Lecture 22 Flashcards
What does ventilation do when you go from set to exercise?
Oxygen and Carbon Dioxide ventilation can increase 20 to 30 fold.
What happens during steady state exercise?
The rate of oxygen consumption is equal to the rate at which oxygen is coming into the mouthing the rate at which oxygen is entering the cells.
What occurs for the max ventilation of oxygen to increase 20fold from when at rest?
When you exercise you increase the tidal volume, frequency of breathing, slightly reducing the oxygen fraction in the lung. Increase the stroke volume, heart rate, and profound increase in amount of oxygen extracted.
What are the respiratory responses to exercise?
The rate of metabolic energy expenditure is proportional the rate of mechanical work = power.
Describe he work of breathing expiraratory
During heavy exercise there is a disproportionate increase in the amount of work of breathing.
Describe “local” (peripheral) circulatory effects of exercise?
There is:
1. Decreased tissue partial oxygen pressure.
2. Decreased tissue pH.
3. Increased tissue partial carbon dioxide pressure.
4. Increased tissue temperature.
Each of these cause local vasodilation (i.e. increased local capillary blood-flow) and elevation of local partial pressure of oxygen.
What causes a right shift of the HbO2 relation?
- Decreased tissue pH - blood becomes more acidic.
- Increased partial carbon dioxide pressure.
- Increased tissue temperature.
This will reduce the amount of oxygen we can onload at lower partial pressures of oxygen.
What happens at the alveolar capillary interface?
The amount of oxygen we can transfer to the capillaries, depends on the diffusing capacity of the lung and the difference in partial pressure of oxygen in the alveoli and the capillary.
How do we increase the diffusing capacity?
By opening up more pulmonary capillaries, this will give us greater area and reduce diffusing distance. With exercise there is decrease in partial pressure of oxygen in the capillary. This is due to the effect of cardiac output on the Transit time of erythrocytes through the pulmonary capillaries.
Describe the effect of transit time on the pulmonary capillary end?
When you decrease transit time you will decrease the saturation of oxygen on the RBC. when we factor the right shift equilibrium in (when exercising), increases the change of saturation (send blood out with less oxygen in it).
Describe the interrelation between blood flow and R–Shift of HbO2 relation?
When you increase cardiac output, and you decrease partial pressure (to get a decrease in oxygen content) you will still get the same ventilation rate. When you have right shift (exercise) you can’t load on as much oxygen, but can come down to a lower value and still keep the same ventilation rate (at 3.6Lmin-1) at reduced cardiac output. Same ventilation at reduced blood flow with no loss of oxygen venous pressure.
Why doesn’t the mixed venous oxygen pressure fall much lower?
There are tissues that are getting blood which are not muscle tissues. Cardiovascular system has to keep other tissues happy (i.e. brain and skin). We are producing heat, and we have to get rid of the heat. So we send the heat to our skin and by perspiring. Increased blood flow to the limbs (particularly the arms). There is a compromise between the need to get rid of heat and keep exercising.
