lungs at altitude

Question 1

impact of altitude on atmospheric pressure

Answer 1

as altitude increases, atmospheric pressure decreases

Question 2

what is atmospheric pressure at sea level

Answer 2

approximately 760mmHg

Question 3

what is acclimatisation

Answer 3

describes the normal physiological changes through which the body adapts to decreasing levels of oxyge

Question 4

what is hyperventilation

Answer 4

• a notable sign of acclimatisation
• occurs when peripheral chemoreceptors detect a decrease in arterial pO2 and increase the respiratory rate to compensate
• can result in hypocapnia and alkalosis
• these prevent a further increase in respiratory rate due to CO2 being sensed by the central chemoreceptors in the cerebrospinal fluid (CSF) by removing carbon dioxide

Question 5

what causes respiratory rate to further increase after hyperventilation

Answer 5

• after a few days, the pH of the CSF and arterial blood are returned to normal following a response from the CSF and kidneys involving bicarbonate ions.
• meaning the respiration rate can continue to increase.

Question 6

what is 2,3-Biphosphoglycerate (2,3-BPG)

Answer 6

• formed during glycolysis in the red blood cell
• binds to one of the beta-chains of the haemoglobin, allowing deoxygenation and a right hand shift of the oxyhaemoglobin curve
• respiratory alkalosis from hyperventilation leads to a rise in 2,3-BPG after a couple of days, which contributes to decreased oxygen in the blood

Question 7

what is Polycythaemia

Answer 7

• a feature of acclimatisation
• an increase in the haematocrit
• much slower to develop

Question 8

what causes polycythaemia

Answer 8

an increase in the number of circulating red blood cells

even though at altitudes polycythaemia is a physiological response, it can cause hyperviscosity which can become pathological

Question 9

what does the kidney release in response to hypoxia

Answer 9

the hormone erythropoietin

Question 10

what does erythropoietin do

Answer 10

stimulates red cell production in the bone marrow
- results in increased haemoglobin levels
- hence an increased capacity to carry oxygen.

Question 11

what is altitude sickness

Answer 11

results from acute exposure to low partial pressure of oxygen at high altitudes

Question 12

symptoms of altitude sickness

Answer 12

• Headaches
• Nausea and vomiting
• Shortness of breath
• Tachycardia
• Peripheral oedema
• Pulmonary oedema

Question 13

what can make altitude sickness worse

Answer 13

ascending to very high altitudes rapidly can often make this worse