Contraindications to lung function testing are controversial but tend to include recent MI, recent abdominal surgery, stress incontinence, confusion and dementia.
The patient should be positioned appropriately:
Record the height, weight, age and current inhaled medication. The patient should try and avoid smoking within 1 hour of the test, alcohol within 4 hours, exercise within 30 minutes and a large meal within 2 hours.
The time volume curve
After spirometry the time volume curve is viewed initially to confirm that a good quality blow has been achieved and a plateau has been reached to record an accurate FVC. A short blow will underestimate the level of obstruction and often misleads practitioners into diagnosing restrictive defects. The best of 3 blows should be used.
Expiratory Flow Loop
Modern spirometers allow a more accurate diagnosis by providing an expiratory flow loop. Patient with COPD have expiratory airflow obstruction which can be viewed as a ‘scalloping’ out of the top curve, as shown below.