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Friday, November 12, 2010

Understanding Blood Pressure ~ Silent Killer -

Blood pressure (BP) is the pressure exerted by circulating blood upon the walls of blood vessels, and is one of the principal vital signs. During each heartbeat, BP varies between a maximum (systolic) and a minimum (diastolic) pressure.[1] The mean BP, due to pumping by the heart and resistance to flow in blood vessels, decreases as the circulating blood moves away from the heart through arteries.

Notes for the above BP table :

1. Why did I do this? I searched high and low on the Internet, and I could find nothing like this in one place - a Summary of human BP range, the Averages, and the Comments relating to each BP level.

2. How did I get the numbers? I started with the commonly seen "Systolic/ Diastolic pairs" seen in the literature - 200/120, 160/100, 140/90, 120/80 and 90/60. From there, I interpolated and extrapolated all the other numbers. Note that these are AVERAGE relationships. For instance, instead of 140/90, your BP may be 140/100, or 140/80. Each individual will have a unique systolic-diastolic relationship. If your S/D difference varies significantly from the averages shown above, this can be helpful in assessing your particular cardiovascular condition.

3. For comparison purposes, I added the "delta" column, which is the difference between the Systolic and Diastolic pressure readings. This relationship is almost linear, with the exceptions of the 40 delta, the 30 delta, and the 15 delta.

4. As for the comments, I have "averaged" the references made in the literature, since not all doctors agree upon the pressures at which to treat, and how aggressively to treat (multiple medications, type of meds, etc.). You can rest assured that the pharmaceutical companies prefer that you take medication at 135/80, since they sell the meds. Most doctors are not so aggressive. Remember that ALL medications have side effects. Heart medications have more serious side effects than any other class of prescription drugs.

5. Be aware of the "Circadian Rhythm" cycle. Your Blood Pressure is highly influenced by the time of day. For normal people, the highest BP occurs about midday, and the lowest at about 3-4 AM in the morning. For some people, described as "non-dippers", this early morning BP dip does not occur. For these people, highest blood pressure usually occurs around 6 AM to 9 AM in the morning. Some doctors are not aware of this, and make erroneous assumptions. A non-dipper may see 150/95 in the morning, and 130/85 in the evening. Non-dipping is usually associated with abnormal sleep conditions, such as sleep apnea, heavy snoring, drug and alcohol abuse, etc.

6. One blood pressure reading means very little. The advice to "Have your blood pressure checked once a year" is useless. What time of day? Had you eaten less salty foods recently? Were you relaxed that day, when you are usually much more stressed? Had you recently exercised vigorously? You must check your BP far more often than once a year, especially if you show "borderline" readings. I can produce a very low, or very high blood pressure AT WILL, based upon what I do during the 24 hours prior to the measurement.

7. Beware of "white coat syndrome", which results in a much higher BP reading than normal, due to the authoritative doctor, the foreboding, sterile exam room, and the smells such as alcohol and disinfectant. All this is not relaxing. Some unaware doctors may prescribe medication, when in fact, you don't need it at all. As soon as you leave the office, your BP returns to normal. This is another great reason to use your own automatic BP wrist monitor, so that you come to know your own body, and the effects of stress, food, mood, sleep, and time of day.

8. MAP = Mean Arterial Pressure. Three formulas are used to compute MAP. All three produce very similar results.

Above, I used Method #1 -
MAP = DP + (1/3 (SP - DP))
Ideal Mean Arterial Pressure is defined as 93 mm of mercury, which corresponds to 120/80.

Alternative Method #2 -
Also, MAP = (2/3 DP) + (1/3 SP)

Alternative Method #3
MAP = ((2*DP) + SP) / 3
where SP= Systolic Pressure,
and DP= Diastolic Pressure