Arterial blood pressure is most often measured through a sphygmomanometer, which historically uses the height of the mercury column to reflect the circulating pressure. Blood pressure values ​​are generally reported in millimeters of mercury (mmHg), although aneroids and electronic devices do not contain mercury.
For every heartbeat, blood pressure varies between systolic and diastolic pressure. Systolic pressure is the peak pressure in the arteries, which occurs near the end of the heart cycle when the ventricles contract. Diastolic pressure is the minimum pressure in the arteries, which occurs near the beginning of the heart cycle when the ventricles are filled with blood. Examples of measured normal values ​​for resting and healthy adult humans were 120 mmHg systolic and 80 mmHg diastolic (written 120/80 mmHg, and pronounced as "one-twenty-eighty").
Systolic and diastolic arterial blood pressure is not static but undergoes a natural variation from one heartbeat to another and throughout the day (in circadian rhythms). They also change in response to stress, nutritional factors, medication, illness, exercise, and momentarily from standing. Sometimes the variations are large. Hypertension refers to abnormally high arterial pressure, compared with hypotension, when it is abnormally low. Along with body temperature, respiratory rate, and pulse, blood pressure is one of the four major vital signs routinely monitored by medical professionals and healthcare providers.
Measure the pressure invasively, by penetrating the arterial wall to take measurements, much less frequently and usually limited to hospital settings.
Video Blood pressure measurement
Non-invasive
Non-invasive auscultation and oscillometric measurements are simpler and faster than invasive measurements, requiring less skill, almost no complications, less pleasurable and less painful for the patient. However, non-invasive methods can produce rather low accuracy and small systematic differences in numerical results. Non-invasive measurement methods are more commonly used for routine checks and monitoring.
Palpate
Minimum systolic values ​​can be estimated roughly by palpation, most commonly used in emergency situations, but should be used with caution. It is estimated that, using 50% percentile, carotid, femoral and radial pulses are present in patients with systolic blood pressure & gt; 70 mmHg, carotid and femoral alone in patients with systolic blood pressure & gt; 50 mmHg, and only carotid pulse in patients with systolic blood pressure & gt; 40 mmHg.
More accurate values ​​of systolic blood pressure can be obtained by sphygmomanometer and palpation of radial pulsation. Methods using a constitutive model have been proposed to measure blood pressure from radial artery pulses. Diastolic blood pressure can not be estimated by this method. The American Heart Association recommends the palpation used to obtain estimates before using auscultation methods.
Auscultation
The auscultation method (from the Latin word for "listening") uses a stethoscope and a sphygmomanometer. It consists of an inflatable cuff ( Riva-Rocci ) placed around the upper arm at a vertical height approximately equal to the heart, attached to a mercury or aneroid manometer. The mercury manometer, considered a gold standard, measures the height of the mercury column, provides absolute results without the need for calibration and, consequently, is not subject to calibration errors and deviations that affect other methods. The use of mercury manometers is often necessary in clinical trials and for clinical measurement of hypertension in high-risk patients, such as pregnant women.
A cuff with the appropriate size fitted properly and fitted, then manually inflated by repeatedly squeezing the rubber ball until the artery is completely blocked. It is important that the cuff size is correct: the cuff is too low to record too high pressure; Cuffs that are too large can produce too low a pressure. Usually three or four cuff sizes should be available to allow measurements on the sleeves of different sizes. Listening with the stethoscope to the brachial artery in the antecubital area of ​​the elbow, the examiner slowly releases pressure on the cuff. As the blood begins to flow in the arteries, turbulent flow creates "whizzing" or hitting (Korotkoff's first voice). Sound pressure is first heard is systolic blood pressure. The pressure of the cuff is released further until there is no audible sound (Korotkoff fifth sound), at the pressure of the diastolic artery.
Auscultation method is the main method of clinical measurement.
Oscillometric
The oscillometric method was first demonstrated in 1876 and involved the observation of oscillations in the pressure of the sphygmomanometer cuff caused by blood flow oscillation, ie the pulse. The electronic version of this method is sometimes used in long-term measurement and general practice. It uses a cuff sphygmomanometer, such as auscultation method, but with an electronic pressure sensor (transducer) to observe cuff pressure oscillations, electronics to automatically interpret it, and automatic inflation and cuff deflation. Pressure sensors should be calibrated periodically to maintain accuracy.
Oscillometric measurements require fewer skills than auscultation techniques and may be suitable for use by untrained staff and for monitoring of patient homes automatically. The auscultation technique is important that the size of the cuff is appropriate for the arm. There are some single cuff devices that can be used for sleeves of different sizes, although experience with this is limited.
The cuff is pumped to a pressure that initially exceeds the pressure of the systolic artery and is then reduced to diastolic downward for a period of about 30 seconds. When the blood flow is zero (cuff pressure exceeds systolic pressure) or unobstructed (cuff pressure under diastolic pressure), the cuff pressure is substantially constant. When blood flow is present, but limited, the cuff pressure, which is monitored by the pressure sensor, will vary periodically in harmony with cyclic expansion and brachial artery contraction, ie, it will oscillate.
During the deflation period, the recorded pressure wave forms a signal known as the cuff deflation curve. A bandpass filter is used to extract the oscillometric pulses from the cuff deflation curve. During the deflationary period, the oscillometric pulse is extracted to form a signal known as the oscillometric wave (OMW). The amplitude of the oscillometric pulse increases to a maximum and then decreases with further deflation. Various analytical algorithms can be used to estimate systolic, diastolic, and average arterial pressure.
Oscillometric monitors may produce inaccurate readings in patients with cardiac and circulatory problems, including arteriosclerosis, arrhythmias, preeclampsia, pulsus alternans, and pulsus paradoxus.
In practice, different methods do not yield identical results; an algorithm and the experimentally obtained coefficients are used to adjust the oscillometric results to provide a reading appropriate to the best possible auscultation results. Some equipment uses computer-aided analysis of momentary arterial pressure waves to determine systolic, average, and diastolic points. Since many oscillometric devices have not been validated, attention should be given as they are largely unsuitable in clinical and acute care settings.
Recently, several free-coefficient oscillometric algorithms have been developed to estimate blood pressure. This algorithm is independent of experimentally obtained coefficients and has been shown to provide more accurate and robust blood pressure estimates. The algorithm is based on finding a fundamental relationship between oscillometric waveforms and blood pressure using modeling and learning approaches. Measurement of pulse transit time has also been used to increase oscillometric blood pressure estimates.
The term NIBP, for non-invasive blood pressure, is often used to describe oscillometric monitoring equipment.
Continuous non-invasive techniques
Continuous Noninvasive Arterial Pressure (CNAP) is a method of measuring arterial blood pressure in real-time without interference and without human body canning. CNAP combines the advantages of the following two "clinical gold standards": it measures real-time continuous blood pressure such as an invasive and noninvasive arterial catheter system such as a standard upper arm sphygmomanometer. Recent developments in this field show promising results in terms of accuracy, ease of use and clinical acceptance.
Pulse wave velocity
Since the 1990s, a new engineering family based on the principle of pulse wave velocity (PWV) has been developed. These techniques depend on the fact that the rate at which arterial pressure travels along the arterial tree depends, inter alia, on the underlying blood pressure. Thus, after the calibration maneuver, this technique provides an indirect estimation of blood pressure by translating the PWV value into the blood pressure value.
The main advantage of this technique is that it is possible to measure the PWV values ​​of the subject continuously (beat-by-beat), without medical supervision, and without the need to inflate the brachial arm. PWV-based techniques are still in the research domain and are not adapted to clinical settings.
Ambulatory and home monitoring
Outpatient blood pressure devices take regular readings (eg every half hour throughout the day and night). They have been used to exclude measurement problems such as white-coat hypertension and provide a more reliable estimate of plain blood pressure and cardiovascular risk. Blood pressure reading outside the clinical setting is usually slightly lower in most people; But studies that measure the risk of hypertension and the benefits of lowering blood pressure are largely based on readings in a clinical setting. The use of ambulatory measurements is not widespread but the guidelines developed by the British National Institute for Health and Care Excellence and the British Hypertension Society recommend that 24 hour ambulatory blood pressure monitoring should be used for the diagnosis of hypertension. Health economic analysis suggests that this approach will be cost-effective compared to repeated clinical measurements.
Home monitoring is a cheap and simple alternative to outpatient blood pressure monitoring, although it usually does not allow the assessment of blood pressure during sleep that may be a disadvantage. Automatic self-blood pressure monitors are available at reasonable prices, but measurements may be inaccurate in patients with atrial fibrillation or other arrhythmias such as frequent ectopic beats. Home monitoring can be used to improve hypertension management and to monitor the effects of lifestyle changes and medications related to blood pressure. Compared with ambulatory blood pressure measurements, home monitoring has been found to be an effective and cheaper alternative, but outpatient monitoring is more accurate than clinical and home monitoring in diagnosing hypertension.
When measuring blood pressure at home, accurate readings require that a person not drink coffee, smoke, or do strenuous exercise for 30 minutes before taking a reading. A full bladder may have a small effect on blood pressure readings; if the urge to urinate arises, one has to do it before reading. For 5 minutes before reading, one should sit upright in a chair with one foot tread on the floor and with no limbs crossed. Blood pressure cuff should always fight against bare skin, because the readings taken on the sleeve are less accurate. The same arm should be used for all measurements. During reading, the arms used should be relaxed and stored at the heart level, for example by placing it on the table.
Because blood pressure varies throughout the day, home measurements should be performed at the same time. The American Heart Association, American Society of Hypertension, and Preventive Cardiovascular Nurses Association recommends that 2 to 3 readings be made in the morning (after awakening, before washing/dressing, taking breakfast/drinking or taking medication ) and 2 to 3 other readings at night, every day for a period of 1 week. It is also recommended that readings from the first day should be discarded and total> = 12 readings (ie at least two readings per day for the remaining 6 days of the week) should be used to make clinical decisions.
Observer error
There are many factors that can play a role in blood pressure reading by the doctor, such as hearing problems, the perception of hearing against the doctor. Karimi Hosseini et al evaluated differences among observers among specialists without hearing impairment, and reported that 68% of observers recorded systolic blood pressure in the range of 9.4 mmHg, diastolic blood pressure in the range of 20.5 mmHg and mean blood pressure in the range of 16 , 1 mmHg. Neufeld et al reported standard deviations for systolic and diastolic readings of 3.5-5.5 mm Hg. In general the standard deviation for diastolic pressure will be greater because of the difficulty in assessing when the sound disappears.
Hypertension white coat
For some patients, blood pressure measurements taken at the doctor's office may not accurately describe their typical blood pressure. In up to 25% of patients, the measurement in the office is higher than their blood pressure. This type of error is called white-coat hypertension (WCH) and can result from anxiety associated with an examination by a health care professional. White coat hypertension can also occur because, in a clinical setting, patients are rarely given a chance to rest for five minutes before blood pressure is taken. Misdiagnosis of hypertension for these patients can cause unnecessary and possibly harmful medications. WCH can be reduced (but not eliminated) by automatic blood pressure measurement for 15 to 20 minutes in a quiet section of the office or clinic. In some cases low blood pressure readings occur in doctors - this has been called 'hypertension masking'.
Alternative settings, such as pharmacies, have been proposed as an alternative to office blood pressure. The threshold for blood pressure from a pharmaceutical reading was 135/85 mmHg, indicating a reduced white effect, similar to daytime ambulatory measurements.
Maps Blood pressure measurement
Invasive
The most accurate arterial blood pressure is measured invasively through the artery path. The measurement of invasive arterial pressure with intravascular cannula involves direct measurement of arterial pressure by placing a cannula needle in an artery (usually radial, femoral, dorsalis pedis or brachialis). The cannula is inserted either by palpation or by using ultrasound guidance.
The cannula must be connected to a sterile, fluid-filled system connected to an electronic pressure transducer. The advantage of this system is that the pressure is monitored continuously from pulse-by-beat, and waveform (time-pressure graph) can be displayed. This invasive technique is regularly used in human intensive care, animal cure, anesthesiology, and for research purposes.
Cannulation for the monitoring of invasive vascular pressure is rarely associated with complications such as thrombosis, infection, and bleeding. Patients with invasive arterial monitoring require very strict supervision, because there is a danger of severe bleeding if the duct is interrupted. It is generally reserved for patients where variations in arterial pressure are quickly anticipated.
Invasive vascular pressure monitors are pressure monitoring systems designed to obtain pressure information for display and processing. There are various invasive vascular pressure monitors for trauma, critical care, and operating room applications. These include single pressure, dual pressure, and multi-parameter (ie pressure/temperature). Monitors can be used to measure and follow up arteries, central venous arteries, pulmonary arteries, left atrium, right atrium, femoral artery, umbilical vein pressure, umbilical, and intracranial arteries.
References
Source of the article : Wikipedia
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