Measurements Taken and Calculations Derived

Blood Pressure:

Blood pressure is measured using a sphygmomanometer. Blood pressure is not the same all over the body and the most accurate way to measure blood pressure is to use an artery closest to the heart, that is, brachial artery blood pressure. This can be measured from above the subject’s elbow. Furthermore, it is convenient and ensures consistency.

After obtaining verbal consent, the subject sits down and rests their arm on a table so the brachial artery is level with the heart. This is important when monitoring blood pressure, as pressure is proportional to height (Δp = ρgΔh).



A sphygmomanometer cuff is wrapped around the subject's upper arm, just above the elbow, with the air tube on the same side of the palm facing up. Place the air tube in line with your middle finger and a stethoscope is placed on the hollow of the elbow.
The cuff is 'pumped-up' to a pressure of 180mmHg, compressing the brachial artery hence causing the artery to collapse once the systolic pressure has been exceeded. At the point where the pressure of the cuff is greater than the systolic pressure, the artery has collapsed thus, there is no flow of blood through the brachial artery.

The valve on the pump is loosened slowly to allow the pressure of the sphygmomanometer cuff to decrease. Once the systolic pressure is reached (approximately 120mmHg in the 'normal' case), the brachial artery opens causing volatile blood flow, which cause vibrations against the artery walls. These noises (called Korotkoff sounds) can be heard through a stethoscope as the pressure exerted onto the brachial artery falls. The blood flow through the brachial artery increases steadily, until the pressure of the sphygmomanometer cuff falls below the diastolic pressure, approximately 80mmHg.


Weight:


The subjects were told to remove their footwear as well as empty their pockets. Body weight was measured (to the nearest 0.5 kg) with the subjects standing motionless on the bathroom weighing scale.


Height:


The subjects were told to remove their footwear. Height was measured (to the nearest 0.5 cm) with the subjects standing in an erect position against a wall that has a measuring tape attached to it. The subjects' heads were positioned so that the top of the external auditory meatus was level with the inferior margin of the bony orbit. A ruler was used to avoid parallax error when taking the readings.


To ensure the accuracy of the height and weight measurements, we took 3 readings for the measurement of each subject. The mean values of weight and height was tabulated and recorded using SPSS.


Body Mass Index (BMI):

BMI was then calculated using the formula:

Mean weight and height was used to calculate BMI for accurate representation.


Mean Arterial Pressure (MAP):

MAP is calculated based on the formula as shown below:

SBP: Systolic Blood Pressure
DBP: Diastolic Blood Pressure
Diastolic and systolic pressure is obtained from the sphygmomanometer readings.