3.1 Spirometry
Lung function can be measured using spirometry. A typical test involves blowing out into a spirometer as hard as possible until the lungs are empty (Figure 10). The forced vital capacity (FVC) is calculated as the total volume of air that can be forcefully blown out. Peak expiratory flow (PEF) measures the maximum speed at which air is forcefully expired (litres per second). The forced expiratory volume 1 (FEV1) is the amount of air that is forcibly blown out within the first second of the test.
Plotting the FVC and PEF values generates a spirograph similar to the one shown in Video 7. The FEV1/FVC ratio (also calculated as a percentage) is used to evaluate lung function. In healthy individuals, the FEV1/FVC ratio is approximately 0.8, meaning that 80% of total volume of air is blown out within the first second.
It is important to note that normal lung function is dependent on an individual’s age, height, sex, ethnicity and general fitness. An example of the predicted FEV1/FVC ratios for particular groups of men and women is shown in Table 1.
Table 1 Predicted FEV1/FVC ratios for asymptomatic, lifelong non-smoker Caucasian men and women over the lifespan.
| FEV1/FVC (%) Male | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Age | 20 | 25 | 30 | 35 | 40 | 45 | 50 | 55 | 60 | 65 | 70 | 75 | 80 |
| All heights | 83.9 | 82.9 | 81.9 | 80.8 | 79.8 | 78.8 | 77.7 | 76.7 | 75.7 | 74.6 | 73.6 | 72.6 | 71.5 |
| FEV1/FVC (%) Female | |||||||||||||
| Age | 20 | 25 | 30 | 35 | 40 | 45 | 50 | 55 | 60 | 65 | 70 | 75 | 80 |
| All heights | 86.6 | 85.5 | 84.4 | 83.4 | 82.3 | 81.2 | 80.2 | 79.1 | 78.1 | 77.0 | 75.9 | 74.9 | 73.8 |
Question 7 Lung function across ages
Looking at Table 1, what happens to lung function with age in both men and women?
Answer
Correct. Lung function, as measured by the FEV1/FVC percentage, decreases with age in both men and women.
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