Lung Function Test (Spirometry)

What it is

Breathlessness is a symptom with many causes and almost no diagnostic value on its own. Spirometry turns it into numbers. You take the deepest breath you can and blow it out as hard and as fast as possible into a mouthpiece, and the machine records both the total volume that came out and how quickly it left. The shape of that curve is what matters. A lung whose airways are narrowed empties slowly — the total may be near normal but it takes too long to get there. A lung that is stiff or small empties briskly but there was less in it to begin with. Those two patterns look identical to a patient and completely different on a spirogram, and they point at different diseases.

This code covers the spirometry itself. Measuring total lung volume, or how well oxygen crosses from the air sacs into the blood, requires different equipment and is billed under different codes.

Why it is done

• To confirm or rule out asthma or COPD when someone is short of breath, wheezing, or coughing persistently
• To measure how severe a known airway disease has become, and to track it over time
• To find out whether a treatment is working, by comparing results before and after
• To assess breathing before surgery or before starting a medication that can affect the lungs
• To monitor people exposed to dusts, fumes or other hazards at work
• To investigate breathlessness that could be coming from the lungs, the heart, or neither

What to expect

You sit upright, a clip is placed on your nose so no air escapes that way, and your lips seal around a mouthpiece. The technician will coach loudly and insistently — that is normal and it is necessary, because the measurement depends on maximum effort. You repeat the manoeuvre at least three times so the best reproducible result is captured. It is tiring and can make you cough or feel briefly light-headed. Often the test is repeated after you inhale a medication that opens the airways, to see whether the numbers improve; that second round is a separate code. The whole visit typically runs half an hour or less.

Questions worth asking

• Was spirometry ordered alone, or as part of a full pulmonary function study? Lung volumes and diffusing capacity are separate codes and the bundle costs considerably more.
• If a bronchodilator is given and the test repeated, ask whether that is billed as an additional code and whether the medication is itemized.
• Ask whether the interpretation by a physician is billed separately from performing the test — both charges exist and are sometimes split.
• Spirometry done in a primary care office, a pulmonology office and a hospital pulmonary lab carry very different prices for the same code. Ask which setting yours is booked in.
• If your employer requires this for occupational surveillance, ask who is being billed. Employer-mandated testing is often not a claim against your own plan.