Cyanosis is the appearance of a blue or purple coloration of the skin
-Dermis:The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbors many Mechanoreceptors that provide the sense of touch and heat...

 or mucous membrane
Mucous membrane
The mucous membranes are linings of mostly endodermal origin, covered in epithelium, which are involved in absorption and secretion. They line cavities that are exposed to the external environment and internal organs...

s due to the tissues near the skin surface being low on oxygen. The onset of cyanosis is 2.5 g/dL of deoxyhemoglobin. The bluish color is more readily apparent in those with high hemoglobin counts than it is with those with anemia
Anemia is a decrease in number of red blood cells or less than the normal quantity of hemoglobin in the blood. However, it can include decreased oxygen-binding ability of each hemoglobin molecule due to deformity or lack in numerical development as in some other types of hemoglobin...

. Also the bluer color is more difficult to detect on deeply pigmented skin. When signs of cyanosis first appear, such as on the lips or fingers, intervention should be made within 3–5 minutes because a severe hypoxia
Hypoxia (medical)
Hypoxia, or hypoxiation, is a pathological condition in which the body as a whole or a region of the body is deprived of adequate oxygen supply. Variations in arterial oxygen concentrations can be part of the normal physiology, for example, during strenuous physical exercise...

 or severe circulatory failure has induced the cyanosis.

The name cyanosis, literally means "the blue disease" or "the blue condition". It is derived from the color cyan
Cyan from , transliterated: kýanos, meaning "dark blue substance") may be used as the name of any of a number of colors in the blue/green range of the spectrum. In reference to the visible spectrum cyan is used to refer to the color obtained by mixing equal amounts of green and blue light or the...

, which comes from kyanos, the Greek word for blue.

Human blood is always a shade of red, and the more oxygenated the blood the brighter the shade of red. The more deoxygenated the blood, the darker red it is within the blood vessels, and the more bluish it appears on the skin. This color shift occurs because the optical properties of skin shift the darker red colors towards the bluer..


Cyanosis is defined as a bluish discoloration, especially of the skin and mucous membranes due to excessive concentration of deoxyhemoglobin in the blood.

Differential diagnosis

Cyanosis is divided in to two main types: central (around the core and lips) and peripheral (only the extremities are affected). Cyanosis can occur in the finger
A finger is a limb of the human body and a type of digit, an organ of manipulation and sensation found in the hands of humans and other primates....

s, including underneath the fingernails
Nail (anatomy)
A nail is a horn-like envelope covering the dorsal aspect of the terminal phalanges of fingers and toes in humans, most non-human primates, and a few other mammals. Nails are similar to claws, which are found on numerous other animals....

, as well as other extremities (called peripheral cyanosis), or in the lip
Lips are a visible body part at the mouth of humans and many animals. Lips are soft, movable, and serve as the opening for food intake and in the articulation of sound and speech...

s and tongue (central cyanosis).

Central cyanosis

Central cyanosis is often due to a circulatory or ventilatory problem that leads to poor blood oxygenation
Oxygenation (medical)
Oxygenation occurs when oxygen molecules enter the tissues of the body. For example, blood is oxygenated in the lungs, where oxygen molecules travel from the air and into the blood...

 in the lungs. It develops when arterial saturation of blood with oxygen is ≤85%. Cyanosis may not be detected until saturation is 75% in dark-skinned

Acute cyanosis can be a result of asphyxiation or choking, and is one of the surest signs that respiration is being blocked.


1. Central Nervous System:
  • Intracranial hemorrhage
  • Cerebral anoxia
  • Drug overdose
    Drug overdose
    The term drug overdose describes the ingestion or application of a drug or other substance in quantities greater than are recommended or generally practiced...

     (e.g. Heroin)

2. Respiratory System:
  • Bronchiolitis
    Bronchiolitis is inflammation of the bronchioles, the smallest air passages of the lungs. It usually occurs in children less than two years of age and presents with coughing, wheezing, and shortness of breath. This inflammation is usually caused by viruses...

  • Bronchospasm
    Bronchospasm or a bronchial spasm is a sudden constriction of the muscles in the walls of the bronchioles. It is caused by the release of substances from mast cells or basophils under the influence of anaphylatoxins...

     (e.g. Asthma
    Asthma is the common chronic inflammatory disease of the airways characterized by variable and recurring symptoms, reversible airflow obstruction, and bronchospasm. Symptoms include wheezing, coughing, chest tightness, and shortness of breath...

  • Lung disease
  • Pulmonary Hypertension
    Pulmonary hypertension
    In medicine, pulmonary hypertension is an increase in blood pressure in the pulmonary artery, pulmonary vein, or pulmonary capillaries, together known as the lung vasculature, leading to shortness of breath, dizziness, fainting, and other symptoms, all of which are exacerbated by exertion...

  • Pulmonary embolism
    Pulmonary embolism
    Pulmonary embolism is a blockage of the main artery of the lung or one of its branches by a substance that has travelled from elsewhere in the body through the bloodstream . Usually this is due to embolism of a thrombus from the deep veins in the legs, a process termed venous thromboembolism...

  • Hypoventilation
    In medicine, hypoventilation occurs when ventilation is inadequate to perform needed gas exchange...

  • COPD
    Chronic obstructive pulmonary disease
    Chronic obstructive pulmonary disease , also known as chronic obstructive lung disease , chronic obstructive airway disease , chronic airflow limitation and chronic obstructive respiratory disease , is the co-occurrence of chronic bronchitis and emphysema, a pair of commonly co-existing diseases...

     (emphysema and chronic bronchitis)
  • Respiratory syncytial virus

3. Cardiac Disorders:
  • Congenital heart disease (e.g. Tetralogy of Fallot
    Tetralogy of Fallot
    Tetralogy of Fallot is a congenital heart defect which is classically understood to involve four anatomical abnormalities...

    , Right to left shunts in heart or great vessels
    Right-to-left shunt
    A right-to-left shunt is a cardiac shunt which allows blood to flow from the right heart to the left heart. This terminology is used both for the abnormal state in humans and for normal physiological shunts in reptiles...

  • Heart failure
  • Heart valve
    Heart valve
    A heart valve normally allows blood flow in only one direction through the heart. The four valves commonly represented in a mammalian heart determine the pathway of blood flow through the heart...

  • Myocardial infarction
    Myocardial infarction
    Myocardial infarction or acute myocardial infarction , commonly known as a heart attack, results from the interruption of blood supply to a part of the heart, causing heart cells to die...

4. Blood:
  • Methemoglobinemia
    Methemoglobinemia is a disorder characterized by the presence of a higher than normal level of methemoglobin in the blood. Methemoglobin is an oxidized form of hemoglobin that has an increased affinity for oxygen, resulting in a reduced ability to release oxygen to tissues. The oxygen–hemoglobin...

  • Polycythaemia

5. Others:
  • High altitude
    Altitude or height is defined based on the context in which it is used . As a general definition, altitude is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. The reference datum also often varies according to the context...

  • Hypothermia
    Hypothermia is a condition in which core temperature drops below the required temperature for normal metabolism and body functions which is defined as . Body temperature is usually maintained near a constant level of through biologic homeostasis or thermoregulation...

  • Congenital cyanosis (HbM Boston) arises from a mutation
    In molecular biology and genetics, mutations are changes in a genomic sequence: the DNA sequence of a cell's genome or the DNA or RNA sequence of a virus. They can be defined as sudden and spontaneous changes in the cell. Mutations are caused by radiation, viruses, transposons and mutagenic...

     in the α-codon which results in a change of primary sequence, H → Y. Tyrosine
    Tyrosine or 4-hydroxyphenylalanine, is one of the 22 amino acids that are used by cells to synthesize proteins. Its codons are UAC and UAU. It is a non-essential amino acid with a polar side group...

     stabilises the Fe(III) form (oxyhaemoglobin) creating a permanent T-state of Hb.
  • Obstructive sleep apnea
    Obstructive sleep apnea
    Obstructive sleep apnea or obstructive sleep apnea syndrome is the most common type of sleep apnea and is caused by obstruction of the upper airway. It is characterized by repetitive pauses in breathing during sleep, despite the effort to breathe, and is usually associated with a reduction in...

Peripheral cyanosis

Peripheral cyanosis is the blue tint in fingers or extremities, due to inadequate circulation. The blood reaching the extremities is not oxygen rich and when viewed through the skin a combination of factors can lead to the appearance of a blue color. All factors contributing to central cyanosis can also cause peripheral symptoms to appear, however peripheral cyanosis can be observed without there being heart or lung failures. Small blood vessels may be restricted and can be treated by increasing the normal oxygenation level of the blood.


  • All common causes of central cyanosis
  • Arterial obstruction
  • Cold exposure (due to vasoconstriction
    Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, particularly the large arteries, small arterioles and veins. The process is the opposite of vasodilation, the widening of blood vessels. The process is particularly important in...

  • Raynaud's phenomenon
    Raynaud's phenomenon
    In medicine, Raynaud's phenomenon is a vasospastic disorder causing discoloration of the fingers, toes, and occasionally other areas. This condition can also cause nails to become brittle with longitudinal ridges. Named for French physician Maurice Raynaud , the phenomenon is believed to be the...

  • Reduced cardiac output (e.g. heart failure, hypovolaemia)
  • Vasoconstriction
    Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, particularly the large arteries, small arterioles and veins. The process is the opposite of vasodilation, the widening of blood vessels. The process is particularly important in...

  • Venous obstruction (e.g. deep vein thrombosis
    Deep vein thrombosis
    Deep vein thrombosis is the formation of a blood clot in a deep vein. Deep vein thrombosis commonly affects the leg veins or the deep veins of the pelvis. Occasionally the veins of the arm are affected...


Differential cyanosis

Differential cyanosis is the bluish coloration of the lower but not the upper extremity and the head. This is seen in patients with a patent ductus arteriosus. Patients with a large ductus develop progressive pulmonary vascular disease, and pressure overload of the right ventricle occurs. As soon as pulmonary pressure exceeds aortic pressure, shunt reversal (right-to-left shunt) occurs. The upper extremity remains pink because the brachiocephalic trunk, left common cartoid trunk and the left subclavian trunk is given off proximal to the PDA.

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.