Microgravity and the intervertebral disc: The impact of space conditions on the biomechanics of the spine.

The environmental conditions to which astronauts and other military pilots are subjected represent a unique example for understanding and studying the biomechanical events that regulate the functioning of the human body. In particular, microgravity has shown a significant impact on various biological systems, such as the cardiovascular system, immune system, endocrine system, and, last but not least, musculoskeletal system. Among the potential risks of flying, low back pain (LBP) has a high incidence among astronauts and military pilots, and it is often associated with intervertebral disc degeneration events. The mechanisms of degeneration determine the loss of structural and functional integrity and are accompanied by the aberrant production of pro-inflammatory mediators that exacerbate the degenerative environment, contributing to the onset of pain. In the present work, the mechanisms of disc degeneration, the conditions of microgravity, and their association have been discussed in order to identify possible molecular mechanisms underlying disc degeneration and the related clinical manifestations in order to develop a model of prevention to maintain health and performance of air- and space-travelers. The focus on microgravity also allows the development of new proofs of concept with potential therapeutic implications.

Space flight and central nervous system: Friends or enemies? Challenges and opportunities for neuroscience and neuro-oncology.

Space environment provides many challenges to pilots, astronauts, and space scientists, which are constantly subjected to unique conditions, including microgravity, radiations, hypoxic condition, absence of the day and night cycle, etc. These stressful stimuli have the potential to affect many human physiological systems, triggering physical and biological adaptive changes to re-establish the homeostatic state. A particular concern regards the risks for the effects of spaceflight on the central nervous system (CNS), as several lines of evidence reported a great impact on neuroplasticity, cognitive functions, neurovestibular system, short-term memory, cephalic fluid shift, reduction in motor function, and psychological disturbances, especially during long-term missions. Aside these potential detrimental effects, the other side of the coin reflects the potential benefit of applicating space-related conditions on Earth-based life sciences, as cancer research. Here, we focused on examining the effect of real and simulated microgravity on CNS functions, both in humans and in cellular models, browsing the different techniques to experience or mime microgravity on-ground. Increasing evidence demonstrate that cancer cells, and brain cancer cells in particular, are negatively affected by microgravity, in terms of alteration in cell morphology, proliferation, invasion, migration, and apoptosis, representing an advancing novel side of space-based investigations. Overall, deeper understandings about the mechanisms by which space environment influences CNS and tumor biology may be promisingly translated into many clinical fields, ranging from aerospace medicine to neuroscience and oncology, representing an enormous pool of knowledge for the implementation of countermeasures and therapeutic applications.

Bilateral chemodectoma: medicolegal considerations on a case report of aeromedical concern.

The authors describe a case of bilateral carotid chemodectoma occurring in a military pilot who was assessed and evaluated in terms of aeromedical and medico-legal aspects for his fitness to fly. In view of the lack of specific guidelines and/or regulations, both national and international, we choose to follow a multidisciplinary clinical approach that included aero-physiological tests in the hypobaric chamber, in order to identify a standard protocol that could be used as reference for similar future cases, where this kind of assessment is necessary.

Predictors of ear barotrauma in aircrews exposed to simulated high altitude.

INTRODUCTION: Ear barotrauma is an adverse effect related to hypobaric exposure. Ear, nose, and throat (ENT) diseases are risk factors for barotrauma in aircrews trained in a hypobaric chamber, but excluding affected subjects from exposure does not abolish the risk in asymptomatic trainees. We investigated other possible predictors, including history of ENT diseases, ENT clinical abnormalities, altitude, and subject's age. METHODS: After a complete ENT evaluation including otoscopy and tympanometry, 314 aircrews underwent hypobaric chamber training. Two altitude training profiles up to 35,000 ft (10,668 m) and 25,000 ft (7620 m), respectively, were used. Subjects were grouped according to if they were asymptomatic, had acute barotitis, or reported delayed ear pain the day after the exposure. RESULTS: There were 7 men who had acute barotitis (incidence of 2.3%) and 28 men who had delayed ear pain (incidence of 9.2%). A significant association resulted between history of ENT diseases and delayed ear pain and between abnormal ENT findings and acute barotitis in subjects exposed to the higher profile. Altitude was associated with increased risk of delayed ear pain. Delayed ear pain was associated with older age in subjects exposed to the lower altitude and younger age in subjects exposed to the higher altitude. DISCUSSION: Our data suggest that in subjects exposed to 35,000 ft (10,668 m), the history of previous ENT diseases and younger age may be valid predictors of delayed ear pain, while abnormal ENT findings may predict acute barotitis. At 25,000 ft (7620 m), subjects with older age may have increased risk of delayed ear pain.

Altitude chamber related adverse effects among 1241 airmen.

INTRODUCTION: Altitude chambers are used for training aircrews, but incidents have been reported, including decompression sickness (DCS) and barotrauma. To minimize chamber-related adverse effects we implemented a set of measures, including altitude restriction and a pre-chamber clinical selection (PCS) of subjects before exposure. METHODS: We reviewed our records regarding 1254 individuals who were trained from 2003 to 2009. After the first 3 subjects, the maximum altitude of the highest training profile was limited to 43,000 ft (13,106.4 m) instead of 45,000 ft (13,716 m) and, after the first 327 subjects, a clinical evaluation of each trainee was performed by an otolaryngologist before altitude exposure. The evaluation included otoscopy and tympanometry, and subjects with abnormal results were not cleared for altitude exposure. Subjects were grouped by having undergone the highest profile before (3 subjects) or after altitude restriction (8 subjects) and received clinical selection (PCS group, 927 subjects) or not (control group, 327 subjects). RESULTS: We recorded 32 total adverse effects (overall incidence 2.6%), 21 in the PCS group (2.3%) and 11 in the control group (3.4%). The difference between groups was not significant. Adverse effects included 19 cases of acute barotitis (1.5%), 1 case of DCS (0.08%), and 4 cases of syncope (0.3%). The incidence of barotitis was 1.1% in the PCS group and 2.7% in the control group. The altitude restriction was ineffective in preventing both barotrauma and DCS. CONCLUSIONS: The incidence of adverse effects in our subjects was low and pre-chamber clinical selection appeared to be effective in reducing the risk of barotitis.

Ear pain after breathing oxygen at altitude: prevalence and prevention of delayed barotrauma.

INTRODUCTION: Military pilots frequently report ear pain with onset several hours after altitude exposure while breathing pure oxygen, but the prevalence of this problem is unknown. A similar problem is described in divers after breathing hyperbaric oxygen and it is related to the oxygen contained in the middle ear. METHODS: In order to assess the prevalence of delayed ear pain after altitude exposure and investigate the effectiveness of preventive use of a nasal balloon (NB), we studied 88 healthy military jet pilots who were asymptomatic after altitude chamber exposure which included 100% oxygen breathing. A group of 44 subjects received the NB shortly after the chamber and they were advised to use it every hour before going to sleep. A control group of 44 subjects was requested to perform the Valsalva maneuver alone over the same period. All subjects underwent clinical examination by an otolaryngologist and tympanometry just before the chamber exposure and again the day after. RESULTS: The day after the altitude exposure, 53.4% of subjects reported ear pain. In the treated group, 61.4% of subjects were free of symptoms, compared to 31.8% in the control group (P < 0.01). Tympanogram was abnormal in eight symptomatic subjects and in six asymptomatic. CONCLUSION: Our data suggest that in our subjects there is high prevalence of delayed ear barotrauma after altitude chamber exposure while breathing pure oxygen and the tympanogram may improve the accuracy of the diagnosis in asymptomatic subjects. The nasal balloon appears to be effective for prevention.

Effect of in-water oxygen prebreathing at different depths on decompression-induced bubble formation and platelet activation.

Effect of in-water oxygen prebreathing at different depths on decompression-induced bubble formation and platelet activation in scuba divers was evaluated. Six volunteers participated in four diving protocols, with 2 wk of recovery between dives. On dive 1, before diving, all divers breathed normally for 20 min at the surface of the sea (Air). On dive 2, before diving, all divers breathed 100% oxygen for 20 min at the surface of the sea [normobaric oxygenation (NBO)]. On dive 3, before diving, all divers breathed 100% O2 for 20 min at 6 m of seawater [msw; hyperbaric oxygenation (HBO) 1.6 atmospheres absolute (ATA)]. On dive 4, before diving, all divers breathed 100% O2 for 20 min at 12 msw (HBO 2.2 ATA). Then they dove to 30 msw (4 ATA) for 20 min breathing air from scuba. After each dive, blood samples were collected as soon as the divers surfaced. Bubbles were measured at 20 and 50 min after decompression and converted to bubble count estimate (BCE) and numeric bubble grade (NBG). BCE and NBG were significantly lower in NBO than in Air [0.142+/-0.034 vs. 0.191+/-0.066 (P<0.05) and 1.61+/-0.25 vs. 1.89+/-0.31 (P<0.05), respectively] at 20 min, but not at 50 min. HBO at 1.6 ATA and 2.2 ATA has a similar significant effect of reducing BCE and NBG. BCE was 0.067+/-0.026 and 0.040+/-0.018 at 20 min and 0.030+/-0.022 and 0.020+/-0.020 at 50 min. NBG was 1.11+/-0.17 and 0.92+/-0.16 at 20 min and 0.83+/-0.18 and 0.75+/-0.16 at 50 min. Prebreathing NBO and HBO significantly alleviated decompression-induced platelet activation. Activation of CD62p was 3.0+/-0.4, 13.5+/-1.3, 10.7+/-0.9, 4.5+/-0.7, and 7.6+/-0.8% for baseline, Air, NBO, HBO at 1.6 ATA, and HBO at 2.2 ATA, respectively. The data show that prebreathing oxygen, more effective with HBO than NBO, decreases air bubbles and platelet activation and, therefore, may be beneficial in reducing the development of decompression sickness.

Acute otitic barotrauma during hypobaric chamber training: prevalence and prevention.

INTRODUCTION: Barotitis media is known to be an adverse effect of altitude changes, but few studies have investigated this condition with respect to hypobaric chamber training and the resulting estimations of prevalence vary. METHODS: In order to assess the prevalence of hypobaric chamber-related barotitis and evaluate a method of prevention, 335 healthy military pilots undergoing high altitude training were subject to clinical examination and tympanometry before entering the chamber. In order to minimize the risk of barotrauma, only subjects with normal preflight findings were cleared for altitude exposure. Barotitis media was diagnosed on the basis of ear pain and clinical findings according to Teed's classification. RESULTS: Barotitis occurred in eight subjects; seven cases were monolateral and one bilateral, prevalence was 2.4%. CONCLUSION: The prevalence of barotitis after hypobaric chamber training is low in our study, suggesting that a pre-chamber medical check including clinical examination and tympanometry could be effective in identifying subjects at risk.

[The heart in extreme sports: hyperbaric activity and microgravity]. / II cuore nello sport estremo: attività iperbarica e microgravità.

The study of the cardiovascular and respiratory modifications in extreme environments could be useful for the understanding of the adaptive mechanisms of the body in particular conditions. The knowledge of how different environmental conditions in terms of extreme pressure, temperature and gravity modify the neurovegetative and cardiovascular system could be useful in daily practice for hypobaric and hyperbaric sports.