Vacuum technology in medical applications
June 19, 2020
Vacuum technology plays an important role in a number of health care and life sciences applications. We find vacuum pumps in all major hospitals and in many analytic instruments used in diagnostics and research.
Central medical vacuum systems in hospitals
In most hospital rooms we find a vacuum connection at the wall delivering vacuum pressure for aspiration. Vacuum is a tool in surgery, anaesthesia and during intensive care. The vacuum 'outlets' in patient rooms and surgery rooms are connected to a central vacuum system. These are usually located in the basement floor. They consist of vacuum pump(s), buffer tank, and control. For redundancy and maximised uptime systems have a minimum of two and in most cases three or four vacuum pumps. The pumps are used alternately or started additionally when more pumping speed is required. Most pumps are single stage rotary vane pumps with ultimate pressure around 1 mbar. The buffer vessels have volumes of 100 to 1000 liters, inlet filters and a draining valve for condensed liquids and particles.
The total vacuum system underlies strong medical regulations of quality, certification (e.g. ISO 7396-1) and maintenance. Please note that the pressure measures ''Hg (inch mercury) and cfm are more commonly used that ISO standard pressure units in this application.
Vacuum cushions and vacuum mattresses
These are used for ideal patient fixation in surgery, imaging methods or for securing patients in transport. Mattresses and cushions are filled with small plastic spheres. During evacuation the mattress or cushion will fit exactly to the shape of the patient, securing them in a fixed position. A vacuum of 30% or better (< 300 mbar) is sufficient so single stage diaphragm pumps are used. In hospitals the central vacuum system can be applied; while in emergency ambulances often a simple manual pump is used.
Plasma sterilization with vacuum
The demand for sterilisation of medical equipment in hospitals is growing. Plasma sterilisation under vacuum is highly efficient and does no damage to the material. Plasma sterilisers create a plasma of hydrogen peroxide (H2O2) using microwaves in a vacuum of 1 mbar. The medical instruments remain at room temperature (for further information see: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3445964/). If sterilised with the classic hot steam (autoclave @ 130 C) method, the medical instruments would be destroyed. Common pumps are mid and large-size 2-stage rotary vane pumps with special traps in the exhaust.
X-ray tubes evacuation with vacuum
X-Ray examinations have been used for the last 100 years for diagnostics. The x-rays are generated in a tube by bombarding an anode with high voltage electrons (up to 150 kV). The anode is made of metal (in most cases copper). The high energy electrons are scattered or stopped in the metal and the copper atoms release an x-ray ('Bremsstrahlung') at a characteristic energy.
Schematic of an x-ray tube
The anodes require water-cooling and are often rotated for better heat dissipation. Since the electrons must not be scattered by air molecules it is obvious that all x-ray tubes are evacuated to high vacuum. In general, a pressure of 10-5 to 10-6 mbar is required. Evacuation is done at the tube manufacturer by mid-size turbomolecular pumps backed by rotary vane pumps. The tubes are sealed and by using getter material, a re-evacuation in the hospital is not required.
In this blog we have shown that vacuum technology is present in numerous medical applications and research. Medical vacuum systems are fundamental for delivering vacuum pressure for aspiration and ensuring that both patient rooms and surgery rooms are safe and efficient. Vacuum technology is also pivotal for the sterilisation of medical equipment as well as the use of x-ray tubes in high vacuum conditions.
