FEV1/FVC Ratio

The FEV1/FVC ratio compares how much air a person can blow out in the first second (FEV1) with the total amount they can blow out in one full breath (FVC). A low ratio points to obstructive disease, such as emphysema or asthma; a normal or high ratio with a small FVC points to restriction, the pattern seen in asbestosis.

Origin

The ratio is also called the Tiffeneau-Pinelli index, after the French physicians who described the timed-expiration measurement in the late 1940s. It became a standard part of spirometry as breathing tests were standardized in the following decades, and today's interpretation guidelines from the American Thoracic Society and European Respiratory Society rely on it.

Significance in Asbestos Context

Asbestosis stiffens the lungs, so the total breath (FVC) shrinks while air still flows out quickly; the ratio stays normal or even rises. Smoking-related emphysema does the opposite: air is trapped, FEV1 falls faster than FVC, and the ratio drops. Because many asbestos-exposed workers also smoked, the ratio helps a doctor sort out which process is driving a person's breathing problem, or whether both are present (a mixed pattern). That matters for a claim. A defense expert may argue that breathlessness comes from smoking, not asbestos; a normal ratio with reduced FVC, total lung capacity or DLCO supports a restrictive, asbestos-type impairment. Many asbestos trust distribution procedures that use breathing tests ask for a reduced FVC or TLC together with an FEV1/FVC ratio at or above a set level, so that obstruction is not mistaken for asbestosis. FEV1 by itself is not what trusts use to qualify a claim. Doctors read the ratio against the lower limit of normal for a person's age, sex and height, or against a fixed cutoff of 0.70; the two methods can disagree, especially in older people.

Example Sentence

His FVC was 68 percent of predicted, but his FEV1/FVC ratio was 0.82, which pointed to restriction from asbestosis rather than smoking-related obstruction.

Related Terms

FEV1, FVC, Spirometry, Pulmonary Function Test (PFT), Restrictive Lung Disease, Obstructive Lung Disease, Total Lung Capacity (TLC), Diffusing Capacity (DLCO)

Notes

• Ask for the full breathing-test printout, including the flow-volume curve and the technician's comments on effort, not just the summary.
• A test done during a chest infection or right after surgery may not reflect your usual lung function; tell your doctor if you were unwell.
• If you have a smoking history, a full test with lung volumes and DLCO helps show whether asbestos scarring is also present.