Practical 2 Blood pressure measurements 2022 student notes

Copyright Information

• Copyright © Monash University 2019. All rights reserved.

• Work cannot be reproduced in any form without permission as per the Copyright Act 1968.

Introduction to Blood Pressure Measurements

• Importance of statistics and uncertainties in scientific experiments.

• Uncertainties provide a range of confidence for experimental results and theory applications.

• Multiple measurements on various individuals are crucial due to physiological variability.

• Mean ± SD (standard deviation) or Mean ± SEM (standard error of mean) are standard reporting methods.

Learning Objectives

• Objectives after practical lab work include:

  • Understanding the use of an Omron for blood pressure measurement.

  • Defining key terms: systolic pressure, diastolic pressure, and pulse pressure.

  • Measuring, recording, analyzing, and interpreting experimental data.

  • Calculating mean, SD, and SEM for results.

  • Explaining sources of uncertainty (random and systematic).

Aim of the Practical

• Investigate aspects of cardiovascular function and variability in measurements.

Practical Work Guidelines

• Marking rubrics focus on:

  • Observations and data recording.

  • Calculation and data analysis.

  • Evaluating mean, SD, and SEM.

• Complete a worksheet to upload to Moodle within 24 hours of lab session.

Background on Heart Rate Measurement

• Arterial pulse of the radial artery measures heart rate:

  • Pulsation detected by palpation, not visible.

  • Count of pulses in a defined time (e.g., pulses in 15 seconds x 4 for bpm).

Device Overview: Omron

• Electronic devices like Omron simplify heart rate and blood pressure measurement.

• Variability exists in measurements between electronic and traditional methods.

• Omron measures blood pressure using the brachial artery:

  • Brachial pulse near the inner elbow;

  • Radial pulse near the base of the thumb;

  • Ulnar pulse opposite the radial pulse at the wrist.

Blood Pressure Measurement Procedure

1. Ensure the subject is seated comfortably with a straight back and feet flat.

2. Adjust the cuff on the upper arm with the pneumatic tube facing inward (2 fingers away from the elbow).

3. Ensure the cuff is aligned with the heart level.

Measurement Process

• Press the on/off button on the Omron:

  • Cuff inflates automatically, then deflates to measure systolic and diastolic blood pressure and heart rate.

Data Recording

• For practical class:

  • Take three blood pressure and heart rate measurements for each student.

  • Record measurements in provided tables and Google spreadsheet.

Results at Rest

• Record values for each student’s heart rate and blood pressures in mmHg:

  • Include Mean calculations.

Exercise Impact on Measurements

• Activities like exercise can affect blood pressure and heart rate.

• Measurement procedure includes:

  • One minute of exercise (running in place).

  • Immediate BP and heart rate measurement post-excercise.

  • Wait five minutes before taking another measurement.

  • Repeat process for multiple readings and calculate means.

Table Organization for Data

1. Results immediately after exercise

   • Record heart rate, systolic and diastolic pressure.

2. Results for recovery - 5 minutes post-exercise

   • Record heart rate, systolic and diastolic pressures.

   • Use Google spreadsheet for mean value documentation.

Statistical Data Analysis

• Perform a statistical analysis of the collected measurements:

  • Calculate average, sample standard deviation, standard error of the mean (SEM).

• Statistical considerations include:

  • Measurements are independent and variations are random.

Calculating Means and Standard Deviations

• Average calculation: Sum of measurements divided by the number of measurements.

• Sample standard deviation formula: σ = √[ ∑(xi – x̄)² / N ]

• SEM definition: u = σ / √N.

Instrumental Uncertainty and Limitations

• Measurement uncertainty due to the resolution of the Omron devices.

• Importance of calibration for accurate readings.

• Systematic vs. random uncertainties discussed.

Comparison of Measurements and Theory

• Analyze blood pressure and heart rate changes under different conditions.

• Recognize the need for multiple measurements for accurate physiological assessment.

General Questions for Review

• Explore definitions of hypertension and identify those at risk for high blood pressure.