A spirometer is an apparatus for measuring the volume of air inspired and expired by the lungs. A spirometer measures ventilation, the movement of air into and out of the lungs. The spirogram will identify two different types of abnormal ventilation patterns, obstructive and restrictive. There are various types of spirometers that use a number of different methods for measurement (pressure transducers, ultrasonic, water gauge).

A spirometer is the main piece of equipment used for basic Pulmonary Function Tests (PFTs). Lung diseases such as asthma, bronchitis, and emphysema may be ruled out from the tests. In addition, a spirometer often is used for finding the cause of shortness of breath, assessing the effect of contaminants on lung function, the effect of medication, and evaluating progress for disease treatment.

The earliest attempt to measure lung volume can be dated back to the period A.D. 129–200. Claudius Galen, a Roman physician and philosopher, did a volumetric experiment on human ventilation. He had a child breathe in and out of a bladder and found that the volume did not change. The experiment proved inconclusive.

Even with the numerical precision that a spirometer can provide, determining pulmonary function relies on differentiating the abnormal from the normal. Measurements of lung function can vary both within and among groups of people, individuals, and spirometer devices. Lung capacity, for instance, may vary temporally, increasing and then decreasing in one person's lifetime. As a result, ideas about what constitutes "normal" are based on one's understanding about the sources of variabilities and can be left to interpretation.

Traditionally, sources of variation have been understood in discrete categories, such as age, height, weight, gender, geographical region (altitude), and race or ethnicity. Global efforts were made in the early twentieth century to standardize these sources to enable proper diagnosis and accurate evaluation of pulmonary function. However, rather than further aiming to understand the causes of such variations, the primary approach for dealing with observed differences in lung capacity has been to "correct for" them. Using results from comparative population studies, attributes are empirically factored together into a "correction factor". This number is then used to form a personalized 'reference value' that defines what is considered normal for one individual. Practitioners may thereby find the percent deviation from this predicted value, known as 'percent of predicted,’ and determine whether someone’s lung function is abnormally poor or excellent.

In particular, 'race correction' or 'ethnic adjustment' effectively has been computer-programmed into the modern-day spirometer. Preconceived notions that 'white' people have greater pulmonary function are embedded in spirometer measurement interpretation and have only been reinforced through this medical stereotyping. In the United States, spirometers use correction factors of 10-15% for those identified as 'black' and 4-6% for those identified as 'Asian.'

In 1960, the European Community for Coal and Steel (ECCS) first recommended guidelines for spirometry. The organization then published predicted values for parameters such as spirometric indices, residual volume, total lung capacity, and functional residual capacity in 1971. The American Thoracic Society/European Respiratory Society also recommends race-specific reference values when available. Even today, the National Institute for Occupational Safety and Health’s Spirometry Training Guide that is linked to the Centers for Disease Control and Prevention’s website notes the use of race correction and a race-specific reference value in step four of "normal" spirometry.

The use of reference values and discrete categorizations of sources of variability has been motivated by ideas of anthropometry and vital capacity. Studies have looked specifically at the relationship between anthropometric variables and lung function parameters.