Hypoxia and hypercapnia

1. Hypoxia & Hypercapnia
Dr. Sara Sadiq
(MBBS, M.Phil)

2. HYPOXIA
• HYPOXIA:- is reduced Oxygen for tissue
respiration
• Anoxia:- complete absence of oxygen in
tissues
• Hypoxia Vs Hypoxemia

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

4. Degrees of Acute Hypoxia
Acute Hypoxia can cause the following according to the degree of
oxygen saturation in arterial blood:
1- 85 % Saturation = Mental Impairment
2- 75 % Saturation = Severe Mental Impairment
3- 65 % Saturation = Unconsciousness

5. Cyanosis
Bluish discoloration of skin and/or mucus membrane due to the presence
of at least 5gm of reduced haemoglobin per 100ml of blood in
capillaries.
Sites to be examined:
i. Mucus membrane of undersurface of tongue
ii. Lips
iii. Ear lobes
iv. Nail beds
v. Tip of nose

8. Chronic Hypoxia
This develops after adaptation for high altitude and
chronically developing lung diseases affecting oxygen
transfer in the lung.

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

10. Types of Hypoxia
• Hypoxic hypoxia
• Anemic hypoxia
• Stagnant hypoxia
• Histotoxic hypoxia

11. Types of Hypoxia
1- Hypoxic Hypoxia in inadequate arterial oxygenation
2- Anemic Hypoxia in inadequate hemoglobin content
3- Circulatory Hypoxia in inadequate perfusion
4- Histotoxic Hypoxia in inability of the cell to utilize oxygen

12. Hypoxic Hypoxia
• Supply Problem
• Causes
• LOW O2 TENSION IN THE INHALED AIR
• IMPAIRED GAS EXCHANGE IN THE LUNGS
e.g CHRONIC BRONCHITIS & EMPHYSEMA
•GROSS VENTILATION/PERFUSION MISMATCH

13. Anemic Hypoxia
• Transport Problem

14. Stagnant Hypoxia
• Distribution Problem
• Causes
• HIGH G FORCES
• HEART FAILURE
• SHOCk

15. FLIGHT
• ASCENT TO ALTITUDE WITHOUT
SUPPLEMENTAL O2
• BREATHING A GAS MIXTURE POOR
IN O2
• EXPOSURE OF HIGH G FORCES
• FAILURE OF O2 EQUIPMENT
• LOSS OF CABIN PRESSURIZATION

16. Histotoxic Hypoxia
• Utilization Problem
• CAUSES:
• CYANIDE POISONING Block Cellular Oxidative Metabolism by
Inhibiting Cytochrome Oxidase
• ALCOHOL & BARBITURATE
• OXYGEN TOXICITY 100% Oxygen for 8-10 hrs Inhibition of
certain enzymes,(Cytochrome Oxidase)

18. Carbon monoxide poisoning
•CO combines with Hb at the same point where
O2 combines
•CO has 250 times more affinity than O2
•Shifts O2-Hb dissociation curve to left
•Treated with 100% O2

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

20. Hyperbaric Oxygen Therapy
• oxygen at a level higher
than atmospheric pressure
• Hyperbaric oxygen therapy
involves breathing pure
oxygen in a pressurized
room/chamber

21. 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

23. Hypercapnia
• Excess carbon dioxide (CO2) in the body (> 45 mm Hg in blood)
• Associated with hypoxia
• Hypoventilation
• Circulatory deficiency

25. Raised PCO2
• 60 to 75 mm Hg – air hunger (rapidly & deeply)
• Dyspnea
• 80 to 100 mm Hg – lethargic & semicomatose
• 120 to 150 mm Hg – anesthesia and death