Hyperbaric

Question 1

hyperbaric:

Answer 1

gas at high pressure

Question 2

Dalton law

Answer 2

the total pressure of a mixture of gases is the sum of their individual partial pressures

Question 3

composition of air, dry and wet at standard atmospheric pressure of

Answer 3

760mmHg

Question 4

Dry air: Gas partial pressures =

Answer 4

N2 = 593
O2 = 160 
CO2 = 0.23
Ar = 7
H2O = 0 

ALL IN mmHG

Question 5

Wet air: Gas partial pressures

Answer 5

N2 = 557
O2 = 150 
CO2 = 0.21
Ar = 6.6
H2O = 47 

ALL IN mmHg

Question 6

concentration of a gas dissolved in a solution can be determined using

Answer 6

Henrys Law

Question 7

Henrys Law =

Answer 7

[Gas]dis = s X Pgas

s = solubility of coefficient (mM/mmHg) 
P  = partial pressure of the gas

Question 8

oxygen-haemoglobin dissociation curve at room pressure

Answer 8

• partial pressure of O2 = 100mmHg

- O2 content 20 mlO2/dl blood

Question 9

every ten metres you dive down barometric pressure increases by

Answer 9

1atm

• so at ten metres down u have 2 times of gas
  N2 –>~600mmHg to ~1200mmHG

O2 –> ~160mmHg to ~320mmHg

These gases will dissolve more into the blood

Question 10

who’s law explains why more gas will dissolve into blood at deep depths

Answer 10

Henrys Law

Question 11

problems of diving arise when

Answer 11

you come back up

Question 12

normally partial pressure of CO2 in mixed venous blood =

Answer 12

~46mmHg

Question 13

following gas exchange pp of CO2 and O2 in alveolar air and at ten metres

Answer 13

CO2 = ~40mmHg 
O2 = ~100mmHg 

they double, so CO2 from the lungs will start to diffuse back into the body, causes increase in arterial CO2

Question 14

at ten metres down there is a ___ of pressure in the gas in the lungs and ___ in volume

Answer 14

doubling

reduction

Question 15

At ten metres due to CO2 diffuse back into lungs and metabolic production elevate arterial CO2 this acts on

Answer 15

respiratory centre –> increases urger to breathe. However O2 levels still high enough so compensation to triggered

Question 16

During return to surface from dive

Answer 16

• pressure in lungs returns to normal
• fall in alveolar CO2 and O2
• causes rapid fall in arterial CO2 and O2
• drop in cerebral O2 can lead to a blackout! (deep water blackout)

Question 17

in short main problem to avoid in diving

Answer 17

damage to lungs as gas expands, breath out as you rise

Question 18

__ areas of body are relatively resistant to effects of high pressure

Answer 18

liquid

Question 19

where do problems with pressure on the body arise:

Answer 19

air spaces: there are no issues if the gas pressures can equilibrate (Barotrauma)

Question 20

Barotrauma:

Answer 20

injury arising from pressure changes, lungs and ear

Question 21

ears and pressure:

Answer 21

problems arise if eustachian tube is blocked and doesnt allow gas movements between throat and middle tube

• as u dive down water pressure increases and pushes on ear drum
• ear drum/blood vessels may burst

Question 22

sinuses and pressure:

Answer 22

• air filled chambers in your head tubes connecting them to throat
• pathways blocked = can’t equilibrate = build up of pressure
• possible bleeding into sinuses

Question 23

over inflation of the lungs: (coming up and u don’t breath out)

Answer 23

• rupture of alveoli so gas can escape from lungs into the body
• arterial gas embolism
• pneumothorax
• mediastinal and subcutaneous emphysema

Question 24

pneumothorax =

Answer 24

• collapsed lung due to gas escaping lungs and rests outside lungs and chest wall (normally plasma there)
• expansion of lungs and chest wall is disrupted

Question 25

arterial gas embolism:

Answer 25

-air can pass into blood vessels, so bubbles of gas in blood = dangerous (brain --> blocks arteriole = stroke / go to heart blocking coronary artery)

Question 26

Mediastinal Emphysema:

Answer 26

- air bubbles in the tissue around the heart/trachea/large blood vessels - if this gas expands increase pressure around these organs/vessels

Question 27

subcutaneous emphysema:

Answer 27

gas bubbles form in the neck, effect blood vessels going to the brain/head

Question 28

nitrogen narcosis:

Answer 28

- nitrogen almost acting as anaesthetic & alters ion conductance - symptoms appear at 30m deep, get worse deeper u go, fatal at 90m - as depths increase the concentration of nitrogen N2 in the blood increases - N2 higher solubility in lipid than blood - being 'drunk' symptoms - 'martini' effect

Question 29

prevention of nitrogen narcosis:

Answer 29

- limit depth and duration of dive | - change in gas composition: use gas mixture replacing N2 with helium

Question 30

oxygen toxicity:

Answer 30

- at atmospheric pressure Hb is almost fully saturated, increasing pressure an extra O2 is dissolved in the plasma - depths of 40m (5atm) oxygen pp is roughly equivalent to breathing 100% O2 at sea level - short term = OK - -long term = respiratory tract damage & CNS problems - problems linked to increased levels of free radicals

Question 31

Oxygen toxicity breathing air at 90m (10atm) can lead to

Answer 31

seizures and coma

Question 32

oxygen toxicity solution:

Answer 32

reduce the oxygen concentration in the mixture

Question 33

decompression sickness:

Answer 33

build up of N2 in tissues with time at depth - if return to sea level too quickly this gas comes out of solution and forms bubbles - overcome by slow return to normal pressures

Question 34

types of decompression sickness:

Answer 34

two main classes: - Type 1 DCS: linked to pains produced by bubbles forming in muscles and joints - Type 2 DCS: more serious: bubbles in CNS, lungs and CVS