Spirometry Interpretation

Spirometry is a forced breathing test, not simply a measurement of how much air a patient can breathe. The patient inhales fully and then exhales as hard and completely as possible; the resulting volumes and flow identify whether air leaves the lungs too slowly, whether the total exhaled volume is unexpectedly small, or whether the tracing is technically unreliable. The experienced reader starts with the quality of the manoeuvre and the shape of the flow-volume loop before attaching a disease label to the numbers. A low FEV1/FVC ratio supports airflow obstruction, but it does not distinguish asthma from COPD, bronchiectasis, bronchiolitis, or an upper-airway lesion. A low FVC with a preserved ratio may suggest restriction, yet spirometry cannot prove that the lungs have reduced total capacity. The clinical history, medication timing, bronchodilator response, and—when indicated—full pulmonary function testing complete the interpretation.