Part 1 ebook the present the content: introduction, the history and development of aviation medicine Viktor Harsch; international standards and requirements, Icao international medical standards and recommended practices Claus Curdt-Christiansen, federal Aviation administration — Aviation medicine, joint aviation authorities (JAA) and European aviation safety agency (EASA) — medical requirements for pilots in Europe; physiology and radiation, fundamentals of aviation physiology, cosmic radiation exposure of flight crews; prevention, physiology and pathophysiology of nutrition; clinical Aviation medicine, introduction: the role of medical factors in accident investigation, cardiovascular risk factors, arterial hypertension, heart diseases and disorder, coronary artery disease, cardiac valve disease/valve replacement, cardiac rhythm and conduction disturbances, congenital heart diseases, vascular diseases and disorders.
PRINCIPLES AND PRACTICE OF AVIATION MEDICINE This page intentionally left blank PRINCIPLES AND PRACTICE OF AVIATION MEDICINE editors Claus Curdt-Christiansen International Civil Aviation Organization, Montreal Jörg Draeger University of Hamburg, Germany Jürgen Kriebel Aero Medical Center, Lufthansa AG, Frankfurt, Germany World Scientific NEW JERSEY • LONDON • SINGAPORE • BEIJING • SHANGHAI • HONG KONG • TA I P E I • CHENNAI World Scientific Publishing Co Pte Ltd Toh Tuck Link, Singapore 596224 USA oflce: 27 W m n Street, Suite 401-402, Hackensack, NJ 07601 UK oflce: 57 Shelton Street, Covent Garden, London WC2H 9HE Library of Congress Cataloging-in-PublicationData Principles and practice of aviation medicine / editors, Claus Curdt-Christiansen, Jorg Draeger, Jiirgen Kriebel p ;cm Includes bibliographical references and index ISBN-13: 978-981-238-861-2 (hardcover : alk paper) ISBN-10: 981-238-861-3 (hardcover : alk paper) I Aviation medicine I Curdt-Christiansen, Claus 11 Draeger, Jorg, Prof Dr 111 Kriebel, liirgen [DNLM: I Aerospace Medicine methods Aerospace Medicine standards WD 700 P952 20091 RC1062.P75 2009 616.9'80213 dc22 Hrilish Library Calaloguislg-in-Publicaliun Data A zatalogue retorJ for thla hook is a\3lllblc from the Br;ll>h Llbrdr) Copyright 2009 by World Scientific Publishing Co Re Ltd AN rights resemed This book, orparts thereoJ may not be reproduced in anyform or by any means, electronic or mechanical, includlngphotocopying,recording or any information storage andrefrieval system now known or to be invented, without writtenpermissionfrom the Publisher For photocopying of material in this volume, please pay a copying fee through the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, USA In this case permission to photocopy is not required from the publisher Typeset by Stallion Press Email: enquiries@stallionpress.com Printed by FuIsland Offset Printing (S) Pte Ltd Singapore This page intentionally left blank Prologue Aviation is at the heart of world development Man, with all his physical and mental shortcomings, is at the heart of aviation But just as modern life is inconceivable without aviation, aviation cannot exist without its weakest link, the human being The aviation environment, however, is hostile to humans Soon after the first balloon flights more than 200 years ago, it became clear that man was unable to function and survive at altitude without special protection and support With the advent of powered flight more than 100 years ago, the need for physiological and medical support became obvious Doctors supporting the military flight operations of World War I realized that selection criteria had to be developed to reduce the high number of losses of both aircraft and pilots Following the Peace Conference in Paris in 1919, the first international medical requirements for licensing of aviators were agreed upon, and over the ensuing years these international standards have been further developed Since then powered flight has evolved considerably and so has the specialty of aviation medicine The medical standards for licensing of pilots, i.e the medical requirements an applicant must meet to be accepted for initial training and which all trained and licensed pilots must meet at their regulatory renewal examinations, have always been restrictive and conservative This is an obvious necessity The purpose of the requirements is to maintain and secure the high level of safety that characterizes modern aviation — a goal that leaves little v vi Prologue room for experimenting with or relaxing the requirements However, many medical conditions that were considered permanently disqualifying in the past are now allowed as a result of continuous improvement in our understanding of the physiology of flight, the evolution of evidence-based medicine, and the vast technical advances of recent years in diagnosis and treatment All medical standards have three different aspects that always must be considered together The first is the requirement per se, e.g., epilepsy entails unfitness for all classes of medical certification, or blood pressure shall be within normal limits The second aspect is the method or methods traditionally employed or sometimes prescribed by the Licensing Authority for carrying out the examination The third aspect is the definitions applied to the requirements For example, how is epilepsy defined or what are the normal limits for arterial tension? Although most countries have accepted the international standards and recommended practices developed and continually updated by the International Civil Aviation Organization (ICAO), there are still significant differences from one country to another pertaining to the methods of examination Examining the visual fields of a pilot by confrontational testing with finger movements compared to examining by automated, computerized perimetry provides results on very different levels of reliability The use of different methods of examination vary from country to country is hardly a surprise; different countries have different cultures, different socio-economical conditions, different prevalences of many diseases, different medical traditions, and different attitudes to the relevance of safety precautions Modern civil aviation, however, is international A modern airliner has the same needs and demands for ground support wherever it happens to be in the world Almost 200 countries are currently connected with each other by regular commercial flights and none can afford to reject the international community and refuse to provide the infrastructure necessary to ensure the safety of aviation All signatories to the Convention on International Civil Aviation (“Chicago Convention”) of 1944, currently totaling 191 countries, have undertaken to collaborate in securing the highest practicable degree of uniformity in relation to aircraft, aviation personnel, licensing Prologue vii procedures, etc., including medical certification of pilots and air traffic controllers Even so, there are still significant differences regarding national approaches to aeromedical certification To some extent, these differences are related to the influence that military aviation medicine has had upon civil aviation medicine Also relevant is the comparative level of development that aviation medicine (as a medical specialty) has reached in different countries While in some countries aviation medicine was a highly-developed medical specialty even before World War II, in other countries aviation medicine is only beginning to establish itself as a recognized specialty Most countries have agreed on the need to implement medical requirements for aviation personnel and have adopted the ICAO International Medical Standards and Recommended Practices or developed their own medical standards in accordance with the ICAO provisions The next step towards uniformity in medical certification must be to help medical examiners and medical assessors worldwide adopt similar methods of examination and similar definitions of diseases and disorders In particular, agreement on definitions and similar interpretation of the signs and symptoms of diseases and disorders are required if global harmonization in aeromedical certification is to be achieved This book contains detailed, experience-based, practical knowledge written to assist aviation medical examiners (AMEs) and other clinicians, as well as medical assessors of the Licensing Authorities, in the often confusing world of medical treatment and aeromedical evaluation of safety-critical aviation personnel such as pilots, cabin crew members, and air traffic controllers In addition, it provides medical guidelines for physicians who have patients with medical conditions who wish to travel by air This book is written by AMEs and clinicians from a wide range of medical specialties that are important to the field of aviation medicine It initially began as a reference book for German physicians who may or may not be AMEs, yet who are involved in the health care of pilots It has expanded to this current English version to address an international audience in order to provide guidance and advice to colleagues in the practice of clinical aviation medicine Considering the European background of the authors, viii Prologue this book represents European points of view and international or European criteria regarding the determination of fitness for duty among civil aviation personnel It is, nonetheless, an excellent and detailed international guide for medical practitioners in all parts of the world who deal with aircrew members and airline passengers Aviation medicine is a scientific discipline that involves the study of the physiological, psychological, operational, and environmental factors that determine the adaptive responses of a human being during flight With regard to flight crews, the focus is different from that of the “conventional” clinical specialties which primarily deal with abnormal physiology within a normal environment, as it is concerned with normal physiology within an abnormal environment With regard to passengers, however, conventional and aviation medicine intersect because at times abnormal physiology may be placed within an abnormal environment This is also the case when it comes to determining exactly to what degree, i.e., with what limitations or restrictions or under what conditions, a pilot with a medical disorder may be able to perform his duties without endangering flight safety It is to this highly specialized field of clinical aviation medicine that most chapters of the book are dedicated Flying represents a hostile environment that imposes a variety of physical, physiological, and psychological demands on human beings who are not genetically adapted to function in such an environment Promoting the health and well being of aviation personnel worldwide is essential for the safety of all flight operations in civil aviation It is also very important to recognize the potential consequences that the flight environment can have on those individuals who have pre-existing medical conditions and wish to travel by air or are required to be transported or medically evacuated by aircraft Therefore, medical practitioners must possess basic knowledge of aviation physiology and medicine in order to make appropriate decisions concerning medical certification of pilots and other flight personnel Such knowledge is also essential in making the correct decisions concerning the safe medical transport of diseased passengers aboard commercial aircraft or the medical transport (elective or emergency) of patients by air ambulance 384 I Janicke Figure ECG in severe pulmonary stenosis or primary pulmonary hypertension with right ventricular hypertrophy is required (only 25% progression) In the case of limited echocardiography, another imaging technique such as cardiac MRI or spiral CT should be utilized Valvulotomy11 is indicated with higher grade symptomatic pulmonary stenosis (pressure gradient >30 mmHg) Intervention with pure valvular PS or surgery with accompanying defect is best performed prior to school age The long-term course with regard to re-stenosis or sudden cardiac death is very good In the case when the post procedural maximal gradient is cm (mortality to 13%) or when an increase in diameter of > 0.5 cm per year can be demonstrated Most aneurysms related to atherosclerosis appear later in life in association with the risk factors of arterial hypertension, diabetes, and smoking The five year mortality is about 35% of all operated patients and is caused by accompanying CAD or rupture of the aneurysm.1 Younger pilots with normal blood pressure and who not smoke are usually not affected by this disease At younger ages, cystic medial necrosis Erdheim-Gsell (focal degeneration of smooth muscle/disintegration of the elastic fibers through gene mutation) is typical for the aneurysms associated with the congenital connective tissue disorders of Marfan and EhlersDanlos syndromes (autosomal dominant with variable expression) A variety of distinctive features are evident (aortic disease, intraocular lens dislocation, arachnodactyly, and familial or sporadic occurence of the disorder) Prevalence is 1.5/100 000, and males are more affected than females (2:1) Because of the risk of progression to aortic/mitral insufficiency, acute aortic dissection or aortic rupture, this is permanently disqualifying for all classes of medical certification Despite successful surgery, the long term prognosis is not favorable, therefore permanent disqualification is the rule: Marfan syndrome carries a five year survival rate of 75%, and the ten year Vascular Diseases and Disorders 391 survival rate is only 56%.2 On the basis of variable expression, Marfan syndrome includes the so-called forme fruste, in which case the diameter of the vessel remains within normal range, but eventually significant aortic or mitral insufficiency develops In as much as the great vessels and those of the heart remain within normal range, both Classes I and II certification are possible if annual cardiology examinations demonstrate stability (echocardiography, X-rays, MRI) Abdominal Aortic Aneurysm (AAA) Abdominal aortic aneurysm is defined as a maximal cross sectional diameter of > 2.5–3.0 cm, or associated with a ratio of dilated segment to normal aorta > 1.5 It is usually an incidental finding in asymptomatic individuals, such as in the case of a sonographic evaluation of elevated liver enzymes In 30–50% of cases, the aneurysm extends into the pelvic arteries The etiology in > 90% of cases is generalized atherosclerosis In the last 30 years, the incidence has increased 10–20 times, the prevalence lies between 2.5 and 5%, and is > 8% in men over 50 years of age Men are affected four times more often than women The following risk factors entail a likelihood of a silent aneurysm which is significantly greater than in the normal population: • • • • First-degree relative with aneurysm Pre-existing peripheral arterial vascular disease (∼14%) Arterial hypertension (∼11%) Age > 60 and with prior vascular risk factors Most aneurysms become larger with time, on the average 0.2–0.3 cm per year The rate of growth depends, among other things, on the initial diameter Complications are fatal rupture, embolism and thrombotic aortic occlusion The average rupture rate is cited as 6–8% every 5–10 years, and is dependent on size At > 6.0 cm diameter, the rupture rate is about 50% per year There is no indication for surgery if the diameter is < cm, due to the low complication rate (< 6.0 cm or about 15% per year) 392 I Janicke Aeromedical Considerations Aeromedical significance and the overwhelmingly asymptomatic presentation of AAA indicates that male pilots > 50 years of age with arterial vascular disease should undergo screening examinations by sonography, CT, or MRI Identified aneurysms entails disqualification Limited certification may be possible for Classes I and II under the following conditions: • • • • If < 5.0 cm, semi-annual sonographic examinations Treatment of hypertension, particularly with β -blockers Due to the high correlation with CAD (about 40–50%), noninvasive and, if necessary, invasive coronary artery diagnostic examinations In cases of rapid growth > cm in months or diameter > cm, surgical intervention and renewed disqualification Concerning therapy, the pilot’s cooperation is important: conventional Y-prosthesis has shown good long term results based on > 30 years experience whereas transfemoral stent graft implantation has been marred by not insignificant complications, such as wire fractures, secondary leakage, etc., and the experience with long term results is limited After successful surgery, medical certification can be renewed with limitations Blood pressure should be normal at rest and during exercise, and stress ECG testing should be normal Following Y-prosthesis implantation, regular ultrasound examinations of the abdominal aorta is required After transfemoral stent graft implantation, frequent X-ray examinations (X ray of the vertebral column, spiral or helical CT with contrast in mm sections, peripheral Doppler pressure testing, etc.) is necessary PERIPHERAL ARTERIAL (OCCLUSIVE) DISEASE (PA(O)D) ICAO Standards and Recommendations: There shall be no significant functional nor structural abnormality of the circulatory system Medical Requirements (JAR-FCL 3): Applicants with peripheral arterial disease before or after surgery shall be assessed as unfit Provided Vascular Diseases and Disorders 393 there is no significant functional impairment, a fit assessment may be considered by the AMS (following noninvasive, and if necessary, invasive clarification of CAD) Arterial occlusive disease encompasses stenotic and occlusive changes of the aorta, extremities, and cerebral vessels Asymptomatic PAD is three times more common than symptomatic disease This is aeromedically relevant, in that PAD is an indicator for atherosclerotic changes in the coronary and cerebral arterial vasculature Patients with symptomatic or asymptomatic PAD (between 55 and 74 years of age, prevalence is 5–10%) have an increased risk of experiencing stroke, heart attack, or sudden cardiac death (incidence 1–3% per year) Atherosclerosis causing PAD is positively correlated with the male gender, age, diabetes, smoking, hypertension, hyperlipoproteinemia, and hyperfibrinogenemia Smoking is the determining risk factor Male patients with PAD have a reduced life expectancy of 10 years and usually die of cardiovascular events Arterial Occlusive Disease: Screening and Secondary Examinations In addition to a history of claudication, which pilots often withhold, corresponding risk factors obligate an evaluation of the status of the peripheral pulses (particularly in the feet) and auscultation of vascular sounds in the typical locations Cessation of stress testing due to leg pain should lead to suspicion of PAD The simplest instrument for evaluating concerns regarding PAD is Doppler pressure measurement (ABI = Ankle Brachial Index), such as with a pocket Doppler: after 15 minutes of rest, a supine patient has blood pressure cuffs placed on both arms and both legs (supramalleolar), and the systolic occlusive pressure is measured with a Doppler probe at the brachialis artery, tibialis posterior, and anterior arteries Proof of PAD lies in the ratio of ankle arterial pressure/arm arterial pressure, which should be < 0.9 This ABI is a very good predictor for mortality Stress testing and imaging examinations necessarily follow Initial diagnosis of PAD requires the following laboratory tests: complete blood count (polycythemia, thrombocytosis, blood sugar, both fasting and postprandial, HbA1c, urinanalysis, and lipid profile 394 I Janicke If PAD is discovered, a complete cardiovascular status report with stress ECG testing/scintigraphy and/or stress echocardiography is necessary Coronary artery changes are found by angiography in about 70% of patients with PAD.3 If claudication pain limits stress ECG testing, other methods of evaluation, such as pharmacological scintigraphy/stress echocardiography, or one of the new imaging techniques (multi-slice CT, Cardiac MRI) should be undertaken The decision to perform a coronary angiogram should be made early Due to the high co-morbidity with cerebral arterial vascular disease (30–40%), a color duplex sonogram of the carotids should be undertaken Of significance is the sonographically measured intimamedia thickness at the maximal wall thickness (normal < 0.9 mm) due to the association with stroke and heart attack.4 Significant cerebral arterial vascular disease is disqualifying for all classes THROMBOSIS, PULMONARY EMBOLISM AND ANTICOAGULATION Medical Requirements (JAR-FCL 3): Systemic anticoagulation therapy is disqualifying Applicants following anticoagulant therapy require review by the AMS Venous thrombosis or pulmonary embolism is disqualifying until anticoagulation has been discontinued Pulmonary embolus requires full evaluation Anticoagulation for possible arterial thromboembolism is disqualifying Thrombosis (DVT), Pulmonary Embolism, and Flight Fitness The incidence of acute deep leg or pelvic venous thrombosis is 6/100 000 The absolute risk of thrombosis in individuals under 40 years of age amounts to 1:10 000, and for those over 75 years, 1:100 The mortality rate is 0.6% 90% of thrombotic events are asymptomatic Asymptomatic pulmonary emboli and thrombosis extension appear in about 1% of cases, and is the main complication Predisposing factors are trauma, surgery, malignancy, thrombophilic diseases, pregnancy, hormone therapy, varicosities, obesity, and prior history of thrombosis Vascular Diseases and Disorders 395 Diagnosis: Symptomatic and clinical signs of thrombosis are relatively sensitive, but quite unspecific The determination of the D-dimer concentration (normal < 500 mcg/l, rapid test simliRED®5) rules out the presence of thromboembolism with a high probability In positive cases (limited specificity), a duplex scan in experienced hands or the gold standard of phlebography is helpful In the case of suspected pulmonary embolism, the method of choice is the spiral CT Ventilationperfusion scans or pulmonary angiography are necessary only in individual cases Consequences for pilots: Venous thrombosis followed by pulmonary embolism is rare in young healthy pilots Regarding recurrence, the etiology of the DVT should be sought for aeromedical considerations A positive diagnosis requires anticoagulation with warfarin, phenprocoumon, or similar medications Prior to therapy, laboratory evidence for the not uncommon thrombophilic diseases should be undertaken, upon which the length of therapy depends All classes are disqualified during therapeutic anticoagulation In the case of a suspected or proven pulmonary embolism, a 2D Doppler-echocardiogram, or if necessary, a right heart catheterization should be performed in order to determine that there is no evidence of pulmonary artery hypertension (systolic < 30 mmHg) Pulmonary hypertension, whether primary or secondary, with an average pressure > 40 mmHg, is permanently disqualifying for all classes Due to a recurrence rate up to 8% in the first year (2% after the third year), recertification may be limited to OML or OSL restrictions in the first two years on the discretion of the AMS Regular cardiovascular evaluations including echocardiography, initially every six months, followed by annually, is required Traveler’s Thrombosis Reports about spectacular fatalities during or after long haul flights in the last few years has lead to a renewed, lively, and partially exaggerated discussion in the lay press, resulting in confusion among 396 I Janicke passengers and physicians What the actual data looks like with regard to this so-called economy class syndrome, more accurately called Traveler’s Thrombosis, and the recommendations that can be given at this time, is described as follows Definition: Traveler’s Thrombosis arises from a deep vein thrombosis (DVT), which can occur up to four weeks after traveling in a primarily seated position (airplane, train, automobile), with or without pulmonary embolism If the travel occurs after several hours on an airplane, it is called air traveler thrombosis Currently, there are several studies regarding this topic Pathophysiology: Regarding causes for this air and travel thrombosis, the following items are discussed: • • • Kinking of the popliteal vein in the popliteal fossa with lengthy seated position (venous stasis) Dehydration through significantly low humidity in the cabin (8–12%), fostered by alcohol and caffeine, through which more fluid is lost by way of diuresis Decreased partial pressure of oxygen in the cabin (2000–2500 m in elevation) may reduce fibrinolytic activity, and by the release of EDRF/NO, facilitate vasodilatation and stasis,6,7 while other studies show no significant effect of hypoxia on the coagulation parameters in the general population.8 Data: In 1954, two thrombosis cases following long flights of over eight hours were first reported Until 1999, the only reports were exclusively case reports or retrospective studies concerning about 200 cases of flight-associated thrombosis.9 More studies since 1999 have investigated the relative risk of long flights and the value of compression stockings The LONFLIT and studies merely showed an incidence of 4–6% for DVT in high-risk groups (with predisposing factors, see below) after over 10 hours flight.10 A few studies showed no association between flight and thrombosis, while others showed a strong association.11 The LONFLIT study demonstrated a significant reduction of edema and DVT in the low and moderate risk factor group for DVT, and in those individuals with edema, a lower rate of microangiopathy.12 Vascular Diseases and Disorders 397 Current consensus: At a WHO conference, it was determined that an association between long haul flights and thrombosis is possible according to the current data, but that it is a weak correlation This association particularly concerns people with predisposing factors (see above) Further prospective studies to determine the thrombosis risk associated with flight involving satisfactory numbers of passengers are currently underway For passengers and airline companies, important consequences may be determined, such as the distance between seat rows and liability issues Current Recommendations (1) For trips less than three hours duration or under 2500 km, no intervention is necessary (2) Without additional risk of thrombosis, the following is recommended for longer trips: foot and ankle circles, isometric exercises, frequent standing, drinking 150 ml fluids/hour (no alcohol or coffee), and avoid taking sedatives (3) With one or more additional risk factors for thrombosis, depending on the risk profile: additional to (2), compression stockings Classes I–II (4) High-risk individuals (prior thrombosis, malignancy, thrombophilic diseases, major surgery in the preceding six weeks), low molecular weight heparin in higher dose subcutaneously two hours prior to departure On the basis of the current studies, there is no indication to use Aspirin® for the prevention of venous thromboembolism Many airline companies are passing out related information with their tickets, or providing further information on their web sites REFERENCES Crawford EF, et al (1989) Surgical treatment of aneurysm and/or dissection of the ascending aorta and transverse aortic arch: Factors influencing survival in 717 patients J Thorac Cardiovasc Surg 98: 659–674 Svennson LG, et al (1989) Impact of cardiovascular operation on survival in the Marfan patient Circulation 80: 1233–1242 398 I Janicke Darbar D, et al (1996) Prediction of late cardiac events by dipyridamole thallium szintigraphy in patient with intermittent claudication and occult coronary artery disease Am J Cardiol 78: 736–740 O’Leary DH, et al (1999) Carotid-artery intima and media thickness as a risk factor for myocardial infarction and stroke in older adults N Engl J Med 340: 12–22 Wells PS, et al (1995) A novel and rapid whole blood assay for d-dimer in patients with clinical suspected deep vein thrombosis Cirulation 91: 2184–2187 Gertler JP, et al (1993) Ambient oxygen tension modulates endothelial fibrinolysis J Vasc Surg 18: 939–946 Bendz B, et al (2000) Association between acute hypobaric hypoxia and activation of coagulation in human beings Lancet 356: 1657–1658 Crosby A, et al (2003) Relation between acute hypoxia and activation of coagulation in human beings Lancet 361: 2207–2208 Landgraf H, et al (1994) Economy class syndrome: Rheology fluid balance and lower leg oedema during a simulated 12-hour long-distance flight Aviat Space Envir Med 65: 930–935 10 Belcaro G, et al (2001) Venous thromboembolism from air travel: The LONFLiT study Angiology 52: 369–374 11 Mendis S, et al (2002) Air travel and venous thromboembolism (Review) Bulletin of the World Heath Organization 80: 403–406 12 Cesarone Mr, et al (2003) The LONFLIT4-Concorde Deep Venous Thrombosis and Edema Study: Prevention with travel stockings Angiology 54: 143–154 .. .PRINCIPLES AND PRACTICE OF AVIATION MEDICINE This page intentionally left blank PRINCIPLES AND PRACTICE OF AVIATION MEDICINE editors Claus Curdt-Christiansen International Civil Aviation. .. 978-9 81- 238-8 61- 2 (hardcover : alk paper) ISBN -10 : 9 81- 238-8 61- 3 (hardcover : alk paper) I Aviation medicine I Curdt-Christiansen, Claus 11 Draeger, Jorg, Prof Dr 11 1 Kriebel, liirgen [DNLM: I Aerospace... dominance of the heart (and therefore of aviation cardiology) makes an extracorporeal depiction necessary The importance of the eyes and ears (and therefore of aviation ophthalmology and otology)