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Lecture 6

Kinesiology 2230A/B Lecture Notes - Lecture 6: Lactate Threshold, Vapor Pressure, Carbonic Anhydrase

Course Code
Kinesiology 2230A/B
Glen Belfry

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Ventilation Lecture 6
Friday, March 15, 2019
6:08 PM
Water Vapour Pressure
Average energy of particles in a fluid are governed by temperature
The greater the temperature, the greater the energy
Some particles may have energy greater than average
o These can escape from the attractive forces holding the water together
The greater the number of particles in the air, the greater the water vapour pressure
o The air you brought in has little vapour pressure
o 100% humidity in the lungs - diffuses from capillaries into lungs and evaporation occurs with
increasing temperature and water vapour molecules end up in the air in the lungs
Condensation occurs during exhalation
o Temperature drops and holds less water vapour
Ventilation Control - At Rest Increasing in Altitude
1. PAO2 decreases as altitude increases
PO2 drops, ventilation doesn’t change
2. Continued change in PO2with increasing altitude, now starting to see a change in ventilation
Deliver less O2 by Hb and chemoreceptors stimulate to increase ventilation
3. PCO2 levels are stable over initial drop in PO2
CO2 levels are associated with metabolism, so amount produced is stagnant unless doing exercise
PCO2 continues to drop, ventilation increases - CO2 drops in blood
Increased ventilation gets rid of more CO2
4. pH doesn't change initially
Becomes more alkaline
Ventilation During Exercise - Estimating Lactate Threshold
Ratio between ventilation and O2 consumption decreases
Ventilation isn't increasing as quickly as O2 consumption
Lactate threshold:
o Ventilation goes up faster than O2 consumption
o Lactate and H+ accumulate
o Carbonic anhydrase upregulates ventilation
Ventilation doesn't change, it levels off:
o As CO2 is produced, ventilation increases (1:1)
o Changes in ventilation are very sensitive to changes in PCO2
o Ventilatory, aerobic, and lactate thresholds all occur at the same time
o Anaerobic threshold - when Ve/VO2 and VCO2/VO2 increases without increases in Ve/VCO2
Ventilation During Exercise - Graph
Exercise intensity increases and ventilation goes up linearly, then CO2 production starts to
increase non-linearly
CO2 production reflects the ventilation changes - very steep at the end
o Respiratory compensation - change in slope
Lactate concentration - extra increase in ventilation and CO2 causes lactate to accumulate
pH starts to drop, which stimulates ventilation independent of changes in CO2 production
H+ starts accumulating when there is no bicarbonate left
o Blood becomes very acidic
PTEO2 - partial pressure entitled O2 - how much O2 is in a breath
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