Mechanical Circulatory Support for the Heart and Lungs

Heart-lung machine or cardiopulmonary bypass is a technique which is used in open heart surgery ,which takes over the function of heart and lungs during surgery,maintaining the circulation of blood and oxygen content of body.The heart lung machine is often refered to as the pump and does the work of heart and lungs during the operation.

Components and Working of Heart-Lung Machine

Heart-Lung Machine which consists of 2 main functional units,the pump and oxygenator,remove oxygen deprived blood from a patients body and replace it with oxygen rich blood. The chamber(pump) receives  blood from the body which is normally the responsibility of heart’s right atrium.This blood is then pumped by the machine through an oxygenator,a function normally the responsibility of right ventricle.The oxygenator removes the co2 and adds oxygen,which is normally done by the lungs.The pump then pumps this newly oxygenated blood back to the body,which is normally the works of heart’s left side.The heart lung machine is connected to the patient by a series of tubes.At the end of the operation the surgeon gradually allows the patient’s heart to resume its normal function and the heart lung machine is “weaned off”.

Uses of Heart-Lung Machine

It is commonly used in heart surgery because of difficulty of operating on a beating heart.When the surgery requires opening of chambers of heart,it becomes necessary to use a heart-lung machine to support the circulation during that period.The heart-lung machine mechanically circulates and oxygenates blood at the time of operating(bypassing) the heart and lungs. 

Complications while using HEART-LUNG Machine

  1. Clotting of blood in circuit
  2. Neurological problems
  3. Air embolism
  4. Capillary leak syndrome
  5. Hemolysis etc.

As a consequence, heart lung machine is only used during the hours of a cardiac surgery

In figure 1. you can see an ecmo circuit. ECMO(Extra-corporeal Membrane Oxygenation) is a twist on the heart lung machine used for open heart surgery, modifying it, so that patients can stay on the machine for weeks instead of just hours.Tubes carry blood out of the body so that a filter can remove carbondioxide and reinfuse oxygen and then pump the blood back.The key is blood doesnt have to bypass the heart if only the lungs need a rest.