IBDP Biology Practical 6: Monitoring Ventilation Rate Tips & Tricks
Practical 6 is one of my favourite labs, I love how simple it is and how much students learn about conducting an investigation with human participants, an important skill before the IA. For this reason I always plan my units so that we complete our study of Physiology and conduct Practical 6 before students begin their Mock IA, and of course their real IA. According to the May 2016 IBDP Biology Subject Guide this practical requires"Monitoring of ventilation in humans at rest and after mild and vigorous exercise" (pg. 78). In case you weren't aware there are six required practical for SL students and a seventh for HL students, these practicals can, and do show up on the IB exams throughout all three papers, but especially in Paper 3 Section A. I recommend doing some past paper questions about the practicals in your units assessments. I have written separate blog posts on the other five SL practicals if you would like to read them, here are the links:
Practical 6 is all about ventilation rate, which is defined as the number of complete breaths per minute, so it includes a complete cycle of inspiration and expiration. The IBO provides this clarification about Practical 6: "Ventilation can either be monitored by simple observation and simple apparatus or by data logging with a spirometer or chest belt and pressure meter. Ventilation rate and tidal volume should be measured, but the terms vital capacity and residual volume are not expected." This will change in the new syllabus, so while this lab can still be used as part of your PSOW it will need some minor changes in the data collected (I'll blog about it soon).
Whenever we do this lab I take the opportunity to teach my students some key investigation skills for conducting any sort of investigation with human participants. The first is the need for informed consent. This is an important skill to practice before we get to IAs as many students initial IA ideas include the use of human participants. We discuss what informed consent means and go through the IBO's expectations, that we do not coerce or intimidate participants in any way, that they can choose to withdraw from the study at any time (even once they have begun) and that their confidentiality must be maintained. You can see the consent form we use in my classes below, feel free to download and modify it for your class.
Once we've discussed consent it's time to plan the methodology, which I like to do collaboratively with the students, it is an excellent teachable moment as they plan a complex investigation using human participants. The first thing we need to decide is what we will use as our mild and vigorous exercise. I have my students collect data as a class (10 participants per student) to get a large sample, so the data must be collected in the same way. Students begin to suggest ideas for the exercise tasks and we begin to narrow down the choice to something which require little to no equipment and can be done by just about anyone. Almost every year the students end up settling on jumping jacks simply because they can be done in little space with no equipment and it is fairly easy to keep things constant. We discuss how to keep the pace and form of the jumping jacks constant (usually students go with a metronome for the pace & an example from the student collecting data for form).
Students also agree on specific environmental constants, such as no music being played, two minutes of rest between the mild and vigorous exercise and no talking during the data collection. We must also establish how the data will be collected, we usually go with having both the participant and the investigator count complete breaths (inhalation & exhalation) for the participant over 30 seconds then doubling that number of breaths to get the ventilation rate in breaths/minute. Thinking through and discussing all of the things that could affect ventilation rate is an important and incredibly valuable exercise for students as they learn how to plan an experimental methodology.
Students then create a Google Doc (usually a Google Sheet) where they can collect their data as a class, you can see an example here (this data is old and has been anonymized). This particular class decided to collect a large amount of data, asking the participants questions about exercise, drug use, smoking history, age, height & weight as well as if the participant had lived anywhere with substantial air pollution. This large and detailed data set meant that each student could put their own twist on Practical 6, seeing how different groups (for example smokers & non-smokers) ventilation rate changed from rest to after mild exercise and then after vigorous exercise.
While working with a large class collaboratively can allow for a large sample size it is important that students establish key constants (controlled variables) and agree upon them. To facilitate this process I have students complete a planning document (below) before we decide upon the final methodology as a class. Using this planning tool also ensures that every student has a chance to practice planning an investigation using human participants.
Once students have agreed upon their methodology and their consent forms are signed I give them a class block to collect data and make the lab due at least a week later so they have enough time to collect all of the data and analyze it. If you use a Google Doc for your class to collect data be sure that you are shared on the doc so if some students haven't collected their data you can remind them to do so. This is usually the 5th lab practical I do, so students have built up some skills already and are ready to apply them in a new situation. I will definitely be keeping this practical in some form or another with the new syllabus, the learning is too important to skip. I hope you found this post helpful & that you enjoy measuring ventilation rate with your students!
Thanks for reading teachers, travelers & curious souls of all kinds.
The Roaming Scientist
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