What is the effect of different body positions i.e. lying down, sitting and standing on the blood pressure?

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Research Question: What is the effect of different body positions i.e. lying down, sitting and standing on the blood pressure?

Hypothesis:

Blood pressure is a measure of “the pressure of the blood in the arteries as the heart pumps it around the body” (Better Health Channel, 2007). When blood pressure is measured, it is usually expressed as two values, the systolic value and diastolic value. The systolic pressure is the higher value and represents “the maximum pressure exerted when the heat contracts”, where the lower number, the diastolic value, “represents the pressure in the arteries when the heart is at rest” (MedlinePlus Medical Encyclopaedia, 2007).

There are numerous factors which influence the blood pressure of a person, including age, fitness, psychological factors such as stress, diet, and body position. This investigation will focus on body position and will investigate the effect of different body positions, i.e. lying down, sitting and standing on blood pressure.

When a person is standing, blood falls to their legs due to gravity, resulting in a decrease in blood pressure. This is supported by the literature stating that “when you stand up, gravity causes blood to naturally want to pool in your leg veins causing a drop in blood pressure”. However, when you are standing up for longer periods of time, your body responds by increasing blood pressure; “the autonomic nervous system tries to correct this by narrowing your blood vessels, increase[ing] blood pressure” (OneTwentyOverEighty, 2007).

When a person is in a lying down position, as the body is in a horizontal position, it is easier to pump blood around the body, this is supported by the literature “blood pressure [decreases] when lying down since the body is not having to work too hard to pump blood around the body” (OneTwentyOverEighty, 2007). However, when a person is sitting down, the body has to work slightly harder to pump blood around the body compared to when the body is in a horizontal position and this will slightly increase the blood pressure.

Literature values for the blood pressure of participants in a lying position is 115/70, 120/79 for participants sitting down and 121/78 for participants standing (OneTwentyOverEighty, 2007), where the lower value represents the diastolic and the higher the systolic pressure.

Based on this literature, it is predicted that the blood pressure of the participants will be the highest when participants are in a standing position, second highest when sitting down on a chair and the lowest when lying down.  


Variables:

Independent: the body position in which the participants remained in for a period of 2 minutes (before blood pressure was measured)

  • Lying down
  • Sitting up
  • Standing up

Dependent: the blood pressure of the participants in each of the different positions

  • Diastolic (mmHG)
  • Systolic (mmHG)

Control: the following variables were controlled:

  • Age of the participants (16 years)
  • Time of the day in which the investigation was undertaken (2pm ± 45 minutes)
  • Amount of time participants remained in each position before measuring their blood pressure (2 minutes)
  • Hand in which the blood pressure monitor was attached to (left hand)
  • The arm position- the wrist was in line with the heart
  • Room temperature (SLC)
  • Height of the chair in which participant sat on
  • Same blood pressure monitor was used for all participants

Materials:

  • 1 x JADCO Time Stopwatch (±0.05 seconds)
  • 1 x CASCADE Health Blood Pressure Monitor
  • Model: CE1541BM
  • Pressure (0 ~ 300mmHg)
  • 1 x Plastic chair
  • 10 x (2 male, 8 female) participants 16 years of age
  • Pen
  • Paper

Method:

  1. The participants were asked to stand up with their left wrist held outwards away from their body in line with the heart
  2. The ‘START’ button was pressed on the stopwatch and the health blood pressure monitor was attached to the participants left wrist, with the top of the monitor facing outwards
  3. Qualitative results were recorded in this period of time
  4. After a period of 2 minutes, the participants were asked to press the ‘Start’ button on the blood pressure monitor
  5. The Diastolic and Systolic pressures were both recorded in the appropriate tables below
  6. Steps 2-6 were repeated, once with the participants sitting down on a chair and another time with the participants lying down flat on their backs
  7. Steps 1-7 were repeated with 9 other participants (a total of 8 females and 2 males)

Data Collection:

Qualitative Data:

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Quantitative Data:


Data Processing:

* Average measurements were calculated using formula x = ∑x

                                                                                        fx  

* Standard deviation was calculated using Microsoft Excel and was used to calculate the confidence value (see ‘table 8’) in order to apply error bars to ‘figure 1’ below

Figure ...

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