Physiology of CVP and Pulmonary artery pressure monitoring

1. CVP & PCWP MONITORING
Sultan Qaboos University Hospital, Muscat

2. AGENDA
 Cardiac cycle
 CVP
 PAP

4. Cardiac Cycle
 The series of electrical and mechanical events that
constitute a single heart beat

5. Cardiac Cycle

6. Cardiac Cycle
• 1 - Atrial Contraction
• 2 - Isovolumetric Contraction
• 3 - Rapid Ejection
• 4 - Reduced Ejection
• 5 - Isovolumetric Relaxation
• 6 - Rapid Filling
• 7 - Reduced Filling

8. Central Venous Pressure
 Venous 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

9. Central Venous Pressure
 CVP is a major determinant of the filling pressure and
therefore the preload of the right ventricle, which
regulates stroke volume

10. Central Venous Pressure

11. Central Venous Pressure
 Factors increasing CVP
Raised intrathoracic pressure
• Eg, IPPV, coughing, expiration in spont
ventilation
Circulatory overload; Venoconstriction
Impaired cardiac function
• Eg, outlet obstruction, cardiac failure, cardiac
tamponade
Superior vena cava obstruction

12. Central Venous Pressure
 Factors decreasing CVP
Reduced intrathoracic pressure
• Eg, inpiration in spont ventilation
Hypovolemia
Venodilatation
• Eg, septic shock

13. CVP monitoring
 In 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

14. CVP monitoring
 When 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

15.  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

16. Central venous
catheterisation

17. Central venous
catheterisation

18. CVP monitoring

19. CVP monitoring

20. CVP waves
Waveform Phase of cardiac
cycle
Mechanism
a wave End diastole Atrial contraction
c 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 atrium
y descent Early diastole Early ventricular filling
h wave Mid- to late diastole Diastolic plateau

21. CVP waves

22. CVP waves

23. CVP abnormalities
Condition Characteristics
Atrial fibrillation Loss of a wave
Prominent c wave
AV dissociation Cannon a wave
Tricuspid regurgitation Tall systolic c-v wave
Loss of x descent
Tricuspid stenosis Tall a wave
Attenuation of y descent
Pericardial constriction Tall a and v waves; Steep x and y descents M
or W configuration
Cardiac tamponade Dominant x descent
Attenuated y descent
Respiratory variations Measure pressure at end-expiration

24. CVP – Atrial fibrillation
absence of the a wave
prominent c wave
preserved v wave and y
descent

25. 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

26. 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

27. CVP – Tricuspid stenosis
End-diastolic a wave is
prominent
Diastolic y descent is
attenuated
Tricuspid stenosis increases mean CVP

28. 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.

29. 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.

30. CVP as hemodynamic
monitor

31. CVP & PEEP

33. PA catheterisation
 The 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

34. PA catheterisation
 The 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

35. Reduced SVR
Stroke Volume
PAWP / LVEDP
Inotropes Volume admin
Vasopressors

36. PA catheter
 PA 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

38. 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

39. 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

40. 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

41. 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

42. 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

43. 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.

44. 0
30

45. 0
120
PAWP a-c and v waves appear to occur later in the cardiac cycle
compared with CVP trace

46. PA catheter: Uses
 There 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

47. 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)

48. 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%

49. PA catheter: Contraindications
• Known pulmonary hypertension
• Unstable arrhythmias
• Anticoagulation therapy
• Bleeding disorder
• Prior pneumonectomy
• Pacemakers
• Prosthetic heart valves

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