Introduction

Question 1

While the atmospheric composition remains unchanged with increasing altitude

Answer 1

an exponential fall in barometric pressure results in a decreased partial pressure of inspired oxygen (PIO2) with height above sea level

Question 2

So while on a standard day the PIO2 at sea level sits at approx. 160mmHg

Answer 2

at high altitude for example base camp everest 5000m above sea level the drop in barometric pressure leads to a PIO2 of approximately 88mmHg, a significant decrease from that of sea-level

Question 3

Therefore when native sea level dwellers travel to high altitude they encounter

Answer 3

alveolar hypoxia and hypoxemia due to the reduced fraction of inspired O2 (FIO2) available in the atmosphere