Negative impact of high-performance flights on aviators with mitral valve prolapse

BACKGROUND

While it appears not to affect healthy aviators' hearts, there are scarce data regarding the impact of high-performance flights on aviators with mitral valve prolapse (MVP).

METHODS

A retrospective, comparative cohort study of military aviators with MVP. Subjects were categorized to either high-performance (jet fighter) or low-performance (transport and helicopter) aviators. The primary outcomes were the rates of mitral interventions and of adverse cardiovascular events since being an aircrew candidate and up to the end of flying career. Additional outcomes were echocardiographic measurements and the cumulative proportion of mitral valve interventions over time.

RESULTS

Of 33 male aviators with MVP, 18 were high-performance aviators. On average, follow-up started at age 18.5 years and lasted 27.8 ± 10.1 years. Baseline characteristics were similar between the study groups. Aviators of high-performance aircraft had increased rates of mitral valve surgery (33 % vs. 0, p = 0.021), MVP-related complications (39 % vs. 6.7 %, p = 0.046), and a higher incidence of mitral valve repair over time (p = 0.02). High-performance flight was associated with increased intraventricular septum thickness (IVS, 9.7 mm vs 8.9 mm, p = 0.015) and IVS index (p = 0.026) at the last echocardiographic assessment. High-performance aviators tended to develop worsening severity of mitral regurgitation.

CONCLUSIONS

High-performance flight may be associated with an increased risk for valvular deterioration and need for mitral surgery in aviators with MVP.

Influence of atmospheric pressure changes on dentin bond strength of conventional, bulk-fill and single-shade resin composites

INTRODUCTION

The purpose of this study was to investigate the dentin bond strength of composite resins in response to environmental pressure changes.

METHODS

Ninety extracted human molar teeth were used. A mould (3 mm x 4 mm) was adapted on dentin, resin composites (conventional [n = 30] and single-shade composites [Ohmnicroma] [n = 30]) were filled in two increments of 2 mm. The bulk-fill composites (n = 30) were filled with one 4 mm increment. The specimens were stored for 30 days in artificial saliva. The specimens were exposed to hyperbaric pressure (283.6 kPa; 2.8 atmospheres absolute [atm abs]) or hypobaric pressure (34.4 kPa; 0.34 atm abs) once daily for 30 days and the control group was stored at atmospheric pressure for 30 days. The bond strength was tested with a universal testing machine and the failures were examined with a stereomicroscope and scanning electron microscope. Statistical analyses were performed using analysis of variance with post hoc tests, and the Weibull analysis.

RESULTS

Regardless of environmental pressure changes, the bulk-fill composites showed the highest bond strength. There was no significant difference in bond strength between the hypobaric and atmospheric pressure (control) groups after 30 days in all resins. The hyperbaric group showed lower bond strength for bulk-fill composites than the control group.

CONCLUSIONS

Dentists experienced in diving and aviation medicine should definitely take part in the initial and periodic medical examinations of divers and aircrew to give appropriate treatment. Bulk-fill composite resins can be preferred in divers and aircrew due to high bond strength values.

Cardiovascular risk in high-hazard occupations: the role of occupational cardiology

Work is beneficial for health, but many individuals develop cardiovascular disease (CVD) during their working lives. Occupational cardiology is an emerging field that combines traditional cardiology sub-specialisms with prevention and risk management unique to specific employment characteristics and conditions. In some occupational settings incapacitation through CVD has the potential to be catastrophic due to the nature of work and/or the working environment. These are often termed 'hazardous' or 'high-hazard' occupations. Consequently, many organizations that employ individuals in high-hazard roles undertake pre-employment medicals and periodic medical examinations to screen for CVD. The identification of CVD that exceeds predefined employer (or regulatory body) risk thresholds can result in occupational restriction, or disqualification, which may be temporary or permanent. This article will review the evidence related to occupational cardiology for several high-hazard occupations related to aviation and space, diving, high altitude, emergency workers, commercial transportation, and the military. The article will focus on environmental risk, screening, surveillance, and risk management for the prevention of events precipitated by CVD. Occupational cardiology is a challenging field that requires a broad understanding of general cardiology, environmental, and occupational medicine principles. There is a current lack of consensus and contemporary evidence which requires further research. Provision of evidence-based, but individualized, risk stratification and treatment plans is required from specialists that understand the complex interaction between work and the cardiovascular system. There is a current lack of consensus and contemporary evidence in occupational cardiology and further research is required.

The global incidence of in-flight medical emergencies: A systematic review and meta-analysis of approximately 1.5 billion airline passengers

BACKGROUND

Medical emergencies during short- or long-haul commercial airline flights have become more commonplace due to the aviation industry's contemporary growth, the popularization of commercial flights, and an increased aging of air travelers with significant comorbidities. However, the precise incidence of onboard medical events on commercial airlines and the most common medical conditions is unclear.

METHODS

In this systematic review and meta-analysis, we explored the incidence of in-flight medical emergencies among airline passengers and estimated the incidence rate by physiological body system, or organ class/syndrome for emergencies that may be associated with different body systems. We limited our search to cohort studies published between 1945 to October 31, 2020 in MEDLINE, Embase, Cochrane Library and official reports from the Federal Aviation Administration/International Air Transport Association, regardless of the language of publication. Only studies that evaluated the overall frequency of onboard medical events on commercial air carriers (in which they also presented the total number of annual revenue passengers) and the frequency of events by physiological body systems or organ class/syndrome were included. We excluded case reports and case series, systematic or narrative reviews, and studies addressing specific health-related conditions. Two independent investigators performed first- and second-phase study screening, abstracted data, and appraised risk of bias. We rated the certainty of evidence using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. Using a quality effect model, we meta-analyzed data associated with the incidence of in-flight medical emergencies, all-cause fatality, incidence of medical events by medical condition category, frequency of en-route diversion, presence of medical personnel on board, and the use of an automatic external defibrillator. We also extracted data regarding the cost of flight diversion.

RESULTS

Of 18 individual studies with approximately 1.5 billion passengers, 11 reported the overall incidence of in-flight medical emergencies. Low certainty of evidence suggested that the global incidence of in-flight medical emergencies was 18.2 events per million passengers (95% CI 0.5 to 53.4 per million; I² = 100%, P < 0.001, very low certainty), and an all-cause mortality rate was 0.21 per million passengers (95% CI 0 to 0.76 per million; I² = 99%, P < 0.001, low certainty). The four most common categories of medical conditions or syndromes during flight were syncope, gastrointestinal events, respiratory and neurological diagnostic groups. The diversion rate was 11.1 per 100,000 flights (95% CI 5.9 to17.6 per 100,000 flights; I² = 97%, P < 0.001), with an average cost ranging from $15,000 to $893,000 per unplanned emergency landing across studies which examined this outcome.

CONCLUSIONS

In-flight medical events on commercial travels are extremely low with a corresponding very low in-flight mortality rate. Associated costs derived from en-route diversion might significantly influence airlines' budgetary equilibrium. Novel and modern standardized reporting systems or platforms should be internationally provided and enforced by health and aviation authorities to obtain higher quality patient-passengers datasets. Onboard volunteer medical providers must be aware of everyday life-threatening events during commercial flights and should consider the establishment of a connection between the aircraft and ground-based medical advisory services while assisting in-flight medical events.

Pandora's box closed: The Royal Air Force Institute of Aviation Medicine and Nazi medical experiments on human beings during World War II

In the months before and after the final surrender of Nazi Germany on 8 May 1945, British aviation medicine specialists were sent to the European continent to learn the progress that German aviation medicine had made since September 1939. For the medical officers at the Royal Air Force Institute of Aviation Medicine at Farnborough in Hampshire, the dilemma over whether the medical data from the Nazi aviation medicine experiments at Dachau concentration camp should be exploited presented profound moral and ethical problems. Their deliberations paralleled those of the 1945-46 Nuremberg Trial, which revealed the crimes that were committed under the Nazi regime. At the same time, the British medical establishment debated the morality of publishing the Nazi medical research to serve humanity. This article shows that on the basis of British wartime and post-war research, and determinations that were made by the British Advisory Committee for the Investigation of German Medical War Crimes, by 1948 the RAF IAM had essentially rejected the results of the Nazi aviation medicine experiments on scientific and ethical grounds.

Cardiac MRI improves cardiovascular risk stratification in hazardous occupations

BACKGROUND

The benefit of cardiovascular magnetic resonance Imaging (CMR) in assessing occupational risk is unknown. Pilots undergo frequent medical assessment for occult disease, which threatens incapacitation or distraction during flight. ECG and examination anomalies often lead to lengthy restriction, pending full investigation. CMR provides a sensitive, specific assessment of cardiac anatomy, tissue characterisation, perfusion defects and myocardial viability. We sought to determine if CMR, when added to standard care, would alter occupational outcome.

METHODS

A retrospective review was conducted of all personnel attending the RAF Aviation Medicine Consultation Service (AMCS) for assessment of a cardiac anomaly, over a 2-year period. Those undergoing standard of care (history, examination, exercise ECG, 24 h-Holter and transthoracic echocardiography), and those undergoing a CMR in addition, were identified. The influence of CMR upon the final decision regarding flying restriction was determined by comparing the diagnosis reached with standard of care plus CMR vs. standard of care alone.

RESULTS

Of the ~ 8000 UK military aircrew, 558 personnel were seen for cardiovascular assessment. Fifty-two underwent CMR. A normal TTE did not reliably exclude abnormalities subsequently detected by CMR. Addition of CMR resulted in an upgraded occupational status in 62% of those investigated, with 37% returning to unrestricted duties. Only 8% of referrals were undiagnosed following CMR. All these were cases of borderline chamber dilatation and reduction in systolic function in whom diagnostic uncertainty remained between physiological exercise adaptation and early cardiomyopathy.

CONCLUSIONS

CMR increases the likelihood of a definitive diagnosis and of return to flying. This study supports early use of CMR in occupational assessment for high-hazard occupations.

Speech Recognition of Cochlear Implant Users Inside a Noisy Helicopter Environment

In this study, we tested whether the speech recognition, through radio communications, of cochlear implant (CI) users inside a noisy helicopter cockpit is adequate for safe flight.

METHOD

Speech recognition tests (sentences, numbers and disyllables) through a very-high-frequency radio were administered to 12 CI users in a soundproof booth, inside a helicopter with the engine turned off and turned on.

RESULTS

In quiet environments, radio communications were impacted only for disyllable intelligibility, but in noisy situations, all tests were affected.

CONCLUSIONS

CI subjects did not achieve the auditory levels recommended by the International Civil Aviation Organization.

Direct Oral Anticoagulants and Travel-related Venous Thromboembolism

Travel- related thromboembolism reflects the relationship between venous thromboembolism (VTE) and long-haul flights. Although this condition is rare, it may cause significant morbidity and mortality. Therefore, travelers should be evaluated for the risks for thrombosis. Travel physicians should employ a clinical risk score and select in vestigations, prophylaxis, and treatment that are appropriate for each individual. This review summarizes current VTE clinical risk scores and patient management from various reliable guidelines. We summarized 16 reliable publications for reviewing data. Direct oral anticoagulants (DOACs) are currently the standard treatment for VTE and a prophylactic measure for VTE in orthopedic surgery. Compared with a vitamin K antagonist (VKA), DOACs show better safety and similar efficacy without the need for monitoring, and have fewer food/drug interactions. Inferred from the data on general VTE, DOACs may be used to treat travel-related VTE. Although the data are lacking, DOACs may be used off-label as VTE prophylax is. Before using DOACs, physicians must know the pharmacology of the drugs well and should realize that the availability of antidotes for bleeding complications is limited.

The prevalence of medical symptoms in military aircrew

Background

The prevalence of medical symptoms in aviators has not been described in the medical literature.

Methods

An anonymous questionnaire was handed to all Israeli Air Force aviators who went through the routine yearly examination. Because only two women filled the questionnaire, we excluded them. The questionnaire contained a list of 49 symptoms and the aviators were asked to mark symptoms that were present in the last month before the examination as well as age, estimated weekly flying hours, military service status (reserve or career) and type of aircraft (jet-fighter, helicopter or transport). A general linear model was used to determine the association between age, weekly flying hours, type of aircraft and type of service with the number of symptoms. Binary logistic regression analyses was used to assess the association of these factors with lack of symptoms, and the top five ranking symptoms.

Results

Data was available for 323 male aviators. 62.5% of the aviators reported at least one symptom in the previous month. 26.9% reported three or more symptoms. 25.1% reported spinal symptoms, 22% respiratory symptoms, 21.4% fatigue, 11.5% headache and 6.5% general weakness. Career service was associated with the number of symptoms, fatigue and general weakness. Age was associated with fatigue and general weakness. Aircraft type and weekly flying hours were not associated with any symptom.

Conclusions

Medical symptoms are prevalent in military aviators. Career personnel report on medical symptoms, especially fatigue, more often than reserve personnel. Further study is warranted to examine this association.

Airplane stroke syndrome

Only 37 cases of stroke during or soon after long-haul flights have been published to our knowledge. In this retrospective observational study, we searched the Royal Melbourne Hospital prospective stroke database and all discharge summaries from 1 September 2003 to 30 September 2014 for flight-related strokes, defined as patients presenting with stroke within 14days of air travel. We hypothesised that a patent foramen ovale (PFO) is an important, but not the only mechanism, of flight-related stroke. We describe the patient, stroke, and flight characteristics. Over the study period, 131 million passengers arrived at Melbourne airport. Our centre admitted 5727 stroke patients, of whom 42 (0.73%) had flight-related strokes. Flight-related stroke patients were younger (median age 65 versus 73, p<0.001), had similar stroke severity, and received intravenous thrombolysis more often than non-flight-related stroke patients. Seven patients had flight-related intracerebral haemorrhage. The aetiology of the ischaemic strokes was cardioembolic in 14/35 (40%), including seven patients with confirmed PFO, one with atrial septal defect, four with atrial fibrillation, one with endocarditis, and one with aortic arch atheroma. Paradoxical embolism was confirmed in six patients. Stroke related to air travel is a rare occurrence, less than one in a million. Although 20% of patients had a PFO, distribution of stroke aetiologies was diverse and was not limited to PFO and paradoxical embolism.