen often needs full testing.
For exercise-related symptoms, we may add a cardiopulmonary exercise test.
Spirometry and full pulmonary function tests both play an important role in diagnosing and monitoring lung conditions, but they serve different purposes. Spirometry is often the first step because it quickly measures airflow and helps detect common issues like asthma or COPD. Full PFTs build on spirometry by adding lung volume and gas exchange testing, which provides a more complete view when symptoms are unexplained, imaging is abnormal, or treatment decisions require deeper detail. Choosing the right test depends on your symptoms, medical history, and what your care team needs to understand about how your lungs are functioning. With accurate testing and expert interpretation, patients can get clearer answers, begin effective treatment sooner, and track progress with confidence over time.
Get expert testing and clear answers about your lung health.
At Gwinnett Pulmonary & Sleep, our board-certified pulmonologists provide spirometry and comprehensive pulmonary function testing to evaluate symptoms, guide treatment, and monitor lung conditions with precision. If you’re experiencing shortness of breath, chronic cough, or need follow-up testing, our team is here to help.
Book your appointment today at gwinnettlung.com or call 770-995-0630 to schedule your visit.
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