Download Mechanical Ventilation

S3a Cardiac A&P
Mechanical Ventilation
Cardiac
Anatomy & Physiology
Section 3a Cardiac A & P
Significance of Monitoring
n Must
have adequate perfusion to meet
metabolic demands of the body
n Circulation
does not guarantee
perfusion
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Section 3a Cardiac A & P
Cardiovascular Monitoring
n Non-invasive
indicators of peripheral
perfusion
n
n
n
n
n
n
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S3a Cardiac A&P
Section 3a Cardiac A & P
Cardiovascular Monitoring
n Invasive
indicators of peripheral
perfusion
n
n
n
n
n
n
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Section 3a Cardiac A & P
Goal of Cardiovascular Monitoring
Optimize cardiac output and
arterial blood pressure to
maintain adequate tissue
perfusion
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Section 3a Cardiac A & P
Cardiovascular A & P - Circuit
n Elastic,fluid-filled
n Heart - pump
n Arteries - distribute
& regulate amount of
oxygenated blood to organs & tissues
n Capillaries - exchange gases, nutrients,
metabolites
n Veins - return system to heart & lungs;
reservoir for blood volume
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S3a Cardiac A&P
Section 3a Cardiac A & P
Cardiovascular A & P - Heart
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Section 3a Cardiac A & P
Cardiovascular A & P - Blood Flow
n Factors
responsible for the forward
movement of blood =
n2
circulatory systems
n
n
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Section 3a Cardiac A & P
Pulmonary Circulation
n
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S3a Cardiac A&P
Section 3a Cardiac A & P
Systemic Circulation
n
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Section 3a Cardiac A & P
Cardiovascular A & P - Cardiac Cycle
•
Atria - entrance chambers for
ventricles; also contract to augment
ventricular filling
•
Ventricles - supply the power that
creates pressure gradients
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Section 3a Cardiac A & P
Cardiovascular A & P - Cardiac Cycle
n Diastole
-
n
n
n Systole
-
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S3a Cardiac A&P
Section 3a Cardiac A & P
Cardiac Output
n=
amount of blood ejected by
ventricles in 1 minute
n Normal =
n Varies with age, sex, size, tissue O 2
demand, blood viscosity
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Section 3a Cardiac A & P
Cardiac Output
˙ T = HR x SV
Q
n
Normal HR:
n
Normal stroke volume:
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Section 3a Cardiac A & P
Cardiac Index
n To
compare people of different age, size,
etc.
CI = QT ÷ BSA
n
Normal CI:
†
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S3a Cardiac A&P
Section 3a Cardiac A & P
Factors Affecting Cardiac Output
n
n
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Section 3a Cardiac A & P
Heart Rate
n Bradycardia
•
•
n Tachycardia
•
•
•
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Section 3a Cardiac A & P
Stroke Volume
n Determined
by
n
n
n
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S3a Cardiac A&P
Section 3a Cardiac A & P
Preload
n Filling
volume of ventricle which
stretches the relaxed ventricular wall
before contraction (end-diastole)
n Demonstrated
by
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Section 3a Cardiac A & P
Preload
n Starling’s
Law states -
n The
greater the ventricular enddiastolic filling volume (i.e. the greater
the stretch on the myocardial muscle
fibers, (the greater the force of the
contraction and stroke volume)
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Section 3a Cardiac A & P
Preload - Ventricular Function Curves
Increased
Contractility
Stroke Volume
Normal
Decreased
Contractility
End-Diastolic Volume
(Preload)
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S3a Cardiac A&P
Section 3a Cardiac A & P
Preload - Ventricular Function Curves
n
Disease can alter the shape of the normal
function curves:
Normal
Compliance
End-Diastolic
Pressure
Decreased
Compliance
End-Diastolic Volume
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Section 3a Cardiac A & P
Preload
n Influenced
by 3 factors:
n
n
n
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Section 3a Cardiac A & P
Preload - Blood Volume
Blood volume Ø
Ø
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S3a Cardiac A&P
Section 3a Cardiac A & P
Preload - Distribution of Blood Volume
n Body position
• Blood to dependant areas
n Intrathoracic pressure
• If ↑ Æ
• Pneumothorax, Valsalva, coughing spells,
CMV
n Venous tone
•
•
•
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Section 3a Cardiac A & P
Preload - Atrial “Kick”
n Lost
if
n
n
n
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Section 3a Cardiac A & P
Afterload
n Refers
to the resistance or impedence to
right or left ventricular ejection of blood
n Imposed by resistance to blood flow
through pulmonary &/or systemic
circulation (i.e. ventricles have to work
harder to move blood)
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S3a Cardiac A&P
Section 3a Cardiac A & P
Afterload (Left Ventricle)
↑ SVR Æ ↑ afterload
Ø
↑ myocardial work
Ø
ØSV (if heart ¨ ↑ myocardial O2
diseased)
requirement
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Section 3a Cardiac A & P
Afterload (Left Ventricle)
SVR =
mean art BP - RVEDP
QT
Normal = ≤ 20 mmHg/L/min
†
Dynes•sec/cm-5 = mmHg/L/min X 80
(900-1600)
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Section 3a Cardiac A & P
Causes of Increased SVR
n Vasoconstriction
n
n
n
n
n
n
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S3a Cardiac A&P
Section 3a Cardiac A & P
Causes of Increased SVR
n Congested
venous system
n
n
n Increased
blood viscosity
n
n Hypervolemia
n Aortic stenosis
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Section 3a Cardiac A & P
Treatment for Increased SVR
n Vasodilators
n
n
n
n Surgery
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Section 3a Cardiac A & P
Afterload (Right Ventricle)
PVR =
†
mean PAP - PCWP
QT
Normal = ≤ 2.5 mmHg/L/min
Dynes•sec/cm-5 = mmHg/L/min X 80
(≤ 160)
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S3a Cardiac A&P
Section 3a Cardiac A & P
Causes of Increased PVR
n Pulmonary
vasoconstriction
n
n Histamine
release
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Section 3a Cardiac A & P
Causes of Increased PVR
n Loss,
dysfunction or destruction of
pulmonary vasculature
n
n
n
n
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Section 3a Cardiac A & P
Causes of Increased PVR
n Increased
pulmonary blood flow
n
n
n
n
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S3a Cardiac A&P
Section 3a Cardiac A & P
Causes of Increased PVR
n Increased
pulmonary venous
pressure
n
n
n
n Increased
blood viscosity
n
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Section 3a Cardiac A & P
Contractility
- strength and speed
of the ventricular contraction
n Contractility
Ø contractility Æ
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Section 3a Cardiac A & P
Contractility
Normal
STROKE
VOLUME
Moderate dysfunction
Severe dysfunction
OUTFLOW RESISTANCE
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S3a Cardiac A&P
Section 3a Cardiac A & P
Causes of Decreased Contractility
n Loss
of contracting muscle mass
n
n Loss
of muscle size
n
n
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Section 3a Cardiac A & P
Causes of Decreased Contractility
n Depressants
n Procaine,
Lidocaine, quinidine,
Pronestyl (procainamide)
n Barbiturates
n Beta-blockers (Inderol)
n Acidosis, hypoxia, hypercarbia
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Section 3a Cardiac A & P
Treatment for Decreased Contractility
n Positive
inotropic agents:
(Digoxin, Lanoxin)
n epinephrine
n Dopamine
n Dobutamine
n Isuprel
n caffeine (Cafergot)
n calcium
n digitalis,
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