Noninvasive Blood Pressure
Measurement at BWH
James H Philip ME(E), MD, C.C.E.
© Copyright 2009, James H Philip, all rights reserved
Noninvasive Blood Pressure
Measurement at BWH
James H Philip ME(E), MD, C.C.E.
Anesthesiologist, Brigham and Women’s Hospital
Director of Bioengineering, Department fo Anesthesiology,
Perioperative and Pain Medicine
Medical Liaison, Partners Department of Biomedical Engineering
© Copyright 2009, James H Philip, all rights reserved
Noninvasive Blood Pressure
problems at BWH in 2008
July 2008 we had NIBP Measurement problems
All those are solved
They were:
Cuff leaks
Hose leaks
No reading and cuff stopped cycling
Temperature changed with ESU interference
Noninvasive Blood Pressure
problems at BWH in 2008
CUFF LEAKS
BWH had old cuffs
GE replaced all cuffs free
BWH agreed to replace cuffs according to AAMI Standards
AAMI Standard = 10,000 cycles
Cuff Life could be 3 months for Anesthesia
Cuffs are being retired at least that fast
Manufacture date is printed on each cuff
Cuff Life could be several years for non-Anesthesia
Noninvasive Blood Pressure
problems at BWH in 2008
HOSE LEAKS
BWH had old hoses - up to 8 years old
New GE PDMs (Patient Data Modules) destroyed old BWH hoses
GE replaced all BWH hoses free
New hoses are compatible with TRAM Brick and PDM
Hoses should last several years
SUMMARY
BWH has all new hoses and cuffs
If you find an old or soiled cuff, trhow it in the trash and get another
Noninvasive Blood Pressure
problems at BWH in 2008
PDM Problems in OR
NIBP Measurement Problems - cuff stopped cycling if
readings were exactly 1 minute apart
readings were exactly 2 minutes apart
Temperature value changed dramatically with ESU use
BWH OR SOLUTION
We are not using PDMs in OR yet
GE is making software and temperature cable changes
We in OR will use PDMs when they are OR-ready
Noninvasive Blood Pressure
Measurement at BWH today
Noninvasive and Non Invasive are both used in the literature
NIBP and NBP are both used in the literature
GE calls it NBP
Methods of Noninvasive Blood
Pressure Measurement
Blood Pressure Measurement History
1773
1859
1896
1901
1904
1905
1934
1961
1976
1992
2000
Stephen Hales - Mean intra-arterial pressure (in horse carotid artery)
Etinne Marey - Sphygmograph
Riva-Rocci - Sphygmomanometer
Von Recklinghausen - Increased cuff width
Von Ricklinghausen and Erlanger - Oscillometer, Oscillotonometer
Korotkov - Auscultation
Hamilton - Intra-arterial recording
Franklin, Rushmer - Doppler blood flow,then wall motion for S, D NIBP
Ramsey - Dinamap® automated oscillometer
Friedman - Dinamap® advances
GE Acquired Critikon Corporation and Dinamap ® and technology
Sphygmomanometer Flow Detection
Techniques
1. Distal pulse - plethysmograph, including pulse oximeter
2. Cuff pulsations - oscillometer, AKA oscillotonometer
3. Auscultation - Korotkoff sounds
4. Doppler - ultrasound
Sphygmomanometer Cuff
1987 AAMI Standard, later Am Col Cardiologists
Cuff width > 0.4 Circumference = 1.3 Diameter of the extremity
Wrap evenly
Trapazoidal arms are a problem
Wrist NIBP = Brachial NIBP + 10 mmHg*
* Emerick DR. An evaluation of non-invasive blood pressure (NIBP) monitoring on the
wrist: comparison with upper arm NIBP measurement. Anaesth Intensive Care. 2002:
30(1):43-7
NIBP Monitors - How they work
Auscultatory NIBP
Systole = 135
Diastole = 83
Raw Cuff Pressure Signal
Korotkoff Sounds
Auscultatory NIBP
Systole = 135
Diastole = 83
Raw Cuff Pressure Signal
Korotkoff Sounds
Completed with cuff,
aneroid manometer or
mercury column,
stethoscope,
ear,
brain,
training
Auscultatory NIBP
Systole = 135
Diastole = 83
Raw Cuff Pressure Signal
Korotkoff Sounds
Completed with cuff,
aneroid manometer or
mercury column,
stethoscope,
ear,
brain,
training
Five Korotkoff sounds:
K1. Snapping sound at systolic pressure. A clear tapping sound; onset of the sound for two consecutive beats is considered systolic.
K2. Thud sounds between the systolic and diastolic pressures.
K3. Loud, crisp tapping sound of unknown etiology.
K4. Muffled sound, at pressures within 10 mmHg above the diastolic blood pressure.
K5. Silence below diastolic blood pressure. Diastolic blood pressure = two mmHg below the last sound heard.
Auscultatory NIBP
Systole = 135
Diastole = 83
Raw Cuff Pressure Signal
Korotkoff Sounds
Approximate Mean
= 1/3 of the way from diastolic up to systolic
= Diastolic + (Systolic - Diastolic) / 3
= 83 + (135 - 83) / 3
= 83 + 52 / 3
= 83 + 17.3 =
= 100.3
Auscultatory NIBP
Systole = 135
Diastole = 83
Raw Cuff Pressure Signal
Korotkoff Sounds
Origin of the 1/3 rule
Approximate Mean (of an arterial wave)
Exact Mean (of a triangle wave)
= Diastolic + (Systolic - Diastolic) / 3
= Diastolic / (Systolic - Diastolic) / 2
Auscultatory NIBP
Systole = 135
Diastole = 83
Raw Cuff Pressure Signal
Korotkoff Sounds
Approximate Mean (of an arterial wave)
Exact Mean (of an arterial wave)
= Diastolic / (Systolic - Diastolic) / 3
= { Integral (BP) / one beat period}
Averaged over several beats
Oscillometric NIBP
Systole = 135
Mean = 100
Diastole = 83
Raw Cuff Pressure Signal
Pulse-Wave Oscillations in Cuff Pressure
Oscillometric NIBP
Systole = 135
Mean = 100
Diastole = 83
Raw Cuff Pressure Signal
Pulse-Wave Oscillations in Cuff Pressure
Best estimate of Mean*
= pressure of maximum oscillation
= 100 mmHg
* Yelderman M, Ream AK. Anesthesiology 50: 1979
Oscillometric NIBP
Systole = 135
Mean = 100
Diastole = 83
Raw Cuff Pressure Signal
Pulse-Wave Oscillations in Cuff Pressure
Best estimate of Mean*
ACCURACY OF ESTIMATE*
= pressure of maximum oscillation
{Cuff Peak Oscillations - Mean Direct BP}
= 100 mmHg
Mean = 1.4 mmHg, SD = 6.2 mmHg, 95% within 14 mmHg
* Yelderman M, Ream AK. Anesthesiology 50: 1979
GE Dinamap®
Oscillometric NIBP
A closer look at the cuff pressure and the oscillations
GE Dinamap®
Oscillometric NIBP
Two hoses,
One for inflation and deflation
Other for measuring the small pressure pulsations
Cuff is inflated to up above Systolic
Cuff is deflated in small steps
Monitor waits for two pulsations of similar amplitude before stepping down
Monitor uses information from earlier readings as best it can
Monitor tries to read in the presence of abnormal pulsations
Monitor reports (publishes) BP if it is sure its results are correct
In not, “NO DETERMINATION” is displayed
Realities of NIBP Measurement
NIBP will fail in many ways
Anything that causes artefact or blocks real
pulsations
Surgeon leaning on cuff
Thyroid surgery
Carotid Surgery
Patient movement
Purposeful
movement
Tremor
Reaction to surgery
Oscillometric NIBP
Systole = 135
Mean = 100
Diastole = 83
Raw Cuff Pressure Signal
Pulse-Wave Oscillations in Cuff Pressure
What causes these pressure pulsations?
What effects stiffness of the artery?
Volume change in the artery in the arm
Arteriosclerosis
What affects volume change in the artery
in the arm?
Pulse Pressure
Stiffness of the artery
Drugs that stiffen the arterial wall
Realities of NIBP Measurement
Pressure too low to create pulsations
Arterial wall too stiff to create volume changes
Arterial wall is too stiff to create arm volume
pulses and NIBP cuff pressure pulses
Myomal injection of Arginine Vasopressin reduces pulse oximeter wave size
measured on the ear (62%) but not on the finger 1
Myomal injection of Arginine Vasopressin reduces pulse oximeter wave size
measured on the ear and simultaneously reduces pulse wave amplitude
measured in a NIBP Cuff on the arm dramatically 2
Myomal injection of Arginine Vasopressin has led to Cardiac Arrest 3,4
Myomal injection of Arginine Vasopressin has preceded NIBP drop-out in 10
patients at BWH in 16 months
1.
2.
3.
4.
Jablonka DH, Awad AA, Stoout RG, Silverman DG, Shelly KH. Comparing the effect of arginine
vasopressin on ear and finger photoplethysmography. Journal of Clinical Anesthesia (2008) 20, 90–93
Philip JH. Friedman B. Data collected at BWH; manuscript in preparation
Hobo R, Netsu S, Koyasu Y, Tsutsumi O. Bradycardia and cardiac arrest caused by intramyometrial
injection of vasopressin during a laparoscopically assisted myomectomy. Obstet Gynecol
2009;113:484–6.
Fishman, G. Vasopressin: If some Is Good, Is More Better? Obstet Gynecol 2009;113:476–478.
Why we see
NIBP Dropout on Solar but present on Eagle
Eagle is very old GE-Marquette Technology
It was created by Marquette before Marquette was purchased by GE and
before Dinamap was purchased by GE
Eagle sometimes made false readings of blood pressure
Entire case performed with BP Cuff under patient’s pillow.
BPs were displayed and recorded every 1 - 5 minutes
Clinician adjusted the NIBP cuff was found under the patient’s pillow
BWH and other institutions complained to GE
GE revised NIBP algorithms to remove artifact readings
Monitor must be sure of a reading before reporting it
Now Dinamap is unable to measure NIBP after vasopressin injection
Observations of
NIBP Dropout after Vasopressin Injection
We have a series of
8 patients who experienced NIBP dropout with Solar-TRAM-Brick
1 patient with A-Line showing no BP change while NIBP fell significantly on
Solar-TRAM-Brick but not on Eagle
1 patient with lowered ETCO2, and lowered I-Eo2 transiently
BWH Reports of
NIBP Dropout after Vasopressin Injection
We observed 8
We reported 3 to GE including the present case.
GE opened an iTrack on each
iTrack is an FDA auditable complaint kept on file by GE
FDA inspects iTracks periodically to see that GE is resolving complaints
We reported the present case as an injury to MedSun
MedSun is the FDA report submission network
FDA proactively checks that GE is resolving MedSun Injury complaints
We believe GE is working on a solution already
GE Progress
Bruce Friedman, PhD
Principal Engineer
Dinamap section of GE
Audio on line with us
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DINAMAP Peak Matching acceptance criterion
Two equal and sequential pulses
are required for acceptance
DINAMAP Motion Artifact rejection
Step Deflation and Peak Matching
help reject Artifacts
SuperSTAT™ NIBP algorithm
Systolic ratio ~ 0.5
MAP Æ Maximum oscillation amplitude
Diastolic ratio ~ 0.625
Cuff Pressure
(mmHg)
New criteria are under consideration
Reduce false positive detection
Reduce false negative detection
Improve pulse artifact rejection
Improve pulse data retention and analysis
BWH Anesthesia Dept Policy 2009
If Vasopressin may be used, especially if Robot will be used
GE Eagle Monitor in the room and connected or connectable
Switch to Eagle if Solar-TRAM-Brick cannot measure NIBP
Observe patient condition in as many ways as possible
Capnogram
Pulse plethysmogram, possibly downstream from cuff
A-Line if situation warrants
Recognize that patient usually has normal or high blood pressure
Enter Equipment Malfunction and description in EARS report
BWH GE Monitor names and pictures
Standard Solar 8000 monitor
with new, insensitive NIBP
Solar 8000 Monitor, mounted on ADS
TRAM
Brick
data
collection
module
Brick or PDM
PDM
Patient
Data
Module
(soon)
Portable Eagle Monitor with
old, sensitive NIBP measurement
Portable Eagle Monitor
Portable Eagle Monitor Screen
Portable Eagle Monitor with
old, sensitive NIBP measurement
Portable Eagle Monitor
Portable Eagle Monitor Screen
Portable Eagle Monitors have RFID Tags so
they can be found electronically, quickly.