Download [1] Hypoxic hypoxia

Hypoxia
Cellular deficiency of oxygen ….4 types:
[1] Hypoxic hypoxia
 low arterial PO2
 low atmospheric O2,
 Inadequate ventilation of the alveoli
 Insufficient diffusion of O2 through the respiratory
membrane.
[2] Anaemic hypoxia
 Normal arterial PO2
 ReducedHb available to carry O2 to the tissues.
[3] Ischaemic hypoxia
 Normal PO2 and Hb concentration
 low blood flow to a tissue due to arterial stenosis.
[4] Histotoxic hypoxia
 Normal PO2 and Hb concentration
 Toxic agents act on respiratory chain enzyme in the mitochondria
and prevent the tissue cells to make use of the O2supplied to
them(eg. cyanide poisoning) or deficiency of oxidative enzymes such
as vitamin B deficiency (Beriberi).
Cyanosis
 Bluish discoloration of the tissues
 Reduced Hb concentration of the blood in the capillaries
is more than 5 gm/dl
 Easily seen in mucus membrane and thin skin areas like
lips, fingers and nail bed.
 In polycythaemia, cyanosis is very common because of
the large amount of Hb in the blood
 In anaemia, cyanosis is rare because it is difficult for
there to be enough deoxygenated Hb to produce the
cyanotic color. Cyanosis divided into 2 types:
[1] Central cyanosis
 Hb-undersaturation or abnormal Hb derivative
 Both mucous membranes and skin are affected(lips, and
tongue)
[2] Peripheral cyanosis
 Slow blood flow(vasoconstriction) causes great extraction
of O2
 Moderate cold exposure, shock, heart failure, and
peripheral vascular disease.
 In very cold weather cyanosis does not developed
because O2 consumption by tissues is reduced so the
affinity of Hb to O2 is reduced.
Hypercapnia
 Excess CO2in the body fluids
 Hypoventilation OR circulatory deficiency causes
poor gas exchange which results in both hypercapnia
& hypoxia.
 Serious hypercapnia usually does not occur because
CO2 diffuses 20 times as rapidly as O2.
O2Therapy
 Is of great value in hypoxic types of hypoxia
and of slight value in other types.
 In chronic hypoxia the respiratory center becomes
adapted to the high PCO2 level and O2 lack becomes
more powerful stimulus to respiration than usual,
for this reason, O2therapy in hypoxia is
sometimes contraindicated.
O2 Toxicity
 Administration of 100% O2 has been demonstrated to
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exert toxic effects.
The toxicity seems to be due to the production of the
superoxide anion (O2-) and H2O2.
When 80-100% O2 administered for periods of 8 hours or
more the respiratory passages become irritated,
causing sore throat and coughing.
Exposure for 24-48 hours causes lung damage as well.
The reason O2 produce the irritation is probably due to
inhibition the ability of lung macrophages to kill bacteria,
and surfactant production is reduced.