2. 2

3. As human beings ascend to higher altitudes
during mountain climbing ,aviation
and space crafts it is important to
understand the
a) Effects of low PO2 at high altitudes
b) Effects of acceleratory forces during
aviation
c) Effects of weightlessness in space
3

4. Barometeric
pressure
mmHg
Atmospheric
pressure
mmHg
At sea level 760 159
At 10,000 feet 523 110
At 50,000 feet 87 18

5. EFFECT OF CO2 AND WATER VAPORS
ON ALVEOLAP PO2
even at high altitude CO2 is continuously
expelled out and water vapor added to
inspired air from respiratory sufaces.PO2
decreases due to dilution. Water vapor in
alveoli is 47 mmHg as long as body
temperature is kept constant

6. At sea level PO2 is 40 mmHg
which is reduced to < 40
In the acclimatized person it may
decrease to 7 mmHg because of
5 fold increase in pulmonary
ventilation

7. At sea level barometric pressure is
760mmHg
At top of mounteverest 253 mmHg
Water vapor pressure -47 mmHg
PCO2 in acclimatized person 199mmHg
It is 1/5th of oxygen and 4/5th of N2

8. At alveolar PO2 35 mmHg only best
acclimatized person can survive when
breathing air
At sea level of alveolar PO2 is
104mmHg
At 20,000 feet it decreases to
40mmHg in un acclimatized and 53
mmHg in acclimatized person

9. In unpressurized air plane when
aviator breaths pure O2 at
39,000 feet alveolar PO2 is 139
mmHg instead of 18 mmHg when
breathing pure air

10. When breathing air arterial blood Hb
saturation is 90% at 10,000 feet and <
70% at 20.000 feet
When breathing pure O2 Hb saturation
with O2 is 90% at 39,000 feet and 50%
at 47,000 feet

11. When breathing pure oxygen aviator has
50% saturation at 47,000 feet.
When breathing air aviator as 50% oxygen
saturation at 23,000 feet.
Importance:
Unacclimatized person can remain concious
until the arterial PO2 saturation falls <
50%
11

12. Effects of hypoxia begin at 12,000 feet
which include;
1. Drowsiness
2. Lassitude
3. Mental & muscle fatigue
4. Some times headache
5. Occasionally nausea &
6. Some times euphoria
12

13. 7.More then 18,000 feet – twitchings or
seizures.
8. More then 23,000 feet- end in coma
following shortly by death .
9. One of the most important effects of
hypoxia is decreased mental proficiency
which decreases judgment, memory &
performance of discrete motor
movements e.g
13

14. if the Unacclimatized person stays at the
height of 15,000 feet for 1 hour, his
mental proficiency is decreased by 50%
of normal & after 18 hours it is
decreased to about 20% of normal.
14

15. When a person stays at high altitude for
days, weeks, or years becomes more &
more acclimatized to low PO2, so it causes
fewer deleterious effects on the body.
And it becomes possible for the person to
work harder without hypoxic effects or
to ascend to still higher altitudes.
15

16. By a great increase in pulmonary
ventilation.
Increase in number of RBCs & Hb
concentration, increase in blood volume to
20%
Increased diffusing capacity of the lungs.
Increased vascularity of the peripheral
tissues.
Increased ability of the tissue cells to use
oxygen despite low PO2.
16

17. Immediate exposure to low PO2
stimulates peripheral chemoreceptor's
which increases alveolar ventilation to a
maximum of 1.65 times normal. Then, if
person remains at very high altitude for
several days, the chemoreceptor’s
increase pulmonary ventilation to about 5
times normal.
17

18. The immediate increase in pulmonary
ventilation blows off large quantities of
carbon dioxide which decreases PCO2 &
increases pH of the body fluids causing
respiratory alkalosis. These changes
inhibit brain stem respiratory center &
there by oppose the effect of low PO2 on
peripheral chemoreceptor’s. But during
next 2-5 days the inhibitory effect fades
away. And increases the ventilation by 5
times the normal.
18

19. The cause of this fading of
inhibition is believed to be mainly a
reduction of HCO3
- concentration in the
CSF & brain tissues. This in turn
decreases the pH in the fluids
surrounding the chemosensitive neurons
of the respiratory center, thus increasing
stimulation of respiratory center. The
HCO3
- ions are decreased by renal
compensation to respiratory alkalosis.
19

20. When a person remains exposed to
low oxygen for weeks time then
hematocrit is increased from 45-
60% & Hb concentration is
increased from 15g/dl to about
20g/dl. In addition, the blood
volume is also increased by 20-30%.
20

21. The normal diffusing capacity for
oxygen through pulmonary membrane is
about 21ml/mmHg/min & this is
increased as much as 3 fold
1. during exercise.
2. at a high altitude.
21

22. Partly it results from
• increased pulmonary capillary surface
area along with increased pulmonary
capillary blood volume.
• increase in alveolar surface area and lung
air volume.
• increase in pulmonary arterial blood
pressure through the increase no of
capillaries– especially the upper parts of
the lungs which are poorly perfused under
usual conditions.
22

23. Immediately cardiac output is
increased by 30% & then over a
period of weeks cardiac output
decreases but hematocrit increases.
Also new capillaries are developed in
non-pulmonary tissues
(angiogenesis).
23

24. This is achieved by increase in cell
mitochondria & cellular oxidative enzyme
systems in natives and acclimatized low
landers. Natural acclimatization of native
human beings living at high altitudes is
better than low lenders who stay for
many days weeks or years at high
altitude. as shown in the following table.
24

25. 25

26. A small number of people who
ascend rapidly to high altitudes
become acutely sick and can die
if not given O2 or removed to low
altitude
It is characterized by acute
cerebral edema and acute
pulmonary edema

27. Occurs as a result of cerebral
vasodilatation due to hypoxia
Dilatation of arterioles
…..increased capillary pressure
and permeability
Characterized by disorientation
and other features of cerebral
dysfunction

28. Cause is still unknown
Severe hypoxia as a result of pulmonary
vasoconstriction
also there are areas of increased
pulmonary capillary permeability

29. Slow or stepwise ascent
Taking complete rest on reaching desired
height
Medicine…… acetazolamide

30. Occasionally a person stays too long at
altitude and develops chronic mountain
sickness (over and excessive adaptation)
Characterized by
Red cell mass and hematocrit becomes
exceptionally high
Increased viscosity of blood …..decrease
blood flow to tissues….Hypoxia
Cyanosis occurs

31. Pulmonary arterial pressure is more even
more than that occurs

32. 32

33. 33

34. Specific procedures and apparatuses
have been developed.
If the aviator tightens his or her
abdominal muscles & leans forwards to
compress abdomen, so that some pooling
of blood in large abdomen vessels can be
prevented.
Special “anti G suits” have be devised.
Limit of safety < -10G.
34

35. Blast off acceleration & landing deceleration:
9G first stage booster.
8G 2nd stage booster.
Human body can not with stand this pressure in
standing position, but in semirecling position. That is
transverse to the axis of acceleration. That is why
astronauts use recling seats.
35

36. 36

37. Problems also occur during deceleration
when the space craft-enters the
atmosphere.
A person traveling at march-I (speed of
sound) can be safely decelerated in a
distance of about 0.12 miles.
37

38. A person traveling at march 100 would
require a distance of 10.000miles for
safe deceleration. Deceleration should be
accomplished much slowly for high
velocities than for low velocities.
38

39. Deceleratory forces associated
with parachute jumps:
When the parachuter jumps from
the airplane velocity of deceleration
is 0feet/sec. after 1second it is
32feet/sec, after 2second it is
64feet/sec & after 12seconds it is
175feet/second.
Resistance of air and use of
parachute decrease the velocity to
20feet/sec.
39

40. Deceleratory forces will cause fracture
of pelvis, vertebrae or extended legs.
Trained parachuter hits the ground with
knees bent but muscles tightened.
40

41. Because there is no atmosphere in
outer space, an artificial atmosphere
& climate must be produced in a
space craft. It is important that
oxygen concentration must be kept
high & CO2 Kept low to prevent
suffocation. Previously pure oxygen
was used but now a days mixture of
gases. This prevents likelihood of
fire & explosion & development of
patches of atelectasion in the lungs.
41

42. For space travel lasting for several
months:
Recycling techniques are used.
Physical process H2O → O2
Use of algae – biological process chlorophil
present in algae under goes p
photosynthesis to release O2
42

43. Weightlessness in space:
A person in an orbiting satellite or
nonpropelled space craft experiences
weightlessness or a state of 0G force
which is sometime called microgravity.
The person is not drawn toward the
bottom, sides or top of the space craft.
43

44. Physiological problems:
Weightlessness→
1. Motion sicknesses during first few days of
travel in the form of nausea & vomiting.
2. Translocation of fluids with body.
3. Diminished physical activity.
44

45. Effects of prolonged stay:
1. Decrease in blood volume.
2. Decrease in red cell mass.
3. Decrease in muscle strength & work
capacity.
4. Decrease in maximum CO.
5. Loss of calcium & phosphate from the
bones as well as loss of bone mass. (at the
rate of 1%/month)
6. Impaired baroreceptor reflexes
45