page_title: Cardiac output
section_title: Pulmonary artery thermodilution (trans-right-heart thermodilution)
hierarchical_section_title: Cardiac output / Historical methods / Pulmonary artery thermodilution (trans-right-heart thermodilution)
caption_attribution_description: Čeština: Schéma zavedení Swanova-Ganzova katétru v angličtině Deutsch: Aufbau eines Pulmonalarterienkatheters (Swan-Ganz-Katheter). Der Katheter beinhaltet vier Lumen. Dies sind der proximale Kanal (1), der im rechten Vorhof zu liegen kommt und u. a. zur Messung des zentralen Venendrucks dient, der Kanal, der zu Temperatursonde führt und eine Kältedilutionsmessung ermöglicht (2), der Kanal zum Aufblasen des Ballons (3) sowie der distale Kanal, mit dem der Druck in der Pulmonalarterie (PAP) sowie der Pulmonalarterienverschlussdruck (PCWP, Wedge-Druck) gemessen wird (4). In diesem Schemabild befindet sich der Katheter in der Wedge-Position, in der der Ballon die Pulmonalarterie verschließt.A simple figure descripting pulmonary artery catheter. Drawn with Inkscape 0.43
context_page_description: Cardiac output, also known as heart output denoted by the symbols, or, is a term used in cardiac physiology that describes the volume of blood being pumped by the heart, by the left and right ventricle, per unit time. Cardiac output is the product of the heart rate, i.e. the number of heartbeats per minute, and the stroke volume, which is the volume of blood pumped from the ventricle per beat; thus, CO = HR × SV. Values for cardiac output are usually denoted as L/min. For a healthy person weighing 70 kg, the cardiac output at rest averages about 5 L/min; assuming a heart rate of 70 beats/min, the stroke volume would be approximately 70 ml.
  Because cardiac output is related to the quantity of blood delivered to various parts of the body, it is an important component of how efficiently the heart can meet the body's demands for the maintenance of adequate tissue perfusion. Body tissues require continuous oxygen delivery which requires the sustained transport of oxygen to the tissues by the systemic circulation of oxygenated blood at an adequate pressure from the left ventricle of the heart via the aorta and arteries.
context_section_description: The indicator method was further developed by replacing the indicator dye with heated or cooled fluid. Temperature changes rather than dye concentration are measured at sites in the circulation; this method is known as thermodilution. The pulmonary artery catheter (PAC) introduced to clinical practice in 1970, also known as the Swan-Ganz catheter, provides direct access to the right heart for thermodilution measurements. Continuous, invasive, cardiac monitoring in intensive care units has been mostly phased out. The PAC remains useful in right-heart study done in cardiac catheterisation laboratories.
  The PAC is balloon tipped and is inflated, which helps "sail" the catheter balloon through the right ventricle to occlude a small branch of the pulmonary artery system. The balloon is then deflated. The PAC thermodilution method involves the injection of a small amount (10ml) of cold glucose at a known temperature into the pulmonary artery and measuring the temperature a known distance away 6–10 cm (2.4–3.9 in) using the same catheter with temperature sensors set apart at a known distance.
  The historically significant Swan-Ganz multi-lumen catheter allows reproducible calculation of cardiac output from a measured time-temperature curve, also known as the thermodilution curve. Thermistor technology enabled the observations that low CO registers temperature change slowly and high CO registers temperature change rapidly. The degree of temperature change is directly proportional to the cardiac output. In this unique method, three or four repeated measurements or passes are usually averaged to improve accuracy. Modern catheters are fitted with heating filaments that intermittently heat up and measure the thermodilution curve, providing serial Q measurements. These instruments average measurements over 2–9 minutes depending on the stability of the circulation, and thus do not provide continuous monitoring.
  PAC use can be complicated by arrhythmias, infection, pulmonary artery rupture and damage to the right heart valve. Recent studies in patients with critical illnesses, sepsis, acute respiratory failure and heart failure suggest that use of the PAC does not improve patient outcomes. This clinical ineffectiveness may relate to its poor accuracy and sensitivity, which have been demonstrated by comparison with flow probes across a sixfold range of Q values. Use of PAC is in decline as clinicians move to less invasive and more accurate technologies for monitoring hæmodynamics.
caption: Diagram of Pulmonary artery catheter (PAC)
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