Superimposed High-frequency Jet Ventilator for Medical Applications

Daniel Pfeifer, Head of Research and Development at ESCATEC talks to AZoSensors about a new superimposed high-frequency jet ventilator for medical applications.

Can you provide a summary of ESCATEC?

ESCATEC is one of Europe’s leading providers of contract design and manufacturing services. It supports European customers via a network of local project managers who are in turn supported by the European headquarters in Heerbrugg, Switzerland. This central European facility houses both the global headquarters of ESCATEC’s Research and Development department and the company’s prototype and low volume production facility.

Once volumes become higher, production moves to ESCATEC’s Malaysian factories which use the same equipment so that control programmes perfected on the Heerbrugg machines are simply ported over to ensure a rapid ramp up to volume. Being Swiss-based, the R&D department places great emphasis on quality and precision which is reflected in the number of industrial, medical and instrumentation clients that it has along with top brand name companies whose reputation is based on quality products.

The new superimposed high-frequency jet ventilator is one of a kind. What was the main inspiration behind the design and development of this ventilator?

A general anaesthetic usually involves inserting a tube into the patient’s throat to ensure that the right mixture of oxygen and other gases is delivered into the patient’s lungs and removed. This forms a closed system with the lungs being mechanically inflated and deflated under the control of the anaesthetist. However, there is a problem if the operation is taking place on the inside of the throat. The system is then an open one as the instruments have to be inserted into the throat and used so there can be no seal and the lungs cannot be inflated and deflated by a normal ventilator. It is rather like inflating and deflating a balloon with a tube into the neck of a balloon that is open all the time through which instruments and lasers can move.

Did you collaborate with healthcare professionals to help shape the design of the Twinstream^TM Multi Mode Respirator?

Our client is Carl Reiner GmbH who is a leading provider of medical equipment so they were able to provide us with detailed operational parameters and specifications. How to actually design it and solve the technical challenges was down to our R&D team. You have to consider what would happen if something went wrong. If 3.5 bar of pressure was suddenly applied inside the patient’s lungs, it would do tremendous damage so you have to build in all kinds of safety protocols to meet every possible ‘what if’ scenario. It took us a couple of years from idea to volume production. We are very proud to have designed a unique product that is saving lives on a daily basis in many leading hospitals around the world.

Can you describe how this respirator works?

The Twinstream™ Multi Mode Respirator actually has two ventilators that operate completely independently with different frequencies and different pressures. The first provides the conventional 12 or so breaths per minute whilst the second provides a high frequency of around 800 breaths per minute. This second, high frequency ventilation reduces the stress on the lungs during lengthy operations that can take many hours, because it is very efficient at moving air in and out. This ensures that CO₂ is removed more easily, and oxygen reaches deep into the lungs to be more effectively absorbed into the bloodstream.

What are the main functional components to this respirator and how have you ensured that this device performs with the highest accuracy and precision?

The heart of the respirator is the pneumatic module which is a custom design of ESCATEC. The main purpose is to blend air (21% oxygen [O₂]) and 100% O₂ to a gas mixture with a defined O₂ concentration with an accuracy of +/-3%. Secondly, the pressure controller is key to applying the right pressure to different patients as lung size and elasticity can vary greatly.  Beside the O₂ concentration and the independent pressure for normal frequency (NF) and high frequency (HF), the expiration and inspiration times need to be controlled by the anaesthetist.

Besides these main functions, there are extensive design features in the monitoring electronics and software.  By sampling small amounts of gas from the patient, the CO₂ and O₂ concentration, as well as the lung pressure, is measured in real-time. There is an independent microcontroller system supervising all the safety relevant functions of a second controller system.

Modern ventilators are controlled electronically by an embedded system that adapts to changes in pressure and flow, which helps tailor the device to individual patients. What are the embedded systems in this device (i.e., are there any sensors embedded in this new device) and how does this novel design compare to the traditional ventilators systems that are applied in surgery?

The embedded system in the respirator consists of three independent microcontrollers with their own peripherals. All supervising functions and the man machine interfaces are implemented on a powerful embedded computer with the Windows CE operating system. This system is not safety relevant and in case of a breakdown, the patient can still be ventilated. The second embedded system is based on a DSP without an operating system to implement all safety relevant functions. The third and smallest controller can be powered through a 9V battery and is used during blackouts. Several sensors are used to measure temperatures, pressures, O₂, CO₂, electrical voltages and currents.

What safety protocols were considered during the design and development process?

ESCATEC is one of the few contract design and manufacturing companies to have the ISO standard for medical equipment – ISO13485. Because of this, we are used to operating to these very exacting standards which are vitally important, as patients’ lives depend on the equipment working correctly all the time.

Are there any aspects to the device that still need further development?

At present, there are no plans to change the design.

How will the surgeons be trained to apply this device during surgery?

Fortunately, the device does not require much special training for surgeons or anaesthetists. It is a facilitator to provide access to the operation site whilst the patient is under anaesthetic and functions in a very similar way to a normal intubation.

About Daniel Pfeifer

Daniel joined ESCATEC Switzerland as a Research and Development Engineer from Munich University where he obtained a Dipl.-Ing., Electrical Engineering and Information Technology in 2003. Over the past ten years he has worked in various positions within the R&D Division and, in 2011, he was appointed Global R&D Manager.