Cardiovascular Stents Lesson Plan...Microsoft Word - Cardiovascular Stents Lesson Plan.docx Author...
Transcript of Cardiovascular Stents Lesson Plan...Microsoft Word - Cardiovascular Stents Lesson Plan.docx Author...
BME Lesson Title Cardiovascular Stents
Grade Level 6-‐8
Time for Activity The activity can take 3 – 5 days depending on the options that are selected, as well as the amount of information on the heart and heart attacks that is discussed. An estimate of the time required for each section is as follows: Engagement: Approximately one 45 minute class period Exploration: 15-‐20 minutes, if stent partially completed in advance 30-‐35 minutes, if full construction done by students Explanation: 45-‐90 minutes depending on the length of the discussion Elaboration: Option 1: 30-‐45 minutes Option 2: The time required depends on the amount of time the students are given during the class period to do their research.
Authors Dr. Brian Davis, Tracy Davis, Dr. Carin Helfer, Melissa Boswell, Visar Berki
Purpose This activity aims at using everyday materials to design and develop devices and approaches to reopen clogged arteries.
Objectives Students will learn about the heart, coronary artery disease, heart attacks, and treatments for coronary artery disease. Students will learn about the circulatory system and biomedical engineering. Students will understand the use of cardiovascular stents to open arteries. Students will be able to define the criteria and constraints for designing a cardiovascular stent. Optional: Students will learn about fluid flow rate, resistance to flow, viscosity, and Poiseuille’s Law.
Materials • For each stent:
o One piece of cut hose approximately 1 in. diameter by 3.5 in. length o 32 push pins; If allowing students to create a second stent during the elaboration section, additional push pins
will be necessary for designs that use more pins o 6 ft. thin wire (easily bent, but stiff enough to hold form); If allowing students to create a second stent, twice as
much wire will be necessary • Several 260Q balloons (thin, long balloons for balloon animals) • Balloon hand pump • Wire cutters • Optional if doing calculation of wire length
o Ruler o Paper and pencil o Calculator
Procedure Preparation Based on the time available for the activity, the students can create the entire stent during the lesson or a portion of the stent can be constructed in advance. The following steps will be completed and the approximate times for completion are as follows:
Steps 1 and 2: 5 minutes Steps 3 and 4: 8 minutes Steps 5 and 6: 15 minutes
These times are only estimates; some students will complete quickly and others may need additional time.
Step 1. Insert 8 pushpins evenly spaced around one end of the tube.
Step 2. Insert 3 more rows of 8 pushpins evenly spaced down the tube. Pins should not be flush against tube; wire will be wrapped around pushpins.
Step 3. Find the center of the wire, fold in half, and loop around a pushpin in one of the middle rows.
Step 6. Repeat this procedure on the other end of tube and remove remaining pins. The wires should end by going under the first loop a second time with another wrap around the loop before the extra wire is cut off.
Extra wrap around the first and last loop
2. Under and through loop to the left
Step 5. After the wires are twisted, choose one end of wire and loop it under and through the loop to its LEFT. Continue an over the pin-‐under and through the loop pattern to the RIGHT until the wire is back to the first loop.
3. Over pin to right
Step 4. Begin wrapping around the center pins in an over-‐under pattern. Use one end of the wire to wrap half of the pins (4 pins on top, 4 pins from a center row) and the other end of the wire to wrap the other half in the opposite direction, until the wire ends meet. Once the wires meet, twist together one time and pull to opposite sides. For next steps, leave center row pins in place and remove as necessary to loop wire.**
1. Wires twisted
4. Under and through loop to the right
Step 7. Remove the stent from the tube. Insert a balloon inside of the stent and inflate. Then deflate the balloon and observe how the stent maintains its form.
** If creating a portion of the stent for the students ahead of time, this is a good stopping point and it should look like this:
For neater storage until use, wrap the extra wire around the tube, at both ends, as shown.
Engagement Have a discussion about heart attacks. Ask the students what they know about this medical condition. Review the basics of the anatomy of the heart (see Useful Resources section for websites with information on the heart and heart attacks). Students can be given the Heart worksheet and asked to fill in the parts of the heart when discussed or the worksheet can be used as an assessment. Review the PowerPoint Presentation Cardiovascular Stents by Dr. Davis. When at the “Create a Stent” slide, tell students that they will create a stent using the items provided. Exploration Have the students work individually or in pairs to create a stent. Provide the students with the Steps for Creating Stent sheet and have them read through all of the steps before starting to construct. (Optional) Have the students estimate and record the total length of wire needed, given the geometry of the pins and tube used to make the stent. Hint: A rough estimate is the length of the tube multiplied by 8 and then multiplied by 2. Eight is the number of pins around the tube. Have the students record the starting length of the wire and after the stent is created, the length of the wire cut off that is not used. Have them subtract the leftover wire value from the starting length to find the actual length of wire that was used. See Wire Length Estimation worksheet. When students have a stent created, use a balloon to expand the stent as shown in the steps above. Note: Several balloons can be partially inflated and tied. When needed, insert the partially inflated balloon into the stent and squeeze part of the balloon so that the balloon section inside the stent will expand. This process will eliminate the need to pump up a balloon for each student’s stent, which is time consuming. Explanation Have the students describe their experiences of making their stent. If the optional calculation of wire length needed was completed, have the students share their results. If the estimate and usage differed, have the students offer suggestions to explain these differences. As a class discuss the following questions:
1) What challenges might an engineer face when creating a similar technology for real arteries? Discuss the criteria and constraints for this engineering problem. Material selection is critical. The material must be strong to survive being inserted into the artery and threaded into the location of the blockage. However, it must also be flexible for placement at the blockage. The material must be
biocompatible to not create an immune response or cause blood to clot. The stent must hold its shape after being expanded (both design and material selection important). The device must be small enough to fit into the artery. Also, the material cannot corrode over time while it is in place in the artery. Currently, bioabsorbable stents are being developed that will degrade in less than 12 months. Technical challenges require the materials and designs to balance mechanical properties, degradation time, and biocompatibility. A 2013 journal article (Lanzer, Strupp, Schmidt, Topoleski, 2013) cites that over 200 different stent types are available. The choice is made based on sizing, pricing, design, material, coating, drug loading, and mode of expansion.
2) What differences might there be between this setup and the actual artery and its location? The stent developed in class is much larger than an actual stent. The wire being used is not biocompatible. The method of testing the stent in class does not replicate the actual use of the stent as the stent is on a catheter that is inserted and threaded in the artery to the site of blockage.
3) What happens to the plaque after using a stent? The plaque is compressed against the arterial wall.
4) What would happen if only part of the blocked artery is cleared? o How might a partially blocked blood vessel affect a person's body?
Full blood flow will not be restored. Also, if some of the plaque particles break free and flow downstream, they can cause additional blockage.
5) What additional complications could occur from use of a stent? Complications could include an allergic reaction to the contrast dye. This dye allows for the arteries to be seen on the X-‐ray. There could be a weakening of the artery wall caused by the procedure. As noted above, if plaque particles break free and flow downstream, additional blockage can occur. Bleeding at the catheter insertion site can occur. Approximately 1-‐2% of patients with a stent develop a blood clot at the location of the stent.
If appropriate for the students, Poiseuille’s Law can be introduced. Poiseuille’s Law describes laminar flow of a Newtonian Fluid through a pipe. ΔP = !!"#
!!! (Equation 1)
where ΔP is the pressure difference across the pipe, μ is the viscosity of the fluid, L is the length of the pipe, Q is the volume flow rate, π is a mathematical constant equal to 3.14159…, and r is the radius of the pipe. Equation 1 can be written as ΔP = QR (Equation 2) where R is defined as the resistance to flow
R = !!"!!! (Equation 3)
The resistance to flow is inversely proportional to the fourth power of the radius, which means for a small decrease in radius, a much larger increase in the resistance to flow is observed. Therefore, when even a small amount of plaque is in an artery, the resistance to flow increases substantially. Rearranging Equation 2 Q = ∆!
! (Equation 4)
shows that an increase in the resistance to flow decreases the volume flow rate of blood in the artery. Blood is actually a Non-‐Newtonian fluid, but Poiseuille’s Law still can be used to provide a basic understanding of blood flow. Additional blood flow examples, can be found at: http://hyperphysics.phy-‐astr.gsu.edu/hbase/ppois2.html Elaboration Option 1: Many different wire patterns can be attempted. Individually or with their partners, if paired, have students brainstorm different wire patterns for the stent. After the students determine a different wire pattern to try, allow them to create and expand the stents. Option 2: Have the students research the prevention or other medical treatments for heart disease and write a short report or presentation based on the research. Assessment Informal assessment is ongoing during the lesson. Be sure that the students are following lab safety procedures. If the students estimate the amount of wire needed to make the stent, their calculations and measurements can be used as an assessment. Final assessment for Elaboration, Option 1: Have the students report their results of the second stent. They should discuss the success of the stent, any advantages or disadvantages, and further modifications that would improve the stent. Final assessment for Elaboration, Option 2 is the written report or presentation.
Useful Resources Heart: http://www.texasheartinstitute.org/HIC/Anatomy/anatomy2.cfm; Image of the heart http://www.webmd.com/heart/picture-‐of-‐the-‐heart; also has definitions of heart conditions, heart tests, and heart treatments http://www.gwc.maricopa.edu/class/bio202/cyberheart/hartint0.htm Heart attacks: http://www.nlm.nih.gov/medlineplus/tutorials/ (select “Heart Attack” for a tutorial with animation of the heart. Specifically, see “Heart Anatomy”)
http://www.womentowomen.com/heartdiseaseandstroke/symptoms.aspx http://www.nlm.nih.gov/medlineplus/ency/article/000195.htm http://www.mayoclinic.com/health/heart-‐attack/DS00094 Stents: http://www.vascularweb.org/vascularhealth/pages/angioplasty-‐and-‐stenting.aspx Angioplasty and Stent Education Guide: http://www.bostonscientific.com/templatedata/imports/collateral/ePatientGuides/StentEducationGuide_90627944-‐02B_01_us.pdf
Lanzer P, Strupp G, Schmidt W, Timmie Topoleski LD. 2013. The need for stent-‐lesion matching to optimize outcomes of intracoronary stent implantation. J Biomed Mater Res Part B 2013: 101B: 1560-‐1570.
Poiseuille’s Law: http://www.physics.usyd.edu.au/teach_res/jp/fluids/viscosity.pdf http://hyperphysics.phy-‐astr.gsu.edu/hbase/ppois2.html http://hyperphysics.phy-‐astr.gsu.edu/hbase/pturb.html Newtonian and non-‐Newtonian Fluids: http://antoine.frostburg.edu/chem/senese/101/liquids/faq/non-‐newtonian.shtml http://www.princeton.edu/~achaney/tmve/wiki100k/docs/Non-‐Newtonian_fluid.html Viscosity: http://www.princeton.edu/~gasdyn/Research/T-‐C_Research_Folder/Viscosity_def.html http://www.spacegrant.hawaii.edu/class_acts/ViscosityTe.html http://www.wisegeek.org/what-‐is-‐viscosity.htm Prerequisites The ability to follow written directions is required. If wire length estimate activity is completed, basic measurement skills with a ruler are necessary. Safety
Be sure that students are using good lab safety practices. Tell the students that they need to handle push pins and the wire carefully to avoid injuries. In addition, request that students check their work areas for push pins on the floor. Materials can be disposed in the trash. Alignment with Standards Next Generation Science Standards: MS-‐ETS1-‐1: Define the criteria and constraints of a design problem with sufficient precision to ensure a successful solution, taking into account relevant scientific principles and potential impacts on people and the natural environment that may limit possible solutions. Common Core State Standards: CCSS.ELA-‐Literacy.WHST.6-‐8.2a Introduce a topic clearly, previewing what is to follow; organize ideas, concepts, and information into broader categories as appropriate to achieving purpose; include formatting (e.g., headings), graphics (e.g., charts, tables), and multimedia when useful to aiding comprehension. CCSS.ELA-‐Literacy.WHST.6-‐8.2d Use precise language and domain-‐specific vocabulary to inform about or explain the topic. CCSS.ELA-‐Literacy.WHST.6-‐8.6 Use technology, including the Internet, to produce and publish writing and present the relationships between information and ideas clearly and efficiently. CCSS.ELA-‐Literacy.RST.6-‐8.3 Follow precisely a multistep procedure when carrying out experiments, taking measurements, or performing technical tasks. CCSS.ELA-‐Literacy.RST.6-‐8.4 Determine the meaning of symbols, key terms, and other domain-‐specific words and phrases as they are used in a specific scientific or technical context relevant to grades 6–8 texts and topics. CCSS.ELA-‐Literacy.WHST.6-‐8.8 Gather relevant information from multiple print and digital sources, using search terms effectively; assess the credibility and accuracy of each source; and quote or paraphrase the data and conclusions of others while avoiding plagiarism and following a standard format for citation. Worksheets Heart Worksheet for Students Heart Worksheet for Teachers Steps for Creating Stent Wire Length Estimation Worksheet