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| Wed. 8 am lab group 1 | Wed. 8 am lab group 2 | |
| Wed. 10 am lab group 1 | Wed. 10 am lab group 2 | |
| Wed. 12 lab group 1 | Wed. 12 lab group 2 |
As we have discussed in previous labs and in lecture, one of the
most widely used methods of work quantification in both clinical and research
applications of exercise physiology involves the measurement of oxygen
consumption. Maximal oxygen uptake (VO2max)
is widely accepted as the best index of cardiorespiratory endurance capacity,
while submaximal and resting oxygen uptake measurements provide useful
information relative to metabolic efficiency.
Maximum oxygen uptake can be measured using any number
of experimental protocols, ergometric devices, and gas analysis procedures.
Regardless of the testing and analysis method utilized, however, at least
three specific criteria must be met to confidently call a VO2max
test a true "max test". These are as follows:
1. a peak or plateau in oxygen uptake with continued increases in workload
2. a peak or plateau in heart rate with continued increases in workload
3. a RER value of >1.10
*4. a blood lactate level of >14 mmol (this criteria is not used as extensively as the others)
5. RPE = or > 18
VO2max measurements
are used for several reasons including:
1. to discriminate between those people with high endurance ability from those with only ordinary or minimal capacityWhen measuring the oxygen uptake of an exercising subject two parameters which must be measured are 1) the minute ventilation--the amount of air the subject inspires or expires per minute, and 2) the oxygen and carbon dioxide concentration of the expired air.
2. to evaluate the effects of different training procedures on endurance ability
3. to measure the metabolic cost of various work tasks under normal or novel environmental conditions (heat, altitude, cold) in order to develop more effective ways of working and eliminating fatigue
4. as a diagnostic tool in the detection of impaired cardiorespiratory function or muscle metabolic diseases
In determining oxygen consumption, we are interested in knowing how much oxygen has been removed from the inspired air. Because the composition of inspired air remains relatively constant, it is possible to determine how much oxygen has been removed from the inspired air by measuring the amount and composition of the expired air. When this is done, the expired air contains more carbon dioxide, less oxygen, and more nitrogen. It should be noted, however, that nitrogen is inert in terms of metabolism; any change in its concentration in expired air reflects the fact that the number of oxygen molecules removed from the inspired air are not replaced by the same number of carbon dioxide molecules produced in metabolism. This results in the volume of expired air ( VE, STPD) being unequal to the inspired volume (VI, STPD). For example, if the RQ is less than 1.00 (ie: less CO2 produced to O2 consumed), and 3 liters of air are inspired, less than 3 liters of air will be expired. In this case, the nitrogen concentration is higher in the expired air than in the inspired air. This is not to say that nitrogen has been produced, only that nitrogen molecules now represent a larger percentage of the VE compared to the VI (see McArdle, Katch, & Katch: pp 799-803). Because nitrogen is an inert gas, its concentration can also be used to determine the volume of air ventilated through a derivation called the Haldane Transformation.
PURPOSE
The purpose of this laboratory is to introduce the manual method of gas collection/analysis and to measure resting and maximum oxygen consumption.
MATERIALS
1. treadmill or bicycle ergometer
2. work clock
3. heart rate monitor
4. 1-way breathing valve; low resistance, large-bore tubing; Hans Rudolph 3-way valve
5. electronic CO2 and O2 analyzers
6. thermometer, barometer
7. meterological balloons or computer system
8. Rayfield ventilation (gas) meter
PROCEDURES
1. choose two men and two women to perform measures of resting and exercise metabolism.
2. choose a trained and untrained subject to perform a maximal treadmill test; attach a heartrate monitor; adjust headset and mouthpiece; adjust noseclip
3. set up gas collection bags using the 100 liter meterological balloons, the 3-way Hans Rudolph valve, and the Rayfield gas meter
4. measure room temperature and barometric pressure; using Tables C-1 & C-2 on pages 797 & 798 in your text, determine the vapor pressure (PH2O) and the STPD correction factor respectively; place in the appropriate place on the datasheet
5. assign group members to perform the following
tasks:
a. monitor workload and clock6. have subject straddle the treadmill belt; start treadmill; begin data collection after subject has warmed up properly (approx 3-5 min of low intensity exercise)b. monitor heartrate
c. operate three-way valve
d. attach and replace ventilatory bags
e. analyze gas composition
f. determine gas volumes (two technicians)
g. record data (two technicians)
7. follow the treadmill protocol as determined prior to the test
8. Gas Collection and Analysis
a. once data collection has begun, make sure that all the subject's expired air is collected in the balloons; one balloon will be collected during for a minute after 5 min of rest. A small sample of gas will be drawn from the balloon into the oxygen and carbon dioxide analyzers (timed 1 min sample); record the gas concentrations on the data sheet in the appropriate place. The volume of the gas will be determined by driving the contents of the balloon through the Rayfield gas meter; record the volume and temperature of the gas in the appropriate place on the datasheet
All the calculations which must be performed in order to determine the oxygen uptake are described below.
1. Gas volumes vary under different conditions of pressure and temperature as described by Charles' and Boyle's laws. Note that respiratory gases are saturated with water vapor-the amount of saturation depends on the gas temperature. If oxygen consumption values and energy expenditures are to be compared under different conditions at different times and places, it is necessary to account for the factors affecting gas volumes. The gas volumes recorded from the Rayfield gas meter are in a condition referred to as ATPS or Ambient Temperature, Pressure, Saturated. Consequently, all volumes are corrected to conditions of Standard Temperature, Pressure, Dry or STPD where:
Temperature = 0o C or 273 absolute or K
Pressure = 1 atmosphere or 760mmHg
Dry = free of water vapor
By correcting to STPD, the molecular quantity of oxygen (ie: the absolute number of oxygen molecules present in a gas) is always constant regardless of the atmospheric conditions. All metabolic data is expressed by convention, in STPD values, whereas ventilatory volumes are expressed as BTPS values or Body Temperature, Pressure, Saturated. Rarely are values published in the ATPS condition (see text pages 796-799).
a. compute the STPD correction factor as follows:
STPD factor = 273 X PB - PH2O
(273 + Tgas) 760
where:
Tgas = temp (in centigrade) of gas passing through meter
PB = atmospheric pressure in mm Hg (from barometer)
PH2O = water vapor pressure in mm Hg (from Table C-1)
b. correct the measured gas volume(s) to STPD according to the following equation:
VE (STPD) = VE (ATPS) X STPD factor
where:
VE (ATPS) = volume of expired air under ambient conditions
2. Calculation of the quantity of inspired air using expired volumes:
FE(N2)
VI (STPD) = VE (STPD) X FI(N2)
where:
FE(N2) = fraction of N2 in expired air; ie: 1.0- [FE(O2) + FE(CO2)]
FI(N2) = .7904
3. Calculation of the oxygen uptake in L/min: **see equations above for variables
VO2(L/min) = VE (STPD) X [(FEN2 X .265) - FEO2
4. Calculate the VO2 in ml/kg/min:
VO2 (L/min) X 1000ml/L
VO2 (ml/kg/min) = body wt (kg)
5. Calculate the workload in METS:
VO2(ml/kg/min)
METS = 3.5 ml/kg/min
6. Calculation of carbon dioxide production:
VCO2 = VE (STPD) X (FECO2 - .0003)
7. Calculation of RQ:
VCO2 produced
VO2 consumed
RESULTS CONTINUED
1. Perform the calculations and complete the table
on the datasheet. Submit your data sheet with your laboratory report.
Make the following 4 Graphs (make sure you have correct
units, We will not accept extra credit graphs unless they are correct).
For 4 extra credit lab points! These graphs are due in lab
in ONE WEEK!