An oxygenator is a medical device used during open-heart surgery to add oxygen to the patient's blood and remove carbon dioxide — temporarily performing the function of the lungs. When a patient's heart is stopped for surgery, the oxygenator takes over gas exchange, keeping the blood oxygenated and the body alive throughout the procedure.
"The oxygenator is the most critical component of the cardiopulmonary bypass (CPB) circuit — it is, in essence, an artificial lung outside the body."
Why is an Oxygenator Needed?
During open-heart surgeries such as coronary artery bypass grafting (CABG), valve replacement, and congenital heart defect correction, the surgeon must stop the heart to operate on it precisely. A beating heart makes surgery nearly impossible. The challenge is: how do you keep the rest of the body alive without a beating heart?
The answer is the Heart-Lung Machine (Cardiopulmonary Bypass Machine), and the oxygenator is its most critical component. Blood is diverted from the patient's body into the machine, oxygenated by the oxygenator, and then pumped back — all while the surgeon works on the motionless heart.
How Does an Oxygenator Work?
The working principle of a modern oxygenator is based on gas exchange across a semipermeable membrane:
- Venous blood (dark, oxygen-poor) is drained from the patient's right side of the heart via cannulas.
- Blood enters the oxygenator chamber and flows over or through thousands of hollow fibre membranes.
- Pure oxygen (and sometimes a mixture with CO₂) flows on the other side of the membrane.
- Oxygen diffuses into the blood through the membrane; CO₂ diffuses out in the opposite direction.
- The now oxygenated, bright-red arterial blood is warmed to body temperature and pumped back into the patient's aorta.
This entire process happens continuously at a flow rate of 4–6 litres per minute for an adult — matching the normal cardiac output.
Types of Oxygenators
1. Membrane Oxygenators (Modern Standard)
Today, almost all cardiac surgeries use hollow-fibre membrane oxygenators. Thousands of microporous hollow fibres (made of polypropylene or polymethylpentene — PMP) create a massive surface area for gas exchange.
- Surface area: 1.5 to 3.0 m² (adult), 0.5 to 1.5 m² (paediatric/neonatal)
- Priming volume: Typically 200–350 mL (adult), less for smaller patients
- Gas exchange efficiency: Excellent — comparable to healthy lungs
- Blood trauma: Minimal due to indirect contact via membrane
- Plasma leakage: PMP fibres are plasma-tight, preventing seepage over long bypass runs
2. Bubble Oxygenators (Historical)
In bubble oxygenators, oxygen bubbles are directly injected into the blood. While effective, this causes significant blood trauma (red blood cell damage, protein denaturation) and was abandoned in the 1980s–1990s in favour of membrane designs. Bubble oxygenators are now obsolete in modern practice.
Key Components of an Oxygenator
- Hollow fibre bundle: The gas exchange module — thousands of fibres packed together
- Heat exchanger: Warms or cools blood to manage patient temperature (hypothermia is used in some procedures)
- Venous reservoir: Collects blood from the patient before it enters the oxygenator — acts as a buffer volume
- Arterial filter: Captures micro-emboli (bubbles, particles) before blood returns to patient
- Cardiotomy suction ports: Return blood lost in the surgical field
- Biocompatible coating: The inner surfaces are coated to reduce complement activation and platelet adhesion
Surface Coatings: Why They Matter
When blood contacts foreign surfaces, the immune system activates — a process called systemic inflammatory response. Modern oxygenators use biocompatible coatings to reduce this:
- Heparin coating (e.g., Sorin LivNova's PHISIO coating) — binds heparin molecules to the surface, reducing clot formation
- Phosphorylcholine (PC) coating — mimics the outer surface of red blood cells, making the surface "invisible" to the immune system
- Albumin coating — creates a protein layer that passivates the surface
Leading Oxygenator Brands
| Brand | Products | Known For |
|---|---|---|
| Sorin LivNova | Inspire 6F, 8F, Kids, Eos | PHISIO heparin coating, flat-sheet technology |
| Eurosets | E-VitaLung, E-Neonatal | Ultra-low priming volume, neonatal specialists |
| Medtronic | Affinity Pixie, Fusion | Integrated reservoir designs |
| Terumo | Capiox FX, SX | PMP hollow fibres, plasma-tight performance |
Sorin LivNova Inspire Series (Distributed by IBP)
The Inspire range is one of the most widely used in India. Key models include:
- Inspire 6F: Adult — 0–75 kg patients, priming volume 255 mL, surface area 1.9 m²
- Inspire 8F: Large adult — up to 100 kg, surface area 2.5 m²
- Inspire Kids: Paediatric — for 3–25 kg patients, priming volume 155 mL
- Inspire Neonatal: For neonates <3 kg, ultra-low priming volume
Eurosets E-VitaLung (Distributed by IBP)
Known for its modular design and compatibility with minimally invasive bypass circuits. The E-Neonatal version is specifically designed for newborn cardiac surgery with an extremely low priming volume of under 50 mL.
How is an Oxygenator Used? Step-by-Step Clinical Flow
- Surgeon places venous cannula in the right atrium (or vena cavae)
- Surgeon places arterial cannula in the ascending aorta
- Perfusionist (CPB technician) connects tubing to the heart-lung machine
- Patient is anticoagulated with heparin (ACT target >400 seconds)
- Bypass is initiated: blood diverts from heart → reservoir → oxygenator → pump → aorta
- Heart is stopped with cardioplegia (cold potassium solution)
- Surgeon operates on still heart while oxygenator sustains body
- After surgery: heart is restarted, bypass slowly weaned off, patient goes off CPB
- Heparin is reversed with protamine sulphate
Oxygenator Selection: What Perfusionists Consider
- Patient weight and BSA — determines size class needed
- Expected bypass duration — longer runs need PMP membranes (plasma-tight)
- Procedure type — paediatric vs adult; complex (redo) vs routine
- Priming volume — smaller volumes reduce haemodilution (especially important in children)
- Integrated vs modular — some systems combine reservoir + oxygenator + filter
- Coating technology — heparin or PC coating for inflammatory response reduction
The Difference Between Oxygenator and Ventilator
A common point of confusion: an oxygenator is NOT the same as a ventilator. A ventilator assists the patient's own lungs to breathe — it pushes air in and out. An oxygenator bypasses the lungs entirely and oxygenates blood outside the body. Ventilators are used in ICUs; oxygenators are used in cardiac operating theatres during CPB.
India's Backbone Pharma is the authorised distributor of Sorin LivNova and Eurosets oxygenators across India, supplying top cardiac surgery centres, government hospitals, and private institutions.
Frequently Asked Questions
How long can an oxygenator run continuously?
Standard membrane oxygenators (especially PMP) can run reliably for 4–6 hours during routine cardiac surgery. For ECMO (Extracorporeal Membrane Oxygenation) — a longer-term support — specialised ECMO oxygenators can run for days to weeks.
Is an oxygenator the same as an ECMO machine?
ECMO uses a similar oxygenator principle but is designed for prolonged respiratory or cardiac support (days to weeks) in ICU patients. Standard CPB oxygenators are single-use, procedure-limited devices. ECMO oxygenators (e.g., Quadrox) are designed for extended use.
What happens if the oxygenator fails during surgery?
Perfusionists are trained to rapidly switch to a backup oxygenator. All cardiac surgery centres that perform CPB maintain a spare primed circuit. Oxygenator failure is an extremely rare event given modern quality standards and pre-procedure checks.