Why is harder to breathe at higher altitudes?

Related questions

1. Do exercise breathing masks work?
2. How quickly can you improve vo2 max?
3. At what age does physical strength peak?
4. At what altitude does hypoxia occur?
5. At what age does athletic ability begin to decline?
6. What is an incubator for startups?
7. What is the opposite of hypoxia?
8. At what elevation do you need oxygen?
9. What is the early sign of hypoxia?
10. Why is it harder to breathe at night?

Tags

1. #causes
2. #difficult
3. #easily
4. #makes
5. #blood
6. #vascular
7. #lower
8. #systems
9. #pounds
10. #level
11. #oxygen
12. #about
13. #atmospheric
14. #altitudes
15. #pressure
16. #membranes
17. #permeable
18. #enter
19. #breathe
20. #selectively
21. #square
22. #through