The Physics of Medical Vacuum Technology

Pressure is the force applied per unit area and is fundamental to understanding medical vacuum technology. In the context of medical devices, pressure is typically measured in units like pascals (Pa) or millimeters of mercury (mmHg). When discussing pressure in a medical setting, it is crucial to differentiate between absolute pressure and gauge pressure.

• Absolute pressure: The total pressure at a point, including atmospheric pressure.
• Gauge pressure: The pressure above atmospheric pressure.

In physics, pressure is the result of a force applied vertically to a surface.

If liquids or gases at rest are in a closed vessel, the pressure acts equally in all directions. It acts equally and always perpendicularly to the surfaces of the vessel.

Gravity, which acts on the air, also causes constant pressure on the earth, i.e. atmospheric pressure. This depends, among other things, on the weather.

Negative pressure refers to a pressure lower than atmospheric pressure. A vacuum is a space devoid of matter, resulting in lower pressure than the surrounding atmosphere. In medical applications, negative pressure is harnessed to facilitate various procedures and interventions.

In a space where the pressure is lower than the ambient pressure, there is negative pressure. In practice, a negative pressure is often also referred to as a vacuum.

What happens to the negative pressure? Medical suction systems use negative pressure to transport air, fluids or both.

An electric or mechanical pump creates negative pressure. This leads to a force which moves air and/or fluid.

Suction is the force that draws in fluids or materials. In medical contexts, suction is commonly used to remove bodily fluids, secretions and air during surgical procedures or in patient care. Understanding suction involves grasping the principles of negative pressure and the controlled application of vacuum forces.

Flow in medical vacuum systems refers to the movement of air or fluids within the system.

Suction is the application of negative pressure to move air, liquids or solids. While negative pressure is static, suction refers to the dynamic effect that sets fluids in motion.

Flow or flow rate is a measurable quantity. It refers to the amount of matter that is moved within a certain time.

Flow is measured by the volume of air or fluid moved per minute. The unit is litre per minute.

Healthcare professionals must consider flow rates when using medical vacuum technology to ensure optimal performance during procedures. Flow is influenced by factors such as the diameter of tubing, the power of the vacuum source, and the presence of any restrictions in the system.

When extracting, the device's maximum flow rate is an important criterion. It indicates how quickly negative pressure can be built up at the beginning of therapy and the maximum volume that can be drained in a given period of time.

A pump can generate a maximum vacuum and transport a maximum volume.

If the fluid drains too quickly, the negative pressure decreases and cannot be maintained.

A distinction is made between devices with high, medium and low vacuum.
The higher the vacuum level is set, the higher the force acting on the material to be drained and the higher the suction.

A high vacuum technology is integral in various surgical procedures in the hospital or resident practices. They are also used for suctioning the airways.

Read more about Medela surgical suction systems

Low-vacuum devices, on the other hand, are primarily used for negative pressure wound therapy and thoracic drainage therapies.

Discover Medela's digital chest drainage system