The Lungs At Altitude

Question 1

The death zone

Answer 1

Over 8000m

Altitude above which difficult to sustain life without added O2

Question 2

At sea level

Answer 2

Altitude = 0m
Atmospheric pressure = 100KPa

PiO2 = 0.20 x 100KPa = 20KPa

Question 3

Normal Barometric pressure

Answer 3

Slide 12

Question 4

A-aDO2

Answer 4

PaO2 does not equal PAO2- Whilst normal pretty complete equilibration of O2, there normally is a small difference between Alveolar and arterial oxygen partial pressure

In healthy people the difference in PaO2 ans PAO2 is 1

= PAO2 – PaO2 = (approx) 1KPa

Question 5

Normal blood gases

Answer 5

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

FiO2 remains constant at approx 0.21
PiO2 falls with altitude

Question 6

Normal response- hypoxia leads to…

Answer 6

Hyperventilation at 10000ft altitude in response to peripheral chemoreceptors sensing hypoxia. This leads to
-Increases minute ventilation
-Lowers PaCO2
-Alkalosis initially
-Tachycardia developed

Adaptive changes if skiing over a longer period of time, eg a week
-Multiple
-Alkalosis compensated by renal bicarbonate excretion to normalise pH

Question 7

Graph

Answer 7

At 10000 ft hyperventilation occurs, enabling you to have a higher PaO2 for a given CO2

Dotted line B- no hyperventilation leads to individual becoming progressively hypoxic with altitude

Line A at 10000ft- hyperventilation starts, enabling a higher PaO2 for a given altitude and a drop in CO2 as the person is elevated

Question 8

High altitude illness

Answer 8

Acute Mountain Sickness

High Altitude Pulmonary oEdema (HAPE)

High Altitude Cerebral Oedema (HACE)

Question 9

Acute mountain sickness- definition:

Answer 9

Recent ascent to over 2500m

Lake Louise score is greater than or equal to 3- sum of the score for the four symptoms (headache, nausea/vomiting, fatigue, and dizziness/light-headedness)

Must have a headache and one other symptom

Question 10

Individuals who are at more of risk of Acute mountain sickness

Answer 10

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 11

Treatment of AMS

Answer 11

Descend; the only reliable treatment [o2, recompress, acetazolamide]
You should never go up higher if you have AMS

Question 12

High Altitude Pulmonary Oedema

Answer 12

Found in 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

Involves oedema being shaded out into the interstitial of the lung

Question 13

Treatments for High Altitude Pulmonary Oedema

Answer 13

O2
Descend urgently
Gamow bag
Steroids
Ca2+ blockers?
Sildenafil

Question 14

Sea level SpO2- measurement of how much oxygen your blood is carrying as a percentage of the maximum it could carry

Answer 14

> 95% No action

92-95% with no risk factors No Action

With risk factors Hypoxic test

< 92% Needs O2

On LTOT Increase flow rate (Long Term Oxygen flow Therapy)

Question 15

High Altitude Cerebral Oedema

Answer 15

Serious

AMS not a pre requisite

Confusion

Behaviour change

Immediate descend

Symptoms may resolve relatively quickly

Gamow bag- if descending is not possible