hypoxia and cyanosis Flashcards
Reduction in oxygen saturation
HYPOXIA
Factors that may bring about hypoxia
o Dysfunction of cardiovascular and respiratory
system.
o Inadequate inspired oxygen supply/gas
o Inadequate RBC and hemoglobin
CAUSES AND TYPES OF HYPOXIA
• Anemic Hypoxia • Carbon monoxide intoxication • Respiratory hypoxia • Hypoxia secondary to high altitude • Hypoxia secondary to right to left extrapulmonary shunting • Specific organ hypoxia • Increased O2 requirements • Improper O2 utilization
- Reduction in hemoglobin concentration
* Decline in oxygen carrying capacity
anemic hypoxia
level of PaO2 in anemic hypoxia
Normal
T or F
In anemic hypoxia, same quantity of oxygen is removed but with greater
degree of decline of PO2 in venous blood than
normal case.
True
there is
accumulation of carboxyhemoglobin and this carboxyhemoglobin is unable to transport oxygen
Carbon monoxide intoxication
if there is decrease transport of O2 the
haemoglobin oxygen dissociation curve is usually shifted to
left.
T or F
CO has higher affinity to RBCs
T
shift to left: Oxygen has _____ attachment to RBCs
increased
T or F
There is a greater degree of tissue hypoxia in anemia than CO intoxication
F
Alkalosis is associated with shift to the
left dissociation curve
- Caused by pulmonary disease
* PaO2 declines in respiratory failure
RESPIRATORY HYPOXIA
When respiratory failure is persistent, the hemoglobin-oxygen (Hb-O2)
dissociation curve is displaced to the
right
are likely to be more
marked when depression of PaO2 results from
pulmonary disease than when the depression
occurs as the result of a decline in the fraction of
oxygen in inspired air (FIO2)
consequent cyanosis
Normal FIO2
21
Common findings in advanced pulmonary
disease:
o Ventilation-Perfusion mismatch or V-Q
mismatch
o Hypoventilation (elevated PaCO2
PaCO2 falls secondary to anoxia-induced hyperventilation and the Hb-O2 curve is displaced to the
left
High V-Q mismatch in the
upper lobe
low V-Q mismatch in the
lower lobe
These two forms (V/Q mismatch and
Hypoventilation) of respiratory hypoxia are
usually correctable by
inspiring 100% O2 for several minutes
Respiratory locations where there is no gas
exchange
dead space - trachea
conditions that may present with Shunting
atelectasis or AV connections in the lungs
Main difference of V/Q mismatch and
shunting:
Shunting cannot be corrected by
100% oxygenation
At higher altitude arterial saturation _______
rapidly and symptoms becomes more serious
declines
At 8,000 ft., the FIO2 is about
120 mmHg,
alveolar PO2 is approx. 80 mmHg and SaO2 is
normal.
At 16,000 ft. FIO2 is
85 mmHg, alveolar PO2 is
50 mmHg and SaO2 is 75%.
At 5000m,
un-acclimatized individuals usually
cease to be able to function normally.
o Develops in person with chronic hypoxemia
secondary to prolonged residence at a high
altitude (>13, 000 ft, 4200m)
• CHRONIC MOUNTAIN SICKNESS
Manifestations of chronic mountain sickness
Blunted respiratory drive, decrease in ventilation, erythrocytosis, cyanosis, weakness, right ventricular enlargement secondary to pulmonary HPN and even stupor
• Caused by congenital cardiac formation such as
Tetralogy of Fallot, transposition of great arteries
and Eisengmenger’s syndrome
HYPOXIA SECONDARY TO RIGHT & LEFT
EXTRAPULMONARY SHUNTING
• PaO2 is normal but venous and tissue PO2 are
reduced.
• Reduced tissue perfusion and greater tissue O2
extraction
• Pathophysiology leads to an increased arterialmixed venous O2 difference, or (A-V) gradient
Circulatory hypoxia
conditions that may cause circulatory hypoxia
heart failure, shock
specific organ hypoxia is usually brought about by:
Arterial obstruction (atherosclerosis) Raynaud’s phenomenon (vasoconstriction)
• Venous obstruction and the resultant congestion
and reduce arterial inflow
• Edema (increases the distance of O2 diffusion)
• Attempt to maintain adequate perfusion of vital
organs in shock or heart failure.
• Signs and symptoms of shock includes cold and
clammy skin due to decrease in blood supply
specific organ hypoxia
Elevated oxygen consumption without
corresponding increase in perfusion
INCREASED OXYGEN REQUIREMENTS
manifestations: Increased oxygen requirements
• Skin is warm and flushed, cyanosis is absent
differs from other types of hypoxia
• Reduced tissue perfusion, increased tissue
extraction of O2
INCREASED OXYGEN REQUIREMENTS
MECHANISM OPERATING IN INCREASED OXYGEN
DEMAND
o Increased cardiac output and ventilation
o Preferentially directing the blood to the exercising muscle
o Increasing O2 extraction from the delivered blood
o Reducing pH of the tissues and capillaries, shifting the Hb-O2curve to right
IMPROPER OXYGEN UTILIZATION is also called
histotoxic hypoxia
• Reduction of PaO2
o Cerebrovascular resistance decreases
o Cerebral blood flow increases in an attempt
to maintain O2 delivery to the brain
However, when the reduction of PaO2 is
accompanied by hyperventilation,
There would be a reduction of PaCO,
cerebrovascular resistance rises causing a
fall in cerebral blood flow → tissue hypoxia
intensifies
o May cause impaired judgment and motor
incoordination maybe seen
• Acute Hypoxia
o May cause fatigue, drowsiness, apathy,
inattentiveness, delayed reaction time and
reduced work capacity
• Longstanding Hypoxia
