PFT / DLCO Testing

What is PFT/DLCO testing?

Pulmonary Function Testing (PFT) is a set of breathing tests that measures how much air your lungs hold, how forcefully you can exhale, and how efficiently your lungs transfer oxygen into the bloodstream. The DLCO portion — Diffusing Capacity for Carbon Monoxide — specifically measures that gas-transfer efficiency.

Together, PFT and DLCO give us a precise, objective picture of your lung health that we use to diagnose, stage, and track conditions over time.

What the test includes

Spirometry — you breathe forcefully into a mouthpiece. Measures forced vital capacity (FVC), forced expiratory volume (FEV1), and the ratio between them — the core numbers for asthma and COPD.

Lung volumes — using a sealed booth or gas dilution. Measures total lung capacity and residual volume.

DLCO (diffusing capacity) — you inhale a tiny amount of a tracer gas and hold your breath for 10 seconds. We measure how much was absorbed by the blood. Reduced DLCO points to problems at the alveolar level — emphysema, pulmonary fibrosis, anemia, or pulmonary vascular disease.

When we recommend it

• New or unexplained shortness of breath
• Asthma evaluation, especially before starting biologic therapy
• Chronic cough that hasn't responded to standard treatment
• Baseline before starting medications known to affect the lungs
• Pre-operative clearance for high-risk surgeries
• Annual monitoring for patients with diagnosed lung disease

Preparing for the test

Skip caffeine for 6 hours before the test, avoid heavy meals for 2 hours, and don't smoke for at least an hour. If you use inhalers, your doctor will tell you whether to hold them — typically short-acting bronchodilators are held for 4-6 hours, long-acting for 12-24 hours.