Environmental physiology-pressure (year 2)

Question 1

what is the concentration O2 in the atmosphere?

Answer 1

roughly 21%

Question 2

partial pressure of O2 does what?

Answer 2

reduces with altitude

Question 3

Dalton’s law

Answer 3

The pressure exerted by a mixture of gases is equal to the sum of the partial pressure of each gas in the mixture

Ptotal=P1+P2+P3+…

Question 4

what is sea-level and Everest pressure?

Answer 4

sea-level= 160 mmHg

Everest= 48 mmHg

Question 5

Law of Gaseous diffusion?

Answer 5

Gas molecules of higher pressure moves in the direction of gas molecules of a lower pressure.

Question 6

movement of air in the cardiorespiratory system.

Answer 6

ambient air–> lungs–>haemoglobin–>cardiac output–>muscle blood flow–>oxygen extraction–>cellular metabolism.

Question 7

Haemoglobin

Answer 7

Partial pressures make theses load (affiliate) or upload (disaffiliate).

Partial 
pressures dictate 
how O2 is 
released and 
acute altitude 
this can shift to 
left (to load lung)

Question 8

Acute responses to altitude?

Answer 8

Acute hypoxia–>chemoreceptors–>ventilation and symp. activation–>Respiratory alkalosis and Hr, CO increases
=Exercise translation= decrease in work for ~phys. cost or increase in phys. cost for ~ work.

Question 9

Altitude?

Answer 9

Mount Everest:
• 29,028 ft (8,848 m)

• Atmospheric P = 230 mmHg
• Inspired PO2 = 21% x (230 mmHg)
• = 48 mmHg

• Oxygen sat. = <60%
– Unacclimatised person
– Unconscious in 45 seconds
– Dead in 4 to 6 minutes

Question 10

Accommodation of altitude?

Answer 10

A) Hyperventilation
Decrease arterial PO2–> stimulation of peripheral chemoreceptors–> increased rate
& depth of breathing

B) Tachycardia
Peripheral chemo. Response –>increase HR &
cardiac output

Question 11

Acclimatisation of altitude (chronic)

Answer 11

Increased 2,3-DPG conc. in RBC:

hypoxia–>H+ ↓(in RBC)–> ↑2,3-DPG –>↓oxygen affinity of Hb–> increased offloading

Question 12

Henry’s Law?

Answer 12

Partial pressure of gases↑ then solubility ↑ (i.e. absorbed into blood/tissue)

So, gases like N2 are released into tissues more easily

Question 13

Henry’s Law: why is it important?

Answer 13

• Help you to understand risk of decompression sickness (coming up too quick!);

• Is used to assess gas requirements as O2 will be
used faster at deeper levels;

Pressure effects on:
• Lung 
• Sinuses
• GI tract 
• Mask

Question 14

Oxygen toxicity?

Answer 14

• FiO2 greater than 0.6 atm (60%) can lead to pulmonary
toxicity

• FiO2 greater than 1.6 atm (160% O2) toxic in minutes

High/prolonged PO2–>

Cellular ROS–>

React in cell =
damage function –>

Damage lung or
brain cells or vessels

Question 15

Nitrogen narcosis (at depth)

Answer 15

• Build of N2 in tissues and blood;

• Deeper = increase release
(Henry’s and Boyle’s)

• Effects on the CNS:

• Effect on synapses owing to ion channel dysfunction (Clark,
2015)

Question 16

Rapid ascents?

Answer 16

• N2 is released from the
tissues too quickly;

• N2 Bubbles cause a variety of
issues:
• Blood flow
• Skin
• Heart
• Joints