Measurements of Lung Function
Patients with asthma frequently have poor recognition of their underlying symptoms and poor perception of the severity of their disease, especially if their asthma is severe, and nonremitting. Assessments of symptoms alone as wheezing and dyspnea are not sufficent, and may be inaccurate. Measurements of lung function provide direct assessment of airflow limitation, and response to treatment. Measurement of lung function for diagnosing and monitoring asthma is analogous to measurement of blood pressure with a sphygmomanometer or measurement of blood glucose with reagent strips.

One method to assess the level or severity of airflow limitation is the use of peak expiratory flow. Ideally, peak expiratory flow measurements should be taken twice daily immediately upon arising and 10 to 12 hours later, before and after using a bronchodilator. Because peak flow measurement is effort dependent, it is essential to use correct techniques and equipments.

Interpreting Peak Flow measurements

Predicted values of normal peak expiratory flow corrected for height, and age
for females.

Height (inches)

Predicted values of normal peak expiratory flow corrected for height, and age for males.