Blood pressure#Measurement
Wherein the blood pressure measurement is determined by means of a technical process the pressure in a blood vessel. One distinguishes the measurement of arterial pressure, venous pressure (eg, the central venous pressure ), and the measurement in the pulmonary artery ( pulmonary arterial pressure ) and in the Lungenkapillargebiet ( pulmonary capillary pressure). While most methods require special investigation procedures and partly special procedures outside of the routine are the measurement of arterial pressure plays an important role in everyday medical practice, since it can easily be carried out.
- 3.1 Methodology
- 3.2 Error Sources
Measurement of the vascular pressure
One distinguishes the direct ( invasive and bloody ) pressure measurement by a pressure sensor in a blood vessel of the indirect ( non-invasive, bloodless ) measurement, which is performed by means of a cuff on a limb.
Direct pressure measurement
In the direct, noninvasive measurement (often with " IBP " invasive blood pressure for short) is a vessel, usually a peripheral artery such as the radial artery or the femoral artery punctured and a catheter inserted. This is connected to a pressure sensor via which the arterial blood pressure waveform can be represented on a monitor. The measurement is accurate and offers the advantage of continuous monitoring, in addition, it measures the arterial pressure, the heart rate and mean arterial pressure ( MAP). Since the method is invasive, which is associated with the risk of bleeding, infection and nerve injury, it is mainly used by anesthesiologists to monitor during surgery and intensive care units. Indications for the invasive arterial pressure measurement cardiopulmonary critically ill patients, and major surgical procedures on the heart, vascular system, breast, liver or brain.
In the venous system of the venous pressure using invasive measurement can be determined. Thus, this type of central venous pressure (CVP, in the superior vena cava ) and in the context of analog ultimately running right heart catheterization of the pulmonary artery ( the pulmonary artery ), and other pressures in the region of the right heart are measured.
Indirect pressure measurement
In the indirect arterial pressure measurement (often with " NIBP ", non- invasive blood pressure, abbreviated ) is the arterial pressure using a sphygmomanometer on a limb, usually the arm, measured. While the measurement is not as accurate as the direct method in this way, the light, fast, safe and cost-effective performance make it an agent of choice in most fields of medicine. There are various methods of measurement differed (see also sphygmomanometer ). It is important that the cuff is kept at heart level during the entire process, it is required especially in wrist devices. The manual measurement can be auscultation, palpation and oscillatory performed. The values of each method differ slightly from one another thereby.
In the auscultatory measurement of a pressure cuff is inflated to a suitable width above the expected arterial pressure at the upper arm. During the slow draining can the occurrence and then again the disappearance of Korotkoff sound using a stethoscope over the artery of the arm listening ( auscultation ). The pressure can be read at the first time, of acoustic noise perceptibility of the scale on the measuring device corresponding to the upper, systolic arterial pressure value, i.e., the systolic pressure at that moment is greater than the pressure of the cuff. The pressure is released at a suitable rate on. Falls below the cuff pressure the minimum arterial pressure value, the noise disappears. This value is called the diastolic pressure and is listed as a lower value. Auscultatory measurement is the standard method of non-invasive measurement method.
Even with the palpatory measurement, a pressure cuff is applied to the upper arm, during deflation, the pulse on the radial artery is palpated. The pressure can be read at the first time pulse gated on the scale of the measuring device corresponding to the upper, the systolic arterial pressure. Diastolic value can not be determined in this way. The method provides for example, noisy environments, especially in the emergency service, at.
Oscillatory measurement is carried out in principle as the two other methods, the upper and lower value is estimated based on the amplitude waveform of a pulse-synchronous pointer deflection to the meter, which is the transmission of vibrations of the vessel wall in the pressure cuff. In manual measurement can be achieved only inaccurate results with this method. This measurement method is, however, quite reliable, used of measuring machines for continuous monitoring, eg postoperatively in the recovery room. This measure as an alternative to continuous invasive pressure measurement of arterial pressure of the patient in the interval of a few minutes. The oscillatory measurement method is also used in the now widespread wrist instruments.
On the same principle, the long-term blood pressure measurement is based (ABPM ). The patient wears permanently (usually about a whole day), a blood pressure cuff that automatically inflates at specified intervals and measures, as well as a recording device. This method is considered the gold standard for the detection and assessment of the severity of arterial hypertension.
Unit, and measurement accuracy
The millimeter of mercury (abbreviated mmHg) (written there without a hyphen ) in the European Union and Switzerland legal entity. In the United States, the unit Torr is used.
The deviation in the measurement, the measurement accuracy should be given for each automatic devices ( / -3 mmHg lt.MPG ). In indirect measurements of "hand" ( and ear) it is approximately plus / minus 5 mmHg, however, is subject to compliance with certain rules that have been agreed by national or international professional associations (discharge speed, time of measurement). If these rules are not followed, and there come quickly to deviations in the range about plus / minus 10 mmHg. The accuracy of a single measurement is thus but mostly in a range of therapeutically has no immediate consequence.
Methodology and sources of error
Methodology
The measurement should be made at rest after five minutes of rest in a quiet room and if possible in a sitting position. The pressure cuff must be chosen correctly. In patients who are taking medication, it should be noted when the measurement was carried out based on the medication. In case of differences between the two arms, the measurement should be carried out on the arm with the higher arterial pressure in the sequence. To assess the arterial pressure level of the average should be taken from several consecutive measurements in diagnostic questions at each visit.
Sources of error
Possible sources of error include not properly calibrated or inappropriate equipment. In the indirect measurement of arterial pressure, in particular the width of the seal is important to narrow cuff to measure high value and vice versa.
Other errors are due to the measured person, the diastolic value is to due to a sometimes observable phenomenon that is " auscultatory gap," falsely too high assumed (in this case disappear noise phenomena in a medium pressure range temporarily), the number of measurements low, a control of the other arm is not being performed, the pressure release rate is too high (over 3 mm Hg / s), the results are listed in error. In the first measurement of systolic arterial pressure during inflation should therefore be determined in addition by palpation and the cuff 30 mm Hg to be inflated via this pressure.
A source of error in the interpretation of the test results is in the situation in which the measurement is performed. In stressful and unusual situations, the arterial pressure will be as measured correctly, but do not match the other level. This can, for example, at a doctor's visit is the case ( white coat hypertension).
The following factors are " The family doctor " 15/ 09, pp. 54 f called in:
Blood pressure measurement in veterinary medicine
Also in veterinary medicine is ( apart from emergencies ), the blood pressure measured indirectly by measuring device. The cuff is applied for example in the dog or cat at front paw or tail. Signs of high blood pressure may be increased demand for water, dull coat, enlarged pupils, or reduced activity. In cats is the blood pressure in the normal range of about 124/84 mmHg in dogs at 133/75 mmHg, but each breed has its specific standard value. Even in animals can be a stressful situation at the vet in the measured values give the appearance of hypertension. It is recommended to measure the blood pressure preventive least once a year, more frequently in diseased animals.
History
1733 was first made by Stephen Hales ( 1677-1761 ), the invasive, bloody measurement in the veterinary field.
An early device of indirect arterial pressure measurement was eg the Sphygmograph the German physiologist Karl Vierordt ( 1818-1884 ). The first sphygmomanometer was invented by the Austrian pathologist Samuel Siegfried Karl Ritter von Basch (1837-1905), the family physician of Maximilian I.
A simple method of using mercury sphygmomanometer was invented by the Italian physician Scipione Riva - Rocci and published in 1896. Therefore, the measured according to this principle arterial pressure values are often marked " RR ". 1901 Harvey Cushing discovered this method on a trip to Italy, she improved for clinical application and popularized them.
Around 1905, was designed by the Russian military surgeon Nikolai Sergeyevich Korotkov through the use of the stethoscope for the purpose of hearing the later named after him Korotkoff sounds method for the measurement of diastolic pressure expands.
Heinrich von Recklinghausen used a wide cuff, which was only able to measure the actual arterial pressures, as opposed to the thin rubber cuff of Riva Rocci (see the measurements of Müller and Blauel of 1907 with a difference of 40%). Only through his use of a spring or Kapselmanometers could also be measured oscillometric.