lecture 20 Flashcards
(10 cards)
what are the components of VO2?
convection
- VO2 = Q x a-VO2diff (fick’s principle)
- Q = HR x SV
- a-VO2 = CaO2 (Hb and %SaO2) - CvO2)
diffusion
- VO2 = Dmo2 x (PO2cap - PO2mito)
- O2 uptake = O2 diffusion capacity for skeletal muscle x (driving pressure for O2 into mitochondria)
possible sites of VO2max limitation
- pulmonary function
- issues in the lungs - cardiac output
- O2 carrying capacity of blood
- muscle diffusion
- skeletal muscle metabolic factors
- Pulmonary Function (Ve)
does reaching a maximal limit of ventilation determine VO2max?
- Normal Vd
- increase Vd (breathing through tube)
- pulmonary diffusion (%SaO2)
does the ability of lungs to transport inspired O2 from aveoli to pulmonary capillaries limit VO2max?
at maximal exercise SaO2 rarely falls below 95% (what it is at rest)
room air — 21%
hyperoxia — 26%
COPD is a condition that prevents adequate ventilation for the alveoli (decrease Va/Q)
- breathing high O2, increase VO2max by improving pulmonary diffusing capacity
- increase 17%
- cardiac output
does the heart’s ability to raise cardiac output limit VO2max?
- no it increases it
if the heart could pump more blood per minute, VO2max would increase
reducing HR via B-blockage decrease VO2max
- O2 carrying capacity of Blood ([Hb])does the amount of O2 that we can carry in the blood determine VO2max?
- increase Hb = increase VO2max
- decrease Hb = decrease VO2max
CaO2 = ([Hb] x 1.34 x SaO2) + (PaO2 x 0.003)
- muscle diffusing capacity
ability of the muscle to extract O2 from blood to muscle mitochondria
muscle diffusion capacity
1. distance between capillary and mitochondria
- decrease distance = increase a-VO2diff
2. contact area
- increase surface area = increase a-VO2diff
3. pressure gradient b/w capillary and mitochondria
- increase capillary pressure = increase a-VO2diff
is there a limit to the amount of O2 that we can extract from arterial blood?
- muscle venous blood containsa fair amount of O2 even at VO2max (O2 saturation= 15%)
decrease driving pressure = decrease VO2max
- skeletal muscle metabolic factors
is their a maximal ability of muscle to utilize O2 for ATP resynthesis?
VO2max related to mitochondria volume
- wood-mouse, fittest animal on planet
VO2max of whole muscle vs a piece of that muscle
- untrained; more utilization problem than delivery
- trained; more delivery problem than utilization
what limits VO2max?
it depends on the person, their environment, and the type of exercise
- if one stops they all stop, it’s a cycle and they all follow the same path
- if one change, they all change
test your self
increase blood volume after exercise
- phlebotomy; just took that blood out, decrease blood volume
increase cardiac output after exercise
- phlebotomy; just took out blood, decrease cardiac output
