SubscribeSince the sarin attacks in Japan in 1995 and particularly since the attack on the World Trade Centre there have been continued concerns about terrorist use of chemical and biological warfare (CBW) agents and how to provide an effective emergency medical response.
Cardiopulmonary resuscitation (CPR) is a fundamental part of modern prehospital emergency medicine and provides special care for management of the patient’s airway, artificial ventilation and circulatory support. Cardiac arrest is the most common situation where CPR is needed and mouth-to-mouth ventilation and chest compression are familiar examples of life support in everyday life.
In a toxic environment the main threat is not usually to the heart but to breathing and to the lungs themselves. Passage of the air to the lungs may be blocked by secretions and by the action of the toxic agent itself. Toxic agents such as sarin depress the control of respiration by the brain and cause paralysis of the muscles of respiration. The result is respiratory failure, followed by cardiac arrest and death unless antidotes and vital life support are provided quickly. Other hazards such as mustard gas and phosgene can cause life-threatening threatening build - up of fluid in the lungs (toxic pulmonary edema), which can require early artificial ventilation of the lungs.
As a response to these hazards, emergency medical organisations around the world have been discussing medical counter measures for CBW attack on civilians. In several countries plans are now in place to bring emergency medical care into a civilian contaminated zone using trained personnel working in protective suits. Such teams are necessary because of the need to provide advanced life support in addition to antidote therapy for patients affected by CBW hazards. Response teams are trained to be able to secure the airway by placing an endotracheal tube or other device. The next key step is to be able to provide artificial ventilation.
This can be done manually using an inflatable bag or by using an automatic portable gas-powered ventilator (PGPV) - which can provide a quality of ventilation using compressed oxygen that is equivalent to the care available in the emergency rooms and intensive care units inside the hospital.Nerve agents and those causing pulmonary edema cause an increase in resistance and stiffness of the lungs and artificial ventilation is best provided by PGPV to avoid life-threatening lack of oxygen in the blood.
Management of casualties following CBW attack involves management not only of the casualty but also of the environment. Artificial ventilation in the contaminated zone may be required for some time while decontamination of casualties takes place, before they can be moved on to hospital care. This presents a problem of re-supply of oxygen cylinders required to drive the ventilator.An average D-sized small cylinder used by most paramedic services will only last for about 30 minutes. If used with other ventilation devices such as a self - inflating bag the duration may be less.
A novel approach to ventilation in a toxic environment, developed over the past decade has been to use a ventilator that uses filtered air from the surroundings as the driving gas. The basic respiratory protective philosophy for personnel operating in contaminated environments is to use a filtration mask and canister, together with a protective suit and gloves. The canister is capable of filtering out the toxic agents from the atmosphere and thus can be used to filter the gas entering the ventilator. This is the basis of the development of the compPAC ventilator, which has been specially produced for use in toxic life support.
The compPAC ventilator is a PGPV, which can be used in both emergency (advanced life support) and transport ventilation for patients in respiratory failure. It is unique in design since the driving gas is provided by compressing filtered ambient air, rather than using bottled compressed oxygen as with conventional PGPV. This means that in situations such as the battlefield or mass civil disasters valuable supplies of compressed oxygen can be preserved.
compPAC can be powered from a variety of sources including an internal rechargeable NiCad battery, external 24v - 28v DC source, step down mains supply or from compressed oxygen if available.The internal NiCad battery provides up to 4 hours of operation in the field. If the unit is powered from the external mains supply the NiCad battery will be on constant trickle charge.
If bottled oxygen is available, its use can be optimised by enriching the air from the ventilator output. In this way concentrations above 60% can be achieved while maintaining cylinder life. The importance of this is illustrated by the fact that a normal D-sized cylinder driving a PGPV to deliver 100% oxygen will last about 30 minutes. If the same cylinder is used to enrich the gas output from compPAC the life span is increased up to 4 hours. The use of modern carbon fibre D cylinders gives over 6 hours of operation. This is comparable with the internal battery life of the ventilator and means that a portable autonomous system can be carried in to a difficult environment and provide stand – alone ventilation for substantial periods.
The ventilator provides variation of frequency between 10 and 30 l/min and minute volume of 3 – 14 l/min. The unit contains both pneumatic and state-of-the-art electronic alarms and a patient pressure manometer.This means that clinical ventilation of intensive care quality can be provided in the CBRN environment. Apart from its CBRN operating capability, compPAC can be used as a conventional PGPV powered by high-pressure oxygen when such supplies are available.
The design of compPAC is very rugged and this, together with its versatile power operation allows it to be used in battlefield or civil disaster situations where conventional resuscitation equipment is inappropriate and bottled gas re-supply often variable. Currently it is in service with armed forces around the world and is part of civil mass disaster contingency plans.
On the battlefield and in civil terrorist attacks there is increasing likelihood of casualties from toxic agents. These can be treated but it is essential to provide an early response with both antidotes and life support. Training and equipment are vital and can radically alter the clinical outcome for the wounded. Emergency ventilation, for many years a feature of standard pre-hospital life support is now feasible in a contaminated zone and is rapidly becoming a feature of planning and response for terrorist attack and other toxic incidents.
