Blood Pressure

• R , resistance, corresponds indeed to the resistance of the small vessels to the flow of blood:

Other physiological elements: pulsated Pressure or differential pressure, Law of One tenth of a poise.

The mechanisms of regulation are of type:

nervous
• : vasodilatation by the Vagus with deceleration of the heart rate
• humoral (i.e. by production of chemical substances which will be diffused in all the organization and will act thus remotely):

That explains the great variability of the figures tensionnels from one minute to another at the same individual: approximately, the effort and the Stress make increase the blood pressure, the rest makes it decrease.

The catch of tension is thus prone to many Artifact S , it must thus be ideally catch in reclining position, the patient being at rest; should not be neglected “the white blouse effect” (the tension of the patient increases because of nervousness induced by measurement). It is also necessary to check the adequacy between the size of the arm-band and that of the arm: if the first is too small, one can have a false rise in the figures tensionnels (effect “large arm”).

Measure

Apparatuses

It is made classically by a circular inflatable arm-band connected to a pressure gauge, called Tensiomètre or sphygmomanometer. The first apparatus of this type was described by Dr. Scipione Rivetted-Rocci on December 10th 1896 in the medical gazette of Turin .

The current instrument is brought to the level of the arm. A stethoscope is laid out with the level of the fold of the elbow to listening of the artery humérale. By inflating the arm-band with a pressure higher than the maximum pressure, the artery of the arm is then occluded. One deflates this one then very gradually and when the pressure of inflation is equivalent to the pressure systolic (or maximum), the artery opens intermittently what appears by the appearance of a noise of beat in the stethoscope; these noises, called “noises of Korotkoff”, are due to turbulences of the flow of the blood, obstructed by the pressure of the arm-band. Important pulsations are also perceptible by the patient and the inspector. When the pressure of the arm-band becomes lower than the minimal pressure (diastolic), the artery is then permanently open: turbulent flow becomes laminar and the noises auscultatoires disappear.

It is the method by “contrepulsion”.

One can also estimate the pressure without stethoscope, but in a less precise way:

• the pulsations of the artery are reflected in the arm-band, the pressure of the arm-band thus oscillates between the systolic pressure and the diastolic pressure; when the arm-band is deflated, one thus records the pressure to which the needle of the pressure gauge starts to oscillate (systolic pressure) and that to which the needle stops oscillating (diastolic pressure);
• by taking the radial Pulse compressed arm: when the arm-band is compressed, the pulse is not perceived; when the arm-band is deflated, the pressure from which the pulse appears is the systolic pressure (this method does not make it possible to have the diastolic pressure).

Association manual tensiometer and stethoscope are more and more often replaced by automatic apparatuses ( electronic tensiometers ) with an arm-band inflated by an engine and detection either of the noises by a microphone (method auscultatoire), or of the variations of amplitude of the wave of pulse (oscillometric method). These apparatuses allow repeated measurements and the monitoring almost in real-time of the blood pressure.

One can also measure the blood pressure by the same techniques but this time Ci with the wrist and even with the finger. That however does not constitute the method of reference.

When one couples an electronic tensiometer with a battery and a memory, one can measure the blood pressure then in a way repeated during 24:00: it is MAPA (= ambulatory monitoring of the blood pressure wrongfully also called Holter tensionnel ).

In certain cases, the blood pressure is measured by introducing into the Artère a Cathéter filled up of liquid and connected to a Pressure pick-up. This more invasive method (thus riskier) give more precise measurement S and gives the blood pressure in Dynamique. Thus, the pressure at each time of each cardiac cycle of the patient is measured, not only the systolic and diastolic pressure over a certain period.

Protocol of use

The method of reference is measurement with the arm-band with stethoscope (contrepulsion). It is done on a patient in position half-base, the arms along the body, after five to ten minutes of rest. The arm must be maintained with height of the heart: if the arm is too low, the pressure will be over-estimated. The size of the cuff must be adapted to the size of the arm: if the cuff is too small, the pressure will be over-estimated. Initially, one measures the pressure with the two arms. It can happen that the pressure is a little higher in an arm than in another: one will regard the highest pressure as being the value of reference.

One currently recommends, during a consultation, to measure the blood pressure at the beginning and the end of the consultation: the “syndrome of the white blouse” (anxiety at the patient generated by the presence of the medical personnel) very frequently involves wrongfully high values at the beginning of examination.

Estimate without apparatus

In the urgency, the fall of the systolic blood-pressure can be estimated by the catch of simple the Pouls, this one involving the disappearance of a distal pulse; in an adult:

• if the radial pulse is perceived, the systolic tension is higher than 80  mmHg ( T   ≥ 8  cmHg);
• if the radial pulse is not perceived but that the pulse carotidien or femoral is, the systolic tension is between 50  mmHg and 80  mmHg (8  cmHg  ≥ T   ≥ 5  cmHg);
• if the pulse carotidien and femoral disappeared, the tension is lower than 50  mmHg ( T   ≤ 5  cmHg).

One can also consider the tension systolic with the “capillary filling”: one exerts a pressure on a nail, this one fades, and one looks at the speed to which it recolore:

• normal capillary filling (lower than two seconds): the systolic tension is higher than 100  mmHg ( T   ≥ 10  cmHg);
• delayed capillary filling (higher than two seconds): the systolic tension is between 85 and 100  mmHg (10  cmHg  ≥ T   ≥ 8,5  cmHg);
• not of capillary filling: the systolic tension is lower than 85  mmHg ( T   ≤ 8,5  cmHg).

Pathologies

• If it is too high permanently, it acts of a arterial Hypertension.
• If it is too low, one speaks about Hypotension.
• If it is broken down, one speaks about cardiovascular collapse, being able to involve a state of shock.

See too

Internal bonds

• cardiovascular Collapse

External bonds

• general Information on the control of the market of the apparatuses of tensionnelle automesure, Afssaps

• Accuracy off the advanced trauma life support guidelines for predicting systolic blood presses using carotid, femoral, and radial pulsate: observational study, Lorraine C.D. Deakin, J. Low, BMJ n°321, pp673-674 (September 16th 2000)
• Letters - Accuracy off ATLS guidelines for predicting systolic blood presses
• Notice of explanation of the French federation of cardiology