Does Putting a Blood Pressure Cuff on Too Tight Affecr Reading
Claret pressure may exist the vital sign we measure the most and understand the least
Nurses and physicians oft debate over differences betwixt arterial line and non-invasive claret pressure (NIBP) cuff readings. Revised guidelines for direction of high blood force per unit area increased thresholds for diagnosing and treating hypertension, causing farther debate and controvery [1].
To brand the best use of blood force per unit area monitoring equipment, it is helpful to have an insight into how the equipment works and the likely sources of error that can affect readings. Download a guide to these tips to go on with y'all for quick reference.
The virtually common blood force per unit area reading mistakes are:
- Using the wrong-sized cuff
- Incorrect patient positioning
- Incorrect cuff placement
- Normal reading prejudice
- Not factoring in electronic units correctly
Here's what many of us do wrong, and how to have a blood pressure reading:
i. You're using the wrong-sized cuff
The nigh common error when using indirect blood force per unit area measuring equipment is using an incorrectly sized cuff. A BP cuff that is too big will requite falsely depression readings, while an overly modest cuff will provide readings that are falsely loftier.
The American Heart Association publishes guidelines for claret pressure level measurement [two]. recommending that the float length and width (the inflatable portion of the gage) should be 80 percentage and 40 per centum respectively, of arm circumference. Nearly practitioners find measuring bladder and arm circumference to be overly time consuming, and so they don't practise it.
The nigh practical style to quickly and properly size a BP cuff is to pick a cuff that covers two-thirds of the altitude betwixt your patient'south elbow and shoulder. Carrying at least three gage sizes (large adult, regular adult, and pediatric) volition fit the majority of the adult population. Multiple smaller sizes are needed if you frequently treat pediatric patients.
Korotkoff sounds are the noises heard through a stethoscope during cuff deflation. They occur in v phases:
- I – first detectable sounds, corresponding to appearance of a palpable pulse
- 2 – sounds become softer, longer and may occasionally transiently disappear
- Iii – alter in sounds to a thumping quality (loudest)
- Four – pitch intensity changes and sounds become deadened
- V – sounds disappear
In their 1967 guidelines, the AHA recommended that clinicians record the systolic BP at the start of phase I and the diastolic BP at beginning of phase IV Korotkoff sounds. In their 1981 guidelines, the diastolic BP recommendation changed to the start of stage V [two].
two. You've incorrectly positioned your patient'south body
The second nearly common error in BP measurement is incorrect limb position. To accurately assess blood period in an extremity, influences of gravity must be eliminated.
The standard reference level for measurement of blood pressure by whatsoever technique — direct or indirect — is at the level of the center. When using a cuff, the arm (or leg) where the cuff is applied must be at mid-heart level. Measuring BP in an extremity positioned above heart level will provide a falsely low BP whereas falsely high readings volition be obtained whenever a limb is positioned below heart level. Errors tin can exist meaning — typically 2 mmHg for each inch the extremity is above or below heart level.
A seated upright position provides the virtually authentic blood pressure level, as long every bit the arm in which the pressure is taken remains at the patient'due south side. Patients lying on their side, or in other positions, can pose bug for accurate force per unit area measurement. To correctly assess BP in a side lying patient, hold the BP gage extremity at mid centre level while taking the pressure. In seated patients, be certain to exit the arm at the patient'southward side.
Arterial pressure transducers are bailiwick to similar inaccuracies when the transducer is not positioned at mid-eye level. This location, referred to as the phlebostatic axis, is located at the intersection of the fourth intercostal space and mid-chest level (halfway between the anterior and posterior chest surfaces.
Note that the mid-axillary line is often not at mid-chest level in patients with kyphosis or COPD, and therefore should not be used equally a landmark. Wrong leveling is the primary source of error in direct pressure measurement with each inch the transducer is misleveled causing a one.86 mmHg measurement fault. When above the phlebostatic centrality, reported values will exist lower than actual; when beneath the phlebostatic centrality, reported values volition exist higher than bodily.
3. You've placed the cuff incorrectly
The standard for blood pressure gage placement is the upper arm using a cuff on bare skin with a stethoscope placed at the elbow fold over the brachial avenue.
The patient should be sitting, with the arm supported at mid heart level, legs uncrossed, and non talking. Measurements tin can be made at other locations such equally the wrist, fingers, anxiety, and calves but will produce varied readings depending on distance from the centre.
The mean pressure, interestingly, varies picayune between the aorta and peripheral arteries, while the systolic pressure increases and the diastolic decreases in the more distal vessels.
Crossing the legs increases systolic blood pressure by two to 8 mm Hg. About 20 percent of the population has differences of more than than 10 mmHg pressure betwixt the right and left arms. In cases where significant differences are observed, treatment decisions should be based on the college of the two pressures.
4. Your readings exhibit 'prejudice'
Prejudice for normal readings significantly contributes to inaccuracies in blood pressure measurement. No doubt, you'd be suspicious if a fellow EMT reported blood pressures of 120/80 on three patients in a row. Equally creatures of habit, human beings expect to hear sounds at certain times and when extraneous interference makes a claret pressure difficult to obtain, there is considerable tendency to "hear" a normal blood pressure.
Orthostatic hypotension is defined as a subtract in systolic blood pressure of 20 mm Hg or more than, or diastolic blood force per unit area decrease of 10 mm Hg or more than measured afterwards iii minutes of standing quietly.
There are circumstances when BP measurement is simply not possible. For many years, trauma resuscitation guidelines taught that crude estimates of systolic BP (SBP) could be made by assessing pulses. Presence of a radial pulse was thought to correlate with an SBP of at least 80 mm Hg, a femoral pulse with an SBP of at least lxx, and a palpable carotid pulse with an SBP over 60. In recent years, vascular surgery and trauma studies have shown this method to be poorly predictive of actual claret pressure [3].
Noise is a factor that tin can also interfere with BP measurement. Many ALS units carry doppler units that mensurate blood menses with ultrasound waves. Doppler units amplify sound and are useful in loftier noise environments.
BP by palpation or obtaining the systolic value past palpating a distal pulse while deflating the blood pressure gage by and large comes within x – 20 mmHg of an auscultated reading. A pulse oximeter waveform tin can also be used to measure return of blood period while deflating a BP cuff, and is as accurate every bit pressures obtained past palpation.
In patients with circulatory aid devices that produce non-pulsatile flow such as left ventricular assist devices (LVADs), the only indirect means of measuring period requires use of a doppler.
The return of catamenia signals over the brachial artery during deflation of a blood force per unit area cuff in an LVAD patient signifies the mean arterial pressure level (MAP). While a normal MAP in adults ranges from lxx to 105 mmHg, LVADs exercise not function optimally against higher afterload, and then mean pressures of less than 90 are often desirable.
Wear, patient access, and cuff size are obstacles that often interfere with conventional BP measurement. Consider using alternate sites such as placing the BP gage on your patient's lower arm above the wrist while auscultating or palpating their radial avenue. This is particularly useful in bariatric patients when an appropriately sized cuff is not available for the upper arm. The thigh or lower leg tin be used in a similar fashion (in conjunction with a pulse point distal to the gage).
All of these locations are routinely used to monitor BP in hospital settings and generally provide results only slightly unlike from traditional measurements in the upper arm.
5. You lot're not factoring in electronic units correctly
Electronic blood pressure level units also chosen Non Invasive Blood Pressure level (NIBP) machines, sense air pressure changes in the gage caused past blood flowing through the BP cuff extremity. Sensors estimate the Mean Arterial Pressure level (MAP) and the patient's pulse rate. Software in the machine uses these two values to calculate the systolic and diastolic BP.
To clinch accurateness from electronic units, it is important to verify the displayed pulse with an actual patient pulse. Differences of more than 10 percent will seriously alter the unit of measurement's calculations and produce incorrect systolic and diastolic values on the brandish screen.
Given that MAP is the simply pressure actually measured by an NIBP, and since MAP varies little throughout the body, it makes sense to use this number for treatment decisions.
A normal adult MAP ranges from seventy to 105 mmHg. As the organ virtually sensitive to pressure level, the kidneys typically require an MAP to a higher place lx to stay alive, and sustain irreversible damage beyond 20 minutes beneath that in virtually adults. Because private requirements vary, nearly clinicians consider a MAP of 70 as a reasonable lower limit for their adult patients.
Increased employ of NIBP devices, coupled with recognition that their displayed systolic and diastolic values are calculated while only the mean is actually measured, have led clinicians to pay much more attention to MAPs than in the past. Many progressive hospitals order sets and prehospital BLS and ALS protocols have begun to treat MAPs rather than systolic claret pressures.
Finally, and especially in the critical care ship environment, providers volition encounter patients with meaning variations betwixt NIBP (indirect) and arterial line (direct) measured blood force per unit area values.
In the past, depending on patient condition, providers have elected to employ i measuring device over some other, often without clear rationale besides a conventionalities that the selected device was providing more authentic claret pressure information.
In 2013, a group of ICU researchers published an analysis of 27,022 simultaneous art line and NIBP measurements obtained in 852 patients [4]. When comparison the a-line and NIBP readings, the researchers were able to determine that, in hypotensive states, the NIBP significant overestimated the systolic blood pressure level when compared to the arterial line, and this difference increased equally patients became more hypotensive.
At the same time, the mean arterial pressures (MAPs) consistently correlated between the a-line and NIBP devices, regardless of pressure. The authors suggested that MAP is the most accurate value to trend and care for, regardless of whether BP is existence measured with an arterial line or an NIBP. Additionally, supporting previously believed parameters for acute kidney injury (AKI) and mortality, the authors noted that a MAP below threescore mmHg was consistently associated with both AKI and increased mortality.
Since 1930, blood force per unit area measurement has been a widely accustomed tool for cardiovascular assessment. Even under the often adverse conditions encountered in the prehospital or ship surroundings, providers can accurately measure out blood pressure if they empathise the principles of claret period and mutual sources that introduce error into the measurement process.
Claret force per unit area assessment tips
Go along learning virtually claret pressure assessment by reading how to mitigate NIBP and auscultating innacuracies by watching the plethysmography waveform on your pulse oximeter and noting the mean arterial pressure.
Read next: Acquire how to read a MAP.
References:
1. James PA, Oparil S, Carter BL, et al. 2014 Prove-Based Guideline for the Management of High Blood Force per unit area in Adults: Report From the Panel Members Appointed to the Eighth Joint National Commission (JNC 8). JAMA. 2014;311(v):507-520. (Available at: http://jama.jamanetwork.com/commodity.aspx?articleid=1791497)
2. Pickering TG, Hall JE, Appel LJ, et al. AHA Scientific Statement: Recommendations for blood pressure level measurement in humans and experimental animals, part ane: claret pressure measurement in humans. Hypertension. 2005; 45: 142-161. (Available at: https://hyper.ahajournals.org/content/45/1/142.full)
3. Deakin CD, Low JL. Accuracy of the advanced trauma life support guidelines for predicting systolic claret pressure using carotid, femoral, and radial pulses: observational report. BMJ. 2000; 321(7262): 673–674. (Bachelor at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC27481/)
4. Lehman LH, Saeed Yard, Talmor D, Mark R, Malhotra A. Methods of claret pressure measurement in the ICU. Crit Care Med. 2013;41:34-40.
This article, originally posted Apr. 9, 2014, has been updated.
Make full out the class beneath to download a guide to reading blood pressure.
Near the author
Mike McEvoy, PhD, NRP, RN, CCRN is the European monetary system Coordinator for Saratoga Canton, New York and a paramedic supervisor with Clifton Park & Halfmoon Ambulance. He is a nurse clinician in cardiothoracic surgical intensive intendance at Albany Medical Middle where he also Chairs the Resuscitation Committee and teaches critical care medicine. He is a lead author of the "Critical Intendance Transport" textbook and Informed® Emergency & Critical Intendance guides published by Jones & Bartlett Learning. Mike is a contributor to EMS1.com and a popular speaker at EMS, Fire, and medical conferences worldwide. Contact Mike by email.
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