Document created: 23 September 03
Air University Review,
March-April 1974
Colonel William H.
King USAF, MC
Colonel Malcolm C. Lancaster USAF, MC
One of the unique functions of the USAF School of Aerospace Medicine (SAM) at Brooks AFB, Texas, is that of conducting a medical evaluation service reserved exclusively for flying personnel. While staff members of SAM’s Clinical Sciences Division participate in the school’s educational programs and conduct a varied program of aeromedical research, their primary job is patient care. They feel that the world’s finest patients are those who report to Building 100 on the SAM campus each morning to begin their evaluations. From the airman at the reception desk to the highly trained medical specialists who participate in the examination, the prevailing philosophy is to regard each patient as singularly important and each case as challenging.
Most patients are active-duty pilots and navigators who have TDY orders to this small base on the outskirts of San Antonio, Texas, because of a specific medical problem. It may have been detected during an annual physical examination by a base flight surgeon or become manifest in some illness, symptom, or dramatic event. Occasionally, small groups of aircrew members are evaluated not because of any health problem but because of their selection for a special flying or aerospace program that requires the highest possible level of physical and mental reliability. The NASA astronauts were examined here. So, for many years, were the candidates for the Air Force’s Aerospace Research Pilots School and SAC’s U-2 and SR-71 operations. Several times each year a few youthful cadets from the Air Force Academy may report for evaluation. The patient roster occasionally includes airmen from the U.S. Army or Navy or flying personnel from the armed forces of Allied countries.
Over 11,000 evaluations have been performed at USAFSAM since the service was established in 1955. It has been termed the Aeromedical Consultation Service, the Aerospace Medical Consultant Service, and (by one patient) the “Aircrew IRAN Center.” The mission has not varied. It is to evaluate difficult, borderline, or obscure medical problems, to evaluate the flyer assigned to special operations, and to provide assistance to unit flight surgeons, command surgeons, the Surgeon General, and the chief medical officers of the Air Force Reserve and Air National Guard, in maintaining a high degree of medical fitness among flying personnel. This assistance is provided by daily telephone conversations and correspondence with these offices. There are also frequent responses to inquiries from other federal agencies (NASA and FAA) and the aeromedical communities of many foreign countries.
Primarily, however, the service provides a backup capability to flight surgeons’ offices throughout the Air Force that offer direct medical support to flying personnel. Where a problem is identified that requires a SAM evaluation, either by regulation or in the judgment of the base flight surgeon, a request is submitted for review to the surgeon of the respective major air command. When this is approved, USAFSAM sets an appointment date and returns a letter of instruction and reporting information to the referral base. The flight surgeon collects the individual’s medical records, X rays, and any other medical data that may be of interest for forwarding to USAFSAM. A letter of evaluation is also requested from the individual’s flying supervisor regarding his experience, aptitude, and motivation as an aircrew member.
The patient finds that his preparations for evaluation precede his arrival at Brooks by three days. During this time he is asked to follow a special high-carbohydrate diet and keep a careful record of his food intake, for correlation with laboratory tests to be conducted at SAM. He arranges his schedule to arrive at Brooks the evening prior to his appointment, where he finds a comfortable room reserved at the base BOQ. The evaluation is not conducted in a hospital setting, and, except for unusual procedures requiring overnight observation, the patient is free during nonduty hours to visit historic San Antonio. The use of alcohol or any drug, except as prescribed by his flight surgeon, is forbidden throughout the course of examination. On the evening prior to the first day of evaluation the patient begins a 12-hour fast, which is essential to standardization of the laboratory data to be collected the next morning.
Thus prepared, the patient begins the first day of his evaluation at 0730 hours, at which time he checks in to the scheduling center and receives an itemized list of procedures or examinations that have been arranged for him. A staff flight surgeon has previously reviewed the patient’s medical records and added any special procedure that may have relevance to his case, in addition to studies considered routine at USAFSAM. The “routine” goes quite beyond what the patient may have experienced during annual physical examinations at base level. Regardless of the primary cause for referral, each patient follows a checklist that effectively screens unsuspected disease in each major organ system of the body.
The first couple of hours are required preliminary studies in the laboratory and X-ray department. Blood samples are drawn to provide a basis for evaluating proper function or disorder of several systems. Specimens are processed, utilizing the latest in automated equipment, under the supervision of a physician specialized in laboratory medicine. Some of the better-known determinations involve measurements of the fractions of lipids or fats carried in the serum portion of the blood. When elevated, these substances are considered to be significant risk factors in the development of heart disease. Each patient undergoes a two-hour screening test for diabetes. Liver and kidney function and the status of the patient’s blood cells are indicated by other tests. The results are transmitted to the flight surgeon on the same day, and further evaluation is undertaken if necessary.
The problem of diet and weight control receives specific attention of the consultation service. Each patient has a body composition study, which quantifies the degree of obesity, if any, and sets a realistic target or “ideal body weight” that the patient is encouraged to achieve. Dietary counseling by a qualified flight nurse is provided to patients who are overweight or who have other medical problems requiring dietary adjustment.
X-ray views are obtained of the chest, abdomen, and paranasal sinuses. Kidney stones are occasionally discovered, and inflammation of the sinuses (of which the patient is often unaware) is found in a surprisingly large number of patients.
At mid-morning the patient is seen by the flight surgeon assigned to his case. His medical history is reviewed in detail, and a complete physical examination is performed. The flight surgeon also reviews the purpose of the visit to the Consultation Service and gives the patient an in-briefing concerning the remainder of the evaluation. This consists of visits to various specialists, who examine the eyes, ears, nose, and throat and specialized procedures, such as those pertaining to the heart, lungs (cardiopulmonary system), and brain (central nervous system).
All patients undergo a thorough evaluation of their cardiac status, usually on the second morning of the examination. A resting electrocardiogram (ECG) is performed on all candidates and compared with those on file in the USAF Central ECG Library. This ECG provides a record of the electrical activity, of the heart with measurements in millivolts and milliseconds. Records are obtained from 12 standard leads, or pairs of electrodes, attached to the patient’s chest, arms, and legs. A special three-dimensional vectorcardiogram is then obtained, which adds pertinent information to the standard ECG tracing. The vectorcardiogram portrays the net electrical activity of the heart at any instant in time on an oscilloscopic screen, with one complete cardiac cycle being captured in a photograph taken by the attending technician. This photographic reconnaissance is performed from three different viewpoints, with enlargements to permit study of certain aspects of the activity in more detail.
After these studies are reviewed by a physician specialized in cardiology, the patient is given clearance to perform further tests, during which ECG data are recorded during and after strenuous exercise. The first of these procedures is called the Master’s test, named after the physician who standardized the procedure, in which the patient climbs up and down a short flight of stairs a certain number of times prescribed for his age. As aircrew members usually are in average or above-average physical condition, the “double” Master’s formula (utilizing the maximum number of steps) is usually employed. Afterwards, electrocardiograms are recorded during eight minutes of the recovery period, while the patient rests on an examining table. This tracing is also reviewed by a physician, and the patient is given a “go” or “no go” for a maximal exercise test on the SAM treadmill. The treadmill requires that the patient engage in a brisk walk on a moving belt traveling at a standard speed of 3.3 miles per hour. Also, as he walks, the treadmill becomes an increasingly difficult uphill climb, as the angle of incline is raised one percent each minute up to a maximum of 24 degrees. During this time the patient is completely instrumented for the simultaneous recording of three electrocardiographic leads. An attending technician carefully monitors his pulse and blood pressure. The cardiologist is always in attendance and directly observes the patient’s ECG record on an oscilloscope; the ECG data are simultaneously fed onto a computer tape for later analysis, and a paper print-out of the tracing is obtained.
When the patient indicates that he has reached a maximum level of exertion, a sample of expired air is collected in a plastic bag; this is used to calculate an efficiency report on the utilization of oxygen by his heart and lungs. The range of performance on the treadmill varies widely, of course, with most aircrew members in the 12- to 15-minute range and those in exceptionally good physical condition performing for longer periods of time. USAFSAM has accumulated wide experience with exercise electrocardiography over the years. This procedure has proved to be the most reliable and sensitive ECG method for the early detection of heart disease in the flying population.
A final bit of ECG recording is conducted over a period of several hours while the patient goes about other activities or portions of the examination. One pair of electrodes is attached to his chest, and the recorder is carried in a little black box on a shoulder strap. He maintains a log of his activities during this time and is supposed to make note of any event that might affect his heart rate.
The electroencephalogram (EEG) or brain wave is a new experience for most SAM patients. A number of small plastic electrodes are glued to the scalp in precisely determined locations. The patient then reclines in an oversized chair and relaxes while a technician pores over a complex console of controls that govern the recording of electrical activity from the brain according to established procedures. Differences in electrical activity are recorded between two points in successive pairs, comparing right to left, front to back, etc. The magnitude of the electrical activity varies markedly from that recorded on the electrocardiogram, as EEG signals are in the microvolt range. The EEG is a valuable tool in evaluating cases of head injury, for example; the majority of cases seen for this purpose at SAM are the result of automobile rather than aircraft accidents, incidentally. For all aircrew members, however, the study is considered a valuable piece of base-line information in the event that a patient should, in his future life, develop some central nervous system problem through disease or injury. All EEG’s are retained on file at USAFSAM for possible future reference. The EEG also records sections during which pertinent types of stresses are applied, not exercise in this case but brightly flashing lights that pulse the brain-wave system or a few minutes’ exposure to mild hypoxia, as might be encountered in the flying environment.
If these studies do not provide all of the information required, the patient may find himself being tested in more exotic surroundings, such as simulated flight in an altitude chamber or during exposure to + Gz forces on the SAM human centrifuge. Either is readily available at SAM and is equipped for biomedical monitoring, e.g., recording of pulse rate, blood pressure, and electrocardiogram. These procedures may seek to duplicate any in-flight circumstance that might have a bearing on the individual case.
But most frequently the cause of a patient’s referral to USAFSAM is not related to a dramatic in-flight illness. The evaluation, however, may seek to prevent the occurrence of such an event. The most common cause of death and disability in the American adult male population is heart disease or, more specifically, coronary artery disease resulting in an acute myocardial infarction or heart attack. Aircrew members are not immune to the hazards of this disease and share most of the risk factors found in the civilian population. Unfortunately, there have been several cases in which flying careers have been prematurely curtailed by heart disease. The Air Force effort in the early detection of coronary artery disease has obvious implications with regard to the safety of flight operations as well as to the health of the individual. Thus, cardiac problems are the leading cause of referral of patients to USAFSAM.
The key to the early detection program is the electrocardiogram recorded on each aircrew member upon entry into flying training and then annually at age 35 and thereafter. Copies of each electrocardiogram are forwarded to the USAF Central ECG Library, located at USAFSAM, for careful review. If any evidence of change from one year to the next is noted by the reviewing cardiologist, further evaluation may be suggested at the patient’s home base, or referral to SAM may be recommended.
Other conditions are also referred to SAM in accordance with Hq USAF policy set forth in a manual of physical standards. For example, any aircrew member who experiences an unexplained loss of consciousness or significant head injury requires evaluation at the Aeromedical Consultation Service prior to consideration of return to flying status. To take advantage of the expertise centralized at USAFSAM, certain organic conditions of the eye, such as glaucoma (an increase in the intraocular pressure), or of the vestibular apparatus (the body’s gyros) are referred to the school. Consultation is also available for an aircrew member experiencing any significant emotional problem. In all these areas his case will be examined by specialists who are also well versed in the Air Force mission and the relevance of his condition to it.
At the conclusion of the evaluation, the patient is given a complete debriefing by the flight surgeon, who has gathered together the results of all procedures and consultations. A detailed report is completed promptly and forwarded to the Surgeon General or other designated reviewing authority, in the event that any administrative action is required. Recommendations for medical treatment, follow-up, or correction of defects are spelled out for the patient and reviewed with his base flight surgeon, by phone, on the day the patient leaves Brooks. The early diagnosis of disease and the prevention of any serious consequences are the goals in each case.
Conduct of the Consultation Service also interrelates with USAFSAM aeromedical research programs and results in a number of by-products of value to the Air Force and to medicine in general. The electrocardiographic library is thought to be the largest in the world, with over 700,000 tracings currently on file. It has added new pages to medical knowledge in the increased appreciation of certain findings in the normal population and the significance of findings developed on serial recordings. There is continual feedback and interchange of ideas with the Aircrew Standards Division of the Surgeon General’s Office in an effort to refine the physical standards for flying duty in order to permit the greatest utilization of trained manpower consistent with flying safety.
Improved knowledge has resulted in significant increases in the number of flying personnel returned to flying duty since the establishment of the Consultation Service. For example, certain conduction defects in the heart’s electrical circuitry were once thought to be indicative of coronary artery disease. Over 100 patients studied at USAFSAM during the past five years have disproved this hypothesis, and the majority of these individuals have been returned to active flying duty.
These and other medical conditions of distinct interest to the Air Force form the basis for a small number of clinical study groups in which patients are followed over a period of several years, with annual evaluations by the Consultation Service, in order to maintain the individual on flying status and learn more about the significance of the condition. In addition to the conduction defects, patients with heart murmurs indicative of mild aortic valvular disease, those with a history of certain irregularities of the heart beat, and patients with history of vertigo and blood loss from the upper gastrointestinal tract are among those currently being followed.
The Consultation Service provides a setting for utilization of the latest medic techniques in seeking the early diagnosis of disease. The SAM clinical laboratory actively engages in research concerning the significance of biochemical findings in their relationships to disease. For example, the widely used glucose tolerance test for the detection of diabetes is under study. The significance of minute amounts of certain metals such as copper, zinc, chromium, and magnesium, which are found in the blood, is being evaluated. The technical problems of accurate determinations are being overcome, and the possible relationship to diseases of the cardiovascular system is currently under study. In addition to the ECG Library and the EEG files, USAFSAM maintains repositories of information on the Air Force’s hearing conservation program and a repository of data on individuals who require medical waiver for continuation of flying duties. Over 6500 aircrew members are currently listed in the waiver file. A complete print-out of these data is distributed quarterly to the Surgeon General’s Office and to the surgeon’s Office of each major air command. SAM has also been designated as the Air Force center for the storage and analysis of medical data pertaining to repatriated prisoners of war from Vietnam.
Utilizing the staff and facilities of the Clinical Sciences Division, the Air Force has conducted specific research projects in support of Air Force mission requirements. For example, the safety of antimalarial drugs was verified in a clinical study at USAFSAM prior to their use in Southeast Asia. Certain types of drugs used in the treatment of high blood pressure were studied at the school and are now being utilized by over 300 individuals, who are able to continue on flying status whereas they might otherwise have been grounded. The SAM experience in telemetry of biological data was directly applied in NASA missions. The knowledge and experience on the staff have contributed to the design of new protective equipment for flying personnel. Current studies seek to evaluate impact resistance of various types of spectacle lenses and to eliminate distortion from windscreens proposed for advanced aircraft, and even to build better dental appliances for flying personnel.
The efforts of the Consultation Service result in considerable savings to the taxpayers when a medical problem in an aircrew member may be satisfactorily resolved. The staff recognizes that its patient population represents enormous investments in training costs and valuable experience. Their greatest satisfaction is in helping another patient return to years of continued aircrew duty.
Clinical Sciences Division, USAFSAM
Colonel William H. King (M.D., University of Texas; M.P.H., Harvard University) is Deputy Chief, Clinical Sciences Division, USAF School of Aerospace Medicine. He has served as Flight Surgeon, SAC B-52 wing, Sheppard AFB; Director of Aerospace Medicine, Vandenberg AFB; and Surgeon, USAF Advisory Group, Tan Son Nhut AB, and medical advisor to the Vietnamese Air Force. Colonel King is a member of several professional societies and author of publications on aerospace and preventative medicine.
Colonel Malcolm C. Lancaster (M.D., University of Texas) is Chief, Clinical Sciences Division, USAF School of Aerospace Medicine. He has served as Chief, Medical Services, 48th Tactical Hospital, RAF Lakenheath, England; Chief, Cardiopulmonary Service, later Chairman, Department of Medicine, USAF Hospital, Wright-Patterson AFB; and Chief, Internal Medicine Branch, USAFSAM. Colonel Lancaster is a member of a number of professional societies and author or coauthor of thirty publications in the field of cardiology.
Disclaimer
The conclusions and opinions expressed in this
document are those of the author cultivated in the freedom of expression,
academic environment of Air University. They do not reflect the official
position of the U.S. Government, Department of Defense, the United States Air
Force or the Air University.
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