CVP Pulmonary artery wedge pressure monitoring: Physiology

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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