Cyanosis Overview and Types

Cyanosis

• Cyanosis is a blue discoloration of the skin or mucous membranes due to high levels of deoxygenated hemoglobin in the blood.
• It is most noticeable in areas with thin tissue and a lot of blood vessels, like the nose, ears, mouth, genitals, and fingers.
• There are two types of cyanosis: central and peripheral.
• Central cyanosis is more common and is caused by low oxygen levels in the blood.
• Peripheral cyanosis occurs when the blood flow to the extremities is reduced.
• Oxygen in the blood is transported in two ways: dissolved in the plasma and bound to hemoglobin.
• The normal oxygen tension in the blood of a person breathing room air is between 80 and 100 mmHg.
• The amount of oxygen bound to hemoglobin is directly related to the oxygen tension in the blood.
• Hypoxemia is defined as a low oxygen saturation level in the blood.

Cyanosis

• Cyanosis is a bluish discoloration of the skin or mucous membranes due to high levels of deoxygenated hemoglobin in the blood.
• It’s easily seen in areas with a lot of blood vessels close to the surface and thin tissue.
• It's classified as central or peripheral cyanosis.

Central Cyanosis

• It’s more common than peripheral cyanosis and usually happens when the blood has a low level of oxygen in the arteries.
• Causes include heart and lung conditions, and blood disorders that affect how oxygen is carried.

Peripheral Cyanosis

• Happens when the blood flow to the extremities is decreased, even though the oxygen level in the arteries is normal.
• This is caused by blood vessels narrowing and reducing blood flow to the limbs.

Oxygen Transport

• Oxygen is transported in the blood in two ways: dissolved in plasma and bound to hemoglobin.
• Normal levels of oxygen dissolved in the blood are 1-2% of the total amount of oxygen in the blood.
• Most oxygen in the blood is bound to hemoglobin, and the amount of oxygen bound is related to the amount of oxygen dissolved in the blood.
• Hypoxemia is a condition where the oxygen levels in the blood are lower than normal.

Cyanosis

• Cyanosis is named after the Greek word kuaneos, meaning dark blue, and refers to the blue discoloration of the skin or mucous membranes.
• It's caused by high concentrations of deoxygenated hemoglobin (Hb) in superficial capillaries.
• It's often noticeable in areas with thin tissue and abundant capillaries, like the nasal planum, pinna, oral cavity, penis, vulva, nail beds, and footpads.
• Cyanosis is categorized into central and peripheral, with central cyanosis being more common.
• Central cyanosis arises from low arterial blood oxygen saturation (SaO2), often due to cardiopulmonary conditions or hemoglobinopathies that hinder oxygen transport.
• Peripheral cyanosis develops with normal SaO2, resulting from vasoconstriction and reduced blood flow to the extremities.

Physiology and pathophysiology

• Oxygen is carried in the blood in two forms: dissolved in plasma and bound to hemoglobin (Hb).
• The normal arterial oxygen tension (PaO2) in an individual breathing room air (FiO2 21%) at sea level is 80-100 mm Hg.
• Dissolved oxygen contributes only 1-2% of total blood oxygen concentration and is measured by PaO2 in blood gas analysis.
• The majority of oxygen in the blood is bound to Hb, and the amount bound depends on PaO2, which is represented in the oxygen dissociation curve.
• Hypoxemia is defined as SaO2 less than 90%.

Cyanosis

• Cyanosis derives from the Greek word kuaneos, signifying dark blue, and denotes a bluish discoloration of the skin or mucous membranes due to elevated levels of deoxygenated hemoglobin (Hb) in superficial capillaries.

• Cyanosis is readily observed in regions with plentiful superficial vasculature and thin tissue, including the nasal planum, pinna, oral cavity, penis, vulva, nail beds, and footpads.

• Cyanosis is categorized as either central or peripheral.

Central Cyanosis

• Central cyanosis is more prevalent than peripheral cyanosis.

• Central cyanosis is typically caused by diminished arterial oxygen saturation (SaO2) resulting from cardiopulmonary diseases or hemoglobinopathies that interfere with oxygen transport.

Peripheral Cyanosis

• Peripheral cyanosis occurs with normal SaO2 and stems from vasoconstriction and decreased peripheral blood flow.

Oxygen Transport

• Oxygen is transported in two forms: dissolved in plasma and bound to hemoglobin (Hb).

• Standard arterial oxygen tension (PaO2) in an individual breathing room air (FiO2 21%) at sea level is 80-100 mm Hg.

• Dissolved oxygen constitutes only 1-2% of the total blood oxygen concentration, quantified by PaO2 in blood gas analysis.

• The majority of oxygen in blood is bound to Hb, with the quantity related to PaO2, visualized in the oxygen dissociation curve.

Hypoxemia

• Hypoxemia is defined as SaO2 less than 90%, a state reflective of inadequate oxygen delivery to the tissues.