Learning Module 2: Measuring ECGs

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Learning Module 2Measuring ECGs
Clark J Cotton
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Calculating Heart Rate from an ECG

• By measuring the distance between R-waves, we can
  calculate heart rate.
• Example
• 1 sec between R-waves.
• HR 60 / 1 60 beats / minute

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Calculating Heart Rate from an ECG

• By measuring the distance between R-waves, we can
  calculate heart rate.
• Example
• 1 sec between R-waves.
• HR 60 / 0.5 120 beats / minute

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What Are Activities that Could Influence Heart
Rate?

• Fill in with ideas as students brainstorm

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Why Does Heart Rate Change?

• Again fill in with ideas as students brainstorm.

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Measuring Your ECG

• Wipe each wrist and your right ankle with an
  alcohol pad.
• Attach gel-electrode pads to each wrist and your
  ankle.
• Attach the red wire to your right wrist, the
  black wire to your left wrist, and the green
  electrode to your ankle.
• Click record on your laptop. Once you see a good
  ECG with 5-10 heartbeats click stop.
• Calculate Heart Rate

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Typical Resting Heart Rates
African Elepant Resting HR 28 bpm
Sam Donaldson Resting HR 75 bpm
Deer Mouse Resting HR 500 bpm
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Test the Effects of Jumping Rope

• Detach the wires from your gel electrodes.
• Jump rope for 5 minutes.
• Re-attach the red wire to your right wrist, the
  black wire to your left wrist, and the green
  electrode to your ankle.
• Click record on your laptop. Once you see a good
  ECG with 5-10 heartbeats click stop.
• Calculate heart rate.

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Effect of Exercise on Heart Rate
Race Horse Resting 25 bpm Racing 215 bpm
Rainbow Trout Resting HR 47 bpm Swimming HR 50 bpm
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Test the Effects of Diving

• Hold your face directly over a tub of ice water.
  
• Click record on your laptop. Once you see a good
  ECG have your subject slowly immerse their face
  in the water.
• Keep recording for as long as your subject can
  stay under water.
• Calculate the heart rate for the last few beats
  you see while the subject is still under water.

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Diving Bradycardia in Nature
Harbor Seal HR before dive 135 bpm HR during
dive 30 bpm
Double-Crested Cormorant HR before dive 210
bpm HR during dive 50 bpm
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Why is Diving Bradycardia Adaptive?

• During a dive, animals have no access to oxygen.
  
• To conserve oxygen, animals reduce blood flow to
  all but the most important areas (heart, brain).
• Since blood flow is greatly reduced, the heart
  only needs to supply blood to a limited area, and
  can therefore reduce its rate and oxygen
  consumption.

Bron et al. 1966