Patient’s spirometry, red curve after bronchodilator
How is spirometry performed and what information does it provide?
When is spirometry indicated?
Describe normal and abnormal spirometry curves.
Describe spirometry in COPD.
What is bronchodilator reversibility testing?
How would you interpret this patient’s spirometry?
Spirometry: the patient inhales until the lungs are full and rapidly and forcefully exhales. The test is dependent on patient effort, so it must be properly performed. The test is repeated until three acceptable and consistent results are obtained.
Forced vital capacity or FVC. This is the total exhaled volume in liters exhaled after full inspiration, typically in the first 6 s.
Forced expiratory volume in liters during the first second or FEV1.
The ratio of the FEV1/FVC as a fraction. Normal is between 0.7 and 0.8.
The forced expiratory flow rate in the midportion of the FEV1, the FEF25–75.
Normal values are obtained from tables, obtained in normal controls, and vary by height, gender, and ethnicity. These data provide objective measurements to determine the severity and follow the course of the pulmonary disease .
These measurements are based on flow over time. Flow volume loops are flow rates plotted against volume and are discussed in a separate chapter.
Spirometry can confirm the presence and severity of obstructive and restrictive lung disease. The response to bronchodilator can assist to differentiate asthma from COPD. It can be useful to assess progression and response to therapy. Spirometry is not routinely necessary in preoperative testing for non-thoracic surgery. In patients evaluated for lung resection, simple spirometry, FVC, and FEV1 should be obtained. The predicted postoperative FEV1 is calculated as ppoFEV1 = preop FEV1% × (1–% functional lung removed/100). A ppoFEV1 < 40% indicates a higher risk of postoperative complications; these patients may need additional testing, and/or a ppoFEV1 < 30% may require post-op ventilation .
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