According to the Harvard Medical School Family Health Guide, normal blood pressure is a systolic pressure of less than 120 and a diastolic pressure of less than 80 (livestrong.com). Systolic pressure is defined as the highest arterial blood pressure reached during any given ventricular cycle (Dictionary.com). Diastolic pressure is defined as the lowest arterial blood pressure reached during any given ventricular cycle (Dictionary.com). The standard way to measure blood pressure is with the patient’s arm extended and relaxed while the patient is sitting (smc.edu).
National Guideline Clearinghouse research shows that diastolic blood pressure is approximately 8 mm/Hg higher in a laying down position that when a patient is sitting (livestrong.com). Results have also shown that systolic pressure is about 8 mm/Hg higher in the lying down position than in the sitting position (livestrong.com). A millimeter of mercury per a unit of pressure is expressed as mm/Hg (webmd.com). According to livestrong.com, back support also plays a role in blood pressure measurements (livestrong.com). How does your body position play a role in your blood pressure measurements when your legs are above your head and heart?
If a subject lays with their buttocks and legs up against a wall above their head and heart for 15 seconds, then the blood pressure will increase by .5mm/Hg, because the body position of having legs above your head and heart will affect the flow of the blood which will cause the systolic and diastolic pressures to change, resulting in a higher blood pressure.
The independent variable in this experiment was the body position. In every trial the body position was controlled by the subject and was the same; legs and buttocks against the wall with back on the ground and left arm extended
for the blood pressure test.
The dependent variable was each subject’s blood pressure. A resting blood pressure was measured before we began the trials on each subject. The blood pressure cuff measured each subject’s blood pressure. The blood pressure cuff was started on each test subject after the legs were up for 00:15 seconds.
There were many factors that could be controlled in the experiment. There were 20 trials for each subject. The gender was consistent with all girls. Age varied from age 15 to age 18. All 3 of the test subjects were tested in the hallways of Fishers High School during a quiet time when the area was empty of other students with no distractions. The temperature was constant throughout at 72 degrees Fahrenheit. The tester varied between test subjects, which could change the reaction times to the blood pressure cuff’s start/stop button. Test subject were also measured at different elevations; two test subjects upstairs, while the other was measured downstairs.
The three test subjects were sitting with their left arm rested and relaxed when the resting blood pressure was measured. The blood pressure cuff was secured on the left arm before the test subjects assumed their testing position. The trials began when the first test subject got into the testing position. The test subjects laid on the floor of the school hallway with legs and buttocks against the wall covered in lockers. The time started as soon as test subjects were in the exact body position on the stopwatch. As soon as the time reached 0:15 seconds, the start button for the blood pressure cuff was pressed. The cuff would inflate until it found the blood pressure, which would beep when finished. The blood pressure was measured in a fraction (mm/Hg) with millimeters of mercury on top and unit of pressure measurement on the bottom. The data was recorded in fractions into a notebook with a pen and later divided to become a decimal (ex. 121/78 = 121 ÷ 78 = 1.551). Decimals were rounded to the thousandths place. After each trial, the legs were brought down until the blood pressure came to a normal
level. The trial was repeated 20 times per each subject.
DATA COLLECTION AND PROCESSING
BLOOD PRESSURE AFTER ELEVATION OF FEET AT 90° ABOVE HEART FOR 15 SECONDS (+/- 1 sec.). Test Subj| Resting BP| Tested BP| Test Subj| Resting BP| Tested BP| Test Subj| Resting BP| Tested BP| A| 131/69| 103/58| B| 121/63| 102/58| C| 119/71| 95/49| A| | 105/63| B| | 104/51| C| | 117/60|
A| | 112/63| B| | 102/54| C| | 117/58|
A| | 113/60| B| | 114/65| C| | 123/62|
A| | 108/61| B| | 102/55| C| | 119/65|
A| | 107/64| B| | 106/50| C| | 122/63|
A| | 87/62| B| | 103/59| C| | 120/57|
A| | 95/65| B| | 110/50| C| | 129/59|
A| | 96/76| B| | 104/45| C| | 123/57|
A| | 109/61| B| | 101/53| C| | 119/56|
A| | 100/53| B| | 98/57| C| | 121/57|
A| | 97/56| B| | 109/52| C| | 117/55|
A| | 104/54| B| | 102/63| C| | 120/55|
A| | 101/51| B| | 108/75| C| | 120/56|
A| | 111/63| B| | 103/57| C| | 123/58|
A| | 90/61| B| | 97/59| C| | 115/50|
A| | 95/63| B| | 102/55| C| | 117/57|
A| | 99/54| B| | 101/54| C| | 125/61|
A| | 103/62| B| | 99/56| C| | 124/61|
A| | 100/67| B| | 100/54| C| | 119/54|
SUBJECT A| | SUBJECT B| | SUBJECT C| |
Resting heart rate was first taken from each subject (A, B, and C). This was recorded in a notepad in a fraction format (mm/Hg) to later be converted to a decimal format. In another column the trials were recorded in a fraction format (mm/Hg) and also converted to decimal format later. Once the data was processed to the decimal formats, the average of the tested blood pressure was subtracted from the average resting heart rate to find the difference.
121/78 mm/Hg (fraction format) 121 ÷ 78 = 1.551 1.551 (decimal format)
Processed Data Table
BLOOD PRESSURE AFTER ELEVATION OF FEET AT 90° ABOVE HEART FOR 15 SECONDS (+/- 1 sec.) AND DIVIDED INTO A DECIMAL FORMAT. Test Subj| Resting BP| Tested BP| Test Subj| Resting BP| Tested BP| Test Subj| Resting BP| Tested BP| A| 1.899| 1.776| B| 1.921| 1.759| C| 1.676| 1.939| A| | 1.667| B| | 2.039| C| | 1.95|
A| | 1.778| B| | 1.888| C| | 2.017|
A| | 1.883| B| | 1.754| C| | 1.983|
A| | 1.77| B| | 1.855| C| | 1.83|
A| | 1.672| B| | 2.12| C| | 1.936|
A| | 1.381| B| | 1.746| C| | 2.105|
A| | 1.462| B| | 2.2| C| | 2.186|
A| | 1.263| B| | 2.31| C| | 2.157|
A| | 1.787| B| | 1.905| C| | 2.125|
A| | 1.887| B| | 1.719| C| | 2.122|
A| | 1.732| B| | 2.096| C| | 2.127|
A| | 1.925| B| | 1.619| C| | 2.181|
A| | 1.98| B| | 1.44| C| | 2.142|
A| | 1.98| B| | 1.807| C| | 2.121|
A| | 1.475| B| | 1.644| C| | 2.3|
A| | 1.508| B| | 1.854| C| | 2.053|
A| | 1.833| B| | 1.87| C| | 2.049|
A| | 1.661| B| | 1.767| C| | 2.033|
A| | 1.492| B| | 1.852| C| | 2.203|
AVG| 1.899| 1.695| | 1.921| 1.863| | 1.676| 2.077| SUBJECT A| | | SUBJECT B| | | SUBJECT C| | |
Presentation of Processed Data
AVERAGE BLOOD PRESSURE AFTER ELEVATION OF FEET AT 90° ABOVE HEART FOR 15 SECONDS (+/- 1 sec.) AND DIVIDED INTO A DECIMAL FORMAT.
AVERAGES BLOOD PRESSURE BEFORE AND AFTER ELEVATION OF FEET AT 90° ABOVE HEART FOR 15 SECONDS (+/- 1 sec.) AND DIVIDED INTO A DECIMAL FORMAT.
CONCLUSION AND EVALUATION
How does the position of the body affect the blood pressure? Blood pressure in this experiment only increased on an average of .046. The average resting blood pressure was 1.832 while the average tested blood pressure was 1.878. Body position does increase the blood pressure of one’s body when the feet are above the heart by 90° by .04mm/Hg, not .5mm/Hg. Evaluation
Like most experiments, there are factors that will affect your experiments; such as errors and things going wrong. The person conducting the experiment could have been off one or two seconds when pressing the start button on the blood pressure cuff. The subject could have not waited for the blood pressure to go back to normal before beginning a new trial. The environment may have not been the best for testing against lockers and on a hard, carpeted floor. Overall, the experiment was completed effectively and shows that body position does, in fact, affect blood pressure.
“Body Position and Blood Pressure.” LIVESTRONG.COM. 28 Feb. 2013 <http://www.livestrong.com/article/167631-body-position-and-blood-pressure/>.
“Hypertension (High Blood Pressure) Health Center – WebMD.” WebMD. WebMD. 28 Feb. 2013 <http://www.webmd.com/hypertension-high-blood-pressure/default.htm>.
“Systolic pressure.” Dictionary.com. Dictionary.com. 28 Feb. 2013 <http://dictionary.reference.com/browse/systolic%20pressure>.
“Understanding Blood Pressure Readings.” Understanding Blood Pressure Readings. 28 Feb. 2013 <http://www.heart.org/HEARTORG/Conditions/HighBloodPressure/AboutHighBloodPressure/Understanding-Blood-Pressure-Readings_UCM_301764_Article.jsp>.