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.

Wednesday, May 3, 2023

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/minute.


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.



Pathological – its mainly due to low peripheral resistance

Increase Fever Anemia. Hyperthyroidism. Beriberi Arteriovenous fistula



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


Thank you.


cardiac output 1

Health & Medicine