What are the primary factors used to identify predicted norms for spirographic measurements?

The primary factors used to identify predicted norms for spirographic measurements are age, height, and gender. These variables play a significant role in determining the expected values for lung function tests such as forced vital capacity (FVC) and forced expiratory volume in one second (FEV1).

Age is crucial because lung function typically peaks in young adulthood and gradually declines with age, affecting the overall lung capacity and performance. Height is another essential factor since it is correlated with lung volume; taller individuals usually have larger lungs and, thus, higher expected measurement values. Gender plays an important role as well; physiological differences between males and females lead to varying lung capacities and airflow metrics. Generally, males tend to have larger lung volumes than females.

Other factors, such as weight and ethnicity, may influence lung function, but they are not considered primary variables in establishing the fundamental predicted values. This distinction is why the combination of age, height, and gender is critical for accurately predicting and interpreting results in spirometry.