Hypoxia. (Subject 7)

1. Hypoxia

January 20, 2017

2. Hypoxia classification

Exogenous
Endogenous
(hypoxic)
respiratory
hypobaric
hemic
normobaric
substrate
circulatory
histotoxic
overload

3. Hypoxia classification

Due to time of development
– Fulminant (immediate) –several seconds
(cyanide poisoning).
– Acute – several minutes (cardiac arrest).
– Subacute – several hours or days
(respiratory failure).
– Chronic – months and years.

4. Hypoxia classification

Due to prevalence of clinical symptoms:
– local and general.
Due to the severity of pathological process:
–
–
–
–
light;
moderate;
severe;
critical (lethal) hypoxia.

5. Exogenous (hypoxic) hypoxia hypobaric type

atmospheric pressure+ partial oxygen
pressure in the air
Mountain sickness factors: low partial
pressure of oxygen, low barometric
pressure, physical loading, cooling,
increased exposure to UV rays.
Altitude sickness factors: low barometric
pressure and low partial pressure of oxygen

6. Exogenous (hypoxic) hypoxia normobaric type

Normal atmospheric pressure +
oxygen % in the air:
- in small rooms with bad ventilation
(elevators, mines, mineshafts);
- in divers, when there are problems
with aqualung function;
- incorrect conduction of artificial lungs
ventilation during surgical operations.

7. Exogenous (hypoxic) hypoxia

Low oxygen
in the air
Low carbon
dioxide
in the blood
ABB
disturbances
Low oxygen
in the blood

8. Exogenous (hypoxic) hypoxia

ABB –
gaseous
alkalosis
Low carbon
dioxide
in the blood
Lungs
hyperventilation
Low oxygen
in the air
Low oxygen
in the blood
Disturbances
of gaseous
exchange
in the tissues

9. Respiratory hypoxia

Causes
Disturbances
of gases diffusion
in the lungs
Alveolar
hypoventilation
Disturbances
of lungs
blood supply

10. Respiratory hypoxia

Alveolar hypoventilation reasons:
Obstructive violations (lung edema, tumors
or foreign bodies in the lumen of bronchi
and bronchioles).
Restrictive violations (chronic inflammatory
or sclerotic processes in the lungs and in the
chest).
Disturbances of respiratory regulation (toxic
substances poisoning, brain trauma).

11. Respiratory hypoxia

Disturbances of lungs blood supply heart failure, decreased circulating blood
volume (after blood loss).
Disturbances of gases diffusion in lungs
chronic inflammatory diseases of the lungs,
lungs edema.
Blood indices: low oxygen, high CO2, low pH
(acidosis)

12. Circulatory hypoxia

Causes
Decreased
heart activity
Hypovolaemia
vascular
disorders

13. Circulatory hypoxia - systemic

Circulatory hypoxia systemic
Decrease of heart activity - myocardial
infarction, myocarditis.
Hypovolaemia - severe blood loss,
dehydration of the organism after burns,
cholera, vomiting.
Vascular disorders (low vascular tone) shock, collapse, aldosterone deficiency.

14. Circulatory hypoxia

Local type of circulatory hypoxia insufficient blood supply of the organ
or tissue (ischemia) or the difficulty of
venous outflow (venous hyperemia,
stasis).
Blood indices: normal oxygen in arterial
blood, low oxygen in venous blood,
low pH (acidosis).

15. Hemic hypoxia

Anemic type – accompanying different
anemias.
Inactivation type - poisoning with CO,
nitrates, sulfonamides and other substances
that yield in methemoglobin formation
Blood indices: low O2 in arterial and
venous blood, non-gaseous acidosis.

16. Hemic hypoxia

The reasons of anemia:
chronic bleedings,
erythrocytes hemolysis,
depression of erythropoiesis.

17. Hemic hypoxia

Carbon monoxide poisoning:
CO has the affinity to Hb 300 times higher than
O2
Carboxy-Hb (HbCO) is formed (stable
substance)
Symptoms: drowsiness and headache,
unconsciousness, respiratory failure, and death.

18. Histotoxic hypoxia

The inability of cells to utilize oxygen
Causes:
tissue poisoning (alcohol, narcotics,
cyanide).
biological oxidation enzymes inhibition
and the disturbance of their synthesis;
the damage of membrane structures
of the cell.

19. Histotoxic hypoxia

Cyanide poisoning
Cyanide ions bind to the Fe atom of
cytochrome C oxidase
The ATP synthesis stops.
Nervous system and the heart are
particularly affected.

20. Histotoxic hypoxia

Disturbance of respiratory enzymes
synthesis results from vitamins deficiency
(B group vitamins, pantothenic acid).
Damage of mitochondrial membranes
and other cellular elements (radiation injury,
over-heating, intoxication, infection,
cachexia, uremia).
Blood indices: the pressure, saturation and
content of O 2 in blood are near normal.

21. Histotoxic hypoxia

Dissociation of oxidation and
phosphorylation processes in
respiratory chain:
– energy is dispersed as a heat.
– ATP synthesis is low.
The factors: hormones of thyroid gland,
excess of Ca, toxins.

22. Overload hypoxia

Occur during physical overload of certain organ or
tissue.
It is observed in skeletal muscles and myocardium.
Blood indices: arterial and venous hypoxemia and
hypercapnia.
Local heart hypoxia may transform to secondary
general circulatory hypoxia
In the excessive muscular work - bloodflow in the
muscles is increased
ischemia of other
tissues.

23. Substrate hypoxia

Deficiency of the substrate to be
oxidized - glucose
Carbohydrate starvation and hypoxia of
insulin-dependent tissues often occur
during diabetes mellitus.

24. Combined hypoxia

It is a combination of 2 and more main
types of hypoxia.
Nitrates
CO
inactivates
Hb
Inhibit
cytochrome
oxidase
Dissociate
oxydationphosphorilation

25. Combined hypoxia

Respiratory
failure
Respiratory
hypoxia
Disturbed regulation
of heart and vessels
Circulatory
hypoxia
heart contractions
vessels permeability

26. Disturbances in the Organs and Physiological Systems

Nervous system –
1. emotional and motion excitation,
inadequate behavior;
2. disturbances of reflex activity and
regulation of breathing and blood
circulation;
3. loss of consciousness and convulsions.
Heart and vessels – tachycardia,
arrhythmia, low BP.

27. Disturbances in the Organs and Physiological Systems

Lungs - irregular breathing; decreased
diffusion of oxygen from the alveolar
air to blood.
Liver (chronic hypoxia) - disturbance of
all kinds of metabolism, inhibition of
detoxication, decreased synthesis of
substances.

28. Disturbances in the Organs and Physiological Systems

GIT organs (chronic hypoxia) violation of appetite, inhibition of
peristalsis and secretion, development
of erosions and ulcers.
Immune system (chronic hypoxia) low functional activity of the immune
cells and innate immunity factors.

29. Adaptation to hypoxia

The reactions of urgent adaptation
(protective-adaptive) manifest in
acute hypoxia.
Permanent -adaptive
(compensatory) - during long-term or
repeating hypoxic effects.

30. Urgent adaptation

The reason of adaptation - lack of
energy supply due to low ATP
amount (lack of biological oxidation).
Respiratory system - blood
oxygen and CO2 irritate
chemoreceptors. This result in the
increase of the alveolar ventilation.

31. Urgent adaptation

Heart – tachycardia, heart stroke
volume and minute blood volume.
Vessels - centralization of bloodflow
(dilation of the brain and heart
arterioles with simultaneous
constriction of the arterioles in others
tissues and organs).

32. Urgent adaptation

Blood - activation of RBC outflow from the
bone marrow and blood depot (liver,
spleen).
Increased affinity of Hb to oxygen and the
degree of oxyHb dissociation in the tissues.
Tissues systems of biological oxidation anaerobic glycolysis, the activation of
respiratory enzymes.

33. Adaptation to hypoxia

Urgent reactions - activation of the
oxygen transport to the tissues.
Permanent compensation activation of biological oxidation and
structural changes of organs and
systems that are transporting oxygen.

34. Permanent adaptation

Lungs - increased surface of alveoli, number
of capillaries, rate of gases diffusion
through alveoli to vessels.
Respiratory muscles - hypertrophy and
increased working capacity.
Heart - the number of myocardial fibers,
capillaries and nerves is increased. of
heart stroke volume and minute volume.

35. Permanent adaptation

Number of the vessels in all organs and
tissues is increased.
Blood – increased blood cells number due to
increased erythropoiesis.
– Chronic lack of oxygen causes the activation of
erythropoietin synthesis in kidneys.
Metabolic processes :
– decrease of metabolism intensiveness;
– high efficiency of anaerobic glycolisis;
– prevalence of anabolic processes in the cells.

36. Clinical application of hypoxia

Intermittent hypoxia - repeated episodes
of hypoxia interspersed with normoxic
periods (Interval Hypoxic Trainings)
Hypoxic episodes are created by exposure to
natural high altitude, sojourns in hypobaric
chambers or by breathing hypoxic gas
mixtures in normobaric conditions.

37. Clinical application of hypoxia

Interval Hypoxic Training is used for the
treatment of bronchial asthma, chronic
obstructive pulmonary diseases, coronary
heart disease, arterial hypertension,
neurocirculatory asthenia, neurodermitis,
diabetes mellitus II type.
The method is effective to increase physical
and mental working capacity.
The counter-indications are: all acute somatic
and infectious diseases.

38. Clinical application of hypoxia

Adaptation to hypoxia provides
resistance to other stress factors
(cross-resistance).
Adaptation to hypoxia is characterized
with structural and functional
changes in many organs and tissues.
Body resistance is increased to
hypothermia, overheating, physical
overstrain, infections