Settings for Sampling Panels in Lt - Blood Pressure and Cardio Microphone

The Blood pressure and cardio microphone preset settings can be used with a blood pressure cuff which has an inbuilt pressure transducer and a cardio microphone to record a volunteer's blood pressure using the PowerLab. 

Exercises you can do with these settings

  • Use the cardio microphone to record arterial sound while deflating the blood pressure cuff. The first and last Korotkoff sounds indicate systolic and diastolic arterial blood pressures, respectively.
  • Investigate the effect of deflating the cuff at different rates on accuracy of blood pressure measurements.
  • Compare the measurement of blood pressure in the arm using cuffs of various sizes.
  • Examine how the position of the arm affects the blood pressure. Compare:
    • Arm hanging down loosely by the side
    • Arm held straight above the head
    • Arm at head level.

The following instructions may be useful for you to copy and paste for your students:

Equipment setup procedure

Pressure Transducer

  1. Connect the pressure transducer to Input 1 on the PowerLab. 
  2. Ensure the pressure transducer is attached to the sphygmomanometer cuff.
  3. Wrap the sphygmomanometer cuff around the upper arm of your volunteer, just above the elbow.

Cardio Microphone

  1. Connect the cardio microphone to Input 2. 
  2. Place the cardio microphone over an appropriate artery (e.g. the brachial artery) below the level of the cuff. Use a Velcro strap to hold it in place.
  3. Ensure the PowerLab is powered on.

Blood pressure measurement procedure

  1. Leave the blood pressure cuff in place around the upper portion of the volunteer's arm (either arm), between the elbow and the shoulder. 
  2. Place the cardio microphone over the brachial artery. It is best to position this just below the cuff and to hold it in place with a Velcro strap. However, it can also be placed under the blood pressure cuff so that it is held in position by the cuff. 
  3. Select Start
  4. Inflate the cuff to 30 mmHg higher than the estimated systolic pressure.
  5. Slowly reduce the pressure in the cuff (approximately  2–3 mmHg per second or per pulse beat).
  6. Deflate the cuff completely once the pressure has gone below 50 mmHg or after the disappearance of the Korotkoff sounds. 
  7. Select Stop

Blood pressure analysis procedure

  1. Examine your recording. The cardio microphone channel displays the Korotkoff sounds as spikes. These spikes can be used to determine systolic and diastolic pressure. 
  2. Select the data corresponding to the Korotkoff sounds (i.e. from the first spike to the last clear spike in the series). 
  3. The first spike occurs at the systolic pressure. The last spike in the series occurs at the diastolic pressure. 

Note: In some people, diastole may not be obvious and you may need to estimate.