Non-invasive methods of blood pressure measurement
Arterial blood pressure curve
SBP
Systolic blood
pressure area
above
MAP
area under MAP
DBP
Diastolic blood
pressure
MAP
Mean arterial pressure
inter-beat interval
Mean arterial pressure (MAP) : mean value of blood pressure in the inter-beat interval (IBI)
• area under MAP = area above MAP
• aproximation: MAP DBP + 1/3 PP (PP = SBP – DBP)
PP
pulse
pressure
Blood pressure (BP): pressure on vascular vall (continual variable)
Definition:
SBP - maximum of BP in
the inter-beat interval
DBP – minimum of BP in
the inter-beat interval
Attention: Values of SBP
and DBP varies in different
parts of cardiovascular
system
MAP is a function of cardiac output and total peripheral resistance
• SBP is given mainly by CO
• DBP is given mainly by TPR
Mean arterial
pressure (MAP)
Total peripheral
resistance
(TPR)
Heart rate
(HR)
Stroke volume
(SV)
=
*
*
Cardiac output
(CO)
Methods of the arterial blood pressure measurement
24-hour blood pressure monitoring
Photoplethysmografic (volume-clamp method, Peňáz)
Palpatory
(sphygmomanometer)
Auscultatory
(sphygmomanometer,
stethoscope)
Oscillometric
In practicals:
Another approaches:
Laminar / turbulent flow, Korotkoff sounds
𝑅𝑒 =
𝑣 ∙ 𝑆 ∙ 𝜌
𝜂
Reynolds number Re: predicts the transition from laminar to turbulent of flo
v: velocity of blood flow
S: area of vascular lumen (.r2)
: density of blod
: viskosit of blood
(higher in anemy)
S1 < S2 a v1≈ v2 → Re1 < Re2 → turbulent flow
laminar flow Re < 2000
turbulent flow Re > 3000
r1
r2
cuff
a. brachialis
laminar flow turbulent flow
Re1
Re2
v1
v2
closely behind narrowing of the artery:
Korotkoff sound
(auscultatory method)
Continually measured BP
Pressure in the cuff
Pressure oscillations in the cuff
(Oscillometric method)
SBP
DBP
SBP MAP DBP
Blood flow in the
artery
Principles of blood pressure measurement
• Patient is sitting for a few minutes before the measurement.
• Only validated apparatus must be used.
• Perform at least two measurements in the course of 1–2 minutes.
• Use cuff of standard size (12–13 cm width and 35 cm length); however smaller and
bigger cuffs must be available for patients with smaller or bigger size of arm,
respectively.
• Cuff must be always at the level of heart of examined person.
• Pressure in the cuff must be decreased slowly: 2mmHg/s.
During BP measurement following rules must be observed
methods advantages disadvantages
measured
value
auscultatory • exact estimation of SBP/DBP
• easy, it doesnt require electricity
• subjective, experience is necesary
• SBP/DBP from differen IBI
STK a DTK
oscillometric • exact estimation of MAP
• automatic, fast
• BP can be measured by layman,
cheap (home measurement)
• DBP/SBP is calculated (dependence
on model, influence on shape of puls
wave)
• SBP/DBP from different IBI
• false values during arrhytmia
MAP,
sometimes
SBP
(it depends
on device)
24 – hour BP
monitoring
• BP record from whole day
• diagnosis of white-coat
hypertension
• disruptive influence of measuring
(during sleeping)
• SBP/DBP from different IBI
BP is
mesured
each
15 – 60 min
photople-
thysmographic
(Peňáz)
• continual BP record
• possibility of beat-to beat
SBP/DBP calculation (BP
variability analysis)
• measuring on the finger, brachial BP
recalculating
• expensive device
continual BP
record