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Blood Pressure
force of blood distending arterial walls
Expressed as systolic/dystolic mmHg
Systolic BP (SBP)
Highest pressure in arteries during left ventricular contraction
Diastolic BP
Lowest pressure in the arteries during left ventricular relaxation
SBP <90mmHg
Hypotension
Considered acceptable (<90mmHg SBP) if:
Dizziness
Syncope
Coldness
Pallor
Nausea
Low urine output
High arterial [blood lactate]
Mean Arterial Pressure MAP
average P in arteries during 1 cardiac cycle
driving force of blood → vascular system
Pulse pressure (PP) needed to calculate MAP: what is the formula?
PP = SBP - DBP
MAP is not an average of systolic/diastolic values. Why?
At rest → more time spent in diastole during a cardiac cycle > systole
During exercise → more time spent in systole during a cardiac cycle than diastole
Calculate MAP at rest
(SBP-DBP)/3 + DBP
Calculate Map during exercise
MAP = (SBP-DBP)/2 + DBP
Normal MAP (at rest values are around…)
70-100mmHg
<70-100mmHg (MAP Values at rest means what)
Low perfusion
>70-100mmHg (MAP Values at rest means what)
High resistance
MAP can reach up to… during exercise
155mmHg+
Total Peripheral Resistance (TPR) consists of
Vessel Diameter
Blood Viscosity
Total Vessel Length
CO is _________ to SBP
directly proportional
TPR is ________ to _____
directly proportional to BP
Arterial BV is _______ to SBP
directly proportional
Arterial compliance/vessel elasticity
Indirectly proportional to BP
Cardiac Output
Volume of blood ejected from LV/min
Frank-Starling Law of Heart
Venous return to heart → increase EDV
Stretch of ___________ of ventricle
_____ force
______ vol
_______ CO
myocardial fibers
contraction,
contraction
Stroke
increase (all)
TPR - Total Peripheral Resistance
Force produced between blood & walls of blood vessel
TPR is __________ to diameter
indirectly proportional
Vasomotor Tone
aMount of vasoconstriction of arteriole vessel (SNS)
Vasoconstriction will → to ______ vessel diameter
decrease
Viscosity
Physical property related → ease which fluid molecules flow past one another
TPR is ________ to viscosity
directly ppt
What factors decrease viscosity/hct
Anemia, Hemorrhage
Increased BT
Factors that increase viscosity/hct
Excess RBC
Cold temp
TPR is ____ to vessel length
directly ppt
Obesity decreases vessel length
F
body fat (increase) → increases no. of BV →
increases vessel length → TPR increase
Arterial BV to SBP
Arterial BV ppt to SBP
Excess na+ →
Increase BV
Dehydration, blood loss →
Blood Vol Decrease
Arterial Compliance/Vessel Elasticity
BP is indirectly ppt to material compliance (elasticity of artery walls)
Increase Arterial Compliance →
Decrease BP
HR * SV = Q
How to calculate CO
BV, HR, SV, Blood Viscosity, Peripheral Resistance increase →
BP increase
Baroreceptors (carotid a. & aortic arch) monitor
BP
Short term reg. is controlled by the sympathetic and parasympathetic nervous system by changes in:
HR, Contractility, Arterial Diameter
Environmental Factors Affecting BP
Exercise → steady-state/resistance
Body position → orthostatic hypotension, inversion
SBP increases with…
intensity increase, but no change in DBP (little)
TPR increases with resistance and upper-body exercise
T
TPR increaess/decreases with steady state aerobics
decreases
Q increases with graded exercise
T
Supine (vs seated upright) ↑ BP
Decreases gravity resistance > ↑ Venous Return ↑ EDV, ↑ SV > ↑ Q and ↑ BP
→ ↑ in SBP (6-7 mmHg) but (1mmhg DBP)
Standing (vs seated upright) ↓ BP
↑ Gravity Resistance > ↓ Venous Return > ↓ EDV ↓ SV ↓ Q ↓ BP
Orthostatic intolerance
↓ in BP with change in posture