Cardiac output 1

DR NILESH KATE
MBBS,MD
ASSOCIATE PROF
DEPT. OF PHYSIOLOGY
CARDIAC
OUTPUT - I

OBJECTIVES
 Definition.
 Measurement of cardiac
output.
 Variations in cardiac output.
 Regulation of cardiac output.
 Heart lung preparation.
 Cardiac & vascular function
curves.
Thursday, February 4, 2016

Some Facts………
 Is about 4.8 inches tall and 3.35 inches wide
 Weighs about .68 lb. in men and .56 lb. in women
 Beats about 100,000 times per day
 Beats 2.5 billion time in an average 70 yr. lifetime
 Pumps about 2000 gallons of blood each day
 Circulates blood completely 1000 times each day
 Pumps blood through 62,000 miles of vessels
 Suffers 7.2 mil. CAD deaths worldwide each year

DEFINITION.
 Amount of blood
ejected by each
ventricle per minute.
 CO = SV * HR…..
 SV – Stroke Volume.
 HR – Heart rate.
 Cardiac output
 80 * 70 = 5.6 L/min.

SIGNIFICANCE
 It’s the cardiac output
that decides the rate of
blood flow to the
different parts of the
body.
 Decrease in cardiac
output
 Decrease in blood flow

RELATIONSHIP OF CARDIAC
OUTPUT & VENOUS RETURN
 VENOUS RETURN
 It is the quantity of
blood returned from all
over the body through
the veins into the right
atrium each minute
 Venous return = cardiac
output

Components…….
 Stroke volume
 Amount of blood
pumped by each
ventricle per beat or per
contraction.
 80 ml.
 Stroke volume
depends on –
 End diastolic volume
 contractility

Components…….
 Heart rate
 Under normal
circumstances 70
times/min.
 Increase in heart rate
increases Cardiac
output… but upto limit
 After it decreases due
to decrease in Cardiac
filling.

MINUTE VOLUME
It is the amount of
blood pumped out
by each ventricle per
minute.
MINUTE VOLUME =
Stroke volume x HR
Normal value:
5litres/ventricle/minut
e.

CARDIAC INDEX.
 Cardiac output
is the amount of blood
pumped out per ventricle
per minute per square
meter of body surface area.
 Expressed in relation to the
body surface area.
 Normal value –
3.2L/min/m2

CARDIAC RESERVE.
 Maximum increase in
the cardiac output
above the normal value.
 Expressed in
Percentage.
 Normal values.
 Adults – 300-400%
 Old age – 200-250%
 Athletes – 500-600%
 Variations
 Maximum – Heavy
exercise.
 Minimum – Cardiac
diseases.

MEASUREMENT OF CARDIAC
OUTPUT.
 Methods based on Fick’s
principle
 Indicator or dye dilution
method.
 Thermodilution
 Inhalation of inert gases.
 Physical methods
 Doppler echocardiography.
 Ballistocardiography.
 Cineradiographic technique.

METHODS BASED ON FICK’S
PRINCIPLE
 Fick’s principle –
Amount of substance
taken up by an organ
per unit of time (Q) is
equal to the arterial
level of the substance
(A) – venous level of
substance (V) × Blood
flow(F)
 Q = (A-V) F
 F = Q
-------
(A-V)
 2 methods
 Direct
 Indirect

METHODS BASED ON FICK’S
PRINCIPLE

DIRECT METHOD.
 Principle – pulmonary
blood flow = Rt
ventricular blood flow = Lt
ventricular blood flow.
 Pulmonary blood flow =
amount of O2 taken by
lungs
-------------------------------
PVO2-PAO2
 Amount of O2 taken
determined by
spirometer.
 PVO2 – from any
peripheral artery
 PAO2 – from
pulmonary artery.

DIRECT METHOD.
 Pulmonary blood flow =
amount of O2 taken by
lungs
-------------------------------
PVO2-PAO2
 CO = 2000/ (200-160) ×
100
 CO = 5000ml/min
 Disadvantages.
 Invasive, risk of
infection &
hemorrhage.
 Pt is conscious so CO is
more than normal
 Complications –
ventricular
fibrillations.

DIRECT METHOD.

INDIRECT METHOD.
 Same as direct
method only
 CO2 excretion by lungs
is measured by
spirometry.
 PACO2 from alveolar
air.
 PVCO2 – Rebreathing
into closed bag.
 CO = CO2 output/min
----------------------
PACO2-PVCO2

INDICATOR OR DYE DILUTION
METHOD.
 Principle – Known
amount of dye injected
into Rt atrium & mean
concentration of its
first passage through
an artery is
determined.
 Blood flow (F)= Q/Ct
 F = blood flow in
L/min.
 Q= quantity of dye
injected.
 C = Mean Conc. of dye.
 T = Time duration in
sec of first passage of
dye.

IDEAL INDICATOR.
 Should be nontoxic.
 Mix evenly.
 Easy to measure.
 Not alter cardiac output
or haemodynamic.
 Not be changed by
body.
 E.g. Evan’s blue,
radioactive isotopes.

PROCEDURE.
 5 mg of Evan’s blue dye
mixed with venous blood.
 Duration of first passage
of dye(t) & mean conc of
dye (C) in arterial blood
estimated.
 CO= Q/ct × 60 = 5/1.5L
×40 × 60 = 5 L/min

THERMODILUTION
 PRINCIPLE – same as
indicator dye dilution
method except cold
saline is used.
 Resultant change in
blood temperature in
pulmonary artery is
determined.

INHALATION OF INERT GASES.
 NO, Acetylene – used.
 Pulmonary blood flow
is determined from
following values
 Quantity of gas
absorbed in given time.
 Partial pressure of gas
in alveolar air.
 The solubility of gas.

PHYSICAL METHODS
 Doppler
echocardiography –
 Ultrasonic evaluations
of cardiac functions.
 B-scan ultrasound at a
frequency of 2.25 MHz
using a transducer.
 Measure EDV, ESV,CO
& Valvular defects.

PHYSICAL METHODS
 Ballistocardiography
 Graphical record of the
pulsations created due
to ballistic recoil of the
pumping heart.

PHYSICAL METHODS
 CINERADIOGRAPHIC
TECHNIQUE.
 The making of a motion
picture record of successive
images appearing on a
fluoroscopic screen.
 Radiography of an organ in
motion, for example, the
heart, the gastrointestinal
tract.

VARIATIONS IN CARDIAC
OUTPUT.
 Physiological causes.
 Age – CI children >
adult.
 Sex – females > Males
 Diurnal variations-
low in early morning.
 Environmental
temperature – direct
relation.
 Anxiety excitement,
Eating, Exercise,
Pregnancy, High
altitude – direct
relation.
 Posture change –
sitting or standing >
lying down due to
venous pooling.

OUTPUT.
 Pathological – its
mainly due to low
peripheral resistance
 Increase
 Fever
 Anemia.
 Hyperthyroidism.
 Beriberi
 Arteriovenous fistula

OUTPUT.
 Decrease
 CCF
 Rapid arrhythmias
 Cardiac shock
 Incomplete heart block
 Hemorrhage
 Hypothyroidism.

Thank you.

Cardiac output 1

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