Learning Module 2:Measuring ECG’s

Clark J Cotton

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

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

What Are Activities that Could Influence Heart Rate?

• Fill in with ideas as students brainstorm

Why Does Heart Rate Change?

• Again fill in with ideas as students brainstorm.

Measuring Your ECG

1. Wipe each wrist and your right ankle with an alcohol pad.

2. Attach gel-electrode pads to each wrist and your ankle.

3. Attach the red wire to your right wrist, the black wire to your left wrist, and the green electrode to your ankle.

4. Click record on your laptop. Once you see a good ECG with 5-10 heartbeats click stop.

5. Calculate Heart Rate

Typical Resting Heart Rates

Sam Donaldson

Resting HR 75 bpm

African Elepant

Resting HR 28 bpm

Deer Mouse

Resting HR 500 bpm

Test the Effects of Jumping Rope

1. Detach the wires from your gel electrodes.

2. Jump rope for 5 minutes.

3. Re-attach the red wire to your right wrist, the black wire to your left wrist, and the green electrode to your ankle.

4. Click record on your laptop. Once you see a good ECG with 5-10 heartbeats click stop.

5. Calculate heart rate.

Effect of Exercise on Heart Rate

Race Horse

Resting 25 bpm

Racing 215 bpm

Rainbow Trout

Resting HR 47 bpm

Swimming HR 50 bpm

Test the Effects of Diving

1. Hold your face directly over a tub of ice water.

2. Click record on your laptop. Once you see a good ECG have your subject slowly immerse their face in the water.

3. Keep recording for as long as your subject can stay under water.

4. Calculate the heart rate for the last few beats you see while the subject is still under water.

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

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