WK3: Pulmonary Responses to Exercise in the Trained State Flashcards
Why does gas exchange between the lungs-blood and blood-tissue levels?
Difference in pressure gradients (mmHg) result in diffusion. From a high pressure gradient to low pressure gradient.
At rest what is the pressure of O2 in the alveoli and in the blood?
Alveoli= 100 mmHg Blood= 40 mmHg
What happens to blood volume in the pulmonary capillaries during exercise?
Increases by 3x the resting volume. This maintains the low velocity of blood flow.
Why does the PO2 of arterial blood remain lower than alveolar blood?
Some of the blood in the alveoli passes through poorly ventilated alveoli (some blood doesn’t get alveolarised) - venous admixture.
What are the two factors that impair gas transfer capacity at the alveolar capillary membrane?
1) A build up of pollutant layer that thickens the alveolar membrane
2) Reduced Alveolar surface area
These both increase the time before alveolar-capillary gas equilibrates.
How long does it take for the Alveolar gas-Blood gas to equilibrate?
0.25 seconds
Why is oxygen concentration in bodily fluids low?
Oxygen is relatively insoluble
How much O2 dissolves in the blood when alveolar PO2 is 100mmHg?
3 ml of O2 for every 1L of blood
What is the blood volume of a 70kg person?
5L
At rest how much O2 is dissolved in the fluid section of blood in a 70kg man?
15ml
This would sustain 4 seconds of life
How much haemoglobin is in 1 Litre of blood?
men= 15g, women= 14g
May explain differences in aerobic capcity
How much oxygen is in 1 gram of haemoglobin?
1.34 ml
How much oxygen is normally carried by haemoglobin ?
20ml of oxygen per 1L of blood
1.34ml (O2 per 1g of haemoglobin) x 15g (haemoglobin in the blood)
What is cooperative binding?
The union of oxygen with haemoglobin
What does the oxygen dissociation curve outline?
The relationship between the partial pressure in the blood and the oxygen saturation in haemoglobin.
The changes in oxygen affinity in a red blood cell in the form of an S shaped curve.
- Oxygen binding to haemoglobin changes its shape
- This change in shape makes it easier for more oxygen to bind to it, increasing the affinity
- More oxygen will bind
- As spaces are filled further by oxygen, the rate of oxygen saturation decreases and plateaus, where increasing levels of PO2 in the blood will not bring about more saturation.
How do you calculate percentage saturation?
O2 combined with haemoglobin
_________________________ x100
O2 capacity of haemoglobin
Why does a large amount of oxygen not detach from haemoglobin at rest?
The demands for oxygen are lower
These act as a reserve for when there is a sudden increase in metabolic needs (higher O2 demands)
What causes the release of large amounts of O2 from haemoglobin?
The decrease in tissue PO2, due to the cells using more oxygen
What does 2,3 DPG stand for and how does it affect the haemoglobin?
2,3 diphosphoglycerate (produced by the RBC)
Loosely binds to haemoglobin, reducing it’s affinity for oxygen and causing a greater release to tissues for a given decrease in PO2
What people have an increased level of 2,3DPG production?
Those with cardiopulmonary disorders
Those who live at high altitude
What is myoglobin?
Iron containing globular protein in skeletal and cardiac muscle that provides an intracellular store for O2
What happens when the dissociation curve is shifted to the right?
There is an increase in dissociation of oxygen from haemoglobin
At any given blood PO2 on the binding curve, the oxygen saturation will be lower
What causes the haemoglobin shift?
- This curve shifts from left to right depending on where in the body the haemoglobin is (muscles and placenta needs O2 to be dissociated from haemoglobin so it is shifted to the right).
- Low PH, high temp, high PCO2, more 2,3 DPG, fast transit time = right shift
- High PH, low temp, low PCO2, less 2,3 DPG = left
- Fetal haemoglobin= larger left shift
How much metabolic CO2 moves into the blood plasma?
5%
Where does most of CO2 get stored?
Most combines with water forming carbonic acid.
Carbonic anhydrous and RBC speed up this process
What is the symbol for maximal oxygen uptake?
VO2 max
What does endurance training result in?
Increases the maximum rate of transport of O2 via the blood (better O2 conductance- easy flow of atmospheric O2 to the mitochondrion)
Utilisation of O2 (at muscles), due to increased capillaries (3x more), increased mitochondria, increased myoglobin and increased slow twitch fibres
Reduced CO2 production at rest and at a given moderate work rate(due to more ffa oxidation for ATP synthesis)
Reduced ventilator demands at any given work rate (reduced CO2 and increased LT)
Higher ventilation rates as higher metabolic rates can be achieved (increased VO2 max)
Increased : SV, HR reserve (due to reduced Resting HR), max Q, active-muscle oxygen extraction, ventilator demands at VO2 max, FFA oxidation at low work rates.
What is the ramp incremental test?
A smooth increase in work rate until a limit is reached.
Provides a gradational stress (gradually harder) that spans the work rate range. This helps to avoid sudden increases in high work rates.
VO2 max established when work rate is seen to continuously increase, however VO2 plateaus
What is the issue with the ramp incremental test?
Only 30% can achieve this plateau and so raises the VO2 max vs plateau issue
Why is VO2 peak/max important?
Best predictor of death
Define moderate work rate and heavy work rate
Moderate= Below lactate threshold and steady state VO2
Heavy= increases in VO2 and lactate production
What is critical power?
The highest stage you can maintain exercise below VO2 max
Anything above this will result in fatigue due to increased lactate production
What should we base work intensity on and why?
Should base it on Lactate thresholds and not VO2 max
Lactate thresholds occur at a particular percentage of someone’s VO2 max. This position can vary depending on the athlete and so they could find a percentage of their VO2 max easier to work at than the untrained working at the same percentage.
What are uses of the LT?
- Judging efficacy of endurance programmes
- Optimising the intensity of work rates
- Judging appropriateness to undergo abdominal/thoracic surgery
- Index of life expectancy in heart disease
What is a main limitation to endurance training improvements?
Lungs cannot adapt and so limit amount of O2 to be delivered
This means even if heart, circulation and muscle systems are trained, they will exceed the pulmonary system, resulting in no further increase in training effects
What were the results of chronic obstructive pulmonary disease patients after 12 weeks of endurance training?
Baseline= low lactate threshold, increased lactate very quickly
Post= increase in lactate was less quick, relying less on anaerobic pathways due to increased LT
Why is resting ventilation lower after endurance training?
Post training you get a shift to fatty acid oxidation
Fatty acid oxidation produces less CO2 than Carbohydrate oxidation, meaning less ventilation is needed to remove it
What is the relationship between ventilation and work intensity?
Ventilation increases linearly up until the lactate threshold
What does MVV stand for and what doe it show
Maximal Voluntary Ventilation
In trained highly fit athletes, they do not reach their MVV as a breathing reserve remains when exercising, so we aren’t limited by the lungs as they are not being used fully
What type of exercise improved diaphragm strength over 2 weeks?
HIIT- high intensity interval training
What is EIAH?
Exercise Induced arterial hypoxaemia
Lower than normal oxygen saturation in the arterial blood (SaO2), after acute exercise
Who is EIAH most prevalent in?
Athletes with high VO2 max
What are the potential causes of EIAH?
- Hypoxia- Is the PO2 of atmosphere sufficient? (YES)
- Hypoventilation (lack of breathing)- Is enough O2 getting to the alveoli? (YES)
- Diffusion- Is there a limitation to O2 diffusing from the alveoli to RBC in the pulmonary (lung) capillaries?(Progressively limited by high Q - transit time)
- Shunt - Is systemic arterial blood (oxygenated blood from the heart to the body) being diluted by systemic venous blood (deoxygenated blood from the body to the heart) in the heart, whilst it beats? (Increased pulmonary shunts)
- Ventilatory Perfusion mismatch- Does the distribution of blood flow in the lungs match to the distribution of ventilation- Does the amount of air getting to the alveoli match the amount of blood reaching the alveoli? (pulmonary hypertension/ high pressure, capillary stress failure and pulmonary oedema may contribute to increasing Va/Q mismatch)
What are the definitions of the different levels of EIAH?
Mild: oxygen arterial saturation(SaO2) is between 93%-95%
Moderate: SaO2 is between 88%-93%
Severe: SaO2 is less than 88%
How much do PaO2 and SaO2 values fall by when working at near VO2 max?
PaO2 (partial pressure of arterial oxygen)- 40mmHg fall
SaO2 (haemoglobin oxygen saturation)- 15% fall
What does EIAH also bring about?
Poor respiratory compensation for metabolic acidosis of high intensity exercise
Suggested to be caused by a reduced ventilator drive or limitations to alveolar ventilation
What comes with an increased maximum cardiac output after endurance training?
Due to being able to work at greater work rates, there is a greater demand for Ve to clear additional CO2.
Also results in faster pulmonary (lung) blood flow. This results in gas exchange problems
Greater stress on vascular system, contributing to hypoxemia
How do you calculate mean capillary transit time (tc) and what does it represent?
capillary volume (ml) \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ capillary flow (ml/s)
The speed at which blood travels through capillaries
What is the transit time at rest?
80ml (cap vol)
____________ = 0.8sec
100ml/s (cap flo)
What is the max transit time during exercise in an untrained individual?
80ml (cap vol) 80ml
_____________ = __________ = 0.24s
20,0 L/min(cap flo) (x1000, /60) 333.3ml/s
What is the max transit time during exercise in a trained individual?
80ml (cap vol) 80ml
_____________ = __________ = 0.16s
30.0L/min (cap flo) (x1000, /60) 500ml/s
What is the issue with the increased transit time in the trained state?
Presents an oxygen diffusion limitation due to reducing the time it takes for pass through capillaries and pick up O2
Normally at rest the PO2 in the blood is 40% which then rises to 100% when they leave after an 0.8 second transit time. Maximal effort in trained athletes produce a transit time of 0.2sec which would severly diminish the percentage of PO2 of blood moving away from the alveoli.
Capillary recruitment is used to prevent critical reductions in transit times.
How does a fast transit time affect the HbO2 dissociation curve?
Shifts it to the right
The level of CO2 in the blood doesn’t change, so CO2 binds to haemoglobin, reducing its affinity for O2.
Who can be affected by the intrapulmonary arteriovenous shunt mechanism?
Anyone at high intense exercise
why can shunt be useful?
reduces pulmonary pressure to avoid damage of capillaries at the lungs
When is the ventilation-perfusion ratio (Va/Q) exaggerated?
High intensity exercise in trained athletes when pulmonary vascular pressure is high
Causes increased capillary filtration, which can lead to interstitial oedema during exercise (interstitial fluid in the space in the chest causing swelling)
Ventilation is not affected
How thin is the blood-gas barrier in the lung?
0.1-0.3mm
What factors can impair the blood-gas barrier in trained athletes?
High Vt and fr can increase mechanical strain in the lung
High Q max (without increased blood distribution) increases pulmonary blood flow, pulmonary filtration and pulmonary vascular pressure
How do you calculate Va
VCO2 x K K- constant (863)
_______ VCO2- CO2 flow out
PaCO2 PaCO2- arterial CO2 levels
What is the ratio of VCO2 and VO2 produced when comparing cho and ffa oxidation?
VO2= 1:1 (CHO:FFA) VCO2= 1:0.7
Need more oxygen to produce ATP when using FFA, but produce less CO2 for every ATP produced
What is the RER?
respiratory exchange ratio -
CO2 produced:O2 used
What is the range and average LT in relation to VO2 max?
40-85%
average=50% VO2 max
Define exercise intensity
A common set of physiological stressor consistent, among subjects with the sensation of exertion
What are average VO2 max readings for different individuals?
HEart failure= 10ml/kg/min Sedentary= 30 ml/kg/min Normal= 45 ml/kg/min Conditioned= 53ml/kg/min Endurance athlete= 85ml/kg/min
