How the LiDCO hemodynamic monitor works

The LiDCO hemodynamic monitor

Designed to support your clinical decision-making

The LiDCO monitor analyses the blood pressure waveform to provide more information in high-risk surgical and critically ill patients to help with fluid and drug management.

The LiDCO uses the PulseCO™ algorithm which converts blood pressure to its constituent parts of flow (CO, SV) and resistance (SVR).  The PulseCO™ algorithm is scaled to each patient with a nomogram using age, height, and weight.

The PulseCO™ algorithm is reliable in unstable patients and patients on vasoactive drugs.

The LiDCO features

  • Very easy to set up and use;
  • Designed to be used to help prevent complications in high-risk surgery;
  • Designed to be used for early use in sepsis;
  • The clinician can see why the blood pressure has changed which helps with important clinical decisions;
  • The LiDCO also provides parameters which help to decide when to start and stop giving fluid;
  • Monitoring from a standard radial line or the non-invasive CNAP™ device;
  • One disposable for both arterial line and non-invasive which is cost effective.

Read below to learn about the LiDCO algorithm which has remained unchanged in over 16 years...


The LiDCO algorithm


The LiDCO uses the PulseCO™ algorithm to derive stroke volume (SV) and heart rate from the blood pressure waveform. The key step in the algorithm is the conversion of the blood pressure to volume to account for both aortic compliance and capacitance. The PulseCO™ algorithm uses a patient-specific factor to adjust the aortic capacitance individually for each patient. The factor can be precisely determined by comparing a known cardiac output with the PulseCO™ estimate. This factor does not change for a patient over the short term.

Because the factor does not change, it was possible to develop a nomogram, or mathematical relationship, using the patient’s characteristics to estimate it. The nomogram used in the LiDCO was developed from carefully controlled studies of the PulseCO™ algorithm with precise determinations of cardiac output using lithium indicator dilution. The result is a robust method for estimation of the factor.

Hemodynamic Window

The LiDCO shows the long-term trend of pressure (MAP, Systolic and Diastolic), Heart Rate (HR) and Scaled Stroke Volume (nSV) or Scaled Cardiac Output (nCO) from the beginning of a procedure. A short term trend of pressure, Heart Rate and Scaled Stroke Volume (nSV) or Scaled Cardiac Output (nCO) is displayed over the current two-minute period.

Dynamic Preload Parameters Window

This LiDCO window also provides you with access to preload response values or volume status indicators of Stroke Volume Variation (SVV%). For closed chest ventilated patients these volume status measurements provide a way of predicting the likely response to volume infusions. A fluid imbalance can have an adverse effect on a patient’s cardiac performance and, in turn, oxygen delivery to key organs.

Blood Pressure Window

At the touch of a button, the arterial pressure waveform is displayed on the LiDCO screen. The LiDCO algorithm and individualized scaling function convert this pressure into nominal stroke volume and nominal cardiac output.

Event Response Window

Pre-Load Responsiveness via the Event Response Display. The Event Response display allows the user to view a selected hemodynamic variable in a higher resolution during a specific period (e.g. fluid challenge, inotrope change). The LiDCO will display percentage change from the start for the variable as a numeric value. This feature is very useful when evaluating the patient’s response to targeted interventions such as a fluid challenge or changes in inotrope therapy.


You can review the clinical papers and case studies by clicking on the button below


Non-Invasive technology

The LiDCO with continuous non-invasive arterial pressure (CNAP™) module provides continuous cardiac output non-invasively, without the requirement for an arterial line.

The CNAP™ dual finger cuffs will provide a continuous, non-invasive pressure which is then analyzed by the validated PulseCO™ algorithm to derive beat-to-beat hemodynamic data.

LiDCO with CNAP™ is safe and easy to use, allowing for effective hemodynamic management of all surgery types;

The device allows for monitoring before induction as well as throughout surgery. This enables immediate fluid and drug management and the setting of hemodynamic baselines;

CNAP™ is used with the PulseCO™ ‘pulse power’ algorithm which reliably tracks the hemodynamic change in the presence of inotropes and vasoactive drugs;

The CNAP™ dual finger cuff system is scaled to the brachial artery with an arm cuff to provide a reliable continuous absolute value for blood pressure.

SVV, HR and change in SV will be comparable to those derived from an invasive arterial line.

How CNAP works

The CNAP uses a vascular unloading technique dates back to the Czech physiologist Jan Peňáz in the 1970s. It is the basic principle for detecting blood volume changes in the finger and transforming plethysmographic signals into continuous blood pressure information.

The dual finger cuff inflates and deflates to maintain a constant blood volume which produces a non-invasive pressure waveform. This is then individually scaled to the patient using a brachial arm cuff measurement.

For cardiac output monitoring, the continuous, non-invasive blood pressure waveform is analyzed by the validated PulseCO™ algorithm.

  • An infrared light source and sensor measure continuous blood volume in the finger;
  • The finger pressure cuff inflates and deflates to maintain a constant blood volume;
  • This counter pressure produces a continuous BP waveform;
  • An absolute BP via the brachial arm cuff is then used to scale this waveform to the brachial artery pressure;
  • The validated PulseCO™ algorithm derives SV, CO, SVR and SVV from the non-invasive waveform.


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