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Introduction

IB Biology Human Physiology - Circulatory System - Open Investigation Planning A Research Question (RQ) How does the position of the arm (cuff) in relation to the heart, affect the blood pressure1 of non-diabetic, female, 16 year olds, in terms of Systolic Pressure2 and Diastolic Pressure3? Hypothesis It is known that there are many factors that influence blood pressure and blood pressure readings one of which will be explored in this experiment - the affect of the position of the monitored extremity (cuff) in relation to the heart. 'Blood pressure readings may be influenced by body position because of variation in the vertical distance between heart and cuff level.' (CAVELAARS Marinel; et al. - 2000) It is hypothesised that blood pressure will increase as the position of the monitored arm moves from 'Below the Heart' to 'In Line With the Heart' to 'Above Heart' in a proportional manner. To investigate this, the systolic pressure and diastolic pressures (mmHg) will be measured when the monitored arm is in various positions. In line with this prediction, literature states that, 'When the blood pressure (BP) is measured, the arm should be at the level of the heart' (STEPHEN S.EHRLICH, M.D., - 2004) and that the values thus produced will be the true blood pressure values.' Therefore the blood pressure values calculated with the monitored arm 'In Line With the Heart' will be treated as the control values and the other values will be analysed in relation to this control as that is the advised method for blood pressure measurement. Past studies into pulse oxygenation (SpO2) have shows that, 'by merely changing the position of the monitored extremity, the SpO2 can change by up to six percent. In this study, the arm was raised 90 degrees from surpine and this resulted in a highly significant decrease in SpO2 with elevation of the monitored arm.'4 (Cooke, J., Johansen, J., 2000) ...read more.

Middle

110.0 91.0 Subject 10 1 101.0 61.0 102.0 71.0 123.0 86.0 2 142.0 93.0 86.0 61.0 143.0 76.0 3 145.0 62.0 157.0 106.0 159.0 104.0 Average: 122.8 74.2 123.7 76.5 133.7 89.8 Uncertainties: Pressure +/- 3mmHg For the following tables and graphs, the average systolic and diastolic pressure (mmHg) values for each of the three positions of the monitored arm have been grouped by these positions and the total average for each position been calculated. This was done so that the tables and graphs can really depict the total averages for the positions of the arm - and thus the resulting difference. Table 4: The Total Average Systolic (SYS) and Diastolic (DIA) Pressures (mmHg) for the respected positions of the monitored arm in relation to the heart grouped by pressure Test SYS (mmHg) DIA (mmHg) 1 (directly above head) 2 (at heart level) 3 (down by side) 1 (directly above head) 2 (at heart level) 3 (down by side) Average: 122.8 123.7 133.7 74.2 76.5 89.8 Uncertainties: Pressure +/- 3mmHg Calculations for Descriptive Statistics: Mean - the average of all data entries Median - the middle value when data entries are placed in rank order Variance - A measure of the spread of the values in a distribution. The larger the variance, the larger the distance of the individual cases from the group mean. 5 The formula says to take a score (X) and subtract the mean (�), then square this difference (X-�)2 and sum up all of these squared differences (?(X- �)2), and divide the sum by the number of scores(N).6 Standard Deviation - a frequently used measure of the variability (spread) in a set of data Standard Error - an error measurement (reliability of your data) The 95% Confidence Interval - used to calculate and reveal on average, 95 times out of 100, the limits which usually contain the true mean P(n - 1) ...read more.

Conclusion

- as is the correct way to monitor blood pressure - it produced the middle value; and that when the cuff is parallel to the body and resting by the side, it results in the highest blood pressure reading. It can be concluded from these results that to obtain accurate and consistent blood pressure readings, it is important to implement the proper arm position - with the monitored arm perpendicular to the body, with a slightly flexed elbow - to correctly determine blood pressure levels with a wrist pressure monitor. Error/Limitation Impact / Significance Improvements The experiment wasn't repeated an adequate amount of times so there wasn't enough data and the data may be inconsistent. There wasn't enough data and the data that was used, was inconsistent. I propose that this experiment be repeated 3 more times so that the data that is collected is more consistent. The CASCADE Blood Pressure Monitor kept coming up with an ERROR message. This resulted in the subject holding their arm (cuff) in a position for a longer period of time. Because they had to hold their arm in a position for longer, it may have affected their results more than the others and this would have resulted in the discrepancies and outliers. I propose that another electronic piece of equipment that is more reliable be used. An example of such a piece of equipment is the Pasco data logger - with heart rate monitors. Because the subject's got bored, annoyed and agitated with having to hold their arm in uncomfortable positions for a consistent period of time, they became distracted and began running around and not remaining in one position for the duration of the experiment. This may have affected the results as because they were moving - and moving quickly - their heart rate and subsequently their blood pressure would have increased. This would have resulted in incorrect data. I propose that next time this experiment is undertaken, the subjects are required to be in a seated as opposed to standing position for the duration of the experiment. ...read more.

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