The ComPAC 200 Ventilator in the Military EnvironmentSmiths Medical International Ltd
These include those related to the environment, the need for robust “soldier proof” hardware, portability, usability and safety.
Specific Factors to be borne in mind when selecting equipment are as follows
Modern warfare is no longer a linear affair where the enemy are behind one line and we are on the other side of it. There is a far more dynamic situation with pockets of activity spread over large areas. More recently areas of operations have included desert and mountainous countries where extremes of cold and heat are experienced, perhaps with altitude factors to be taken into account. Equipment must have in built tolerances to withstand extremes of environment
Robustness and portability
With the dynamic and fast moving nature of modern conflicts there is a need for portability of all equipment which can if necessary be man packed or borne for an airborne insertion. Hence, the innate mechanical durability is essential in an environment where troops are used to “lifting and shifting” unfamiliar kit which they assume will have the usual durability of most military hardware. In addition the functionality must not be hampered by adverse conditions experienced such as dust, sand, heat, cold etc
Simplicity and user friendliness are obvious factors to be borne in mind when selecting equipment of the military environment.The facility to use various power sources is helpful as well as option of an internal battery.
Recent UK Military Deployments
Within the British Defence Medical Services a lot of energy and resources have expended to raise the functionality of our deployable medical resources, in particular the anaesthetic scale of equipment. With the introduction of minimal standards (e.g. monitoring) across the UK, raised patient expectations and the requirement to provide similar standards of care in the military environment as to those found in the National Health Service, the new scale of deployable anaesthetic and ITU equipment is far removed from previous large scale deployments ( e.g. the 1991 Gulf War)
The Royal Marines have developed a concept of far forward resuscitation and surgery as part of the new Commando concept, resulting is the formation of Commando Forward Surgical Groups (CFSG) which are available for short notice global deployments to provide resuscitation and surgical care in a role 2 capacity as far forward as possible. This may be in conjuction with a role 3 facility (Field Hospital) some way further back or as a single facility in a remote location with a holding facility of up to 48 hours (and subsequent resource implications)
In May 2002, CFSG1 were deployed at short notice to Afghanistan to provide medical support to specific operations in a remote location. This was the first live trial of this new concept and after a period of equipment rationalisation the team were flown out to establish a surgical facility by a remote dust airstrip. Conditions were as one would expect; hot and dusty (exacerbated by helicopter down draft regularly throughout the day). Three sandbagged containers were available, one of which served as resuscitation and the other two as operating rooms.
The following year the, both CFSG 1 and 2 deployed to Kuwait and subsequently Iraq for OP TELIC. The equipment was the same as the previous year with some refinements in terms of volume and capability. CFSG 2 were set up as the ready facility on the border at the start of the war while CFSG were packed and ready for early insertion into the AL FAW peninsula.
Around noon on the first day of the war CFSG 1 were flown onto the AL FAW peninsula where they rapidly established a surgical/resus facility.
Over the next few weeks CFSG 1 were moved 5 times, usually at short notice, setting up as a ready facility within 25 minutes at each location. On cessation of hostilities CFSG1 returned to a holding location where CFSG2 (who had moved twice) were still “open”
The following year I returned to Iraq to the British Military Hospital near Basrah where we experienced a high case throughput of trauma cases (high velocity, blast and burn injuries). We used the C200 for the majority of these cases utilising mains power as the driving source with no major problems.
Personal experience and impression of the comPAC200 ventilator (Smiths Medical International, Hythe, Kent)
My initial impression of the comPAC 200 was that it seemed to have been designed with the rigours of military life in mind. It appeared robust (stuck in a hard metal case and green!). The tubing was simple and robust and fitted together well. The ventilators coped well with frequent packing and unpacking from cases not specifically designed for the it, repeated loading and unloading off lorries and helicopters and being transported as under slung loads.
A big advantage of the ComPAC 200 was the versatility of power sources which is important in the military environment. It can be run from an external power source, ambulance batteries or internal batteries (the same battery as the military clansman radio hence availability is not an issue) which drive the internal compressor. Whilst running off the external power source , in our case a small generator, the internal battery charges up to allow up 2-3 hours battery life. There is also the facility to run the ventilator of a pressurized gas source (recommended mode of use by the manufacturers) although this has resource implications in the battle situation.
The setting up and running of the ventilator is fairly intuitive with simple minute volume and respiratory rate settings and an analogue pressure gauge. Pre use safety checks are mandatory. It is important to remember that the S10 respirator filter is attached at the back to allow air filtering and removal of dust and other particles. This also allows the ability for this ventilator to be used in an NBC environment for transfer and treatment. It has been noted that the filter also acts as an effective noise reduction tool!
For a GA in the military environment we usually induce anaesthesia intravenously after a period of pre-oxygenation using a slightly modified TSA circuit. The Triservice anaesthetic (TSA) apparatus remains the main stay of UK military anaesthesia and in conjunction with modern monitors is a safe and in my opinion the best and most reliable method of performing GA's in these circumstances. After securing the airway and establishing an appropriate depth of anaesthesia the comPAC 200 is attached to the breathing system on the upstream side of the OMV (Oxford Miniature Vaporiser).
This is in contrast to the traditional teachings for the TSA which employs a form of draw over anaesthesia with the OMV's (Ref 1) and the comPAC 200 is utilised in a pushover style. This does not cause a problem as long as one uses clinical skills to monitor depth of anaesthesia and keeps an eye on the level of volatile in the OMV's. It has been shown that volatile output is consistent when similar ventilators are used in both drawover and pushover mode (Ref 2). There is also a volatile agent monitor facility on our monitors which we always use in conjunction with end tidal CO2 monitoring. Lack of volatile agent is of course not an issue when employing TIVA techniques. It is important to remove the self inflating bag from the circuit when employing the ventilator as the compliance of the system would be too high to allow effective ventilation.
Unless there is a strong reason to use the no air mix, then the air mix option is chosen giving an FiO2 of around 45% when using gas as the driving source. For external/internal electrical power sources additional oxygen is added upstream of the vaporisers as required either next to the NBC filter (max 4l/min) or, as is my practice immediately, upstream to the vaporisers.
To maintain view of the control panel it is necessary to be sitting down at the level of the ventilator or to have it tilted up slightly (this is afforded by the use of the metal /rubber base plate). A built in light illuminates the display. The alarm set up is simple and will alert you to disconnection, overpressure, low battery life or gas supply failure.
The comPAC 200 is relatively quiet in operation and assembles very easily. Care must be taken in keeping all the power leads and connectors together during deployments involving frequent moves as these are in my opinion the most vulnerable parts of the system both from a “getting lost” viewpoint and overenthusiastic assembling. The former is a local domestic issue although the design of a robust ventilator specific box would be ideal and is something we are pursuing. We encountered one broken lead for the external powers source outlet which survived the campaign after the application of some superglue (connector 15). The pressure relief valve was broken off in two of our ventilators although interestingly this appears to have taken place during recovery to the United Kingdom.
Whilst being used in the role of delivering ventilatory support during general anaesthesia the comPAC 200 was extremely simple to use, functional and a reliable minute volume divider. As an ITU ventilator it obviously lacks the options of a spectrum of FiO2's (although this can be overcome by additional oxygen downstream from the ventilator) and the choice of ventilation modes (altered I: E ratios, SIMV, ASB etc) which one would expect as the norm. Despite these limitations, we used it successfully for overnight ventilation in a seriously injured casualty with no obvious ill effects, prior to transfer out the following day. The comPAC 200 also serves as a transfer ventilator within the British Military but my experience of this is limited and I will not comment on this.
Previous Military experience
Having served in the RN for 20 years I have been exposed to a myriad of medical devices provided for deployment. Over the last 3- 4 years there has been a lot of work done to streamline our medical supply (particularly with regards to Role 2 medical support) and update the standards and versatility of the equipment. The comPAC 200 has proved itself to be a robust, dependable and simple to use ventilator which is now found throughout the evacuation chain (excluding the specialist RAF aero-medevac teams). It is not intended for use in pressurised aircraft. It is intuitive to use and many junior anaesthetists will have had experience of its close relative the, Pneupac ventilator. I have no experience of using it in the paediatric setting and it is not recommended for patients less than 20 kg.
I have confidence in the abilities of the comPAC 200 to perform in the conditions to which UK military forces deploy. Importantly, it has been designed to remain operational in an NBC environment and in conjunction with the Tri-Service anaesthetic apparatus, this system provides a robust, safe and reliable means of delivering anaesthesia.
I have no conflict of interest pertaining to Smiths Medical or the comPAC 200 ventilator.
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For further information regarding Surgeon Commander Stephen Bree the original author of this article click hereto access a biography.