Review Article
Post stapedotomy aviation: A changing scenario Abstract Aeromedical implications of stapedotomy like rapid barometric changes and G forces are generally thought to put an end to the aviation career of an aviator. Aviation industry has grown tremendously in the last few decades, and aviation now is not only occupational but also recreational. The Indian Military Aviation rules state that, “Stapedectomy cases will be assessed permanently unfit for flying duties. These cases will be cautioned against flying in an unpressurised aircraft.” The basis of this is the aeromedical concerns associated with stapedotomy as clinical conditions which are of minor significance on the ground may become aggravated in the air. With an ever expanding civil and military aviation industry, the number of aviators who have undergone stapedotomy has also increased. Though grounding the aircrew is the safest option, but if medical certification is denied to all, then the majority who can fly safely will also be excluded, thus denying the organization of its trained resources. This paper discusses post otosclerosis and post stapedotomy aeromedical concerns, reviews existing literature concerning post stapedotomy aviation and various post stapedotomy aviation policies. Key words: Aeromedical concerns, aviation policies, otosclerosis, poststapedotomy flying
INTRODUCTION Return to aviation duties following stapedectomy or stapedotomy has been controversial within the aeromedical community for the past 40 years. In many countries, especially in Military, concerns with barometric pressure changes causing a perilymph fistula have led to policy that prevents return to flying duties for aviators after these procedures. Newer techniques involving small fenestra stapedotomy, precision laser stapedotomy and the fitting of a small diameter piston into the fenestration have reduced the risk of operative inner ear damage and postoperative perilymph fistula. The permanent disqualification of even a single crewman because of stapedectomy represents a loss of professional skill to the aviation sector as well as a great financial loss to the government. As a result, many countries have developed a more reasonable policy, and aviators after careful selection by the medical authorities have successfully returned to flying duties post stapedotomy. The following sections of
this paper discuss post otosclerosis and post stapedotomy aeromedical concerns, review existing literature concerning post stapedotomy aviation and compile various post stapedotomy aviation policies. Aeromedical concerns and Otosclerosis Otosclerosis is a localized hereditary disorder affecting enchondral bone of the otic capsule that is characterized by disordered resorption, deposition of bone and vascular proliferation leading to conductive hearing loss due to stapes fixation.[1,2] For many aviators with otosclerosis, no treatment is indicated initially. In fact the phenomenon of “Paracusis of Willisi” allows aviator with otosclerosis to hear better in a noisy environment than in a quiet locations. As the hearing loss progresses, hearing in the cockpit environment becomes more difficult and may compromise flight safety. Use of hearing aids is a handicap as the aviator will be unable to tune out unwanted sounds and transmissions. Hence, surgery is offered at this stage as it offers freedom from having to use amplification. With modern techniques like small fenestra stapedotomy with use of vein graft, the rate of complications is much less and there is a statistically significant advantage for hearing gain.[3-6] Also, early detection of any postoperative complication is possible with the advancing technology.[7-9]
Renu Rajguru ENT Specialist, Institute of Aerospace Medicine, Near HAL Airport, Bangalore, Karnataka, India For correspondence: Dr. Renu Rajguru, Department of ENT Specialist, Institute of Aerospace Medicine, Near HAL Airport, Bangalore - 560 017, Karnataka, India. E-mail: renurajguru@ yahoo.com
Access this article online Website: www.ijoem.com DOI: 10.4103/0019-5278.146905 Quick Response Code:
Fortunately complications following surgery are rare, but may be significant. [1,2] These include the following: Hearing loss (conductive or sensorineural), alteration of taste, suppurative labyrinthitis, vertigo, perilymph fistula, facial paralysis and rarely meningitis. Vertigo may occur
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immediately after stapedectomy, or its onset may be delayed by weeks or years. Vertigo that is not resolved with treatment is incompatible with flying duties. Postoperative perilymph fistula should be suspected in patients with persistent vertigo, or worsening hearing loss. The risk of postoperative perilymph fistula is 0.25% to 0.6% in stapedotomy, and if untreated it is incompatible with flying duties. Facial nerve paralysis may occur in 0.07% cases and can cause dry eye which may present significant problems for aviators flying in dry cockpit conditions, or facial droop which may interfere with wear of aviator masks. Persistent perforation of one tympanic membrane could lead to alternobaric vertigo and is not compatible with flying duties.[1] Post stapedectomy aviation: Review of literature of the changing scenario Several studies were conducted in the late 1960s and early 1970s to assess the stability of the stapes prostheses and footplate. In 1967, Ashe et al. conducted a systematic survey as a joint venture of the Aviation Medicine Research Laboratory, Ohio State University, and the Aeromedical Certification Division, Office of Aviation Medicine, Federal Aviation Agency, in an attempt to secure specific data regarding problems caused by otosclerosis surgery in airmen.[10] They interviewed 80 airmen who had undergone stapes surgery. Out of these, four airmen experienced a dislodged prosthesis, one case involved a tefl on strut which became detached from a congenitally deformed incus, two cases involved polyethylene tube strut and one had a wire loop dislodged from the shaft of the incus. Out of these four, only one prosthesis (polyethylene tube strut) had become dislodged during flight. They argued that if medical certification is denied to all civil airmen who have had surgical procedures for relief of otosclerosis, then the majority who can fly safely will also be excluded in order to deny one or two who may have difficulty in flight. They suggested that airmen requiring surgery for otosclerosis should inform their surgeons of their flying interests and polythene struts should not be used in these cases, where possible. Airmen should be observed for Eustachian tube patency and for signs of vertigo or sudden pressure change in the middle ear prior to returning to flying status. Airmen who have been free of symptoms for 2 years following surgery would be unlikely to develop complications due to disruption of prosthesis thereafter and they may be inducted back into flying. It was suggested that in the absence of signs of Eustachian tube malfunction, or vertigo or unsteadiness caused by pressure changes in the middle ear, and if hearing is sufficient to allow the airman to communicate effectively in flight, he can safely return to flight duties. In 1968, Garlington and Singleton studied the effect of rapid decompression and recompression in the stapedectomized 106
cats.[11] They placed stapedectomized cats and controls in specially designed decompression box which was compressed rapidly to 70,000 feet. Within 40 seconds, the chamber was recompressed to 4500 feet and then recompressed to ground level in 2 minutes. They observed that rapid pressure changes were well tolerated by the normal cat ear and the stapedectomized cat ear reconstructed with fat-wire and wire-gelfoam prosthesis. However, no definite conclusions about polyethylene-gelfoam reconstruction could be reached because of the excessive middle ear fibrous tissue response. The evidence from this study suggested that wire-fat and wire-gelfoam prosthesis are certainly adequate to withstand severe pressure changes that occur within the ear with the explosive decompression and rapid recompression as one might encounter in modern, high performance aircraft. In no instance was there any evidence of damage to the inner ear or a tear in the oval window area about the prosthesis. In 1974, Hanna and Collins studied the effect of barometric pressure change on the ear following stapedectomy in Cebus monkeys.[12] The experiment was performed at 1 year post surgery. The monkeys were subjected to a barometric pressure change profile, which simulated the extreme exposures that may occur in high-performance jet aircraft. During these altitude-chamber exposures, the monkeys were monitored by electronystagmography. Despite clinical evidence of barotraumas in about 75% of the animals, no fistula was found. But the results were considered inapplicable to man due to excessive fibrosis in the monkey middle ear. Dr R B Rayman in his paper in 1974 asked the basic question, “Will a pilot, with a prosthesis in place of the stapes and a graft over the oval window, develop complications which will incapacitate him, particularly while flying a high performance aircraft which is capable of subjecting its crew to pressure changes in a rapid climb or a steep dive?”.[13,14] At that time it was not possible to quantify the actual risk factors because of lack of data. Consequently he proposed the following criteria for crewmen with stapedectomy who can be selectively chosen for waiver: • The patient must be at least 1 year post-surgery • The operation should be the type advocated by House; that is, a wire-gelfoam procedure • Hearing must have been restored to Air Force standards • The patient must be completely free of vestibular symptoms (such as vertigo, dizziness, and nausea) and demonstrate normal Eustachian tube function • The patient must undergo a complete physical examination at Air Force Base, Texas. He must be subjected to free fall and rapid decompression in the altitude chamber to be sure the prosthesis cannot be dislodged by violent pressure changes.
Indian Journal of Occupational and Environmental Medicine - December 2014 - Volume 18 - Issue 3
Rajguru: There has been a change in aviation policies following stapedectomy in aircrew
It was this proposed criteria that led the way to a consistent and reasonable approach to these airmen and was incorporated by US Air Force. Katzav et al., at Israel Air Force Aeromedical Center at Tel Hashomer, Israel, conducted a study between 1977 and 1995, in six high-performance airplane pilots diagnosed with otosclerosis in whom nine stapedectomies using the Robinson-vein graft technique were performed in.[15] All of them received piston prosthesis and a tissue graft. Three months after surgery, they were all put through a decompression chamber test, and none of them experienced any vestibular or otologic symptoms. All of them returned to full active duty after stapedectomy without any vestibular symptoms. Three years postoperatively, they had accumulated 4160 hours of combat or simulated combat flying time and experienced no inner ear problems. The authors suggested that it can be safe for fighter or test pilots to return to full flight status after stapedectomy and full flight status can be re instated as soon as 3 months after stapedectomy without endangering flight safety. Later in 1998, Thiringer and Arriaga examined the aeromedical outcomes of 16 U.S. Air Force crew members who returned to flight duties after stapedectomy, and also evaluated appropriateness of specific aeromedical testing before return to the cockpit.[16] They discussed the practical question that what specific testing, if any, should be done before returning the aviator to the cockpit after stapedectomy? They suggested that only two postoperative testing modalities should be applied to all aircrew members who were to be granted a waiver: Postoperative audiograms and altitude chamber testing as they represent a reasonable screening tool for susceptibility to acute vestibulopathic conditions because of the rapid pressure changes. They argued that the risk of sudden incapacitation by perilymphatic fistula is too small to warrant grounding or any additional testing but they suggested that the risk was justified in certain subsets, namely, in patients who fly single-controlled tactical aircraft. So they recommended a set of guidelines for return to flying duties after stapedectomy: • Evaluation for return to flight status should begin after 3- to 6-month postoperative observation period. The aircrew should have completely recovered from surgery, be completely asymptomatic and should pass any applicable aeromedical physical examination • The wire loop/gelatin sponge technique is not applicable • Any vestibular symptoms, spontaneous nystagmus or documented sudden or progressive sensorineural hearing loss 6 months after surgery, during any phase of a chamber ride, upon pneumatic otoscopy, during physical examination, or during actual flight after stapedectomy should be a cause for permanent grounding with no waiver recommendation. They further suggested that for waiver recommendation, all non-pilots and pilots of multicontrolled non-high performance
aircrafts must meet all the above-mentioned conditions. For single controlled high- performance aircraft pilots, if they meet all the above-mentioned conditions, a waiver for multicontrolled aircraft should be recommended. A waiver for single controlled high-performance aircraft pilots may be recommended under specific circumstances, depending on the experience of the pilot, mission requirements and personal limitations, if apart from the above-mentioned conditions, the candidate successfully passes an altitude chamber evaluation to include free fall and rapid decompression to test the integrity of the oval window seal. The authors in the text book “Fundamentals of Aerospace Medicine” state that with newer techniques involving precision laser fenestration of the footplate (stapedotomy) and the fitting of a small diameter piston into the fenestration have reduced the risk of operative inner ear damage and postoperative perilymph fistula.[17] The US Navy, US Air Force, and National Aeronautics and Space Administration (NASA) now consider a 3-month grounding period sufficient as long as hearing has stabilized and there have been no episodes of vertigo or imbalance beyond the immediate postoperative period; the US Army grounds its aviators for 6 months, then restricts them to dual-pilot status for another 2.5 years. They also state that there is no universal requirement for an altitude chamber test, although the US Air Force does require a chamber test with rapid decompression and rapid descent, if a complete stapedectomy was done. If the newer stapedotomy technique was done, then altitude chamber exposure will not contribute anything further to a waiver decision if the subject is able to easily clear the ear on the ground without any vertiginous sensation. Aeromedical disposal in US air force In US Air Force,[1] if the aviator undergoes successful surgical treatment, an evaluation at the USAF Aeromedical Consultation Service (ACS) is required for single seat high performance aircrew only, and is scheduled no earlier than 12 weeks postoperatively. It includes evaluation by an otolaryngologist with review of all medical records, pre and post-operative testing, and surgical report. Diagnostic audiology includes air and bone conduction threshold measurement, speech reception threshold, speech discrimination testing, impedance audiometry and ENG. An altitude chamber flight with a flight surgeon is required only for those who have had the traditional stapedectomy surgery, to test for perilymph fistula. For those who have undergone the newer stapedotomy surgery, an altitude chamber evaluation is not required. If a chamber flight is performed, it includes a rapid descent (5000 feet/min) from 10,000 feet. A rapid decompression is also required. Additional tests are done as clinically or aeromedically indicated. If ACS evaluation reveals no post-op sequelae, the aviator is recommended for an unrestricted waiver.
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U.S Navy Aeromedical Reference and Waiver Guide states that a stapedectomy done to treat otosclerosis requires a waiver.[18] Designated aviators are grounded for three months following stapedectomy, before waiver is recommended.
2.
Post-stapedotomy disposal of Indian civil aircrew The applicants are not allowed to fly for a period of one to three months following stapes surgery to allow complete healing to take place. Thereafter, a specialized ENT assessment is made to ascertain Eustachian tube patency and the absence of vertigo, nystagmus or unsteadiness during valsalva maneuver and while blowing the nose forcibly.
4.
If after this 3 month period, the applicant who has not had vertigo and has post-operative acceptable hearing, is allowed to fly only under operational restrictions such as flying with or as a co-pilot only or with a safety pilot for a 2-year observation period. After that the pilot is revaluated and the final decision to remove the restrictions is considered. He/she is also informed of the potential hazards of upper respiratory tract infections or other conditions which may interfere with ventilation of the middle ear.
With technological improvements in the surgical techniques, the rate of complications encountered during stapedotomy has come down. However, the presence of complications like persistent vertigo, hearing loss, perilymph fistula, facial paralysis and persistent perforation if not treated definitively are incompatible with flying duties. Though the association between diving, barotrauma and the production of perilymphatic fistula is well known,[19] but various studies reveal no extra risk in poststapedectomy population and do not recommend extra barorestrictions.[20,21] Though permanently grounding all aircrew after stapedectomy remains the safest option, many studies quoted in this article reveal that carefully selected military and civil aircrew have been able to perform all flying duties post stapedotomy without any complications. This has benefitted the aviation organization and the individual aircrew, as it avoids the aircrew to be downgraded from flying duties with the incumbent re-training costs for downgraded personnel and training costs for new/replacement aircrew.
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12. 13. 14.
15. 16. 17.
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19. 20.
21.
REFERENCES
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3.
Schall D, Van Syoc D. Clinical Practice Guideline for otosclerosis/ stapedectomy. American Society of Aerospace Medicine Specialists. Aerospace Medical Association; Available from: http://www.asams. org/guidelines/Completed/NEW%20Otosclerosis.htm. [Last updated on 2011 Nov 14].
Merchant S, Mc Kenna MJ, Browning G, Rea P, Tange R. Otosclerosis. 7th ed. In: Gleeson M editors. Scott-Brown’s otorhinolaryngology, Head and Neck Surgery. Great Britain: Edward Arnold (Publishers) Ltd; 2008. p. 3475-8. Fisch U. Stapedotomy versus stapedectomy. Otol Neurotol 2009;30:1166-7. Thamjarayakul T, Supiyaphun P, Snidvongs K. Stapes fixation surgery: Stapedectomy versus stapedotomy. Asian Biomed 2010;4:429-34. Gristwood RE, Venables WN. Effects of fenestra size and piston diameter on the outcome of stapes surgery for clinical otosclerosis. Ann Otol Rhinol Laryngol 2011;120:363-71. Hazarika P, Singh R, Nayak DR, Sajilal Ma, Deviprasad D, Prabhjot R. Comparison between conventional stapedectomy and KTP-532 laser stapedectomy. Indian J Otol 2010;16:13-8. Ikezono T, Shindo S, Sekine K, Shiiba K, Matsuda H, Kusama K, et al. Cochlin-tomoprotein (CTP) detection test identifies traumatic perilymphatic fistula due to penetrating middle ear injury. Acta Otolaryngol 2011;131:937-44. Ikezono T, Shindo S, Sekiguchi S, Morizane T, Pawankar R, Watanabe A, et al. The performance of Cochlin-tomoprotein detection test in the diagnosis of perilymphatic fistula. Audiol Neurootol 2010;15:168-74. Available form: http://www.american-hearing.org. Hain TC. Perilymph Fistula; American Hearing Research Foundation. [Last updated on 2012 Oct]. Ashe AF, Billings CE, Shillito FH. Aeromedical problems associated with surgical procedures for the relief of otosclerosis. Aerosp Med 1967;38:407-11. Garlington JC, Singleton GT. Rapid decompression and recompression in the stapedectomized cat. Aerosp Med 1968;40:475-8. Hanna HH, Collins FG. Effect of barometric pressure change on the ear following stapedectomy. Aerosp Med 1974;45:548-50. Rayman RB. Stapedectomy: A threat to flying safety? Aerosp Med 1972;43:545-50. Rayman RB, Hastings JD, Kruyer WB, Levy RA, Pickard JS. Clinical Aviation Medicine. 4th ed. New York; Professional Publishing Group, Ltd; 2006. p. 138-40. Katzav J, Lippy WH, Shamiss A, Davidson BZ. Stapedectomy in combat pilots. Am J Otol 1996;17:847-9. Thiringer JK, Arriage MA. Stapedectomy in military aircrew. Otolaryngol Head Neck Surg 1998;118:9-14. Phelan JR. Otolaryngology in aerospace medicine. In: Davies JR, Johnson R, Stepanek J, Fogarty JA, editors. Fundamentals of Aerospace Medicine. 4th ed. United State: Lippincott Williams and Wilkins; 2008. p. 385-6. U.S Navy Aeromedical reference and waiver guide. In: Metzger J, Maur E, editors. 6.5 Hearing Loss/Stapedectomy. Pensacola, USA: Navy Medicine Operational Training Centre (NMOTC); Available from: http://www.med.navy.mil/sites/nmotc/nami/arwg/Pages/ AeromedicalReferenceandWaiverGuide.aspx. [Last updated on 2006 Jun 22]. Pullen FW 2nd. Perilymphatic fistula induced by barotrauma. Am J Otol 1992;13:270-2. Harrill WC, Jenkins HA, Coker NJ. Barotrauma after stapes surgery: A survey of recommended restrictions and clinical experiences. Am J Otol 1996;17:835-45. House JW, Toh EH, Perez A. Diving after stapedectomy: Clinical experience and recommendations. Otolaryngol Head Neck Surg 2001;125:356-60.
Cite this article as: Rajguru R. Post stapedotomy aviation: A changing scenario. Indian J Occup Environ Med 2014;18:105-8. Source of Support: Nil, Conflict of Interest: None declared.
Indian Journal of Occupational and Environmental Medicine - December 2014 - Volume 18 - Issue 3
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Post stapedotomy aviation: A changing scenario Abstract Aeromedical implications of stapedotomy like rapid barometric changes and G forces are generally thought to put an end to the aviation career of an aviator. Aviation industry has grown tremendously in the last few decades, and aviation now is not only occupational but also recreational. The Indian Military Aviation rules state that, “Stapedectomy cases will be assessed permanently unfit for flying duties. These cases will be cautioned against flying in an unpressurised aircraft.” The basis of this is the aeromedical concerns associated with stapedotomy as clinical conditions which are of minor significance on the ground may become aggravated in the air. With an ever expanding civil and military aviation industry, the number of aviators who have undergone stapedotomy has also increased. Though grounding the aircrew is the safest option, but if medical certification is denied to all, then the majority who can fly safely will also be excluded, thus denying the organization of its trained resources. This paper discusses post otosclerosis and post stapedotomy aeromedical concerns, reviews existing literature concerning post stapedotomy aviation and various post stapedotomy aviation policies. Key words: Aeromedical concerns, aviation policies, otosclerosis, poststapedotomy flying
INTRODUCTION Return to aviation duties following stapedectomy or stapedotomy has been controversial within the aeromedical community for the past 40 years. In many countries, especially in Military, concerns with barometric pressure changes causing a perilymph fistula have led to policy that prevents return to flying duties for aviators after these procedures. Newer techniques involving small fenestra stapedotomy, precision laser stapedotomy and the fitting of a small diameter piston into the fenestration have reduced the risk of operative inner ear damage and postoperative perilymph fistula. The permanent disqualification of even a single crewman because of stapedectomy represents a loss of professional skill to the aviation sector as well as a great financial loss to the government. As a result, many countries have developed a more reasonable policy, and aviators after careful selection by the medical authorities have successfully returned to flying duties post stapedotomy. The following sections of
this paper discuss post otosclerosis and post stapedotomy aeromedical concerns, review existing literature concerning post stapedotomy aviation and compile various post stapedotomy aviation policies. Aeromedical concerns and Otosclerosis Otosclerosis is a localized hereditary disorder affecting enchondral bone of the otic capsule that is characterized by disordered resorption, deposition of bone and vascular proliferation leading to conductive hearing loss due to stapes fixation.[1,2] For many aviators with otosclerosis, no treatment is indicated initially. In fact the phenomenon of “Paracusis of Willisi” allows aviator with otosclerosis to hear better in a noisy environment than in a quiet locations. As the hearing loss progresses, hearing in the cockpit environment becomes more difficult and may compromise flight safety. Use of hearing aids is a handicap as the aviator will be unable to tune out unwanted sounds and transmissions. Hence, surgery is offered at this stage as it offers freedom from having to use amplification. With modern techniques like small fenestra stapedotomy with use of vein graft, the rate of complications is much less and there is a statistically significant advantage for hearing gain.[3-6] Also, early detection of any postoperative complication is possible with the advancing technology.[7-9]
Renu Rajguru ENT Specialist, Institute of Aerospace Medicine, Near HAL Airport, Bangalore, Karnataka, India For correspondence: Dr. Renu Rajguru, Department of ENT Specialist, Institute of Aerospace Medicine, Near HAL Airport, Bangalore - 560 017, Karnataka, India. E-mail: renurajguru@ yahoo.com
Access this article online Website: www.ijoem.com DOI: 10.4103/0019-5278.146905 Quick Response Code:
Fortunately complications following surgery are rare, but may be significant. [1,2] These include the following: Hearing loss (conductive or sensorineural), alteration of taste, suppurative labyrinthitis, vertigo, perilymph fistula, facial paralysis and rarely meningitis. Vertigo may occur
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Rajguru: There has been a change in aviation policies following stapedectomy in aircrew
immediately after stapedectomy, or its onset may be delayed by weeks or years. Vertigo that is not resolved with treatment is incompatible with flying duties. Postoperative perilymph fistula should be suspected in patients with persistent vertigo, or worsening hearing loss. The risk of postoperative perilymph fistula is 0.25% to 0.6% in stapedotomy, and if untreated it is incompatible with flying duties. Facial nerve paralysis may occur in 0.07% cases and can cause dry eye which may present significant problems for aviators flying in dry cockpit conditions, or facial droop which may interfere with wear of aviator masks. Persistent perforation of one tympanic membrane could lead to alternobaric vertigo and is not compatible with flying duties.[1] Post stapedectomy aviation: Review of literature of the changing scenario Several studies were conducted in the late 1960s and early 1970s to assess the stability of the stapes prostheses and footplate. In 1967, Ashe et al. conducted a systematic survey as a joint venture of the Aviation Medicine Research Laboratory, Ohio State University, and the Aeromedical Certification Division, Office of Aviation Medicine, Federal Aviation Agency, in an attempt to secure specific data regarding problems caused by otosclerosis surgery in airmen.[10] They interviewed 80 airmen who had undergone stapes surgery. Out of these, four airmen experienced a dislodged prosthesis, one case involved a tefl on strut which became detached from a congenitally deformed incus, two cases involved polyethylene tube strut and one had a wire loop dislodged from the shaft of the incus. Out of these four, only one prosthesis (polyethylene tube strut) had become dislodged during flight. They argued that if medical certification is denied to all civil airmen who have had surgical procedures for relief of otosclerosis, then the majority who can fly safely will also be excluded in order to deny one or two who may have difficulty in flight. They suggested that airmen requiring surgery for otosclerosis should inform their surgeons of their flying interests and polythene struts should not be used in these cases, where possible. Airmen should be observed for Eustachian tube patency and for signs of vertigo or sudden pressure change in the middle ear prior to returning to flying status. Airmen who have been free of symptoms for 2 years following surgery would be unlikely to develop complications due to disruption of prosthesis thereafter and they may be inducted back into flying. It was suggested that in the absence of signs of Eustachian tube malfunction, or vertigo or unsteadiness caused by pressure changes in the middle ear, and if hearing is sufficient to allow the airman to communicate effectively in flight, he can safely return to flight duties. In 1968, Garlington and Singleton studied the effect of rapid decompression and recompression in the stapedectomized 106
cats.[11] They placed stapedectomized cats and controls in specially designed decompression box which was compressed rapidly to 70,000 feet. Within 40 seconds, the chamber was recompressed to 4500 feet and then recompressed to ground level in 2 minutes. They observed that rapid pressure changes were well tolerated by the normal cat ear and the stapedectomized cat ear reconstructed with fat-wire and wire-gelfoam prosthesis. However, no definite conclusions about polyethylene-gelfoam reconstruction could be reached because of the excessive middle ear fibrous tissue response. The evidence from this study suggested that wire-fat and wire-gelfoam prosthesis are certainly adequate to withstand severe pressure changes that occur within the ear with the explosive decompression and rapid recompression as one might encounter in modern, high performance aircraft. In no instance was there any evidence of damage to the inner ear or a tear in the oval window area about the prosthesis. In 1974, Hanna and Collins studied the effect of barometric pressure change on the ear following stapedectomy in Cebus monkeys.[12] The experiment was performed at 1 year post surgery. The monkeys were subjected to a barometric pressure change profile, which simulated the extreme exposures that may occur in high-performance jet aircraft. During these altitude-chamber exposures, the monkeys were monitored by electronystagmography. Despite clinical evidence of barotraumas in about 75% of the animals, no fistula was found. But the results were considered inapplicable to man due to excessive fibrosis in the monkey middle ear. Dr R B Rayman in his paper in 1974 asked the basic question, “Will a pilot, with a prosthesis in place of the stapes and a graft over the oval window, develop complications which will incapacitate him, particularly while flying a high performance aircraft which is capable of subjecting its crew to pressure changes in a rapid climb or a steep dive?”.[13,14] At that time it was not possible to quantify the actual risk factors because of lack of data. Consequently he proposed the following criteria for crewmen with stapedectomy who can be selectively chosen for waiver: • The patient must be at least 1 year post-surgery • The operation should be the type advocated by House; that is, a wire-gelfoam procedure • Hearing must have been restored to Air Force standards • The patient must be completely free of vestibular symptoms (such as vertigo, dizziness, and nausea) and demonstrate normal Eustachian tube function • The patient must undergo a complete physical examination at Air Force Base, Texas. He must be subjected to free fall and rapid decompression in the altitude chamber to be sure the prosthesis cannot be dislodged by violent pressure changes.
Indian Journal of Occupational and Environmental Medicine - December 2014 - Volume 18 - Issue 3
Rajguru: There has been a change in aviation policies following stapedectomy in aircrew
It was this proposed criteria that led the way to a consistent and reasonable approach to these airmen and was incorporated by US Air Force. Katzav et al., at Israel Air Force Aeromedical Center at Tel Hashomer, Israel, conducted a study between 1977 and 1995, in six high-performance airplane pilots diagnosed with otosclerosis in whom nine stapedectomies using the Robinson-vein graft technique were performed in.[15] All of them received piston prosthesis and a tissue graft. Three months after surgery, they were all put through a decompression chamber test, and none of them experienced any vestibular or otologic symptoms. All of them returned to full active duty after stapedectomy without any vestibular symptoms. Three years postoperatively, they had accumulated 4160 hours of combat or simulated combat flying time and experienced no inner ear problems. The authors suggested that it can be safe for fighter or test pilots to return to full flight status after stapedectomy and full flight status can be re instated as soon as 3 months after stapedectomy without endangering flight safety. Later in 1998, Thiringer and Arriaga examined the aeromedical outcomes of 16 U.S. Air Force crew members who returned to flight duties after stapedectomy, and also evaluated appropriateness of specific aeromedical testing before return to the cockpit.[16] They discussed the practical question that what specific testing, if any, should be done before returning the aviator to the cockpit after stapedectomy? They suggested that only two postoperative testing modalities should be applied to all aircrew members who were to be granted a waiver: Postoperative audiograms and altitude chamber testing as they represent a reasonable screening tool for susceptibility to acute vestibulopathic conditions because of the rapid pressure changes. They argued that the risk of sudden incapacitation by perilymphatic fistula is too small to warrant grounding or any additional testing but they suggested that the risk was justified in certain subsets, namely, in patients who fly single-controlled tactical aircraft. So they recommended a set of guidelines for return to flying duties after stapedectomy: • Evaluation for return to flight status should begin after 3- to 6-month postoperative observation period. The aircrew should have completely recovered from surgery, be completely asymptomatic and should pass any applicable aeromedical physical examination • The wire loop/gelatin sponge technique is not applicable • Any vestibular symptoms, spontaneous nystagmus or documented sudden or progressive sensorineural hearing loss 6 months after surgery, during any phase of a chamber ride, upon pneumatic otoscopy, during physical examination, or during actual flight after stapedectomy should be a cause for permanent grounding with no waiver recommendation. They further suggested that for waiver recommendation, all non-pilots and pilots of multicontrolled non-high performance
aircrafts must meet all the above-mentioned conditions. For single controlled high- performance aircraft pilots, if they meet all the above-mentioned conditions, a waiver for multicontrolled aircraft should be recommended. A waiver for single controlled high-performance aircraft pilots may be recommended under specific circumstances, depending on the experience of the pilot, mission requirements and personal limitations, if apart from the above-mentioned conditions, the candidate successfully passes an altitude chamber evaluation to include free fall and rapid decompression to test the integrity of the oval window seal. The authors in the text book “Fundamentals of Aerospace Medicine” state that with newer techniques involving precision laser fenestration of the footplate (stapedotomy) and the fitting of a small diameter piston into the fenestration have reduced the risk of operative inner ear damage and postoperative perilymph fistula.[17] The US Navy, US Air Force, and National Aeronautics and Space Administration (NASA) now consider a 3-month grounding period sufficient as long as hearing has stabilized and there have been no episodes of vertigo or imbalance beyond the immediate postoperative period; the US Army grounds its aviators for 6 months, then restricts them to dual-pilot status for another 2.5 years. They also state that there is no universal requirement for an altitude chamber test, although the US Air Force does require a chamber test with rapid decompression and rapid descent, if a complete stapedectomy was done. If the newer stapedotomy technique was done, then altitude chamber exposure will not contribute anything further to a waiver decision if the subject is able to easily clear the ear on the ground without any vertiginous sensation. Aeromedical disposal in US air force In US Air Force,[1] if the aviator undergoes successful surgical treatment, an evaluation at the USAF Aeromedical Consultation Service (ACS) is required for single seat high performance aircrew only, and is scheduled no earlier than 12 weeks postoperatively. It includes evaluation by an otolaryngologist with review of all medical records, pre and post-operative testing, and surgical report. Diagnostic audiology includes air and bone conduction threshold measurement, speech reception threshold, speech discrimination testing, impedance audiometry and ENG. An altitude chamber flight with a flight surgeon is required only for those who have had the traditional stapedectomy surgery, to test for perilymph fistula. For those who have undergone the newer stapedotomy surgery, an altitude chamber evaluation is not required. If a chamber flight is performed, it includes a rapid descent (5000 feet/min) from 10,000 feet. A rapid decompression is also required. Additional tests are done as clinically or aeromedically indicated. If ACS evaluation reveals no post-op sequelae, the aviator is recommended for an unrestricted waiver.
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Rajguru: There has been a change in aviation policies following stapedectomy in aircrew
U.S Navy Aeromedical Reference and Waiver Guide states that a stapedectomy done to treat otosclerosis requires a waiver.[18] Designated aviators are grounded for three months following stapedectomy, before waiver is recommended.
2.
Post-stapedotomy disposal of Indian civil aircrew The applicants are not allowed to fly for a period of one to three months following stapes surgery to allow complete healing to take place. Thereafter, a specialized ENT assessment is made to ascertain Eustachian tube patency and the absence of vertigo, nystagmus or unsteadiness during valsalva maneuver and while blowing the nose forcibly.
4.
If after this 3 month period, the applicant who has not had vertigo and has post-operative acceptable hearing, is allowed to fly only under operational restrictions such as flying with or as a co-pilot only or with a safety pilot for a 2-year observation period. After that the pilot is revaluated and the final decision to remove the restrictions is considered. He/she is also informed of the potential hazards of upper respiratory tract infections or other conditions which may interfere with ventilation of the middle ear.
With technological improvements in the surgical techniques, the rate of complications encountered during stapedotomy has come down. However, the presence of complications like persistent vertigo, hearing loss, perilymph fistula, facial paralysis and persistent perforation if not treated definitively are incompatible with flying duties. Though the association between diving, barotrauma and the production of perilymphatic fistula is well known,[19] but various studies reveal no extra risk in poststapedectomy population and do not recommend extra barorestrictions.[20,21] Though permanently grounding all aircrew after stapedectomy remains the safest option, many studies quoted in this article reveal that carefully selected military and civil aircrew have been able to perform all flying duties post stapedotomy without any complications. This has benefitted the aviation organization and the individual aircrew, as it avoids the aircrew to be downgraded from flying duties with the incumbent re-training costs for downgraded personnel and training costs for new/replacement aircrew.
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REFERENCES
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Schall D, Van Syoc D. Clinical Practice Guideline for otosclerosis/ stapedectomy. American Society of Aerospace Medicine Specialists. Aerospace Medical Association; Available from: http://www.asams. org/guidelines/Completed/NEW%20Otosclerosis.htm. [Last updated on 2011 Nov 14].
Merchant S, Mc Kenna MJ, Browning G, Rea P, Tange R. Otosclerosis. 7th ed. In: Gleeson M editors. Scott-Brown’s otorhinolaryngology, Head and Neck Surgery. Great Britain: Edward Arnold (Publishers) Ltd; 2008. p. 3475-8. Fisch U. Stapedotomy versus stapedectomy. Otol Neurotol 2009;30:1166-7. Thamjarayakul T, Supiyaphun P, Snidvongs K. Stapes fixation surgery: Stapedectomy versus stapedotomy. Asian Biomed 2010;4:429-34. Gristwood RE, Venables WN. Effects of fenestra size and piston diameter on the outcome of stapes surgery for clinical otosclerosis. Ann Otol Rhinol Laryngol 2011;120:363-71. Hazarika P, Singh R, Nayak DR, Sajilal Ma, Deviprasad D, Prabhjot R. Comparison between conventional stapedectomy and KTP-532 laser stapedectomy. Indian J Otol 2010;16:13-8. Ikezono T, Shindo S, Sekine K, Shiiba K, Matsuda H, Kusama K, et al. Cochlin-tomoprotein (CTP) detection test identifies traumatic perilymphatic fistula due to penetrating middle ear injury. Acta Otolaryngol 2011;131:937-44. Ikezono T, Shindo S, Sekiguchi S, Morizane T, Pawankar R, Watanabe A, et al. The performance of Cochlin-tomoprotein detection test in the diagnosis of perilymphatic fistula. Audiol Neurootol 2010;15:168-74. Available form: http://www.american-hearing.org. Hain TC. Perilymph Fistula; American Hearing Research Foundation. [Last updated on 2012 Oct]. Ashe AF, Billings CE, Shillito FH. Aeromedical problems associated with surgical procedures for the relief of otosclerosis. Aerosp Med 1967;38:407-11. Garlington JC, Singleton GT. Rapid decompression and recompression in the stapedectomized cat. Aerosp Med 1968;40:475-8. Hanna HH, Collins FG. Effect of barometric pressure change on the ear following stapedectomy. Aerosp Med 1974;45:548-50. Rayman RB. Stapedectomy: A threat to flying safety? Aerosp Med 1972;43:545-50. Rayman RB, Hastings JD, Kruyer WB, Levy RA, Pickard JS. Clinical Aviation Medicine. 4th ed. New York; Professional Publishing Group, Ltd; 2006. p. 138-40. Katzav J, Lippy WH, Shamiss A, Davidson BZ. Stapedectomy in combat pilots. Am J Otol 1996;17:847-9. Thiringer JK, Arriage MA. Stapedectomy in military aircrew. Otolaryngol Head Neck Surg 1998;118:9-14. Phelan JR. Otolaryngology in aerospace medicine. In: Davies JR, Johnson R, Stepanek J, Fogarty JA, editors. Fundamentals of Aerospace Medicine. 4th ed. United State: Lippincott Williams and Wilkins; 2008. p. 385-6. U.S Navy Aeromedical reference and waiver guide. In: Metzger J, Maur E, editors. 6.5 Hearing Loss/Stapedectomy. Pensacola, USA: Navy Medicine Operational Training Centre (NMOTC); Available from: http://www.med.navy.mil/sites/nmotc/nami/arwg/Pages/ AeromedicalReferenceandWaiverGuide.aspx. [Last updated on 2006 Jun 22]. Pullen FW 2nd. Perilymphatic fistula induced by barotrauma. Am J Otol 1992;13:270-2. Harrill WC, Jenkins HA, Coker NJ. Barotrauma after stapes surgery: A survey of recommended restrictions and clinical experiences. Am J Otol 1996;17:835-45. House JW, Toh EH, Perez A. Diving after stapedectomy: Clinical experience and recommendations. Otolaryngol Head Neck Surg 2001;125:356-60.
Cite this article as: Rajguru R. Post stapedotomy aviation: A changing scenario. Indian J Occup Environ Med 2014;18:105-8. Source of Support: Nil, Conflict of Interest: None declared.
Indian Journal of Occupational and Environmental Medicine - December 2014 - Volume 18 - Issue 3
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