Lungs At Altitude

Question 1

How is the death zone defined

Answer 1

Over 8000 m

Question 2

Sea level

Answer 2

Altitude = 0m
Atmospheric pressure = 100KPa
PiO2 = 0.20 x 100KPa = 20KPa

[PiGas = FiGas x Patm]

Question 3

Sea level normal blood gases

Answer 3

PaO2 10.5 - 13.5 KPa
PaCO2 4.5 - 6.0 KPa
pH 7.36 - 7.44

Question 4

Sea level normal PaO2

Answer 4

10.5-13.5 KPa

Question 5

Sea level normal PaCO2

Answer 5

4.5-6.0 KPa

Question 6

Sea level normal pH

Answer 6

7.36-7.44

Question 7

Right shift oxygen dissociation curve due to

Answer 7

Acidity
2,3 DPG*
Increased temperature
Increased PCO2

[*2,3 biphosphoglycerate]

Question 8

FiO2 does what with altitude

Answer 8

Remains constant at approx 0.21

Question 9

PiO2 does what with altitude

Answer 9

Falls

Question 10

Lungs at altitude- normal response

Answer 10

Hypoxia leads to..
Hyperventilation at 10000ft altitude
Increases minute ventilation
Lowers PaCO2
Alkalosis initially
Tachycardia
Adaptive changes
Multiple
Alkalosis compensated by renal bicarbonate excretion

Question 11

Barometric pressure at an altitude of 0m

Answer 11

101 KPa

Question 12

Barometric pressure at an altitude of 4800m

Answer 12

57 KPa

Question 13

Barometric pressure at an altitude of 6300m

Answer 13

46 KPa

Question 14

Barometric pressure at an altitude of 8100m

Answer 14

37.5 KPa

Question 15

Barometric pressure at an altitude of 8848m

Answer 15

33.5 KPa

Question 16

A-aDO2- alveolar arterial O2 difference

Answer 16

Whilst normal pretty complete equilibration of O2, there normally is a small difference between Alveolar and arterial oxygen partial pressure

= PAO2 – PaO2 = (approx) 1KPa

Question 17

PAO2 =

Answer 17

PiO2 - PaCO2/R

Question 18

PaO2 =

Answer 18

PAO2 - (A-aDO2)

Question 19

Adaptive changes of lungs at altitude

Answer 19

Multiple
Alkalosis compensated by renal bicarbonate excretion

Question 20

Hyperventilation at 10000ft altitude

Answer 20

Increases minute ventilation
Lowers PaCO2
Alkalosis initially
Tachycardia

Question 21

High altitude illness examples

Answer 21

Acute mountain sickness
High altitude pulmonary oedema (HAPE)
High altitude cerebral oedema (HACE)

Question 22

Why does oxygen dissociation curve shift to the right

Answer 22

Shifts to right to give off more oxygen because areas which are more metabolically active have a higher CO2 concentration and lower pH

Question 23

Acute mountain sickness

Answer 23

Recent ascent to over 2500m
Lake Louise score >/= 3
Must have a headache and one other symptom

Question 24

Ascending…

Answer 24

PiO2 falls
Decreased PAO2
decreased PaO2
Peripheral chemoreceptors fire (eg carotid)
Activates increased ventilation (Va), reducing PaCO2
Increased PAO2
increase PaO2

Question 25

Hyperventilation

Answer 25

PaCO2 DROPS PaO2 REMAINS HIGHER

Question 26

Alveolar oxygen tension as you go higher

Answer 26

Linear drop in PaO2

Question 27

Treatment of acute mountain sickness

Answer 27

Can only be reliably treated by descent [o2, recompress, acetazolamide]

Question 28

Blood gases at height

Answer 28

Lower PaO2 Lower PaCO2 Higher end of pH (alkalosis)

Question 29

At risk of acute mountain sickness if

Answer 29

Recent travel to over 2500m, after a few hours Sea level normal dwelling Altitude, rate of ascent and previous history of AMS Younger people

Question 30

Respiratory quotient

Answer 30

0.8

Question 31

High altitude pulmonary oedema

Answer 31

Unacclimatised individuals Cough, shortness of breath Rapid ascent above 8000ft (2438m) 2-5 days -Risk less if sleeping below 6000ft (1829m) -Speed of ascent slower (300-350m/day) -Individual susceptibility -Exercise -Respiratory Tract Infection Incidence 2% at 4000m

Question 32

Treatment of high altitude pulmonary oedema

Answer 32

O2 Decent urgent Gamow bag Steroids Ca2+ blockers? Sildenafil

Question 33

High altitude cerebral oedema

Answer 33

Serious AMS not a pre requisite Confusion Behaviour change Immediate descent Symptoms may resolve relatively quickly

Question 34

Treatment of high altitude cerebral oedema

Answer 34

Immediate descent Gamow bag

Question 35

Who should avoid flying

Answer 35

Pneumothorax -Not with a closed pneumothorax Infectious TB Major haemoptysis Very high oxygen requirements at sea level -> 4L/minute

Question 36

High altitude pulmonary oedema cause

Answer 36

Pulmonary capillaries become leaky

Question 37

Effective cabin atmosphere

Answer 37

1890m

Question 38

Cabin pressure

Answer 38

81 KPa

Question 39

Atmospheric pressure at altitude of 10000m

Answer 39

21 KPa

Question 40

If SpO2 is low, what must happen before flying <95%

Answer 40

Physiological test eg hypoxic test

Question 41

Hypoxic hypoxia

Answer 41

Low PaO2 due to high altitude Above 10000ft

Question 42

Symptoms of HAPE

Answer 42

Cough Frothy sputum Breathlessness Chest pain

Question 43

Symptoms of HACE

Answer 43

Confusion Ataxia