Respiratory Adaptation Flashcards
1
Q
Describe the changes in ventilation in exercise
A
- Respiratory- resting (12-18), peak exercise (45-60)
- Tidal volume- resting (0.5L), peak exercise (2.25L)
- Minute ventilation- resting (6L/min), peak exercise (175L/min)
2
Q
What are the respiratory responses to exercise?
A
- Increased rate and depth of ventilation
- In exercise both oxygen consumption and carbon dioxide production increase
- To facilitate oxygen delivery & carbon dioxide removal, both respiratory rate and tidal vol increase
- Respiratory function normally chemically controlled
3
Q
Describe blood gases in exercise
A
- Arterial bg unchanged in moderate exercise
- Ventilation appropriate- adjusted to maintain arterial PaCO2
- PO2 doesn’t change (drop in arterial pH at high intensity, lactic acid- anaerobic resp, arterial pH drops- acidotic hyperventilation)
- Maintaining bg by maintaining ventilation
- Ventilation increases exponentially with exercise
4
Q
How is respiration controlled in exercise?
A
- Dorsal respiratory group firing more frequently
- Peripheral receptors firing within normal ranges
- Mechano/chemoreceptors in skeletal muscles
- All involved in fine-tuning to control respiration
5
Q
Do the lungs limit oxygen?
A
- Low-to-moderate intensity exercise- pulmonary system is not a limitation
- Maximal exercise- not thought as limitation in healthy at sea level, may limit in elite endurance athletes, new evidence that resp muscle fatigue occurs at high intesity
6
Q
What are the effects on respiration?
A
- Reduced ventilation at same work rate- maybe lower blood lactic acid levels–>less feedback to stimulate breathing
- Overall- training has little effect on vent capacity
- Can go longer without becoming acidotic
- Any given work rate before training- higher vent- comes down to how acidotic at any given rate
- No direct impact on ventilation
7
Q
Describe the effect of altitude on respiration
A
- Atm press drops –> oxygen drops
- Oxygen ~12kPa, PaO2-~7kPa, respiratory failure occurs at <8kPa
- Inspired gas less, alveolar gas less, arterial blood less, mixed ve§nous blood is less, extracting relatively more oxygen
8
Q
What is the interaction between PaO2 and PaCO2?
A
- When oxygen drops–> vent increases (peripheral receptor firing)- hyprventilation leads to low PCO2
- Nothing occurs with central chemoreceotors- carbon dioxide drops–> decreased vent
- Vent increases and slows again as central chemoreceptors try to normalise PaCO2
9
Q
How does respiratory adaptation occur during ascent to high altitude initially?
A
- Initially- hypoxic hyperventilation due to peripheral chemoreceptors
- Leads to lower PaCO2 and respiratory alkalosis (altitude sickness)
10
Q
Describe the action of the central chemoreceptor
A
- CSF contains little protein- buffer capacity much less than plams- sensitive pH changes
- Plasma H+ won’t cross BBB
- Plasma CO2 does, so CSF pH proportional to PaCO2 (short-term)
- Settles higher vent than at sea level- not as high as initially
11
Q
How does respiratory adaptation to occur after 2-3 days at high altitude?
A
- Respiratory alkalosis and decrease in PaCO2- decreases vent response to low PaO2
- Hyperventilation decreases and PaO2 falls
- CSF compensation for alkalosis returns CSF pH to normal after 1-2 days- hypoxic hyperventilation recovers
- Renal compensation for alkalosis by excreting extra HCO3- takes ~2-3 days
12
Q
Describe chronic adaptation to altitude
A
- Regulation of 2 mutually exclusive factos
- HR decreases, decreased hyperventilation and hypoventilation
- Increased RBC
- Over generations- response less pronounced
- Pulmonary arteries constrict during hypoxia
- High altitude pulmonary oedema- major vasoconstriction in lungs, fluid leaks out of capillaries
13
Q
Describe hypoxia and erthropoiesis
A
- Normally, production of erythropoietin stimulated by tissue hypoxia
- Erythropoietin- glycoprotein coming from mainly from kidney
- Increases RBC production in bone marrow and promotes red cell maturation
- Increases oxygen carrying capacity
14
Q
How does BPG stabilise deoxy-Hb?
A
- BPG binds between lysine and histidine residues of β glib chains
- Oxygenated Hb has a different conformation and prevents binding
15
Q
Describe BPG and haemoglobin dissociation
A
- BPG has limited impact on loading
- Reduced BPG increases the saturation
