This document defines hypoxia and its types. There are four main types of hypoxia: hypoxic (low oxygen in inspired air), anemic (low hemoglobin to carry oxygen), stagnant (low blood flow delivering oxygen to tissues), and histotoxic (tissues cannot use delivered oxygen due to toxins). Each type is caused by different physiological derangements and produces characteristic clinical features depending on the underlying pathophysiology and tissue response to low oxygen levels. Treatment focuses on addressing the underlying cause and providing supplemental oxygen therapy.

1. HYPOXIA AND
ITS TYPES
Dr Sara Ahmed

2. DEFINITION
• Hypoxia means lack of
oxygen at tissue level.
• Anoxia means complete
absence of oxygen in the
tissues.

3. TYPES OF
HYPOXIA
1) HYPOXIC HYPOXIA
2) ANAEMIC HYPOXIA
3) STAGNANT HYPOXIA
4) HISTOTOXIC HYPOXIA

4. 1) HYPOXIC HYPOXIA
It is characterized by a low arterial pO2 when the O2 carrying
capacity of blood and rate of blood flow to the tissues are normal
or elevated.
CAUSES:-
• Low pO2 in inspired air - for example
- High altitude ( more than 3000 mts
above sea level)
- Breathing in a closed space
- Breathing an artificial gas mixture
containing low pO2

5. • Decreased pulmonary ventilation - seen in
- Airway obstruction
- Weakness/paralysis of respiratory muscles
- Depression of respiratory centres by drugs specially
morphine
• Venous arterial shunts - i.e. venous blood enters the arterial
blood without going into the lungs,therefore,arterial pO2
decreases. For example - cyanotic heart disease( Fallots
Tetrology )

6. • Defect in exchange of gases - through alveolar-capillary
membrane.This includes all the factors affecting the V/P ratio.
- Bronchial Asthma
- Pneumothorax
- Emphysema
- Pulmonary fibrosis
- Congestive heart failure
- Pulmonary embolism

7. Characteristic Features of Hypoxic Hypoxia

8. PATHOPHYSIOLOGY OF HYPOXIC HYPOXIA
via peripheral chemoreceptors stimulate
Hypoxic Hypoxia
Respiratory centre
Pulmonary ventilation increases
CO2 wash out from the body
Arterial pCO2 decreases
Oxygen-haemoglobin curve shifts to left
Less release of O2 from haemoglobin
Tissue Hypoxia

9. 2) ANAEMIC HYPOXIA
Hypoxia in which arterial pO2 is normal but the amount of haemoglobin
available to carry O2 is reduced.
• Anaemia
• Haemorrhage
• Conversion of haemoglobin to some abnormal form- for
example
- Methaemoglobin
- Carboxy Haemoglobin
CAUSES:-

10. Characteristic Features of Anaemic Hypoxia

11. PATHOPHYSIOLOGY OF ANAEMIC HYPOXIA
In anaemic hypoxia at rest,hypoxia is not severe,because in anaemia
there is increased amount of 2,3 DPG in the RBC’s which combine with
oxyhaemoglobin and results in increased liberation of O2.
But during exercise when there is
increased O2 demand by tissues due
to increased O2 consumption,the
tissue demand is not met fully and
severe hypoxia develops.
HbO2 + 2,3DPG —> Hb 2,3DPG + O2

12. 3) STAGNANT/ISCHAEMIC HYPOXIA
Hypoxia in which the blood
flow to the tissues is so low
that adequate O2 is not
delivered to them despite a
normal arterial pO2 and
haemoglobin concentration.

13. CAUSES:-
• Circulatory failure
• Haemorrhage - via baroreceptors produces reflux
vasoconstriction and thus blood flow to tissue decreases
• Congenital heart failure - It is associated with pulmonary
congestion which produces defect in
oxygenation,therefore,patient also suffers from hypoxic
hypoxia in addition to stagnant hypoxia.

14. Characteristic Features of Stagnant Hypoxia

15. 4) HISTOTOXIC HYPOXIA
Hypoxia in which the amount of oxygen delivered to the tissues is
adequate,but because of the action of a toxic agent the tissues
cannot make use of the O2 supplied to them.
CAUSES:-
• Cyanide poisoning - It produces
hypoxia at tissue level causing
poisoning of cellular enzymes
specially cytochrome oxidase and
also produces tissue oedema.

16. Characteristic Features of Histotoxic Hypoxia

17. Basic treatment of hypoxia includes :
• Treatment of the underlying cause
• Oxygen therapy -
A. By inhalation of 100% pure O2
B. By inhalation of 100% O2 at high barometric pressure
called hyperbaric oxygen therapy.
4
TREATMENT OF HYPOXIA