BSL PRO Lesson H19 - Biopac

Updated 01-26-12 

BSL PRO Lesson H19: 

VO 2 and RER Measurement 

Recording established using the VO2 and RER 

graph template file (h19.gtl) 

Overview 

Oxygen Consumption (VO 2 ) and Respiratory Exchange Ratio (RER) 

Real-time Oxygen Consumption (VO 2 ) and Respiratory Exchange Ratio (RER) measurements can be obtained 

using the MP35/MP30 System with the Gas-System2 module and some airflow accessories. When performing 

tests of this kind, many factors exist to confound the measurement. 

 

For example, it may be reasonable to think that the volume of expired air is always the same as 

inspired air, but this is only true when the volume of carbon dioxide expired is equal to the volume of 

oxygen consumed. The inspired and expired volumes are equal only when the RER equals one. 

RER is defined as VCO 2 produced divided by VO 2 (where V is volume). Accordingly, when performing these 

measurements, precise determination of inspired and expired volumes and accurate assessment of the gas 

concentration level are required. 

The Gas-System2 measures O 2 and CO 2 concentrations in vapor. 

 

When the subject inspires, air will be drawn into the Gas-System2 through the SS11LA airflow 

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BSL PRO Lesson H19 

BIOPAC Systems, Inc. 

 

transducer. The SS11LA is placed on the inspiration side to eliminate any effects associated with 

expired air humidity (see Hardware Setup for more detail). 

When the subject expires, air will be directed to the Gas-system2 module. The Gas-System2 is 

designed to work with saturated expired air. 

When using a mixing chamber to average O 2 and CO 2 concentrations over several breaths and measuring 

these changes for arbitrarily high breathing rates, there is no performance degradation. Accordingly, a mixing 

chamber (such as the Gas-System2 utilizes) is typically recommended for quick, accurate and easy metabolic 

analysis. 

IMPORTANT CONCEPT! 

The non-rebreathing “T” valve directs only expired air to the Gas-System2. Because only expired air is directed 

to the module, the system acts to average respiratory outflows. This averaging effect causes the CO 2 and O 2 

concentrations to vary in accordance to the mean values resident in a few expired breaths. The size of the 

system’s chamber determines the extent of the averaging effect. 

For example, if the subject’s expired breath volume is 0.5 liters, the Gas-System2’s chamber will 

average about 10 expired breaths. 

Definitions 

Click here for definitions of abbreviations used in this lesson and the calculation channel Expression formulas 

used for VO 2 and RER. 

Objectives 

1. To obtain absolute VO 2 and RER values for a subject at rest (optional segments include 

hyperventilation and recovery from exercise). 

2. To demonstrate the relationship between VO 2 and RER. 

Equipment 

 

 

 

 

 

 

 

 

 

 

 

 

 

BIOPAC Gas Analysis System (GASSYS2-EA) 

BIOPAC Pneumotach Airflow Transducer [High Flow] (SS11LA) 

BIOPAC Calibration Syringe (AFT26 or AFT6) 

BIOPAC 22 mm Non-Rebreathing T Valve (AFT22) 

BIOPAC Rigid Coupler (AFT11E) for T-valve to tubing 

BIOPAC Coupler (AFT11C) for T-valve to calibration syringe 

BIOPAC Smooth Bore Tubing-35 mm (AFT7) 

BIOPAC Disposable Nose Clip (AFT3) 

BIOPAC Disposable Mouthpiece (AFT2) 

BIOPAC Disposable Bacterial Filters (AFT1)—requires 2 filters 

Computer running Windows XP or higher, or Mac OS X 

Biopac Student Lab PRO software 

BIOPAC Data Acquisition Unit (MP36/MP35/MP30) 

OPTIONAL: BIOPAC Calibration Gas Cylinder (16% O 2 , 4% CO 2 ), with regulator and tubing 

The following measures are also required: 

Ambient temperature in °C 

Ambient barometric pressure in mmHg 

Pressure of water vapor at ambient temperature = 22.4 mmHg 



Setup 

Hardware 


The Gas-System2 sensors are factory calibrated prior to shipping. 

 

 

The O 2 sensor is a zirconia solid electrolyte with a 0.1-25% sensing 

range and an estimated 5-year lifetime. It runs hot, which helps to 

burn off humidity. 

The CO 2 sensor uses a humidity-repellant (hydroponic) membrane 

and has a sensing range of 0-5%. It uses non-dispersive infra-red 

diffusion with single-beam IR and a self-calibrating algorithm. It also 

runs hot, which helps to burn off humidity. 

1. The Gas-System2 module is supplied with a 5 VDC @ 4 amp wall adapter. Plug the adapter into the 

main power supply and insert the adapter plug into the DC Input on front of the Gas-System2 module. 

2. Flip up the power switch on the Gas-System2 to turn it "ON." 

o The unit should warm up for at least five minutes before calibration, so it is suggested that 

you turn it on now and then complete setup. 

3. Plug the transducers into the MP3X as follows: 

Transducer MP3X CH # 

SS11LA CH 1 

O2 line (from the Gas-System2) CH 2 

CO2 line (from the Gas-System2) CH 3 




4. Turn on the MP unit (assuming the AC100A power adapter has already been connected). 

5. Connect the airflow accessories as follows: 

Air Flow Accessory 

AFT1 filter 

SS11LA transducer 

AFT22 non-rebreathing T-valve 

AFT11E coupler 

AFT7 tubing 

AFT26 or AFT6 calibration syringe 

AFT11C coupler 

Connects to 

SS11LA transducer, on the "Inlet" side 


AFT11E coupler 

AFT7 tubing 

Gas-System2 inlet (back side) 

AFT11C coupler 


Note: The above setup uses the AFT26 or AFT6 calibration syringe. For recording, 

you must replace the calibration syringe with an AFT1 filter and an AFT2 

disposable mouthpiece (connected to each other and to the AFT22 T-Valve). 




AFT7 tubing to Gas-System2 inlet 

6. Pump the calibration syringe through enough cycles to fill the chamber with ambient air. 

o AFT26, pump 3-4 times. 

o AFT6, pump 10-12 times. 

Software 

1. Launch the BSL PRO software on the host computer. 

The program should create a new "Untitled1" window. 

2. Open the VO 2 and RER Template by choosing File > Open > choose Files of type: Graph Template 

(*GTL) > File name: “H19 V02 & RER.gtl” 

The template will establish the required settings. 

This particular setup will provide a reading that, at any point in time, indicates the absolute 

volume of oxygen consumed, carbon dioxide produced, and the respective respiratory 

exchange ratio in the last 60 seconds. Units are liters because it is a volume measure, not a 

flow rate. 

3. Save As the desired file name. 

Calibration 

The following calibration steps are outlined below: 

A. Calibrate flow transducer 

B. Calibrate O 2 channel (CH2) 

C. Calibrate CO 2 channel (CH3) 

D. Normalize moist gas to volume occupied by dry gas at 0°C, 760 mm. 

E. Optional: Calibrate for time interval (template is based on 60-second interval). 

Note: In the calculation channel formulas, the following assumed values were used for gas concentrations in 

normal atmosphere (chamber flooded with ambient air): 

0 2 = 20.93% CO 2 = 0.04% N 2 = 79.03% 

The optional Stage 2 gas calibration is not required, but can be performed using the small line inlet on the back 

panel of the Gas-System2 module. If you introduce calibration gases into the chamber, adjust the calculation 

channel expressions for the real gas values. 

If you perform a gas calibration, use the following ranges: 

Flow (inspired): calibrate within the range of 0 to 13 liters/sec 

O 2 concentration: calibrate in range of 21% to 16% O 2 

CO 2 concentration: calibrate in range of .04% to 4% CO 2 



Flow 


1. Select MP3X > Setup Channels. 

2. Click the wrench icon for CH 1. 

3. Click the Scaling button. 

4. Hold the Calibration Syringe such that the SS11LA hangs from it in an upright position. 

5. Click on the Cal1 button. 

6. Subtract “3,000” from the Cal1 input value and enter the result in Cal2 input value (Cal2 input value 

should be 3,000 less than Cal1 input value). 

7. Confirm Cal1 scale value= 0 and Cal2 scale value=10. 

8. Click OK. 

9. Set the equipment down. 




O 2 

Per Setup, the chamber should have been flooded with ambient air prior to O 2 calibration! 



3. Click the Cal2 button. 

4. Enter “20.93” into the Cal2 scale value. 

5. Confirm both Cal1 input value= 0 and Cal1 scale value=0. 

6. Click OK. 

CO 2 

Per Setup, the chamber should have been flooded with ambient air prior to CO 2 calibration! 




4. Enter “0.04” into the Cal1 scale value. 

5. Add “10” to the Cal1 input value and enter the result as Cal2 input value. 

6. Confirm Cal2 scale value=1.04 

7. Click OK. 

Note: The sensor output is 10 mV per 1% C0 2 . With proper calibration, if the sensor rails, it will read as 5% 

CO 2 . 




OPTIONAL Stage 2 Calibration (BIOPAC Calibration Gas Cylinder required) 

O 2 

Per Setup, the chamber should NOW be flooded with a calibrated gas (16% O 2 , 4% CO 2 )! 




4. Enter “16” into the Cal1 scale value. 

5. Click OK to dismiss scaling dialog. 

6. Click OK to dismiss “Input Channel Parameters” dialog for CH 2. 

CO 2 

Per Setup, the chamber should NOW be flooded with a calibrated gas (16% O 2 , 4% CO 2 )! 




4. Enter “4” into the Cal2 input value. 

5. Click OK to dismiss the scaling dialog. 

6. Click OK to dismiss “Input Channel Parameters” dialog for CH 3. 



Gas Normalization 


Normalize moist gas to volume occupied by dry gas at 0 deg C, 760mm 

1. Use this table to find the normalization factor. 

2. Click the wrench icon for C3 Vis (STPD). 

3. Enter the normalization factor in the formula: C2*(normalization factor) 

Be sure to enter the value as 0.x, with the leading decimal. 

4. Click OK. 

Optional: Interval 

Only required if you change the time interval from the template, which is set for a 60-second interval. 

1. Click the wrench icon for C2. 



3. Calculate the Samples entry as follows: 

Integration Samples = Time Interval x Sample rate 

(Template setting: Integration Samples = 60 sec x 100 samples/sec = 6000 samples) 

4. Enter the new Samples value. 

5. Click OK. 

Recording 


This lesson records absolute volume of O 2 and CO 2 in a 60-second interval. Units are “liters” because this 

provides a volume measure, not a flow rate. If you change the time interval, you must adjust the Integrate 

formula. 

Hints for minimizing measurement error: 

1. Ensure that the connections among the various pieces of equipment are fairly 

tight to prevent contamination via room air. 

2. Try to start the recording immediately after a full exhale. This will prevent 

receiving results with an O 2 inspiration value less than that of the total expiration 

value (although the averaging will minimize the inaccuracies that this would 

cause). 

3. It's very important that any extraneous volumes are minimized between the 

subject and the T-valve. Additional volumes affect the effective expired gas 

concentration levels. 

4. The tubing must be connected to the SS11LA on the unlabeled side (that does 

NOT say "Inlet"). 

Preparation 

1. Remove the calibration syringe from the transducer setup. 

2. Establish the recording connections as shown below: 

Airflow Accessory Connects to 

AFT1 Filter 

AFT22 T-Valve (in the existing setup) 

AFT2 disposable mouthpiece AFT1 Filter 




Segment 1 

1. Have the subject put a nose clip on. 

2. Click START in the PRO software. 

3. Have the subject breathe normally for at least 2 minutes. 

o Subject must breathe long enough to ensure that the 5-liter mixing tank has been filled, thereby 

enabling it to average those breaths. 

o The subject should breathe into the disposable bacterial filter (AFT1) through a disposable 

mouthpiece attachment (AFT2). 

4. Click STOP in the PRO software. 

Optional Segments 

Recovery from Exercise 

Breathe through the mouthpiece 

1. Have the subject perform several minutes of medium-to-strenuous exercise. 

o If desired, record the heart rate and correlate VO 2 to heart rate. 


3. Have the subject breathe normally for at least 2 minutes. 




Hyperventilation 



2. Have the subject breathe normally for at least 1 minute. 

3. Have the subject hyperventilate for at least 1 minute; enter a marker at start of hyperventilation (Esc on PC, F9 on 

Mac). 

4. Have the subject breathe normally for at least 1 minute. 


Notes 

To save recorded data, choose File menu > Save As… > file type: BSL PRO files 

(*.ACQ) File name: (Enter Name) > Save button 

To erase all recorded data (make sure you have saved it first), and begin from Time 0, 

choose: MP menu > Setup Acquisition > Click Reset 



Analysis 


The VO 2 and RER template will display channels as follows: 

Channel Displays Measure 

CH 1 Fi (inspired Air Flow) Value 

CH 2 O 2 E (expired O 2 ) Value 

CH 3 CO 2 E (expired CO 2 ) Value 

CH 40 (C1) N 2 E (expired N 2 ) Value 

CH 41 (C2) Vi (ATP) Value 

CH 42 (C3) VIS (STPD; inspired) Value 

CH 43 (C4) VES (STPD; expired) Value 

CH 44 (C5) VO 2 (STPD) Value 

CH 45 (C6) VCO 2 (STPD) Value 

CH 46 (C7) RER Value 

1. Channels 40-43 are not displayed because they are calculation channels required for conversions. You 

can show/hide channels by Ctrl-clicking the channel box. 

2. Note that the VO 2 and RER measurements (bottom two channels) vary smoothly with time. The 

graphical and continuous nature of this recording and calculation method provides significant 

information regarding the changes of these variables over time. 

3. To display measurements, click the measurement icon. 

4. To display markers, click the flag icon. 

5. To display grids, click the grid icon. 



Appendix 

GRAPH TEMPLATE SETTINGS 


Click here to open a PDF of the graph template file settings. The BSL PRO Graph Template file automatically 

establishes the settings shown in the table. 

Definitions 

These abbreviations are used in the discussion and calculation channel Expression formulas for VO 2 and RER: 

ATP 

Concentration of gas at ambient temperature and pressure 

CO 2 

Fi 

Carbon dioxide 

Est. concentration ambient environment: 0.04% 

CO 2 e = Carbon Dioxide fractional concentration in expired air 

Inspired air flow (ATP) 

N 2 

Nitrogen 

N 2 e = Nitrogen fractional concentration in expired air 

N 2 e = 100 – (CO 2 e + O 2 e) 

O 2 

Pb 

PH 2 0 

RER 

STPD 

Oxygen 

Est. concentration in ambient air: 20.93% 

O 2 e = Oxygen fractional concentration in expired air 

Est. concentration in expired breath: 16% oxygen 

Ambient barometric pressure (e.g. 745 mmHg) 

Ambient pressure of water vapor (e.g. 22.4 mmHG) 

Respiratory Exchange Ratio 

RER = VCO 2 / VO 2 

Concentration of gas at standard temperature and pressure, dry 

Ta Ambient temperature (e.g. 24 deg. C) 

VCO 2 

VO 2 

Vi 

Volume of carbon dioxide produced (STPD) per 60-sec interval 

Real-time carbon dioxide production 

VCO 2 = (1/100)*[(Ves* CO 2 e) – (Vis*.04)] 

Volume of oxygen consumed (STPD) per 60-sec interval 

Real-time oxygen consumption 

VO 2 = (1/100)*[(Vis*20.93) – (Ves*O 2 e)] 

Inspired air volume (ATP) per 60-sec interval 

Vi = Integrate (Fi) over 60 seconds. The number of samples is equal to the time interval x sample 

rate (template is 60 sec. x 100 samples/sec = 6000 samples). Select "Average over samples." 

Vis 

Inspired air volume (STPD) per 60-sec interval 

Vis = C2 * Normalization Factor (see Table of Normalization Factors) 

If normalization factors are unavailable, you can use this formula: 

Vis = Vi*(273/(273+Ta))*((Pb-PH 2 0)/760) 

where 

Ta = ambient temperature 

Pb = barometric pressure 

PH 2 O = 22.4 mmHg (assumed value) 

Ves 

Expired air volume (STPD) per 60-sec interval 

Ves = (Vis*79.03) / N 2 e 

Note: If you change the time interval from 60 seconds, you must adjust the Vi formula. 



Normalization Factors 


The following table lists the factors required to reduce volume of moist gas to volume occupied by dry gas at 

0°C, 760 mm. OBR is an abbreviation for observed barometric reading, uncorrected for temperature. 

Fahrenheit values are roughly converted and rounded from Celsius values as T F =(9/5*T C )+32ºF. 

Important! 

All factors are 0.x, with x being the value from the table. Be sure to 

include the leading decimal when you complete your calculation. 

ºC 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 

ºF 59 61 63 64 66 68 69 72 73 75 77 79 81 82 84 86 88 90 

OBR 

700 855 851 847 842 838 834 829 825 821 816 812 807 802 797 793 788 783 778 

702 857 853 849 845 840 836 832 827 823 818 814 809 805 800 795 790 785 780 

704 860 856 852 847 843 839 834 830 825 821 816 812 807 802 797 792 787 783 

706 862 858 854 840 845 841 837 832 828 823 819 814 810 804 800 795 790 785 

708 865 861 856 852 848 843 839 834 830 825 821 816 812 807 802 797 792 787 

710 867 863 859 855 850 846 842 837 833 828 824 819 814 809 804 799 795 790 

712 870 866 861 857 853 848 844 839 836 830 826 821 817 812 807 802 797 793 

714 872 868 864 859 855 851 846 842 837 833 828 824 819 814 809 804 799 794 

716 875 871 866 862 858 853 849 844 840 835 831 826 822 816 812 807 802 797 

718 877 873 869 864 860 856 851 847 842 838 833 828 824 819 814 809 804 799 

720 880 876 871 867 863 858 854 849 845 840 836 831 826 821 816 812 807 802 

722 882 878 874 869 865 861 856 852 847 843 838 833 829 824 819 814 809 804 

724 885 880 866 872 867 863 858 854 849 845 840 835 831 826 821 816 811 806 

726 887 883 879 874 870 866 861 856 852 847 843 838 833 829 824 818 813 808 

728 890 886 881 877 872 868 863 859 854 850 845 840 836 831 826 821 816 811 

730 892 888 884 879 875 871 866 861 857 852 847 843 838 833 828 823 818 813 

732 895 890 886 882 877 873 868 864 859 854 850 845 840 836 831 825 820 815 

734 897 893 889 884 880 875 871 866 862 857 852 847 843 838 833 828 823 818 

736 900 895 891 887 882 878 873 869 864 859 855 850 845 840 835 830 825 820 

738 902 898 894 889 885 880 876 871 866 862 857 852 848 843 838 833 828 822 

740 905 900 896 892 887 883 878 874 869 864 860 855 850 845 840 835 830 825 

742 907 903 898 894 890 885 881 876 871 867 862 857 852 847 842 837 832 827 

744 910 906 901 897 892 888 883 878 874 869 864 859 855 850 845 840 834 829 

746 912 908 903 899 895 890 886 881 876 872 867 862 857 852 847 842 837 832 

748 915 910 906 901 897 892 888 883 879 874 869 864 860 854 850 845 839 834 

750 917 913 908 904 900 895 890 886 881 876 872 867 862 857 852 847 842 837 

752 920 915 911 906 902 897 893 888 883 879 874 869 864 859 854 849 844 839 

754 922 918 913 909 904 900 895 891 886 881 876 872 867 862 857 852 846 841 

756 925 920 916 911 907 902 898 893 888 883 879 874 869 864 859 854 849 844 

758 927 923 918 914 909 905 900 896 891 886 881 876 872 866 861 856 851 846 

760 930 925 921 916 912 907 902 898 893 888 883 879 874 869 864 859 854 848 




762 932 928 923 919 914 910 905 900 896 891 886 881 876 871 866 861 856 851 

764 936 930 926 921 916 912 907 903 898 893 888 884 879 874 869 864 858 853 

766 937 933 928 924 919 915 910 905 900 896 891 886 881 876 871 866 861 855 

768 940 935 931 926 922 917 912 908 903 898 893 888 883 878 873 868 863 858 

770 942 938 933 928 924 919 915 910 905 901 896 891 886 881 876 871 865 860 

772 945 940 936 931 926 922 917 912 908 903 898 893 888 883 878 873 868 862 

774 947 943 938 933 929 924 920 915 910 905 901 896 891 886 880 875 870 865 

776 950 945 941 936 931 927 922 917 912 908 903 898 893 888 883 878 872 867 

778 952 948 943 938 934 929 924 920 915 910 905 900 895 890 885 880 875 869 

780 955 950 945 941 936 932 927 922 917 912 908 903 898 892 887 882 877 872 

ºF 59 61 63 64 66 68 69 72 73 75 77 79 81 82 84 86 88 90 

ºC 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 

From Peters and Van Slyke, Quantitative Clinical Chemistry, vol. 11. (Methods) Baltimore: Williams and Wilkins, 1932, reprinted 1956.

BSL PRO Lesson H19 - Biopac

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