Transcript cardiovascular haemodynamics 2

Cardiovascular Assessment
Cardiac Output
• Blood Pressure
– Systolic / Diastolic
• Pulse
 Perfusion

Blood Pressure
Systolic - Normal 95 - 140 mmHg
 Diastolic - Normal 60 - 90 mmHg
 Children vary with age
 Neonate 60 - 90 over 30 - 60
mmHg

Systolic

Maximum pressure exerted on
arterial wall during ventricular
contraction
Diastolic

Pressure in vasculature during
ventricular relaxation
Indirect Blood Pressure
Measurement via Cuff
Wrap blood pressure cuff around
upper arm
 Auscultate over artery in antecubital
fossa
 Inflate cuff rapidly
 Deflate cuff slowly while listening

Mechanism
Cuff inflated - occludes artery - no
sound
 Slowly deflate cuff - first sound =
systolic
 Continue to deflate cuff until
sound disappears = diastolic
 Tapping sounds heard with each
heart beat called Korotkoff’s
sounds (Ko rot kof)

Technique
Usually use non-dominant arm
 Inflate to approx 160 mmHg
 Drop pressure approximately 3
mmHg/sec
 Standard adult cuff 5 inches wide
 Pediatric 3 inches wide

Sources of Error Resulting in
High BP Measurements




Cuff too narrow
• Width of cuff approx 40% circumference
of arm
Applied too tight or too loose
Excessive cuff pressure
• should start 30 mmHg above systolic
Pressing stethoscope too tightly over
artery will affect diastolic pressure
Hypertension
BP persistently > 140-160 / 90
 Secondary means cause is known
• May be a side-effect of medication


Primary Hypertension means cause
is unknown
Hypotension
BP < 95 / 60
 Late sign of hypovolemia, cardiac
failure, shock


90 / 60 not uncommon in young
females
Low blood pressure results in
inadequate perfusion

Brain
Heart - (70% coronary artery
perfusion occurs during diastole)
(Diastolic pressure < 50 mmHg
compromises perfusion of heart)
 Kidneys

Low blood pressure a late sign
of circulatory problems
Normal compensatory mechanisms
maintain blood pressure initially
 When these fail - pressure falls

Use blood pressure to
calculate Mean Arterial
Pressure
S-D+D
3
 MAP is average pressure for circulation
 Indicator of adequate tissue perfusion
 Normally 70 - 105; 90 average

Mean arterial pressure (MAP)
MAP < 60 mmHg inadequate
 Resistance = Pressure gradient /
Flow
 or re-arranged: MAP = C.0. x SVR

Two factors determine blood
pressure
Cardiac output = stroke volume x
heart rate
 Systemic vascular resistance (SVR)

Stroke Volume (SV) determined
by
Preload
 Contractility
 Afterload

Increased Preload Increases
SV
Preload = filling volume of ventricles
 Increased blood volume stretches
muscle fibers
 Increases strength of contraction
 Requires longer time for ventricular
filling

Increased Contractility
Increases SV
Contractility = force of muscle
contraction
 No change in muscle fiber length
 Increase force of contraction over
same time period
 Inotropic drugs

Decreased Afterload Increases
SV
Afterload = resistance ventricles
contract against
 Primarily systemic vascular
resistance
 Systemic vasodilation reduces
afterload

Factors afftecting Systemic
Vascular Resistance
Radius of arterioles
 Blood volume
 Blood viscosity (Hematocrit)

Factors affecting Cardiac Output
primarily affect systolic blood
pressure



Ex. Exercise using large muscle mass
(legs) will require increase in cardiac
output to supply more oxygen to
working muscles
Will see an increase in systolic
Diastolic will stay the same or
decrease since arteries of large
muscle mass dilated
Factors affecting Systemic
Vascular Resistance will primarily
affect diastolic pressure
Ex. Exercise using small muscle
mass (arms)
 Vasoconstriction of large muscle
mass not being used
 Vasoconstriction increases
vascular resistance
 Diastolic will increase

Maximal Heart Rate correlates
with Maximal O2 Consumption

HR max = 220 - age
75% HR max ------ 60 % VO2 max
 80
------- 70
 90
------- 82


Aerobic exercise 75 - 80% HR max
Heart Rate or Pulse - Evaluate
for
Rate
 Rhythm
 Strength

Normal Heart Rate
60 - 100 Adults
 90 - 120 Children
 70 - 170 Newborns
 < normal = bradycardia
 > normal = tachycardia

Tachycardia
One of the cardinal signs of
hypoxemia
 Increasing heart rate increases
cardiac output
 Increase oxygen delivery to
tissues

Increasing HR increases C.O.
Until HR > 150
 C.O. decreases due to inadequate
filling time

Rhythm
Regular or irregular
 Irregular beat may
indicate arrhythmias

Strength
Bounding?
• Arteriosclerosis
 Weak and thready?
• shock

Pulsus Paradoxus
Strength decreases with
spontaneous inhalation
 Increases with exhalation
 normal unless extreme
 Common in COPD
 Seen in 50% patients with
pericarditis

Pulsus Alterans
Alternating strong and weak
pulses
 May be sign of left ventricular
failure
 Not related to respiratory disease

Pulse Pressure
Systolic - Diastolic
 Normal 35 - 40 mmHg
 < 30 mmHg pulse hard to detect
 Decreasing pulse pressure early
sign of inadequate circulating
blood volume

Can estimate systolic blood
pressure if can palpate
Carotid pulse - then systolic is at
least 60 mmHg
 Femoral
70 mmHg
 Radial
80 mmHg

Pulse sites
Radial
 Brachial
 Carotid
 Femoral
 Dorsalis pedis

Check radial pulse before and
after administering therapy
Aerosol medication may produce
side-effects
 First cardinal sign of hypoxemia is
tachycardia
 After taking pulse, continue
palpating pulse as count respiratory
rate

Assessment of Perfusion
(microcirculation)
Peripheral skin temperature
• cold extremities indicate reduced
perfusion
 Urine Output
• one of the best indicators of C.O.
and arterial pressure
• < 20 ml/ hr oliguria ( o lig uria)


Sensorium
• Brain sensitive to lack of oxygen
and/or lack of glucose
• Both depend on blood supply to
the brain - perfusion
• Confusion may signal inadequate
perfusion or hypoxemia
Determine patient’s level of
consciousness (LOC)
Oriented to person - know who they
are
 Oriented to place - know where they
are
 Oriented to time - know what today
is, what year
 Will typically see “Alert and oriented
to PPT” in chart

Summary
 Patient assessment includes
evaluating patient’s
cardiovascular system
• Cardiac Output
• BP/Pulse
• Perfusion
 Many of the therapeutic
interventions of respiratory care
will affect the cv system