Incentive spirometers are used for patients with conditions affecting breathing. Pulmonologists assign their patients to use them in order to measure and improve lung capacity. The device contains a lightweight ball or piston that the patient holds aloft by inhaling; floating the object is an "incentive" that shows users how well they are doing and makes using the spirometer into a game. Incentive spirometers can be used for several types of experiments.
Lung Capacity of Different Populations
In this experiment, the lung capacity of two different populations (smokers and non-smokers, pregnant and non-pregnant women, males and females, etc.) are compared. To design the experiment, recruit as many members as possible from each population. To reduce uncontrolled variables, use a matched-subject design; in this design, each member of one population will be matched with a member of the other, chosen to be as similar as possible except for the variable. For example, in comparing smokers and non-smokers, you would ideally pair a 40-year-old male smoker with a 40-year-old male non-smoker. Make a hypothesis as to which population, if either, has greater lung capacity.
Lung Capacity as a Function of Size
This experiment has only one experimental group. Two factors are recorded for each individual: lung capacity as measured by the incentive spirometer, and a measurement of size (for example, height, weight or chest circumference). Ideally, the members of the group will be as similar as possible in other respects, such as age, gender and lifestyle. An advantage of this type of experiment is that, unlike a comparison of populations, matching subjects is not necessary. The hypothesis should be a prediction of how much, if at all, the chosen size parameter will affect lung capacity. For the results, create a graph comparing lung capacity with physical size, with each test subject recorded as a point on the graph.
Effect on Lung Capacity With Practice
This experiment requires no more than one test subject, though more than one can be used. Because it can be done over a period of days or weeks, it is ideal for a science fair project. Each subject practices with the incentive spirometer at least once a day, testing lung capacity at regular intervals (such as daily or weekly). Make a hypothesis as to how much lung function will improve, and whether the rate of improvement will be steady or variable. For a variation on this experiment, compare the results for two similar subjects practicing with different types of incentive spirometer. The rate and amount of improvement are recorded for the results.