IB Biology SL

Revision Notes

6.4.4 Skills: Monitoring Ventilation

Practical 6: Monitoring Ventilation

  • The volume of air within the lungs of an individual will change depending on their level of activity
    • When at rest, breathing is shallow and slow
    • When exercising, breathing is deeper and more frequent
  • The volume of air breathed in and out during normal breathing is the tidal volume
    • Normal breathing here refers to a breath that does not involve forced expiration
  • The ventilation rate is the number of breaths taken per minute
  • A piece of equipment called a spirometer can be used to create a trace to show the volume changes in the lungs

Practical 6: Monitoring of ventilation in humans at rest and after mild and vigorous exercise

  • It is possible to investigate the effect of exercise on ventilation using the following variables
  • Dependent variable: The ventilation parameter that is measured
    • This could be the ventilation rate, the tidal volume, or a combination of both
    • These measurements can be taken using a variety of methods, e.g. Basic observations such as counting breaths to measure ventilation rate
    • A data logger such as an inflatable chest belt and pressure sensor to measure ventilation rate
    • A spirometer can measure both ventilation rate and tidal volume
  • Independent variable: The type or intensity of exercise
    • The type of exercise could include a range from inactive e.g. lying down, to very active e.g. sprinting, and everything in between
    • E.g. the intensity of the exercise could be measured by increasing speed on a treadmill

Apparatus

  • Stop watch
  • Inflatable chest belt and pressure sensor OR spirometer

Method: Using an inflatable chest belt

  1. Taking breathing measurements using an inflatable chest belt and pressure sensor
  2. The person (subject) being examined breathes in and out with a chest belt placed around the thorax, that has had air pumped into it
  3. As the subject breathes the pressure sensor logs the changes in pressure due to ventilation; the data logged can be viewed on a computer
  4. From the data collected, the rate of ventilation can be deduced
  5. The subject then repeats steps 1-4 after a period of exercise
    • The type or intensity of exercise should be specified
  6. The subject then repeats step 5 several more times after exercise of different specified type or intensity e.g., gradually increasing in intensity
  7. A repeat of all measurements should be taken and several subjects should be tested in order to collect reliable results

Method: Using a spirometer

  1. Taking breathing measurements using a spirometer
  2. The subject being examined breathes in and out through the spirometer after a period of rest
  3. As the subject breathes through the spirometer, a trace is drawn on a rotating drum of paper, or a graph is formed digitally which can be viewed on a computer
  4. From this trace, the subject’s tidal volume and breathing rate can all be calculated
  5. The person then completes steps 1-4 after a period of exercise
    • The type or intensity of exercise should be specified
  6. The subject then repeats step 5 several more times after exercise of different specified type or intensity e.g., gradually increasing in intensity
  7. A repeat of all measurements should be taken and several subjects should be tested in order to collect reliable results

Spirometers (1), downloadable AS & A Level Biology revision notes

Spirometers (2), downloadable AS & A Level Biology revision notes

Using a spirometer to monitor ventilation

Analysis

  • The effect of exercise on ventilation can be seen in the spirometer trace below
    • Exercise can be seen to increase the rate of ventilation resulting in more breaths taken per minute
    • It is also evident that after exercise the tidal volume of the person has increased, which means more air is breathed in and out in each breath
    • After exercise, both tidal volume and ventilation rate eventually return to resting values

Author: Ruth

Ruth graduated from Sheffield University with a degree in Biology and went on to teach Science in London whilst also completing an MA in innovation in Education. With 10 years of teaching experience across the 3 key science disciplines, Ruth decided to set up a tutoring business to support students in her local area. Ruth has worked with several exam boards and loves to use her experience to produce educational materials which make the mark schemes accessible to all students.
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