Week 9

Proposal Report Draft:

Literature Review research

Below is a collection of medical devices article that related to the development of portable digital blood pressure monitor using micro-controller.

1. Sphygmomanometer

Among the many common tools used in a doctor’s office is one which we’re all familiar with, but whose real name is little-known. That device is the sphygmomanometer, which is used to measure blood pressure. The sphygmomanometer has been in wide use since the early 20th century, and consists of a cuff placed around the arm, as well as a device to measure the pressure at which blood flows freely, and the pressure at which blood flow is restricted.
When a sphygmomanometer is used, the cuff is inflated, usually around the upper arm, and the pressure is gradually released. A digital sphygmomanometer often operates at the touch of a button, and the blood pressure data is displayed on a digital screen. Many manual sphygmomanometers are also still in use, which usually require a medical professional to operate correctly.
In a manual device, the pressure is displayed as the height of a column of mercury in a tube. As the cuff is manually inflated, the height of the column increases, and then decreases as the pressure is released. While the cuff deflates, the doctor usually listens with a stethoscope to the main artery of the arm.

When the flow of blood begins to flow again after being stopped by the cuff, there begins to be a rushing or pounding sound that the doctor is able to hear through the stethoscope. The pressure at which this occurs is noted, and is called the systolic pressure. The cuff is allowed to further deflate, and the pressure at which the sound is no longer audible is also noted, and is called the diastolic pressure. These two values are the pair of numbers that are recognizable as a blood pressure value.
It is important that a person’s blood pressure be measured when he is relaxed, otherwise the reading will be falsely elevated. Hormones such as adrenaline can increase blood pressure dramatically by constricting blood vessels. A person who has just been severely startled, for example, will have an elevated blood pressure compared to someone who is watching television. Accurate readings are essential to determine the health of the heart and therefore the rest of the body.
The use of a manual sphygmomanometer, like many things in medicine, takes some practice before you can consistently get correct readings. For those with hypertension, however, this may be a valuable skill, since it is important in that case to measure your blood pressure frequently. Apart from the convenience involved, some patients get nervous when their blood pressure is taken by a doctor, sometimes referred to as lab coat syndrome. This can throw off the reading, so being able to measure your own blood pressure at home is not only convenient but also medically relevant.


2. Oscillometric

A second type of noninvasive blood pressure measurement strategy, the oscillometric method, also employs an occluding cuff. However, in contrast to the auscultatory method, which relies on detection of Korotkoff sounds, the oscillometric method operates by sensing the magnitude of oscillations caused by the blood as it begins to flow again into the limb.
Typically, very faint blood flow oscillations begin to be detected as the air pressure in the cuff coincides with SBP. As air pressure is slowly released from the occluding cuff, the amplitude of these pulsatile oscillations increases to a point and then decreases as blood flow to the limb normalizes. Although the oscillation with the greatest amplitude has been shown to correspond reliably with mean arterial pressure (Mauck et al., 1980), determinations of SBP, which are associated with a marked increase in amplitude of oscillations, and DBP, which are associated with the point at which oscillations level off, are often less accurate when compared with auscultatory measures (Fowler et al., 1991).
Therefore, while oscillometric methods tend to overestimate SBP and underestimate DBP (Maheswaran et al., 1988; Manolio et al., 1988), they can be useful for determining accurate estimates of mean arterial pressure.

Larkin, K. T., and Zayfert, C.
Published with assistance from the foundation established in memory of Amasa Stone Mather of the Class of 1907, Yale College.

3. Wrist Blood Pressure Monitor

The onset of new medical technology paved the way for a more modern and convenient way to measure blood pressure. While the old way to measure blood pressure was by using a cuff that goes on the upper left arm and uses a stethoscope, the new method now is by way of attaching it to the wrist and is known as the wrist blood pressure monitor. The advantages of the wrist blood pressure monitor are that it is easier to use and can fit in any wrist size regardless if the person is thin or fat. The comparison between the two methods is now more focused on the accuracy of the blood pressure readings of the person rather than the size of the monitors.
The wrist blood pressure monitor is effective if it is properly used. The exact directions and procedures must be followed to get accurate results. The accuracy of this monitor is somehow affected by the position of the body so extra care should be observed when using this monitor. Doctors advise that the arm and wrist should be at heart level to get an accurate reading. Because of this required positioning of the arm and wrist, more wrist monitors are made to adapt to this requirement to record blood pressure.
The convenience of taking blood pressure at home is another advantage of the wrist monitor. You can instantly get a reading of your blood pressure. If you have been trained and guided properly to the use of the wrist monitor, then you would be confident enough to get the accurate reading of your blood pressure. In cases that you are unsure, then it is wise to go to your doctor so he can correctly supervise and check the accuracy of your blood pressure reading.
However, there are some instances that you cannot really validate the accuracy of your blood pressure so you have no choice but to consult your doctor and have him validate it. The use of the old traditional method is helpful in this case to double check the accuracy of the results. These cases are very few and have not affected the good effects of the wrist blood pressure monitors.
The use of the wrist blood pressure monitor is widely accepted because it has its good uses. It is an effective tool to measure accurate blood pressure immediately especially during travel. Most monitors have a memory recall to check any fluctuations in the readings. It even has a system to monitor irregular heartbeat. It has been clinically validated and has passed the rigid standards of safety and accuracy set by most independent medical organizations.
Most people are now aware that having a weak heart means taking more necessary precautions in food intakes and exercise. Such is the use of the wrist blood pressure monitor, it is like a security blanket that helps monitor blood pressure based on the accuracy and the convenient way it was made to be.

4. Blood Pressure Monitors

Which type of blood pressure monitor is recommended to use at home?

High Blood Pressure affects millions of people in the UK increasing the risk of stroke, heart attack and heart failure.

• High blood pressure usually has no symptoms.
• The only way for you to know if you have normal, high or low blood pressure is to have it measured
• You can measure your blood pressure in your own home ideally with a reliable, accurate blood pressure monitor.
• The information below is intended to help you make an informed purchase should you decide to buy a machine to use at home.
• These machines are available to buy online at First Aid Warehouse, Medisave and Amazon

Types of Machines

 

For ease of use machines can be fully automatic and measure blood pressure correctly on the upper arm at heart level. The readings are given on a digital display and can be stored in the monitor's memory or printed out. There are many different types of machines available however the standards of accuracy may vary. The information on these pages will hopefully help you make an informed decision on your purchase - which machines are best, where to buy them from trusted online stores and how to use the blood pressure monitor correctly.

Sometimes your blood pressure is raised when taken in a clinical or medical environment, such as your doctor’s surgery. This is called white coat hypertension and can be caused by feeling anxious, or by being in a busy or noisy environment. Blood pressure readings taken at home are often lower than those taken at a doctor’s surgery, whether a doctor or a nurse takes them. Readings taken away from the clinic are now seen to give a more accurate picture of your normal blood pressure.
Research published in the British Medical Journal revealed that people who monitor their blood pressure at home have better blood pressure control. The paper, "Blood pressure control by home monitoring.." shows clear evidence that patient involvement in the monitoring of blood pressure brings better results than those monitored solely at their surgery or clinic.

Recommended Blood Pressure Monitors

Staff taking general enquiries at the Blood Pressure Association became aware that increasingly people are measuring their own blood pressure at home, and are keen to know what machines are recommended. There is a wide range of machines available to the public. If you are considering buying a blood pressure monitor it is important that you make an informed purchase, it is worth investigating the quality, types and check prices before you buy a machine for home use.
Details of blood pressure monitors suitable for home use, compiled by the British Hypertension Society (BHS) are available on their Web site you may find it a useful guide when you buy a blood pressure monitor. All of the monitors on this list are digital upper arm monitors and have been through independent testing shown in research to be accurate and are currently available.