Books and Documents - Army Aeromedical Evacuation
U.S. ARMED FORCES MEDICAL JOURNAL, VOLUME V, NO. 2 (FEBRUARY 1954)
MEDICAL CONSIDERATIONS IN
HELICOPTER EVACUATION
SPURGEON H. NEEL, Jr., Lieutenant Colonel, MC, USA
Helicopter evacuation of the seriously wounded from the forward combat area is a sound and feasible medical practice. It has been battle tested in Korea and subjected to formal field testing within the zone of the interior. While current organizational structure and various helicopter models are still under evaluation, it is generally accepted that ambulance helicopters, under the control of the Army Medical Service, will contribute materially to the medical service of any future military operation.
Battle and training experiences have indicated a requirement for more understanding regarding the role of helicopter evacuation within the over-all medical effort in forward combat areas. Full exploitation of the capabilities of helicopter evacuation depends upon a sound understanding of the medical and tactical considerations involved. The surgeon who best understands the principles and procedures utilized in helicopter evacuation can best exploit its capabilities in the care of the individual casualty and the command. The basic procedures used in helicopter evacuation are prescribed in Department of the Army Training Circular Number 32, 1952. Ground assistance required for helicopter operations is described in Department of the Army Training Circular Number 22, 1952. Tactical considerations in helicopter evacuation will be the subject of a separate article. Organizational and developmental matters are, likewise, beyond the scope of this discussion.
Air evacuation, under the control of the United States Air Force, has been proved the primary and best means of moving casualties between the combat zone and the communications zone or the zone of the interior. Normal air evacuation is used after the casualty has been moved into the army service area and has received initial surgical intervention In the forward combat area, however, the majority of casualties will continue to move by surface evacuation.
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From U. S. Army Medical Field Service School, Fort Sam Houston, Tex. Col. Neel now at Headquarters, 30th Medical Group, APO 301, San Francisco, Calif.
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With the advent of helicopter ambulances, air evacuation has been pushed steadily forward until it is now available within the regimental area. Every field surgeon is now concerned with air evacuation and must appreciate its capabilities, limitations, and procedures, and, most of all, his own responsibilities. Helicopter ambulances are but auxiliary means of evacuation. They supplement, but do not replace in any way, conventional surface means of evacuation. Helicopter ambulances afford the forward surgeon greater speed, flexibility, and selectivity in evacuation but he must realize that lie has accrued many new responsibilities with helicopter evacuation.
The advantages, or capabilities, of helicopter evacuation can be considered under five major headings: (1) speed in evacuation, (2) flexibility of medical service, (3) patient comfort, (4) selective evacuation, and (5) economy. All of these factors reduce the mortality and morbidity of the individual casualty, and improve the medical practices within the command. An understanding of these considerations will facilitate exploitation of helicopter evacuation and the better integration of its capabilities into the over-al1 medical support of the command.
SPEED IN EVACUATION
Speed in evacuation is most important in the severely wounded. Casualties area "perishable commodity." They cannot be "stockpiled," but must receive proper treatment as early as possible. A man dies in so many minutes, not over a distance of so many miles. Any measure that will reduce the time lag between wounding and treatment will reduce both the mortality and morbidity of war wounds. The ambulance helicopter gives more rapid evacuation in two specific ways. Its speed over unfavorable terrain permits the rapid evacuation of casualties from the forward pickup point to a medical facility capable of initial surgery anywhere within the army service area. This, in effect, places all hospitals and special treatment centers in direct support of the regimental or battalion surgeon. Secondly, the minimum landing site requirements of rotary-wing aircraft permit their use well forward.
A basic principle of field medical service is flexibility, which is enhanced by the use of helicopter ambulances. The speed and range of rotary-wing aircraft and their minimum landing site requirements permit their concentration whenever and wherever required. Thus, the controlling surgeon can quickly shift his evacuation means to support any unit which is becoming immobilized with severely wounded casualties. The surgeon now has the capability of evacuating and providing limited medical resupply to units which are isolated by enemy action or terrain.
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The importance of flexibility of medical service is increasing with the advent of new "mass destruction" weapons and the tactical concept of defense on a wide front with small, relatively isolated units.
Comfort of the patient is not merely a luxury. Antitraumatic evacuation is essential if shock is to be prevented or minimized. Proper preparation of the casualty for evacuation is as important when using helicopters as any other evacuation means. With helicopter evacuation, the casualty not only reaches the proper treatment facility faster, but also in much better condition. Helicopter evacuation is in no sense a form of treatment, but it is a valuable adjunct to subsequent surgical intervention in that it moves the casualty to the surgeon in the shortest period of time and in the best possible condition.
SELECTIVE EVACUATION
Selectivity in evacuation is less obvious than the other factors listed and bears further consideration. Evacuation is no longer limited so that all casualties must move to the particular hospital supporting the major tactical command. The speed, range, and flexibility of helicopter evacuation permit the removal of the casualty to the treatment facility best equipped and staffed for his particular type of wound. The effectiveness of this procedure depends on helicopter ambulances remaining under medical control and the co-operation of forward surgeons in providing adequate clinical information.
Economy may sound paradoxical when one considers only the cost of the individual helicopter ambulance. Actually, the proper use of helicopter evacuation permits considerable economy in medical means. Specialized personnel can now be concentrated in designated treatment facilities located well forward in the combat zone and there is no need for equipping and staffing every forward hospital for the care of every type of casualty. More and better surgery can be provided with less personnel. When one considers the value of the individual soldier, including both his military and subsequent civilian contribution, the true economy of saving a life becomes obvious.
These five basic advantages of helicopter evacuation bear analysis by all concerned with the use of the helicopter ambulance, but particularly by the field surgeon due to his key role in forward air evacuation. Full use of helicopter evacuation depends on the intelligent co-operation between the medical officers located in forward installations and the pilots of ambulance helicopters.
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A brief consideration of the limitations of forward helicopter evacuation will assist the field surgeon in maintaining a proper perspective. The helicopter ambulance is no panacea. Most limitations can be minimized if they are understood and steps are taken to circumvent them or prevent undue interference with forward medical support. The limitations of the ambulance helicopter can be considered under four general headings: (1) cost, (2) maintenance requirements, (3) sensitivity to weather and darkness, and (4) tactical integration.
The cost of each ambulance helicopter will constitute a limitation on the number that will be available to the Army Medical Service. The H-13 aircraft, which transports two litter patients externally, costs about $34,000. The H-25 aircraft, which transports three litter patients internally, costs about $340,000.* Compare these figures with the $4,621 that will buy a field ambulance capable of transporting five litter patients. High skill and training requirements of pilots and maintenance crew contribute even further to the expense. The cost can be minimized by insuring that ambulance helicopters are used with maximum efficiency and that they are reserved for emergency evacuation of severely wounded casualties requiring immediate initial surgical intervention or routine evacuation from isolated military units where other means of evacuation are not feasible. The helicopter, like any other type of aircraft, is of value only when flying. Delay at either terminus in air evacuation, whatever the cause, increases the relative expense of the aircraft by wasting its usefulness. Lack of information in request for a helicopter and slowness in loading procedures are the most common sources of delay in helicopter evacuation.
In Korea the ratio of maintenance time to flying time was found to be about 6:1. While maintenance is not strictly a medical problem, field surgeons should appreciate its requirements when projecting the use of helicopter evacuation for a particular operation.
Helicopters are very sensitive to weather and darkness. Instrument equipment is limited, and the pilots normally fly VFR (Visual Flight Rules) which preclude their use when ceiling or visibility are below minimum standards. Night evacuation missions are rarely flown. Only when there is a most urgent need, when the pilot has previously entered the area, and when the landing site can be lighted can pilots safely execute night evacuation missions. This requires the maintenance of an effective surface evacuation system. Provision must be made for
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*Price based on minimum quantity orders.
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initial surgery well forward within the reach of surface evacuation to cover those periods when helicopter evacuation is not available.
TACTICAL INTEGRATION
Helicopter evacuation poses many problems which are new to the Army Medical Service. A full discussion of these problems is being made the subject of a separate article, but the field surgeon should realize their impact on medical practices in the forward combat area. While most of these-considerations are nonmedical, the field surgeon must know all the factors which influence the care and evacuation of casualties to develop sound forward medical practices. Among the problems inherent to integration of helicopter evacuation are: site selection and marking, control of aircraft in flight, visual and electronic air-ground communications, co-ordination of supporting fires with helicopter sorties, preservation of concealment of forward medical and tactical installations, and safety.
The surgeon exercising detailed control of helicopter sorties receives evacuation requests through medical channels over "common user" electronic facilities. Each request contains appropriate clinical information on each casualty plus data on the place and time pickup is desired, the marking of the site, and required tactical information. Each intervening surgeon has screened the request and established priorities where indicated. Based on this information, the surgeon exercising operational control over helicopter evacuation dispatches individual helicopters with instructions as to the proper destination of casualties. These are medical decisions, and can be made only by those with sufficient training and experience.
SELECTION OF CASUALTIES
The selection of casualties for helicopter evacuation is normally the initial problem confronting the field surgeon using helicopter ambulances. Considerations involved include: (1) the nature and severity of the casualty`s condition, (2) the availability of helicopters for evacuation, (3) the number of casualties requiring expeditious evacuation, and (4) other means of evacuation available.
The following types of casualties should be evacuated by ambulance helicopter to the nearest medical facility capable of the type of initial surgery required:** (1) casualties in shock, who have been in shock, and those with continuing hemorrhage; (2) all traumatic amputations; (3) open fractures of long bones, complicated by shock or hemorrhage, or without complete and
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*Extracted from addresses presented 19 and 30 April 1951 at Army Medical Service Graduate School, Washington, D. C., by Howard S. Snyder, M. D.
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comfortable immobilization; (4) wounds of the extremities with impaired blood supply, or with a tourniquet in place, or with history of tourniquet application; (5) wounds with extensive muscle damage; (6) abdominal wounds; (7) all sucking chest wounds; (8) chest wounds in which there is any degree of respiratory difficulty or dyspnea; (9) all thoracico abdominal wounds; (10) maxillofacial or neck wounds that are severe or in which there is respiratory difficulty; (11) head injuries in coma with signs of increased intracranial pressure; and (12) suspected gas gangrene. These are the same type of casualties that are eligible for initial surgery in the mobile army surgical hospital when helicopter evacuation is not available.
There will rarely be sufficient helicopters to evacuate all these casualties. The medical officer must, in each case, decide which of the more seriously wounded are to be evacuated by helicopter and which by field ambulance. This is a matter of clinical judgment, and "rules of thumb" are not only useless, but dangerous. When making such decisions, the surgeon considers the time separating his installation from the mobile army surgical hospital. It is poor medical practice to delay unduly the evacuation of a casualty pending availability of a helicopter ambulance when it is feasible to expedite his evacuation by field ambulance.
Any casualty that is at all transportable is transportable by helicopter. The low altitudes and short flights characteristic of helicopter evacuation permit transportation of casualties who might be unsuitable for evacuation infixed-wing aircraft. The principal limiting factors in air evacuation are altitude pressure changes and, to a lesser degree, anoxia. Neither of these two limitations is significant in helicopter evacuation.
PREPARATION OF PATIENT
In the preparation of casualties for helicopter evacuation, hemorrhage must be controlled and treatment for shock must be instituted and continued while waiting for the arrival of the helicopter ambulance. The casualty should have a systolic blood pressure of at least 80 mm. Hg and an adequate airway must be established. Prior to take-off, the casualty`s tracheobronchial tree should be emptied of any blood or mucus. Those with severe maxillofacial injuries should be evacuated in a prone position to prevent aspiration of vomitus in event they should become air sick. Rarely, tracheotomy may be indicated. Fractures should be immobilized and adequate sedation should be given to reduce pain and shock. Open chest wounds, whether sucking or not, should be tightly bandaged. In short, all possible medical care should be given the casualty prior to take-off without delaying his evacuation.
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Limited medical treatment can be continued in flight if the casualty is evacuated in cargo-type helicopters. These helicopters may carry a medical attendant in addition to the pilot, who is also a qualified medical assistant. It must be realized that, although helicopter ambulance pilots are qualified medical assistants, their medical function in flight is limited to judgment because they are too occupied flying the aircraft to devote any direct attention to casualties. If treatment is to be continued in flight, detailed instructions should be given to the medical attendant. Active medical care in flight is impracticable when casualties are evacuated in utility type helicopters such as the H-13 because the casualty is carried on external litter racks.
Helicopter evacuations normally terminate in evacuation hospitals. Use of an evacuation hospital rather than a mobile army surgical hospital as the rear terminus for helicopter evacuation is preferable because transportation of casualties from the regimental area to a properly located mobile army surgical hospital (within the division area) does not fully make use of the speed, range, and flexibility of helicopter evacuation. The capacity of the mobile army surgical hospital should be conserved for severely wounded casualties which exceed the capabilities of available helicopter evacuation. At night and during inclement weather it is advantageous to have beds and medical personnel ready in the mobile army surgical hospital to care for all casualties pending the resumption of helicopter evacuation support. In Korea, the rear terminus for helicopter evacuation was the mobile army surgical hospital but there, until late in the campaign, the mobile army surgical hospital usually functioned as an evacuation hospital and was located from 30 to 60 miles behind the line of contact. This validated the procedure recommended rather than being an exception.
The helicopter ambulance, like any other ambulance, is capable of limited medical resupply. Whole blood, plasma, biologics which have extreme storage requirements or short expiration dates, and other urgently needed medical items are advantageously distributed by air. Routine evacuation of tactical units isolated by enemy action or terrain can be done effectively by helicopter. River crossing and amphibious operations are good examples of this latter use. The ferrying of patients from army medical installations to U. S. Navy hospital ships located off-shore is another effective use; Helicopters afford considerable flexibility in meeting unforeseen medical requirements in rear areas such as are incident to area damage control operations.
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SUMMARY
The helicopter ambulance has won a place in the Army Medical Service. It is not contemplated that helicopters will ever be available in sufficient quantities to replace conventional surface means of evacuation, nor that such would be desirable. The role of the helicopter ambulance is that of an auxiliary means supplementing, but not replacing, field ambulance evacuation in the forward combat area. Helicopter ambulances must be under medical control to achieve the selectivity in evacuation that is inherent to utilization of helicopter evacuation. The field surgeon must understand the capabilities and, even more important, the limitations of helicopter evacuation. He must accept his own responsibilities as a member of the ground-air team that is essential to the full value of forward air evacuation. It is not a matter of whether the Army can afford to use helicopter ambulances but more a matter of whether we can afford not to use them.
