SUPPLEMENT

The Medical Aspects of Mines Rescue Work

It has been said that mining engineering is the art of providing an underground environment in which men can work. The words 'with safety' need hardly be added; safety is axiomatic in this engineering discipline and the low fatality rate of miners in Britain, when compared with that of coalminers in other countries, demonstrates the care taken to eliminate dangers from the working environment.

Nevertheless from time to time, in spite of the attention devoted to safety, incidents endangering groups of men do arise. These incidents vary from a heating, in which a small area of coal ignites spontaneously with the production of carbon monoxide, to a fire such as occured in 1967 at Michael Colliery in Scotland or a major explosion such as that at Cambrian Colliery in South Wales a few years ago. A mines rescue service covers every coalfield in Britain. Of the 3270 members, some are full-time rescue men but the majority are part-timers who normally work as miners but volunteer for special rescue training and who are 'on call' for any emergency.

The basic organisation of the rescue service is set out as a legal requirement in the Mines and Quarries (Fire and Rescue) Regulations which also lay down certain medical examination routines.

From the medical point of view the first essential is that men entering the rescue service must be fit for rescue duties. In the course of these duties rescue workers may well be exposed to high ambient temperatures in heatings and fires, are highly likely to require to use breathing apparatus because of danger from carbon monoxide and may well require to work at a high level of energy expenditure when sealing off a section of the pit to contain a fire or when carrying a stretcher (see Supplement to last year's report). It must be remembered that self-contained breathing apparatus presently in use weighs approximately 35 lbs., has a noticeable resistance to breathing and inevitably provides inspired air at an uncomfortably high temperature after it has been in use for half-an-hour or so.

It will be obvious that mines rescue workers must be particularly fit; stringent and detailed medical examination is necessary before entry to the service. There are two aspects of this examination which call for special mention. The first is the measurement of physical and mental fitness and the second is the assessment

of individual tolerance, or rather intolerance, to hot working conditions.

Just as the performance of a motor-car cannot be measured by inspecting it when it is stationary, so physical fitness cannot be accurately judged by medical examination of the human body at rest. Some form of exercise tolerance test, in which muscles, heart and lungs must all react to exercise is necessary. There are a number of tests of fitness which can be used in the laboratory situation with the subject exercising on a treadmill while a variety of detailed physical measurements are made. However the complexity of such tests and the extent of the equipment required make them impractical for use on relatively small groups of men scattered through the coalfields from Scotland to South Wales and Kent.

Instead a simple field test, the Havard Pack Test, was introduced some fifteen years ago. Briefly the subject wearing a weighted pack equivalent to one-third of his body weight steps up and down on a 2 seconds cycle from a block 30 cms high for 5 minutes; hand grips are provided so that he can use his arms and shoulders to assist himself. The pulse rate is counted at intervals over 41⁄2 minutes following cessation of exercise and a fitness index based on these pulse rates is calculated. The test is strenuous but is the only one suitable for use in the field. It provides a reasonably accurate, objective measure of fitness.

The second aspect mentioned was intolerance to heat. There is no evidence that any individual has an inherent high tolerance to hot conditions when working hard. On the other hand, although most people react in much the same way to work in heat, a small proportion react adversely and are termed 'heat intolerant.'

Some 12 years ago Dr. A.R. Lind, when head of the Physiology Branch of the Medical Service, studied the reaction of rescue men to work in hot conditions. He prepared tables of the times which rescue men could be expected to work at different levels of heat and humidity when wearing and using different types of breathing apparatus. These tables have been widely accepted for rescue work throughout Europe. During 1967 he completed comparable work on the latest design of breathing apparatus including the Aerorlox. See Fig. 3. His experiments were carried out on a large group of men some of whom were less than normally tolerant to heat. If it were possible to identify and exclude these heatintolerant individuals at entry medical examinations, the permitted working times could be increased appreciably without danger.

Much effort has been devoted to attempts to devise a practicable test of heat tolerance, but so far no procedure, which could be used outside the laboratory, is available.

Of course a single examination on entry does not guarantee that the rescue man remains fit and therefore annual examinations

Figure 3: Maximum Safe Periods under Specified Conditions of Temperature and Humidity for Personnel wearing Aerorlox (Liquid Oxygen) Apparatus

are carried out. These follow the pattern of the entry examination. Should a full-time rescue worker be found unfit, there are formal arrangements to fit him into other suitable work. If a parttimer becomes unfit for rescue work, he generally remains fit for his normal pit job or for alternative work at the colliery. In any event rescue men do not carry on active rescue duties after the