QS Study

Cyanosis is a clinical condition characterized by a dusky bluish discoloration of the skin and/or mucous membrane due to excess deoxygenated lib in the peripheral blood. It is a bluish or purplish tinge to the skin and mucous membranes. Cyanosis can be present at birth, as in a ‘blue baby,’ an infant with a malformation of the heart that permits into the arterial system blood that is not fully oxygenated.

Cause of cyanosis

It occurs when deoxygenated Hb is more than 5 g/dl.

(A) Inadequate oxygenation of blood in the lung.

  • High altitude, lack of Oxygen.
  • Disease of the lung Emphysema, pneumonia.
  • A collapse of the lung.
  • Obstruction of trachea and bronchus.
  • Heart failure.
  • CO Poisoning.

(B) Admixture of venous and arterial blood, congenital heart diseases.

(C) Greater reduction of oxyhaemoglobin.

  • Local chilling
  • Venous obstruction
  • ↑ Metabolic state.

Site of cyanosis: Most easily seen, nail bed, mucous membrane, earlobes, lips, fingers, where the skin is thin.

Types of cyanosis

  1. Central cyanosis: in the tip of the tongue,
  2. Peripheral cyanosis: Seen in the lips, nose, earlobes, nail beds.

Individuals who do not show cyanosis

(a) Individual suffer from carbon monoxide poisoning –

  • COHb is cherry pink
  • HbO2 is the presence of COHb doesn’t reduce.

(b) A person with anaemia who never becomes cyanotic because there is not enough haemoglobin to 5 gm, to be deoxygenated.

(c) Cyanosis doesn’t occur in histotoxic hypoxia.