Editing Cardiac output (section)

=====Calibrated PP – PiCCO, LiDCO=====
{{abbr|PiCCO|Pulse contour cardiac output}} ([[:de:PULSION Medical Systems|PULSION Medical Systems]] AG, Munich, Germany) and PulseCO (LiDCO Ltd, London, England) generate continuous ''Q'' by analysing the arterial PP waveform. In both cases, an independent technique is required to provide calibration of continuous ''Q'' analysis because arterial PP analysis cannot account for unmeasured variables such as the changing compliance of the vascular bed. Recalibration is recommended after changes in patient position, therapy or condition.{{citation needed|date=June 2015}}

In PiCCO, transpulmonary thermodilution, which uses the Stewart-Hamilton principle but measures temperatures changes from central venous line to a central arterial line, i.e., the femoral or axillary arterial line, is used as the calibrating technique. The ''Q'' value derived from cold-saline thermodilution is used to calibrate the arterial PP contour, which can then provide continuous ''Q'' monitoring. The PiCCO algorithm is dependent on blood pressure waveform morphology (mathematical analysis of the PP waveform), and it calculates continuous ''Q'' as described by Wesseling and colleagues.<ref name="Wesseling">{{cite journal | vauthors = Wesseling KH, Jansen JR, Settels JJ, Schreuder JJ | title = Computation of aortic flow from pressure in humans using a nonlinear, three-element model | journal = Journal of Applied Physiology | volume = 74 | issue = 5 | pages = 2566–73 | date = May 1993 | pmid = 8335593 | doi = 10.1152/jappl.1993.74.5.2566 }}</ref> Transpulmonary thermodilution spans right heart, pulmonary circulation and left heart, allowing further mathematical analysis of the thermodilution curve and giving measurements of cardiac filling volumes ([[End-diastolic volume|{{abbr|GEDV|Global end diastolic volume}}]]), intrathoracic blood volume and extravascular lung water. Transpulmonary thermodilution allows for less invasive ''Q'' calibration but is less accurate than PA thermodilution and requires a central venous and arterial line with the accompanied infection risks.{{citation needed|date=June 2015}}

In LiDCO, the independent calibration technique is [[lithium chloride]] dilution using the Stewart-Hamilton principle. Lithium chloride dilution uses a peripheral vein and a peripheral arterial line. Like PiCCO, frequent calibration is recommended when there is a change in Q.<ref name="Bein2">{{cite journal | vauthors = Bein B, Meybohm P, Cavus E, Renner J, Tonner PH, Steinfath M, Scholz J, Doerges V | title = The reliability of pulse contour-derived cardiac output during hemorrhage and after vasopressor administration | journal = Anesthesia and Analgesia | volume = 105 | issue = 1 | pages = 107–13 | date = July 2007 | pmid = 17578965 | doi = 10.1213/01.ane.0000268140.02147.ed | s2cid = 5549744 | doi-access = free }}</ref> Calibration events are limited in frequency because they involve the injection of lithium chloride and can be subject to errors in the presence of certain muscle relaxants. The PulseCO algorithm used by LiDCO is based on pulse power derivation and is not dependent on waveform morphology.{{citation needed|date=March 2021}}