Pulmonary Exercise Physiology Flashcards
What is anaerobic threshold?
VO2 at which anaerobic energy production begins to supplement the aerobic energy system
The point during graded exercise that a greater rate of energy production is required than what can be met by the aerobic system.
How is anaerobic threshold measured?
Disproportionate increase in lactate accumluation in blood and ventilatory parameters during exercise on increasing intensity
What are the major aspects of lactate threshold?
1) Lactate Threshold
- Phase during graded exercise when blood lactate exhibits an abrupt increase
2) OBLA
- point of further increase in blood lactate (greater than 4.0mM)
What causes LT?
Increase in required anaerobic glycolytic supply to contribute to total energy needs Increase epinephrine (stimulate glycogenolysis) Blood shunt causing vasoconstriction in non-working tissue
What are the 2 major aspects of ventilatory threshold?
1) Ventilatory threshold
phase when VE increases disproportionately in relation to VO2
2) Respiratory Compensation
Process of respiratory assistance in buffering anaerobically generated H+ via bicarbonate reaction
What are other methods of identifying VT?
V-shaped slope
Ventilatory equivalent for VO2 (VE/VO2)
Ventilatory equivalent for VCO2 (VE/VCO2)
Excess CO2 elimination
What causes VT?
Increase in perception of energy demand by respiratory center in the brain resulting in increased VE
Increased afferent neural activity from muscle and joint receptors
Increase H+ and CO2 level that stimulate chempreceptors and stimulate an increase in VE
What is the link between VT and LT?
Increase H+ and CO2 levels
Stimulation of central and peripheral chemorecptors
Both stimulate and increase in VE
Does LT cause VT?
No
How can VT occur without an LT?
primary neural factors that stimulate ventilation and are not directly dependent on anaerobic stimulation of the chemoreceptors
LT does not necessarily cause VT
Is AT important?
YES especially for endurance athlete
AT is highly correlated with performance times
AT is a quantifiable setting for aerobic endurance training
Does VE limit Exercise?
Not likely in healthy individuals because the lung is over built for exercise (greater capacity than what is used)
Limiting factor under some environmental conditions and in combination with some medical conditions
What are ventilation training results?
1) VE is somewhat lower at rest and is lower during sub-maximal exercise (greater efficiency and lower afferent neural activity, greater aerobic capacity)
2) VE max is increased with endurance training (higher overall cardiorespiratory training (higher VO2max requires higher VE
Does AT respond to training?
There is an increase in the speed, PO and VO2 at AT after training which enhances performance Due to: increase oxidative capacity of skeletal muscles increase in lactate and H+ removal rate glycogen sparing increase fat oxidation Increase O2 delivery Delay FT Delay epinephrine release
What is the function of the pulmonary system?
Supply O2
Remove CO2
Assist with regulation of acd-base balance
What is inspiration?
Increase in thoracic cavity due to downward contraction of the diaphragm Lifting and rotating of the rib cage by the scaleni and external intercostals Causes a drop in pressure in the lung Allows the air to flow in
What is expiration?
VE is due to relaxation of the diaphragm and scaleni and external intercostal
During rest it is a passive recoil of lung and related tissue
During exercise the internal intercostals and abdominal assist
Increase in intrapulmonic pressure pushes air out of the lung
What are static volumes?
Measured through forced vital capacity which is the total amount of air that can be expired after a full inspiration
What are dynamic volumes?
Depends on the lung volume and speed of the moving volume
FEV1= forced expiratory volume in one second
FEV1/FVC = measure of expiratory ability and general resistance
Normal is greater than 80%
What does pulmonary ventilation refer to?
movement of air in and out of the lungs
What is minute ventilation?
The product of frequency and tidal volume
VE=f x TV
VE at rest = 3-15 l/min
VE max = can exceed 200 l/min
What is alveolar ventilation?
The portion of air inspired that is used for gas exchange
What is anatomical dead space?
What is physiological dead space?
the piping to the alveoli
the portion of alveoli that are not well perfused with air and not full involved in gas exchange.
What is actual gas exchange at alveoli primarily dependent on?
Tidal volume, frequency and dead space
What are the four controls of ventilation?
1) The brain
- Medial medulla, hypothalamus and other sub cortical areas
2) Afferent neural activity
- Joint/limb and chest wall movement stimulates VE response
3) Chemoreceptors (stimulated by partial pressures)
- Central: medulla chemoreceptors
- Peripheral: carotid and aortic arch
- Pulmonary and muscles
4) Temperature Receptors:
- Blood temperature can influence ventilation
What happens to ventilation during exercise?
Before: disproportionate increase mostly due to the stimulation from cerebral cortex to VE (anticipatory response)
Onset of exercise: VE increases rapidly to match the demand for O2
Steady State: the can be a slight overshoot in VE during the adjustment to a workload that does not precisely match metabolic demand most likely due to the effects of several stimuli on VE
What happens during a graded exercise test up to anaerobic threshold?
During GXT up to AT VE increases in proportional
What happens during a graded exercise test above anaerobic threshold?
VE increases disproportionately and is highest at max exercise intensity
What is VO2max?
Max rate at which the body can intake, transport and utilize O2 for phosphorylation of ATP
Measure of the aerobic system
What is absolute VO2max?
total amount of oxygen/min the body is consuming
What is relative VO2max?
absoulte VO2max/body mass
What is the fick equation?
VO2 = Q x a-vO2diff
What are the limiting factors of VO2max?
1) Central Factors: Blood volume CaCo2 (content of O2 in blood) Stroke volume Heart Rate Hemaglobin concentration 2) Peripheral Factors O2 extraction (amount the will diffuse) Capillarization Oxidative capacity (number and size of mitochondria) Myoglobin concentration (stores O2 in cell)
What are characteristics of VO2max?
Gender differences: higher in men (larger heart, blood volume,muscle mass) Exercise Mode: Treadmill-Bike-Rowing-Swimming-hand ergometer Age: Decreases 10%/10yrs after the age of 30 Hereditary and training: 80% genetic 20% training Effects of Environment Altitude, pollution, diet
What are the effects of training on VO2 max?
Increase central factors = increase Q max
Increase peripheral factors = increase a-vO2 difference
Other Factors
-Systolic BP stays the same or increases
-HR stays the same or slightly decreases
What is gas exchange?
Primary gases involved are O2 and CO2
Diffusion of O2 into the blood from the alveoli and CO2 out of the lungs
What are the 3 key points about gas exchange?
1) Gases exert pressure
2) The greater the concentration of gas on a volume the greater the pressure
3) Gas flows from high to low pressure to low pressure
What is Henry’s law?
The amount of gas dissolved in a fluid depends on pressure and solubility
What is partial pressure?
It is determined by:
1) Pressure of the gases (barometric pressure)
2) The concentration of gas in a volume (fractional percent)
What are the gas exchange concepts?
Gas exchange as the tissue is simply a reversal of what occurs at the lungs but with different PO2 and PCO2
Arterial O2 diffuse onto tissue and CO2 diffuse out of tissue into venous blood
There is a continuous mix of O2 and CO2 at the capillaries
What is the oxyhemoglobin dissociation curve?
As pressure increases saturation increases
1) partial pressure of the lungs
2) partial pressure of O2 in the cell
Where does the oxyhemoglobin curve shifts during exercise?
Why?
Shifts down and to the right
Increase in O2 extraction
Decrease content and saturation of O2
There is more oxygen in the cell
Is lung gas exchange a limiting factor during maximal exercise?
Not under normal conditions. PO2 in arteries decreases during max exercise. This decreases % of saturation Hb leaving the lungs. EIH
Decrease less than 91%
Less O2 delivered to working muscles
What are possible mechanisms for pulmonary limitation?
1) Capillary transit time too quick
2) Pulmonary Capillary Damage
3) Air Quality
4) Intrapulmonary Shunts (blood vessels that bypass the alveoli)
What is the result of high Q on lung function?
Some elite endurance athletes also have reported tasting blood after intense exercise.
High mechanical stress of high blood pressure/ volume disrupts pulmonary capillaries
What is pulmonary training?
Pulmonary diffusion capacity is increased.
Refers to the volume of gas that diffuses through the alveolar capillary membranes/min for a pressure difference of 1mmHg
Increased due to an increase in lung surface area utilization and possibly some increase in lung volumes with training
EIB and EIA
10% lower FEV1 after exercise EIB recover quickly
15% lower FEV1 EIA 30-90 min
