Blue skin: what does blueness of the skin (cyanosis) of the hands, feet, lips or face mean?

Blue skin (technically also cyanosis) is the name given to the symptom of blue skin discoloration. The skin can be dark blue to blue-violet in color. This bluish skin discoloration is a symptom for several diseases.

What is cyanosis?

Cyanosis (from Greek kyanos = blue) is a blue to purple discoloration of the skin and mucous membranes. It occurs as a result of inadequate oxygenation of the blood. It occurs when there is an increased concentration of reduced (non-oxygenated) hemoglobin in the blood.

The haemoglobin to which oxygen (_O2) is bound is known as oxyhaemoglobin (oxyHb). One molecule of haemoglobin is able to bind 4 molecules of oxygen. When _O2 is released, it becomes deoxyhaemoglobin (deoxyHb), otherwise known as reduced haemoglobin.

Cyanosis occurs at approximately 50 grams per litre of deoxyHb.

How is cyanosis distributed?

Cyanosis is divided into three groups: central cyanosis, peripheral cyanosis and methaemoglobin cyanosis. Each type has its own specific characteristics.

In general, cyanosis is best recognized by:

• on the fingertips and especially on the nail beds
• on the lips
• on the auricle
• mucous membranes
• and places where the skin is thin

Central cyanosis manifests itself by blueness of the skin evenly over the whole body, not just on the periphery, especially on the following parts:

• lips
• tongue
• the mucous membranes of the oral cavity
• on the face in the cheek area
• torso
• extremities, nail beds

Peripheral cyanosis is mainly manifested on the terminal or acral parts of the body. It is therefore also referred to as acral cyanosis. It is mainly visible on:

• fingertips and nail beds
• lips
• the tip of the nose
• the earlobe

Methaemoglobin cyanosis (metHb) and sulphhaemoglobin cyanosis are also known. Methaemoglobin cyanosis occurs when methaemoglobin is formed in an increased amount. It occurs at a value of more than 15 g/l. Its peculiarity is that it has a peculiar brownish colour.

What causes cyanosis?

There are many factors that cause cyanosis. Some of these are disease-related, but others are not. It may be a symptom of hypothermia. Alternatively, if the extremities are blue, low body temperature is most likely to blame. In this case, warming them up will help.

However, bluing of the skin can also indicate serious problems in the body, whether it be circulatory problems, heart problems or a problem with the lungs and lack of oxygen. The blue colour itself is therefore caused by a preponderance of haemoglobin in the blood, which has no oxygen attached to it.

Cyanosis does not occur in persons with severe anemia.

There is therefore little oxygen in the blood, which subsequently manifests itself on the surface of the skin as a general blueness. The lungs, heart and vascular system, for example, are involved in the cause of this condition.

Blue discolouration of the skin occurs in various heart defects. For example, a defect in the septum between the atria and the ventricles of the heart. There is a mixing of deoxygenated blood from the right heart and oxygenated blood from the left heart.

Similarly, in aortic coarctation, which is a congenital developmental defect of the heart and large blood vessels. It is a narrowing of the aorta (the main artery that carries blood from the heart to the body). Here, cyanosis is present mainly in the lower part of the body.

Even diseases of the arteries and veins are manifested by the affected person having blue skin. In tetralogy of Fallot, for example, fainting, breathing problems and general malaise also occur. This is a complex disease of the heart and large heart vessels. It requires complex cardiac surgery.

Also, in various lung diseases and disorders, there are problems with blue discoloration of the skin due to lack of oxygen in the body. This is for example pulmonary emphysema, which is a disease that causes destruction of the lung tissues.

Alternatively, pneumoconiosis, which are various lung diseases. Even pulmonary embolism, in which there is an obstruction in the pulmonary bloodstream, causes oxygen deficiency and cyanosis.

Common bronchitis and pneumonia can also cause blue skin. Inflammation of the lining and mucous membrane of the airways in the lower airways and lungs occurs. This is especially the case when right ventricular failure occurs at the same time.

In epiglottitis or laryngitis in young children. Epiglottitis is an inflammation of the laryngeal flange and laryngitis is an inflammation of the larynx. Blue discolouration of the skin occurs when the air passage to the lungs in the upper airways is narrowed or blocked.

Sometimes inflammation of the veins can also be manifested by blueness, especially of the extremities. In inflammation, there is then a reduction in blood flow and tissue haemorrhage. But often various forms of poisoning are also responsible for blue skin, especially nitrite and nitrate or sulphur compounds, which reduce the binding of oxygen to haemoglobin.

Epileptics also have breathing problems when their bodies convulse. This occurs during an epileptic seizure when, in addition to the skeletal muscles, the respiratory muscles are also affected by the convulsions. Cyanosis is, however, only a temporary symptom that subsides after the seizure has subsided.

Causes of central cyanosis

This type of cyanosis is manifested by an even colouration of the skin and mucous membranes, i.e. the lips, tongue, oral mucous membranes and even the skin on the chest, limbs and acral areas are coloured blue. The colouration of the nail beds or earlobes is also noticeable.

The appearance of this type of cyanosis is conditioned by:

• lack of oxygen in the inhaled air, for example at high altitudes
• lack of oxygen supply to the lungs, in the case of airway obstruction, such as:
  • inhalation of a foreign body
  • inflammation (epiglottitis and laryngitis)
  • laryngospasm (constriction of the larynx)
  • swelling of the airways, such as in allergic reactions, angioedema
  • chronic obstructive pulmonary disease
  • asthma
• ARDS (acute respiratory distress syndrome)
• pulmonary oedema
• pneumonia
• drowning
• pulmonary embolism
• in congenital heart disease, Fallot's tetralogy of Fallot, but also other right heart shunts
• pneumothorax (air in the pleural space)
• sarcoidosis
• pulmonary fibrosis
• lung cancer and metastases to the lungs
• carbon monoxide, cyanide poisoning
• hypoventilation, even after head and chest trauma, after cerebral haemorrhage, in sepsis

Differentiated cyanosis is a type of cyanosis in which bluing of only the lower extremities is present. As noted in those affected with ductus arteriosus patens, in pulmonary hypertension, and in right heart shunt. Cyanosis of the upper half of the body occurs with transposition of the great arteries.

Why peripheral cyanosis occurs

In this type, the bluish discoloration is present only on the skin. The mucous membranes are not affected. It is mainly the skin on the extremities of the body. Namely, the nail beds, the tip of the nose, the auricles, the lips. It arises with reduced blood flow and with vasoconstriction. As in the case of:

• heart failure
• heart valve defects
• shock
• blockage of arteries and veins
• vasculitis, thrombophlebitis
• exposure to cold, hypothermia, cold water or air
• Raynaud's syndrome and other neurovascular diseases