Metabolic Rates

Metabolism is the set of chemical reactions that occur in living organisms in order to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into catabolism that breaks down large molecules to collect energy and anabolism that uses energy to construct molecular components.

The energy produced or used may be measured by calorimetry, which is the science of measuring the heat of chemical reactions or physical changes. This measurement may be performed directly or indirectly. For example in direct calorimetry, the entire organism is placed inside the calorimeter to measure the heat generated by the living organism. Indirect calorimetry calculates heat that living organisms produce from their production of carbon dioxide and nitrogen waste or from their consumption of oxygen. In humans, calorimetry is the measurement of an individual's energy expenditure and is often performed using indirect calorimetry (IC) techniques. The indirect calorimetry measures energy expenditure (caloric burn rate) from the amount of oxygen that is consumed over a period of time.

Metabolic Measurements in Humans
Indirect calorimetry requires the accurate measurement of oxygen consumption (VO₂) and is easily performed using the Exercise Physiology System. This system includes an:

• An eight channel PowerLab data acquisition unit
• Gas Analyzer for accurate O₂ and CO₂ measurements
• Gas Mixing Chamber for mixing expired gases prior to sampling
• Spirometer for differential pressure measurements of respiratory air flow
• Thermistor Pod for measuring the temperature of expired gases and is necessary to correct for differences between expired and atmospheric conditions.
• Single Channel Bio Amp for optional recordings of biopotentials such as ECG or EMG
• Metabolic Module for LabChart (Win or Mac) software that provides online or offline calculation and display of
• VE, VO₂, VCO₂ and Respiratory Exchange Ratio (RER)

Metabolic Measurements in Animals
Metabolic function in animals can be measured using a custom configuration that includes the Spirometer and Gas Analyzer. For example, the unrestrained or restrained animal may be kept in a plethysmograph chamber and respiratory air flow and gas concentrations monitored.

Note: For more information on related topics please see:

• Temperature application page for temperature measurements
• Dissolved O2 _{application page for direct determination of oxygen concentration in solutions}
• _{Respiratory Gas Analysis application page for O2 and CO2 analysis in respiratory gasses}

LabChart
LabChart software (for Windows and Macintosh) combines the familiar simplicity of a traditional strip chart recorder with the powerful analysis features of a digital acquisition system. LabChart software and a PowerLab data acquisition unit provide data integrity, easy selection of hardware settings, powerful online and offline analysis, procedure automation, seamless extraction of experimental data and flexible display options. Acquisition and analysis capabilities can be further increased with LabChart Extensions and LabChart Modules. LabChart Modules are available as part of LabChart Pro and LabChart Extensions are free for download from the website for existing LabChart users.

Respiratory rate can be calculated online or offline using the Cyclic Measurements (Win) or Computed Input/Cycle Variables (Mac) features in LabChart.

Metabolic Module (Windows or Macintosh)
The MLS240/6 Metabolic Module for LabChart in combination with ADInstruments hardware is ideal in the determination of cardiorespiratory function and exercise physiology measurements. Typical applications include:

• Metabolic measurements
• Respiratory gas analysis
• Student exercise testing
• Pulmonary function analysis
• Indirect calorimetry
• Anaerobic threshold
• Biopotential measurements and spirometry.

The Metabolic Module records CO₂ and O₂ concentrations sampled from a gas mixing chamber and interprets these values in real time to provide parameters such as: VCO₂/min, VO₂/min, VE/min and RER. The module also provides options for setting subject details, recording parameters and environmental conditions that includes:

• Hardware preferences: choice of appropriate hardware
  
• Subject details: name, age, weight, height, gender, id number, comments
• Calibration preferences: settings for automated first and second gas calibrations
• General preferences: Averaging time (data logging) and recording time (duration of experiment) settings
• Environment settings: Expired/inspired, atmospheric and air conditions

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.

ADInstruments provide a range of data acquisition systems, signal conditioners, respiratory flow heads, pressure transducers and amplifiers that connect to PowerLab data acquisition systems for monitoring air flow and calculating respiratory data.

PowerLab Data Acquisition Systems
The PowerLab is a high-performance data acquisition unit suitable for a wide range of research applications. Typical applications include human and animal physiology, pharmacology, neurophysiology, biology, zoology, biochemistry, and biomedical engineering. Units are capable of recording at speeds of up to 400 000 samples per second continuously to disk (aggregate), and are compatible with instruments, signal conditioners and transducers supplied by ADInstruments, as well as many other brands. 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. These systems include:

• ML866 PowerLab 4/30 - 4 Channels
  
• ML870 PowerLab 8/30 – 8 Channels
• ML880 PowerLab 16/30 – 16 Channels

System and Instruments
ML870B80 Exercise Physiology System
This is a complete physiology recording system for monitoring cardiorespiratory and metabolic function during exercise. The system records and displays continuous real-time measurements of metabolic parameters such as CO2 and O2 concentrations, airflow, air temperature, ECG or EMG.
The Exercise Physiology System includes:

• ML870 PowerLab 8/30 (LabChart and Scope software)
• MLS260 LabChart Pro software
• ML132 Bio Amp
• ML206 Gas Analyzer
• MLA246 Gas Mixing Chamber
• ML141 Spirometer
• ML309 Thermistor Pod
• MLA240 Exercise Physiology Accessory Kit

ML206 Gas Analyzer
The Gas Analyzer can be used for the measurement of respiratory gas concentrations from small animals, such as rats, through to humans. It contains an infrared carbon dioxide sensor and optical oxygen detector fed from a damped microvacuum sampling pump.

Metabolic costs induced by lactate in the toad Bufo marinus: new mechanism behind oxygen debt?

I Pinz and H-O Portner, Journal of Applied Physiology, 1177-1185, 2003

B. marinus of either sex weighing between 220 and 350 g were were anaesthetized in tap water containing 2 g/l 3-aminobenzoicacidethylester (MS-222, Sigma Chemical, St. Louis, MO; pH neutralized with NaHCO3). The ischiadic artery of the right hindleg was cannulated occlusively according to McDonald et al. (26)………the experiment was conducted in a respirometer chamber (2-liter volume, containing 200 ml of water). The inspired gas mixture was prepared from pure nitrogen and air with gas-mixing pumps (type 5 KM 402/A-F, Wösthoff, Bochum, Germany). The oxygen content of the inspired gas mixture was reduced to 12% for 12 h and then to 7% for another 12 h…….Oxygen consumption was measured with a paramagnetic oxygen and a photometric CO2 sensor (Oxynos-100 and Binos-100, Rosemount). Data were recorded on a MacLab System (AD Instruments) and evaluated by using equations………….

Influence of vestibular activation on respiration in humans

K D Monahan, M K Sharpe, D Drury, A C Ertl and C A Ray, American Journal of Physiology: Regulatory, Integrative and Comparative Physiology, R689-R694, 2002

healthy volunteers (5 men and 4 women) [age: 28 ± 1 (SE) yr; height: 170 ± 1 cm; weight: 68 ± 1 kg] were studied……….Subjects performed several experiments isolating the respective influences of the semicircular canals and otolith organs on respiration in humans. Additional experiments were performed to minimize input from other potentially confounding variables (e.g., neck muscle afferents). The order of trials was randomized and counterbalanced. All protocols contained a 3-min baseline period followed by 1 min of the respective intervention and a 3-min period of recovery. All trials were performed with the subjects’ eyes closed. ………….Respiratory measures were taken, breath by breath, by a metabolic cart (Sensormedics, Yorba Linda, CA) interfaced with a Macintosh computer through a MacLab analog-todigital converter (8E, ADInstruments, Milford, MA). A face mask that covered both the mouth and nose was securely fastened to the subject’s head before data collection. The face mask included a two-way valve that was directly connected to a pneumotachograph and allowed measurement of inspiratory, expiratory, and whole breath respiratory measures and minimized dead space. The facemask allowed subjects to breathe comfortably and spontaneously through either their noses or mouths. Continuous measurements of arterial blood pressure (Finapres, Louisville, CO), R-R interval (electrocardiogram), and respiratory measures were made through all experiments. Respiratory measures included: inspiratory time (ms), expiratory time (ms), tidal volume (ml), breathing frequency (breaths/min), and minute ventilation (l/min). The right hand, used for measuring arterial blood pressure, was maintained at heart level throughout all trials. All data were collected (MacLab 8E) and routed to a computer for continuous collection and for data-monitoring purposes.