Haemodynamic Variables

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Measuring haemodynamic variables using different techniques and examining the effects of diving reflex, isometric muscle contraction and psychological stress on these variables.

Introduction

Haemodynamics is the study of factors that determine the movement of blood (Widmaier et al, 2011). The main haemodynamic factors are heart rate and blood pressure. Heart rate is defined as the number of times the heart contracts per minute. Normal resting heart rate in adults ranges between 60 – 100 beats per minute. Monitoring heart rate regularly is important to diagnose medical conditions such as high heart rate (tachycardia) and low heart rate (bradycardia). Heart rate monitors are also used during exercise to heighten efficiency of and individual’s training (Pocock and Richards, 2004).

Blood pressure is the pressure that the blood exerts against the blood vessel walls, especially the walls of the arteries. Two types of blood pressure are recorded; systolic blood pressure – when pressure is high during ventricular systole – and diastolic blood pressure – when pressure is low during ventricular relaxation. Monitoring blood pressure is important because it allow changes to be detected. The common condition of high blood pressure is often asymptomatic, making it difficult to be realised until complications occur (Walerstein, 2010). Diving reflex is a reflex of mammals, reptiles, and birds that causes the body to respond in a number of different ways when the trigeminal facial nerves are stimulated or when the body undergoes apnea. These nerves are stimulated when the face comes in contact with cool water (below 21C). The colder the water, the quicker the physiological changes occur. The physiological changes that occur are bradycardia (slowing down of heart rate) and peripheral vasoconstriction (narrowing of blood vessels). Peripheral vasoconstriction occurs to reduce blood flow to limbs and increase blood flow to organs that require the most oxygen. A decrease in blood flow increases pressure (Rennie, 2012) Isometric contraction is a phase of normal muscle contraction in which the muscle does not produce any movement externally but internal muscle tension increases. (Marieb and Hoehn, 2004). Isometric contraction causes heart rate to quickly increase initially and depending on the duration and intensity of the exercise heart rate can increase again gradually. Both systolic and diastolic blood pressures also increase. Stress is defined as the changes the body undergoes as it reacts to a stressor. Psychological stress refers to stress that affects the mind such as trauma. A stressor is an agent which causes the body to deviate from its normal homeostatic state. Stress reducing responses that occur include increased adrenaline and noradrenaline production. This increases heart rate and blood pressure (Torpy et al, 2007). The aims of this experiment were to measure heart rate/blood pressure using different methods and to determine the effects of different stressors on haemodynamic variables. Method

The methods were carried out as described in the laboratory schedule (Coventry University, 2012) Results
Blood pressure was measured using two different techniques; a sphygmomanometer and an automatic BP monitor. The results from the sphygmomanometer showed a mean systolic blood pressure (SBP) of 90mmHg and a standard deviation value of 3.74mmHg. Diastolic blood pressure (DBP) had a mean value of 63.4mmHg and a standard deviation value of 4.22mmHg. Mean arterial pressure (MAP) which is calculated below, had a mean value of 72.2mmHg and a standard deviation value of 3.77mmHg. This is shown below in (Fig 1.).

| 1| 2| 3| 4| 5| Mean| Standard Deviation|
Sphygmomanometer| SBP (mmHg)| 92| 90| 94| 90| 84| 90| 3.74| | DBP (mmHg)| 65| 60| 70| 60| 62| 63.4| 4.22|
| MAP(mmHg)| 74| 70| 78| 70| 69| 72.2| 3.77|
Automatic BP monitor| | SBP (mmHg)| 104| 95| 110| 95| 99| 99.8| 6.90| | |...
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