A detailed mechanism of hypoxia

1. ROMAISA
ROLL NO 514

2. ■ Hypoxia
■ Respiration adaptation to hypoxia

3. Hypoxia:
Hypoxia is a state in which oxygen is not available in
sufficient amounts at the tissue level to maintain adequate
homeostasis; this can result from inadequate oxygen delivery
to the tissues either due to low blood supply or low oxygen
content in the blood (hypoxemia)

4. Early signs of hypoxia:
■ Restlessness
■ Anxiety
■ Tachycardia
■ Tachypnea
■ Late signs of hypoxia:
■ Bradycardia
■ Extreme restlessness
■ Dyspnea
■ Cyanosis

5. Causes of hypoxia:
Inadequate oxygenation of lungs due to lack of oxygen in atmosphere and
hypoventilation.
■ Pulmonary diseases
■ Venous to arterial shunt
■ Inadequate transport and delivery of oxygen eg in anemia and tissue edema
■ Inadequate tissue capability of utilizing oxygen eg cyanide poisoning of
cytochrome oxidase and vit B deficiency.

6. Classification of hypoxia:
■ Hypoxemic hypoxia
■ Anemic hypoxia/hemic hypoxia
■ Stagnant hypoxia or circulatory hypoxia/ischemic hypoxia
■ Histotoxic hypoxia

7. ■ Hypoxemic hypoxia:
■ the hypoxemic type, in which the oxygen pressure in the blood going to the tissues is
too low to saturate the hemoglobin.
■ Causes of hypoxemic hypoxia:
■ The hypoxemic type of hypoxia is due to one of two mechanisms: (1) a decrease in
the amount of breathable oxygen—often encountered in pilots, mountain climbers,
and people living at high altitudes. cardiopulmonary failure in which the lungs are
unable to efficiently transfer oxygen from the alveoli to the blood.
■ 2. Anemic hypoxia:
■ the anemic type, in which the amount of functional hemoglobin is too small, and
hence the capacity of the blood to carry oxygen is too low;

8. ■ Causes of anemic hypoxia:
■ In the case of anemic hypoxia, either the total amount of hemoglobin is too
small to supply the body’s oxygen needs, as in anemia or after severe bleeding,
or hemoglobin that is present is rendered nonfunctional. Examples of the latter
case are carbon monoxide poisoning and acquired methemoglobinemia, in both
of which the hemoglobin is so altered by toxic agents that it becomes unavailable
for oxygen transport, and thus of no respiratory value.
■ 3. Stagnant hypoxia:
■ the stagnant type, in which the blood is or may be normal but the flow of blood
to the tissues is reduced or unevenly distributed.

9. ■ Histotoxic hypoxia:
■ the histotoxic type, in which the tissue cells are poisoned and are therefore
unable to make proper use of oxygen.
■ In histotoxic hypoxia the cells of the body are unable to use the oxygen, although
the amount in the blood may be normal and under normal tension. Although
characteristically produced by cyanide poisoning, in which the action of the
enzyme cytochrome oxidase is completely blocked by the cyanide—to
such an extent that the tissues simply cannot use oxygen even when
plenty is available.

10. ■ Effects of Hypoxia on the Body
■ Hypoxia, if severe enough, can cause death of
cells throughout the body, but in less severe
degrees it causes principally (1) depressed
mental activity, sometimes culminating in coma,
and (2) reduced work capacity of the muscles.

11. Respiration adaptation in hypoxia:
1. Hypoxic pulmonary vasoconstriction:
When ventilation is blocked,the lung can protect against the loss of blood oxygenation
by activating localized arterial vasoconstriction, reducing blood flow to under
ventilated regions, and redirecting flow to better ventilated alveoli.
2. More active capillaries in lungs
3. Increased mitochondria:
■ Increased number of mitochondria help to maintain cellular functions.
■ Also plays an important role in the production of energy in the form of ATP.
4. High concentration of RBCs:
Hypoxia induces systemic increase of erythropoietin(EPO) level Which stimulates the
production of mature RBCs from the bone marrow.

12. 5.Hypoxia induce factor(HIF):
■ Hypoxia inducible factor(HIF)-1 is a chimeric protein complex that plays an
integral role in the body’s response to low oxygen concentrations,or hypoxia.
■ HIF-1 is among the primary Gene’s involved in the homeostatic process, which
increase the vascularization in hypoxic areas such as localized ischemia and
tumors.
■ HIF-1 further mediates cellular responses to hypoxia by regulating glucose
uptake and anaerobic respiration in oxygen depleted environments.

13. ■ 6. Hyperventilation:
■ Increased levels of Carbon Monoxide and exposure to toxic substances are both triggers. Also,
when the level of Oxygen is reduced significantly, this can lead to Hyperventilation. Hypoxia
definitely will lead to Hyperventilation.
■ Hyperventilation is rapid or deep breathing.

14. 7. . 2,3 DPG( Diphosphoglycerate):
■ The function of erythrocyte 2,3-DPG is to bind to deoxyhemoglobin and facilitate oxygen
transport. When 2,3-DPG binds to deoxyhemoglobin, the deoxyhemoglobin molecule is
stabilized