Cardiac Output

Overview:

Cardiac output (CO) is the quantity of blood that is pumped by the heart each minute. It is the product of stroke volume (SV; the volume of blood ejected from the heart in a single beat) and heart rate (HR; expressed as beats per minute or BPM).

Cardiac Output = Stroke Volume × Heart Rate

Cardiac Output can be affected by respiration, especially under mechanical ventilation, and should therefore be measured at a defined phase of the respiratory cycle, which is usually the end-expiratory phase.

There are many experiments that measure or calculate CO including:

• Working heart experiments
• In vivo cardiovascular experiments
• Exercise physiology experiments

Method:

Thermodilution (Invasive)

Whilst CO may be determined using ultrasonic, Fick or Indirect Fick methods, the thermodilution (TD) technique is the most commonly used technique in small animals.

• The thermodilution technique involves the injection of a cold bolus solution (usually 9% isotonic saline) of a known volume and temperature into the right side of the heart and measuring the change in temperature within the circulation. The resultant temperature change in the blood ejected from the heart is measured with a thermocouple placed in the aorta or carotid artery. A TD curve (temperature versus time) is recorded and CO determined by calculating the area under this curve. Note: A fast responding thermocouple probe is necessary for measuring the temperature change in small animals.
• Please refer to the following documentation for more information relating to the thermodilution technique and ADInstruments products.
  • Cardiac Output Technique For Small Animals  
  • Technique for Thermocouple & Catheter Preparation  

Transit-Time Ultrasound Flowmetry (Invasive)

• Calculates CO by measuring fluid flow (e.g. blood, physiological buffer) out of the heart. In contrast to traditional ultrasound techniques, transit-time ultrasound flowmetry is a technique that incorporate two transmitters/sensors and a reflector plate that allows them to provide calibrated measurements of blood flow rate in milliliters per minute. Transit-time ultrasound technologies are not subject to problems with electrical interference or baseline drift and do not require close/direct contact with the vessel.
• ADInstruments offer flow systems and CO probes available in various sizes for implanting in animals as small as mice through to adult pig aorta or pulmonary artery.

Volume-Clamp (Non-invasive)

The volume-clamp technique involves measuring finger arterial pressure with a finger cuff and an inflatable bladder in combination with an infrared plethysmograph (infrared light source and detector). The infrared light is absorbed by the blood, and the pulsation of arterial diameter during a heart beat causes a pulsation in the light detector signal. The first step in this method is determining the proper unloaded diameter of the finger arteries, the point at which finger cuff pressure and intra-arterial pressure are equal and at which the transmural pressure across the finger arterial walls is zero. Then the arteries are clamped (kept at this unloaded diameter) by varying the pressure of the finger cuff inflatable bladder using the fast cuff pressure control system.

The Finometer MIDI is a non-invasive continuous blood pressure measuring instrument used to monitor the brachial arterial pressure using a finger arterial pressure measurement in human subjects. Beat-to-beat values of systolic, diastolic and mean arterial pressure can be recorded and cardiac output can also be calculated using the BeatScope software.

Software:

The LabChart Advantage:

(may require additional Modules and Extensions)

• LabChart data files can be marked with events using the Comments feature
• The Units Conversion feature can be used to convert signals into relevant units e.g. ml/min, l/min
• The Cardiac Output Module for Windows provides the user with ability to easily extract and calculate cardiac output from small animals, using the thermodilution technique
• Macros can automate many tedious and repetitive analysis tasks
• Data can be easily transferred into popular spreadsheet and graphing programs for further analysis and reporting

LabChart

LabChart software (for Windows and Macintosh) together with a PowerLab data acquisition system offers up to 32 channels of real-time data acquisition, data integrity, easy selection of hardware settings, powerful online and offline analysis, procedure automation, seamless extraction of experimental data and flexible display options. Additional acquisition and analysis functionality is provided with the use of specialized LabChart Extensions and LabChart Modules. Modules are available as part of LabChart Pro while Extensions are free for download from the website for existing LabChart users. 

Cardiac Output Module

The Cardiac Output Module (Windows) provides easy extraction and calculation of cardiac output from small animals recorded in LabChart, using the thermodilution technique.

The Cardiac Output Module allows:

• Automatic calculation of cardiac output in mL/min from a thermodilution curve
• Automatic calculation of baseline temperature and baseline slope correction
• Automatic calculation of the area under the curve
• Automated extraction of exportable parameters in a spreadsheet format

 

 

Beatscope Software (for Finometer MIDI)

The BeatScope 1.1a software (Windows) for use with the MLE1054 Finometer MIDI provides blood pressure waveform values including systolic, diastolic, MAP and heart rate parameters such as cardiac output.

Additionally, BeatScope 1.1a offers statistical analysis of data from the Finometer MIDI file (*.fpf, Finometer Packet File) as well as extended functionality to present and analyse blood pressure waveforms and related hemodynamic parameters including;

• stroke volume (SV)
• total peripheral resistance (TPR)
• cardiac output (CO)
• baroreflex sensitivity (BRS)
• pulse rate variability (PRV)

The BeatScope Easy software (Windows), a simpler and basic version of the software is also available.

GLP and 21 CFR Part 11

For those researchers working within a laboratory requiring GLP and 21 CFR Part 11 compliance the GLP Client and GLP Server are available for use with LabChart (Windows only) and PowerLab data acquisition systems. For more information, visit the Good Laboratory Practice application page or contact your nearest ADInstruments representative.

Hardware:

PowerLab Data Acquisition Systems

The PowerLab is a high-performance data acquisition unit capable of recording at speeds of up to 400,000 samples per second continuously to disk (aggregate). PowerLab units are compatible with instruments, signal conditioners and transducers supplied by ADInstruments, as well as many other third-party companies. In addition to standard single-ended BNC inputs, 4 differential Pod ports are also available for direct connection of Pod signal conditioners and appropriate transducers. Research PowerLab units include:

• PL3504 PowerLab 4/35 - 4 Channels
• PL3508 PowerLab 8/35 – 8 Channels
• PL3516 PowerLab 16/35 – 16 Channels

Research Systems 

Transit-Time Ultrasound Blood/Fluid Flow Systems

ADInstruments provide flow systems and probes of various sizes for implanting in blood vessels in animal models from mice through to adult pig. These probes are available for both chronic and acute applications and are calibrated to provide the user with blood flow measurements in milli-liters per minute in conscious and anesthetized animals. The flow meters easily integrate with any PowerLab data acquisition systems.

These systems include:

• PL3508B11 One Channel Perivascular Flow System - measuring blood flow from a single vessel
• PL3508B12 One Channel Tubing Flow System - measuring flow in a single tube
• PL3508B13 Two Channel Perivascular Flow System - simultaneously measuring blood flow from two vessels
• PL3508B14 Two Channel Tubing Flow System - simultaneously measuring flow from two tubing setups
• PL3508B15 Two Channel Perivascular/Tubing Flow System - simultaneously measuring flow from a single blood vessel and single tube

Instruments

MLE1054 Finometer® MIDI is a non-invasive continuous blood pressure measuring system used to monitor the brachial arterial pressure using a finger arterial pressure measurement in human subjects. The Finometer can be connected to a PowerLab to provide a display of the brachial artery reconstruction from the finger pressure and beat-to-beat values of Systolic, Diastolic and Mean pressure. It features hydrostatic height correction, remote and automatic control. Optional hardware may be ordered separately for recording ECG, viewing the finger pressure waveforms, and calculating Cardiac Output using Beatscope software.

Signal Conditioners

The ML313 Cardiac Output Pod (no thermocouple) is used with T-type thermocouples (thermodilution technique) to determine the cardiac output in small animals (mice, rats, guinea pigs or rabbits) ONLY. The Pod can be used with any appropriate T-Type thermocouples and has a 'delta' temperature mode to allow a signal offset to be applied so that small temperature variations are monitored accurately.

The ML313C Cardiac Output Pod (with thermocouple) configuration consists of the Cardiac Output Pod with additional products including:

• MLT1402 T-type Ultra Fast Thermocouple Probe with a fast response time of 0.005 seconds
• Cardiac Output Module (Windows) for LabChart

Transducers and Accessories

Perivascular Flowprobes

For a guide to the appropriate flow probe for measurement of blood flow in a specific vessel in a specific species view the Probe Application Guide.  The PAX-Series perivascular flowprobes are designed to measure cardiac output in larger vessels such as adult pig aorta or pulmonary artery while the Nanoprobe-Series can be used for cardiac output measurements in mice. Detailed information about the physical and operational specifications of the Flowprobes is available in the Perivascular Probe Specifications. When ordering a Perivascular Flowprobe please consult the Flowprobe Ordering Guide. 

Cardiac Output

The MLA313 Cardiac Output Accessory Kit helps facilitate the measurement of cardiac output from small animals. It can be used with the ML313C Cardiac Output Pod (with thermocouple) or ML313 Cardiac Output Pod (no thermocouple). It includes:

• Hamilton LR (Luer tip)
• Glass syringe (250µl)
• Repeating dispenser
• Luer needle hubs
• Three-way stop-cocks 
• Touhy Borst Adaptors
• Polyethylene tubing

Superior cardiac function via anaplerotic pyruvate in the immature swine heart after cardiopulmonary bypass and reperfusion
Olson A K, Hyyti O M, Cohen G A, Ning X H, Sadilek M, Isern N, Portman M A, American Journal of Physiology: Heart and Circulatory Physiology, H2315–H2320, 2008

Transpulmonary cardiac output measurement in a rat model of cardiac arrest and CPR: Impact of vascular access
Kelm R F, Wagenfuhrer J, Schmidtmann I, Engelhard K, Werner C, Noppens R R, Resuscitation, 248–254, 2010

Impaired ATP turnover and ADP supply depress cardiac mitochondrial respiration and elevate superoxide in nonfailing spontaneously hypertensive rat hearts
Hickey AJ, Chai CC, Choong SY, de Freitas Costa S, Skea GL, Phillips AR, Cooper GJ., American Journal of Physiology: Cell Physiology, C766–C774, 2009