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CVP & PCWP MONITORINGPhysiology of
SANEESH P JSultan Qaboos University Hospital, Muscat
AGENDACardiac cycleCVPPAP
Cardiac Cycle
Cardiac CycleThe series of electrical and mechanical events
that constitute a single heart beat
Cardiac Cycle
Cardiac Cycle• 1 - Atrial Contraction• 2 - Isovolumetric
Contraction• 3 - Rapid Ejection• 4 - Reduced Ejection• 5 - Isovolumetric Relaxation• 6 - Rapid Filling• 7 - Reduced Filling
Central Venous Pressure
Central Venous PressureVenous pressure is a term that represents the
average blood pressure within the venous compartment.
The term "central venous pressure" (CVP) describes the pressure in the thoracic vena cava near the right atrium therefore CVP and right atrial pressure are
essentially the same
Central Venous PressureCVP is a major determinant of the filling
pressure and therefore the preload of the right ventricle, which regulates stroke volume
Central Venous Pressure
Central Venous PressureFactors increasing CVP
Raised intrathoracic pressure• Eg, IPPV, coughing, expiration in spont
ventilationCirculatory overload; Venoconstriction
Impaired cardiac function• Eg, outlet obstruction, cardiac failure,
cardiac tamponadeSuperior vena cava obstruction
Central Venous PressureFactors decreasing CVP
Reduced intrathoracic pressure• Eg, inpiration in spont ventilation
Hypovolemia
Venodilatation• Eg, septic shock
CVP monitoringIn CVP monitoring, a catheter is inserted
through a vein and advanced until its tip lies in or near the right atrium
Because no major valves lie at the junction of the vena cava and right atrium, pressure at end diastole reflects back to the catheter
CVP monitoringWhen connected to a manometer, the catheter
measures central venous pressure (CVP), an index of right ventricular function
CVP monitoring helps to assess cardiac function, to evaluate venous return to the heart, and to indirectly gauge how well the heart is pumping
The phlebostatic axis is the reference point for zeroing the hemodynamic monitoring device. This reference point is important because it helps to ensure the accuracy of the various pressure readings.
4th intercostal space, mid-axillary line
Level of the atria
Central venous catheterisation
Central venous catheterisation
CVP monitoring
CVP monitoring
CVP waves
Waveform Phase of cardiac cycle
Mechanism
a wave End diastole Atrial contractionc wave Early systole Isometric ventricular
contraction; Tricuspid motion towards RA
x descent Mid systole Atrial relaxation; descent of base
v wave Late systole Systolic filling of atriumy descent Early diastole Early ventricular fillingh wave Mid- to late
diastole Diastolic plateau
CVP waves
CVP waves
CVP abnormalitiesCondition CharacteristicsAtrial fibrillation Loss of a wave
Prominent c waveAV dissociation Cannon a waveTricuspid regurgitation Tall systolic c-v wave
Loss of x descentTricuspid stenosis Tall a wave
Attenuation of y descentPericardial constriction Tall a and v waves; Steep x and y
descents M or W configuration Cardiac tamponade Dominant x descent
Attenuated y descentRespiratory variations Measure pressure at end-expiration
CVP – Atrial fibrillation
absence of the a wave
prominent c wave
preserved v wave and y descent
CVP – AV dissociation
Early systolic Cannon a wave
Retrograde conduction of the nodal impulse throughout the atrium causes atrial contraction to occur during ventricular systole while the tricuspid valve is closed
CVP – Tricuspid regurgitation
Tall systolic c-v wave
Loss of x descent
In this example, the a wave is not seen because of atrial fibrillation
CVP – Tricuspid stenosis
End-diastolic a wave is prominent
Diastolic y descent is attenuated
Tricuspid stenosis increases mean CVP
CVP & Intrathoracic pressure
CVP measurement is influenced by changes in intrathoracic pressure.
It fluctuates with respiration.Decreases in spontaneous
inspiration.Increases in positive pressure
ventilation.
CVP & Intrathoracic pressure
CVP should be taken at the end expiration.PEEP applied to the airway at the end of
exhalation, may be partially transmitted to the intrathoracic structures ► measured CVP will be higher.
CVP as hemodynamic monitor
CVP & PEEP
Pulmonary Artery Pressure
PA catheterisationThe pulmonary artery (PA) catheter (or Swan-
Ganz catheter) was introduced into routine practice in operating rooms and intensive care units in the 1970s
The catheter provides measurements of both CO and PA occlusion pressures and was used to guide hemodynamic therapy, especially when patients became unstable
PA catheterisationThe pulmonary artery (PA) catheter (or Swan-
Ganz catheter) was introduced into routine practice in operating rooms and intensive care units in the 1970s
The catheter provides measurements of both CO and PA occlusion pressures and was used to guide hemodynamic therapy, especially when patients became unstable
Perioperative intensive care; Cardiac anesthesia
Reduced SVR
Stroke Volume
PAWP / LVEDP
Inotropes Volume admin
Vasopressors
PA catheterPA catheter can be used
to guide goal-directed hemodynamic therapy to ensure organ perfusion in shock states
7 - 9 FR catheter
4 lumens
110-cm long
Polyvinylchloride body
Pressure guidance is used to ascertain the localization of the PA catheter in the venous circulation and the heart
Upon entry into the right atrium, the central venous pressure tracing is noted
Passing through the tricuspid valve right ventricular pressures are detected
Higher systolic pressure than seen in the right atrium, although the end-diastolic pressures are equal
At 35 to 50 cm depending upon patient size, the catheter will pass from the right ventricle through the pulmonic valve into the pulmonary artery
A diastolic step-up compared with ventricular pressure
When indicated the balloon- tipped catheter will wedge or occlude a pulmonary artery branch.
Similar morphology to right atrial pressure, although the a-c and v waves appear later in the cardiac cycle relative to ECG
PA pressure equilibrates with that of the left atrium which, barring any mitral valve pathology, should be a reflection of left ventricular end-diastolic pressure
From a right internal jugular vein puncture site, the right atrium should be reached when the PAC is inserted 20 to 25 cm, the right ventricle at 30 to 35 cm, the pulmonary artery at 40 to 45 cm, and the wedge position at 45 to 55 cm.
0
30
0
120
PAWP a-c and v waves appear to occur later in the cardiac cycle compared with CVP trace
PA catheter: UsesThere is no consensus on standards for PA
catheter use PA catheters should only be used when a
specific clinical question regarding a patient’s hemodynamic status can not be satisfactorily investigated by clinical or noninvasive assessments
…. when the clinician is in need of knowing an in-depth and continuous assessment of hemodynamics in order to properly guide changes in the management of a patient
PA catheter: Measurements
Parameter
Normal range Relevance
CVP 0-6mmHg Volume status & RV function; correlates with RVEDP
RVP 20-30 / 0-6mmHg RV function and volume
PAP 20-30 / 6-10 mmHg
State of PVR and RV function
PAWP 4-12mmHg LV function; correlates with LVEDP
Stroke vol.
60-80ml
SV index 33-47ml/beat/m2 SV adjusted to body surface area (BSA)
PA catheter: Measurements
Parameter Normal range
Cardiac Output 4 – 8 L/min
Cardiac Index 2.5 – 4 L/min/m2
Pulmonary Vascular Resistance
20-120 dynes/sec/cm5
Systemic Vascular Resistance
750-1500 dynes/sec/cm5
RV stroke work
LV stroke work
SvO2 (Mixed Venous O2 saturation)
60 -75%
PA catheter: Contraindications
• Known pulmonary hypertension
• Unstable arrhythmias
• Anticoagulation therapy
• Bleeding disorder
• Prior pneumonectomy
• Pacemakers
• Prosthetic heart valves
PA c
athe
ter:
Com
plica
tions
Concluding……
CVP
PAWP
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