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Class: Date:

# ___ Lab – Tidal Volume and Lung Capacity

Problem: What factors can affect lung capacity?

Introduction: When you inhale, air rushes into your lungs. The amount of air that rushes in during a normal breath is called the tidal volume. Your lungs have the capacity to accept a much larger volume of air than you normally inhale. For example, you might be asked to take a deep breath during a medical exam. Scientists use the term vital capacity to describe the largest volume of air that you can exhale after you take a deep breath.

In this lab, you will measure tidal volume and vital capacity. Then you will design an experiment to investigate a factor that can affect vital capacity.

Skills Focus: Measure, Form a Hypothesis, Design an Experiment, Interpret Graphs

Materials: round balloons, metric ruler, meter stick

Safety: Do not test your vital capacity if you are ill or have difficulty breathing. If at any point you feel faint or dizzy, stop what you are doing and sit down. Ask your partner to inform your teacher of the problem. Do not handle balloons if you are allergic to latex. You and your partner must use different balloons.

Pre-Lab Questions: (3 pts.)

  1. Control Variables. What is the difference between the procedures in Part A and Part B?
  1. Design an Experiment. Why must you use round balloons for this experiment?
  1. Predict. Which do you think will be greater – your estimated vital capacity or your measured vital capacity? Why?

Procedure & Data:

Part A: Tidal Volume(2 pts.)

Data Table 1: Tidal Volume
Trial / Diameter (cm) / Volume (cm3)
1
2
3
Mean
  1. Stretch a round balloon lengthwise several times
  2. Stand up and inhale normally, then exhale normally, but quickly into the balloon. Immediately pinch the balloon shut so that no air escapes.
  3. Keep pinching the balloon as you place it on a flat surface. Have your partner measure the diameter of the balloon at its widest point as shown in figure 1. Record the measurement in Data Table 1.
  4. Allow the balloon to deflate. Repeat Steps 2 and 3 two more times.
  5. Calculate the mean for the measurements from the three trials and record your answer in the data table.
  6. On the graph in Figure 2, balloon diameter in centimeters is plotted against volume in cubic centimeters (cm2). Use the graph to find the volumes that correspond to your diameter measurements. Record your results in Data Table 1.

Data Table 2: Vital Capacity
Trial / Diameter (cm) / Volume(cm3)
1
2
3
Mean

Part B: Vital Capacity(2 pts.)

  1. Stand up and take as deep a breath as possible. Then, exhale as much air as you can form your lungs into the balloon. Immediately pinch the balloon shut so that no air escapes.
  2. Keep pinching the balloon as you place it on a flat surface. Have your partner measure the diameter of the balloon at its widest point. Record the measurement in Data Table 2.
  3. Allow the balloon to deflate. Repeat Steps 6 and 7 two more times.
  4. Calculate the mean for the measurements from the three trials and record y our answer in the data table.
  5. Use Figure 2 to find the volumes that correspond to your diameter measurements. Record your results in Data Table 2.

Figure 1 How to measure the diameter of the balloon / Figure 2 Lung volume verses balloon diameter

Source:

Part C: Estimating Vital Capacity(2 pts.)

Data Table 3: Estimated Vital Capacity
Height (cm)
Weight (kg)
Surface Area (m2)
Vital Capacity (cm3)
  1. You can use the meter strips taped on the door to measure your height in centimeters. Or you can convert your height in inches to centimeters by multiplying the number of inches by 2.54. Record your height in Data Table 3.
  2. To convert your mass in pounds to kilograms, multiply the number of pounds by 0.454. Record your weight.
  3. Use Figure 3 to estimate the surface area of your body. Find your height on the scale on the left. Find your mass on the scale on the right. Use a ruler to draw a straight line between those points. The location where the line crosses the middle scale is your estimated surface area.
  4. To calculate the estimated vital capacity of your lungs, multiply your surface are in square meters by the ratio of vital capacity to surface area. Based on research, the ratio is 2000 cubic centimeters per square meter for females. For males, the ratio is 2500 cubic centimeters per square meter. Calculate and record your answers in Table 3.

Figure 3 Estimated surface area based on height and mass

Part D: Design Your Own LabWould the results of your lab have been different if you were seated? Would your posture when seated affect the results?

  1. Form a Hypothesis How will you changing the position of your body affect your vital capacity? Record the hypothesis you will test to answer this question. (2)

Hypothesis:

  1. Describe Your Plan Describe the procedure you will use to test your hypothesis. How will you modify the procedure from Part B? What variables will you need to control during your trials? (3)

Experimental Plan:

  1. Construct a data table in the space below. Make as many rows for recording data as the number of trials you plan to do. Include a row for recording the mean of your trials. (2)

Analyze and Conclude:

  1. Analyze Data How did you estimated vital capacity compare with your measured vital capacity? Was your prediction in Pre-lab Question 3 correct? (1)
  1. Draw Conclusions What could have caused any difference between the estimated value and the measured value? (2)
  1. Design an Experiment Why is it important to do more than one trial when making measurements? (1)
  1. Infer In Step 14, why did females and males use different ratios to calculate estimated vital capacity? (1)
  1. Perform Error Analysis In Part A, why might the volume in the first trial be smaller than in the second and third trials? How could the procedure be adjusted to avoid this results? (2)
  1. Predict How would smoking affect lung capacity, and why? (2)