this PPT describes about all aspects related to hypoxia.

1. Dr Rajesh Reddy P
Associate Professor
Department of Physiology
Mediciti IMS
Hypoxia

2. Learning Objectives:
 Definition
 Etiology
 Types
 Stages
 Diagnosis
 Treatment

3. Hypoxia
 Hypoxia is defined as a deficiency in either the
delivery or the utilization of oxygen at the tissue
level.

4. Etiology
 High altitude
 Anemia
 Decreased oxygen supply to an area
 Low oxygen carrying capacity
 Poor tissue perfusion
 Impaired ventilation
 Decreased diffusion of oxygen

5. Etiology

6. Acute Hypoxia
It can be due to :
1. Respiratory depression
2. Airway obstruction
3. Atelectasis
4. Ventilation/Perfusion mismatch
5. Reduced Functional Residual Capacity (FRC)

7. Direct Effects of Acute Hypoxia
1. Cyanosis
2. Confusion, Drowsiness
3. Excitement
4. Headache
5. Nausea
6. Myocardial Depression
7. Arrhythmias
8. Bradycardia
9. Renal Impairment

8. Indirect Effects of Acute Hypoxia
These are mediated through stimulation of Carotid
and Aortic Bodies :
1. Tachycardia
2. Hypertension
3. Hyperventilation

10. Degrees of Acute Hypoxia
Acute Hypoxia manifestations depends on the degree
of oxygen saturation in arterial blood:
Saturation
1. 85 % = Mental Impairment
2. 75 % = Severe Mental Impairment
3. 65 % = Unconsciousness

11. Chronic Hypoxia
 Develops in,
 after adaptation for high altitude
 chronically developing lung diseases.

12. Effects of Chronic Hypoxia
1- Hyperventilation
2- Polycythemia
3- Increased 2-3-DPG
4- Proliferation of peripheral capillaries
5- Alteration in Intracellular Oxidative Enzymes

14. Types
1. Hypoxic / hypotonic hypoxia: PO2 of the arterial
blood is low (less than 60mmHg).
2. Anaemic / Hemic / isotonic hypoxia: amount of Hb
to carry O2 is low
3. Stagnant / ischemic / circulatory / hypokinetic
hypoxia: blood flow to the tissues is low
4. Histotoxic / histogenous hypoxia: tissue can not
utilize 02.

15. Features of hypoxia
Features Hypoxic H Anemic H Stagnant H Histotoxic H
Arterial PO2 Decreases Normal Normal Normal
Hb amount Normal Decreases Normal Normal
Rate of blood flow to
tissues
Normal Normal Decreases Normal
Arterial O2 content Decreases Markedly
reduced
Normal Normal
Arterial %-02
saturation of Hb
Decreases Decreases Normal Normal
A-V O2 difference Decreases Normal More than
normal
Less than
normal
Cyanosis Present Absent Present Absent
Stimulation of
peripheral
Present Absent Present Present

16. Stages of Hypoxia
1. Asymptomatic or indifferent
2. Compensatory
3. Deterioration or Disturbance
4. Critical

17. 1. Asymptomatic or Indifferent
• Generally not aware about the effects.
• Primary symptoms: loss of night vision and color
vision.
• These changes can occur at relatively modest
altitudes (as low as 4,000 feet) and are most
significant to pilots operating at night.
• Arterial O2 sat between 90 - 95%

18. 2. Compensatory
• In healthy people, this stage may occur at altitudes
between 10,000 and 15,000 feet.
• The body generally has the ability to starve off
further effects of hypoxia by increasing the rate and
depth of ventilation and cardiac output.
• Arterial O2 sat between 80 - 90%.

19. 3. Deterioration or Disturbance
 People are unable to compensate for the lack of oxygen.
• Unfortunately, not everyone recognizes or experiences the
signs and symptoms associated with this stage.
• Arterial O2 sat between 70 - 80%.
• The signs that are associated with this stage:

20. ● Shortness of breath ● Incoordination
● Cyanosis ● Difficulty with simple tasks
● Drowsiness ● Diminished vision
● Headache ● Tingling
● Euphoria ● Numbness
● Aggression ● Hot/cold flushes
● Poor Judgment

21. 4. Critical
• This is the terminal stage leading up to death.
• People are almost completely incapacitated physically
and mentally.
• People in this stage will lose consciousness, have
convulsions, stop breathing and finally die.
• Arterial O2 sat are less than 70%.

22. Diagnostic parameters
 PO2
 CO2max
 CO2
 SO2
 P50

23. PO2 partial pressure of oxygen
 PO2 is the tension produced by the oxygen
molecules physically dissolved in plasma.
 Normal PaO2: 100mmHg
PvO2: 40mmHg
 Determined by PiO2 and pulmonary function

24. CO2max oxygen binding capacity of hemoglobin
 CO2max refers to the maximal amount of oxygen
that could be bound by the hemoglobin, which
reflects the ability of hemoglobin carrying oxygen.
 Normal value: 20ml/dl
 Determined by quantity and quality of Hb

25. CO2 oxygen content
 CO2 includes oxygen that is bound to hemoglobin
and physically dissolved in the blood (0.3ml/dl).
 Normal value: CaO2:19ml/dl
CvO2:14ml/dl
 Determined by PO2 and CO2max
 The A-V O2 content difference (CaO2-CvO2)
reflects the oxygen volume of tissue uptake.

26. SO2 oxygen saturation
 SO2 is the percentage of hemoglobin present as
oxyhemoglobin.
 Normal value: SaO2: 95%
SvO2: 75%
 The relation between O2 partial pressure and O2
sat is shown as oxygen dissociation curve (ODC).

27. P50
 P50 means the oxygen partial pressure required to
saturate 50% of the hemoglobin, which reflects the
affinity of hemoglobin for oxygen.
 Normal value: 26-27 mmHg

28. Treatment
 Eliminating causes
 Oxygen therapy
 Hyperbaric oxygen therapy

29. Oxygen therapy
Oxygen administration is of importance in hypoxic
hypoxia.
A. Inhalation of 100% O2 at normal atmospheric
pressure
B. Hyperbaric oxygen therapy

30. Oxygen therapy
Indications:
1- Cardio Pulmonary Resuscitation (CPR)
2- Respiratory Failure
3- Cardiac Failure
4- Shock of any Cause
5- Increased Metabolic Demands
6- Carbon Monoxide (CO)-Poisoning
7- Postoperative States

31. Oxygen Toxicity
1- Retrolental Fibroplasia / retinopathy of prematurity:
In Neonates (especially prematures) if breathing Oxygen
Concentration more than 40 % (FiO2 more than o.4)
2- Lung Toxicity:
In Adults if breathing Oxygen Concentration more than
60 % (FiO2 more than 0.6) for a long time

32.  Oxygen toxicity will occur early
 Inhibits tissue enzyme activity
 Cerebral vasoconstriction
 Muscular twitches, tinnitus, convulsions and coma

33. Hazards of Oxygen Therapy
1. CO2 Narcosis / CO2 poisoning: hypercapnia will
develop.
2. Barotrauma: by increased air pressure in the lungs.

34. Normobaric 100% O2 therapy
 It is useful in hypoxic hypoxia.
Dangers of inhaling 100% oxygen:
 Nasal congestion, throat pain, cough, substernal
discomfort.
 Bronchopneumonia if given for more than 24 hrs by
inhibiting alveolar macrophages
 Newborns should not be given more than 40% oxygen

35. Hyperbaric O2 Therapy
 Hyperbaric oxygen therapy is defined as inhalation
of oxygen at increased pressure for potential
therapeutic benefit.
 Useful in anemic, stagnant and histotoxic hypoxia

36. Benefits of HOT
 Increased O2 tension
 Vasoconstriction
 Increased fibroblast replication
 Increased collagen response
 Angiogenesis
 Enhanced leukocyte function
 Attenuation of reperfusion injury

38. THANK YOU…..