Outline the components required to measure blood pressure from an intra-arterial catheter (75% of marks). What information (other than blood pressure) may be gained from an arterial line trace (25% of marks)?
Most of the marks were allocated to the components of the measuring system (as detailed in the question), hence a level of detail was required. An explanation of how the various components work was required; e.g. hydraulic coupling and transducers. Some candidates forgot to include heart rate as a piece of information derived from the trace.
Components of the measurement system:
Information derived from from the measurements by the arterial line transducer:
Information derived from the waveform shape:
From Bersten and Soni's" Oh's Intensive Care Manual", 6th Edition; plus McGhee and Bridges Monitoring Arterial Blood Pressure: What You May Not Know (Crit Care Nurse April 1, 2002 vol. 22 no. 2 60-79 )
Scheer,Perel and Pfeiffer.Complications and risk factors of peripheral arterial catheters used for haemodynamic monitoring in anaesthesia and intensive care medicine. Crit Care. 2002; 6(3): 199–204.
For those who like hardcore physics, this excellent resource will be an enormous source of amusement. It appears to be a free online textbook of anaesthesia.
LITFL also link to this comprehensive FRCA self-assessment document:
Abby Jones, Oliver Pratt; PHYSICAL PRINCIPLES OF INTRA-ARTERIAL BLOOD PRESSURE MEASUREMENT - ANAESTHESIA TUTORIAL OF THE WEEK 137 8TH JUNE 2009
McCanny, Peter, et al. "Haemodynamic monitoring and management." (2013). PACT, ESICM
This FRCA study document on arterial pressure monitoring is a goldmine of detailed information.
Lodato RF, Schlichting R: "Arterial pressure monitoring. Arterial catheterization: complications." In Principles and Practice of Intensive Care Monitoring. Volume Part III. 2nd edition. Edited by Tobin MJ. New York: McGraw Hill; 1998::733-756.
Winsor, Travis, and George E. Burch. "Phlebostatic Axis and Phlebostatic Level, Reference Levels for Venous Pressure Measurements in Man." Experimental Biology and Medicine 58.2 (1945): 165-169.
McCann, Ulysse G., et al. "Invasive arterial bp monitoring in trauma and critical care: Effect of variable transducer level, catheter access, and patient position." CHEST Journal 120.4 (2001): 1322-1326.
Thomas, E., M. Czosnyka, and P. Hutchinson. "Calculation of cerebral perfusion pressure in the management of traumatic brain injury: joint position statement by the councils of the Neuroanaesthesia and Critical Care Society of Great Britain and Ireland (NACCS) and the Society of British Neurological Surgeons (SBNS)." British journal of anaesthesia (2015): aev233.
Gondringer, N., and J. D. Cuddeford. "Monitoring in anesthesia: clinical application of monitoring central venous and pulmonary artery pressure (continuing education credit)." AANA journal 54.1 (1986): 43-56.