Spirometry is currently the most important diagnostic tool that clinicians have in the assessment of asthmatic patients. It is inexpensive, convenient, and easy to perform in almost any physician’s of ce. The spirometer can measure volume over time, or both ow and volume in a procedure during which the patient takes a full, deep breath, exhales as forcefully and for as long as possible, followed
spirometry include the vital capacity (VC), the forced vital capacity (FVC), the forced expiratory volume in 1 second (FEV1), peak expiratory ow rate (PEFR), and the forced expiratory ow at 25-75% of the volume expired (FEF25-75%). The maximal voluntary ventilation (MVV) is another useful measure. The pattern of expiration and inspiration can also be recorded as a ow-volume curve to visualize characteristic patterns of obstruction. The information obtained from spirometry provides reproducible information on the presence or severity of air ow obstruction in both large and smaller airways. Characteristic patterns also can differentiate between obstructive and restrictive lung disease. It can con rm the diagnosis of asthma and help in monitoring response to treatment. Numerous studies have shown that symptoms and physical examination frequently underestimate or miss the presence of signi cant airway narrowing, making spirometry essential for good patient management.