Central venous pressure (CVP)

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Central Venous Pressure (CVP)

  • Normal range (supine, spontaneous ventilation): 2–6 mm Hg (≈3–8 cm H₂O). Mechanically ventilated or positive end-expiratory pressure (PEEP) ≥10 cm H₂O can raise baseline values by ~3 cm H₂O. CVP ≃ right-atrial pressure (RAP).

CVP.png

Physiology & Determinants

Variable Effect on CVP
Venous return (VR) = (MSFP–RAP)/Rv ↑ MSFP (fluid, venous tone) or ↓ Rv → ↑ CVP
Rightand left-ventricular compliance & function RV failure, tamponade, pulmonary hypertension → ↑ CVP
Intrathoracic & pleural pressures PEEP, Valsalva, pneumothorax ↑ CVP; spontaneous inspiration ↓ CVP
Intra-abdominal pressure Abdominal compartment syndrome ↑ CVP without ↑ preload
  • ΔCVP = ΔV / Cᵥ, where Cᵥ = venous compliance.

Waveform

  • a wave–atrial contraction
  • c wave–bulging tricuspid valve in early systole
  • x desent–atrial relaxation/downward RV contraction
  • v wave–passive atrial filling with closed tricuspid valve
  • y descent–rapid ventricular filling after valve opens

Abnormal Patterns

Finding Typical aetiology
Dominant a Pulmonary HTN, tricuspid stenosis
Cannon a Complete heart block, VT with AV dissociation
Dominant v Tricuspid regurgitation
Absent x Atrial fibrillation
Deep x Tamponade, constrictive pericarditis
Steep y Severe TR, constrictive pericarditis
Slow y Tricuspid stenosis, atrial myxoma

CVPtracings.png

Measurement Best Practice

  • Zero transducer at phlebostatic axis (4th ICS mid-axillary).
  • Read end-expiration (mean of several cycles).
  • Flush test: optimal damping coefficient 0.6-0.8.
  • Avoid infusions through the measuring lumen.
  • Ultrasound confirmation of tip in lower SVC/RA junction reduces arrhythmia & malposition.
  • PEEP of 10 cm H₂O → ↑CVP ≈ 3 cm H₂O (compliance-dependent); adjust interpretation accordingly.

Clinical Utility

Diagnostic Waveform Clues

  • RV infarction, cor pulmonale, tamponade, tricuspid disease, constrictive pericarditis, complete heart block.

Procedural/monitoring Roles

  • Confirm atrial capture during AV pacing.
  • Identify P waves in narrow-complex tachyarrhythmias.
  • Rapid confirmation of central line placement.

Limits as a Preload Guide

  • Static CVP poorly predicts fluid responsiveness; use trends, ∆CVP with fluid challenge, or dynamic indices (PPV, SVV, echo Doppler) for decision-making.

Pulmonary Capillary Wedge Pressure (PCWP)

Definition–Pressure measured with a balloon-tipped pulmonary artery catheter (PAC) wedged in zone 3; reflects left-atrial pressure and approximates LV end-diastolic pressure (LVEDP) when mitral valve is normal. Normal 4–12 mm Hg.

Indications for PAC/PCWP

  • Cardiogenic vs non-cardiogenic pulmonary oedema.
  • Refractory or undifferentiated shock (especially rightor left-sided).
  • Complex heart failure, advanced pulmonary hypertension, peri-transplant evaluation.
  • Mixed venous oxygen saturation and thermodilution cardiac output monitoring when less invasive modalities are unreliable.

Technique Tips

  • Zone 3 placement (PA diastolic > PCWP) avoids false low readings.
  • Measure at end-expiration in supine 30 ° head-up; over-wedging may occlude flow and cause infarct.
  • Large v waves during occlusion suggest severe MR or non-compliant LA.

Factors Causing PCWP ≠ LVEDP

Situation Effect
Mitral stenosis/atrial myxoma PCWP > LVEDP
↓ LA or LV compliance (ischaemia, hypertrophy) PCWP > LVEDP
Positive-pressure ventilation, PEEP PCWP overestimates true filling pressure
Pulmonary veno-occlusive disease / ↑ PVR PCWP < LVEDP
Intracardiac shunts Variable error

Complications of PAC

  • Dysrhythmia (PVCs, VT, VF)
  • RBBB & potential complete heart block in pre-existing LBBB.
  • PA rupture or infarction (balloon inflation distal).
  • Infection, thrombosis, catheter knotting
  • Risk is reduced by ultrasound-guided insertion, balloon inflation under waveform guidance only, limiting wedging time to ≤15 s, and daily need assessment.

Evidence & Current Position

Robust RCTs show no outcome benefit from routine PAC use in general ICU/surgical patients; selective use in cardiogenic shock, pulmonary hypertension and complex peri-cardiac surgery may improve short-term haemodynamics and, in observational studies, survival. Clinicians should integrate PAC data with echocardiography and less invasive monitors rather than rely on single parameters.

Links

References:

  1. Chambers D, Huang CLH, Matthews G. Basic physiology for anaesthetists. Cambridge, United Kingdom: Cambridge University Press; 2015.
  2. Bootsma, I. T., Boerma, E. C., Lange, F. d., & Scheeren, T. (2021). The contemporary pulmonary artery catheter. part 1: placement and waveform analysis. Journal of Clinical Monitoring and Computing, 36(1), 5-15. https://doi.org/10.1007/s10877-021-00662-8
  3. Nickson, C. (2024, November 8). CVP Measurement. Life in the Fast Lane. Retrieved March 16, 2025, from https://litfl.com/cvp-measurement/
  4. Raj, T. D. (2017). Data interpretation in anesthesia.. https://doi.org/10.1007/978-3-319-55862-2
  5. Hensley FA, Gravlee GP, Martin DE. Practical Approach to Cardiac Anesthesia. 5th Ed. Philadelphia Wolters Kluwer. Ann Arbor, Michigan. Proquest; 2014: 118-37.
  6. Nickson C. CVP Measurement. LITFL 2024. Available from: https://litfl.com/cvp-measurement/ litfl.com
  7. StatPearls Publishing. Physiology, Central Venous Pressure. Updated 2024. Available from: https://www.ncbi.nlm.nih.gov/books/NBK519493/ ncbi.nlm.nih.gov
  8. Oostendorp N et al. Haemodynamic monitoring during non-cardiac surgery: past, present and future. J Clin Monit Comput 2024;38:123-134. link.springer.com
  9. Bishop DG, Dyer RA, Crowther M. Balancing haemodynamic priorities in obstetrics. SAJAA 2024;30:72-75. Available from: http://www.sajaa.co.za sajaa.co.za
  10. Van Zyl-Smith M. Haemodynamic monitoring in high-risk surgery. SAJAA 2020;26:68-74. sajaa.co.za
  11. Nair R, Lamaa N. Pulmonary Capillary Wedge Pressure. StatPearls 2023. Available from: https://www.ncbi.nlm.nih.gov/books/NBK557748/ ncbi.nlm.nih.gov
  12. Lee J et al. Effectiveness of pulmonary artery catheter monitoring for cardiogenic shock: systematic review & meta-analysis. J Thorac Dis 2023;15:1115-1123. Available from: https://pubmed.ncbi.nlm.nih.gov/37065575/ pubmed.ncbi.nlm.nih.gov
  13. StatPearls Publishing. Pulmonary Artery Catheterization. Updated 2024. Available from: https://www.ncbi.nlm.nih.gov/books/NBK482170/ ncbi.nlm.nih.gov
  14. Raisi-Estabragh Z et al. Relationship between PEEP and CVP in ventilated adults. Crit Care Res Pract 2017; Article ID 5941312.
  15. Connor C, Conley C. Commonly Used Monitoring Techniques. In: Barash PG. et al (ed). Clinical Anesthesia. 8th Ed. Philadelphia; Wolters Kluwer; 2017: 706-30.

Summaries:

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