Integrating physiological monitoring systems in military aviation: a brief narrative review of its importance, opportunities, and risks.

Military pilots risk their lives during training and operations. Advancements in aerospace engineering, flight profiles, and mission demands may require the pilot to test the safe limits of their physiology. Monitoring pilot physiology (e.g. heart rate, oximetry, and respiration) inflight is in consideration by several nations to inform pilots of reduced performance capacity and guide future developments in aircraft and life-support system design. Numerous challenges, however, prevent the immediate operationalisation of physiological monitoring sensors, particularly their unreliability in the aerospace environment and incompatibility with pilot clothing and protective equipment. Human performance and behaviour are also highly variable and measuring these in controlled laboratory settings do not mirror the real-world conditions pilots must endure. Misleading or erroneous predictive models are unacceptable as these could compromise mission success and lose operator trust. This narrative review provides an overview of considerations for integrating physiological monitoring systems within the military aviation environment.Practitioner summary: Advancements in military technology can conflictingly enhance and compromise pilot safety and performance. We summarise some of the opportunities, limitations, and risks of integrating physiological monitoring systems within military aviation. Our intent is to catalyse further research and technological development.Abbreviations: AGS: anti-gravity suit; AGSM: anti-gravity straining manoeuvre; A-LOC: almost loss of consciousness; CBF: cerebral blood flow; ECG: electrocardiogram; EEG: electroencephalogram; fNIRS: functional near-infrared spectroscopy; G-forces: gravitational forces; G-LOC: gravity-induced loss of consciousness; HR: heart rate; HRV: heart rate variability; LSS: life-support system; NATO: North Atlantic Treaty Organisation; PE: Physiological Episode; PCO2: partial pressure of carbon dioxide; PO2: partial pressure of oxygen; OBOGS: on board oxygen generating systems; SpO2: peripheral blood haemoglobin-oxygen saturation; STANAG: North Atlantic Treaty Organisation Standardisation Agreement; UPE: Unexplained Physiological Episode; WBV: whole body vibration.

Biomechanical comparison of concussions with and without a loss of consciousness in elite American football: implications for prevention.

Loss of consciousness (LOC) associated with concussion is no longer considered an indicator of severity of injury in concussion management protocols. Studies investigating the association between LOC and recovery time or neurophysiological performance have reported ambiguous findings and resulted in a limited understanding of the severity of LOC-inducing head impacts. Concussive injuries with and without LOC from helmet-to-helmet and shoulder collisions and falls in elite American football were reconstructed in laboratory using a hybrid III headform and finite element model to obtain peak linear and rotational acceleration and brain tissue deformation metrics in the cerebral cortex, the cerebral white matter, the corpus callosum, the thalamus and the brainstem. Impact velocity, peak linear and rotational acceleration were significantly greater in the LOC group than the no LOC group. The brain tissue deformation metrics were greater in the LOC group than the no LOC group. The best overall predictor for LOC was impact velocity. Concussions with LOC are characterised by greater magnitudes of brain tissue deformation. This was mainly the result of higher impact velocities in the LOC group providing league decision-makers with an understanding of the importance of managing impact velocity through athlete education and rule enforcement or change.

[A life-saving shock from a subcutaneous ICD during skydiving]. / Lebensrettender Schock durch einen subkutanen ICD während eines Fallschirmsprungs.

We report the case of a 38-year-old man who was implanted a subcutaneous implantable cardioverter-defibrillator (S-ICD) and then performed a skydive from a height of 3000 m. During the jump, he lost consciousness due to ventricular fibrillation (VF). The S­ICD detected the VF properly and successfully shocked the arrhythmia. Our illustrative case emphasizes the S­ICD as an appropriate therapy in patient with life-threatening arrhythmias even under extreme conditions.

[The suspension trauma syndrome: preventive features.] / Sindrome da sospensione inerte (sindrome da imbracatura): peculiarità preventive.

OBJECTIVES: The suspension trauma syndrome is a clinical condition that could lead to death, also in short time, by coupling the suspension with loss of consciousness and multiorgan failure. Health risks linked to temporary work in suspension are characterized both by infortunistic ones (for instance: trauma, falls, etc.) and by clinical ones, like the suspension trauma syndrome or compressive issues due to different fall protection systems. METHODS: This study deal with the technical and medical meseasures devoted to the prevention of the suspension trauma syndrome. Italian 81/08 and 164/56 laws prescribes that, when no collective protection systems could be used, any single worker has to used personal safety equipment like energy absorbers, anchoring devices, lanyards, retractable devices, flexible life guides or lines, guides or rigid life lines, harnesses. Persons working in height have to undergo a medical surveillance, devoted in particular to identify such illnesses (frequently cardiologic or muscleskeletal disorders, both temporary or chronical) that prevent the exposures possibly leading to the suspension syndrome. RESULTS: In some cases, the occupational physician could express a judgement of fitness to work in which only specific personal protection devices are allowed and/or the time to dedicate to work in suspension is limited, to efficiently protect the workers' health. CONCLUSIONS: Qualora emergano quadri patologici (in particolare cardiologici ed osteomuscolari) con caratteristiche di cronicità e irreversibilità, è indicato esprimere un giudizio di inidoneità permanente alle attività che prevedono il lavoro in sospensione con imbracatura. In casi specifici, è possibile formulare giudizi di idoneità con limitazioni/prescrizioni rispetto al tempo di sospensione o rispetto alla tipologia di DPI impiegati, in maniera tale da garantire lo svolgimento dell'attività in sospensione minimizzando il rischio di insorgenza della sindrome.

Increasing the probability of surviving loss of consciousness underwater when using a rebreather.

Re-circulating underwater breathing apparatus (rebreathers) have become increasingly popular amongst sport divers. In comparison to open-circuit scuba, rebreathers are complex life support equipment that incorporates many inherent failure modes and potential for human error. This individually or in combination can lead to an inappropriate breathing gas. Analysis of rebreather diving incidents suggests that inappropriate breathing gas is the most prevalent disabling agent. This can result in spontaneous loss of consciousness (LoC), water aspiration and drowning. Protecting the airway by maintaining the diver/rebreather oral interface may delay water aspiration following LoC underwater; the possibility of a successful rescue is, thus, increased. One means of protecting the airway following LoC underwater is the use of a full-face mask (FFM). However, such masks are complex and expensive; therefore, they have not been widely adopted by the sport diving community. An alternative to the FFM used extensively throughout the global military diving community is the mouthpiece retaining strap (MRS). A recent study documented 54 LoC events in military rebreather diving with only three consequent drownings; all divers were reported to be using a MRS. Even allowing for the concomitant use of a tethered diving partner system in most cases, the low number of fatalities in this large series is circumstantially supportive of the efficacy of the MRS. Despite drowning featuring as a final common pathway in the vast majority of rebreather fatalities, the MRS has not been widely adopted by the sport rebreather diving community.

Very prolonged episode of self-terminating ventricular fibrillation in a patient with Brugada syndrome.

We report the case of a very prolonged spontaneous episode of self-terminating ventricular fibrillation in a patient with Brugada syndrome (BrS). The patient first underwent implantation of an internal loop recorder after an episode of prolonged loss of consciousness (several minutes) that was suggestive of a nonarrhythmic cause. After a second episode of prolonged syncope, subsequent interrogation of the loop recorder revealed a very prolonged episode of self-terminating ventricular arrhythmia, lasting 2 minutes and 41 seconds. This short report emphasizes the fact that an arrhythmic cause of syncope should not be ruled out in patients with BrS presenting with very prolonged loss of consciousness.

Effects of motivational interviewing intervention on blackouts among college freshmen.

PURPOSE: Alcohol and illicit drug abuse is a serious public health issue facing college students. This study examined the impact of motivational interviewing (MI) as an intervention on the rate of blackouts among freshmen who engaged in high-risk drinking and illicit drug use. DESIGN: A sample of 188 volunteer freshmen from a university were administered the Daily Drinking Questionnaire, the Rutgers Alcohol Problem Index, and the Government Performance and Results Act at baseline and again at 6 months postintervention. MI was applied at baseline and then again at 2 weeks, 3 months, and 6 months. METHODS: Generalized estimated equations and logistic regression models were used to determine associations between the rate of blackouts and time, ethnicity, gender, illicit drug use, and alcohol consumption. FINDINGS: At 6 months, the rate of blackouts decreased from 40% at baseline to 16% (p < .0001). The average number, time, and days of drinking and frequency of drug use also decreased significantly (p < .0001). An association between rate of blackouts and gender was observed, but not with ethnicity. CONCLUSIONS: MI had an impact on reducing alcohol consumption and the rate of blackouts among college freshmen who were engaging in high-risk drinking and illicit drug use. CLINICAL RELEVANCE: The findings support the importance of using MI with freshmen college students to decrease drinking and the associated negative consequences, including blackouts, which has particular relevance for advanced practice registered nurses, physicians, and community health nurses who conduct MI as an intervention with college students.

Signs and symptoms during supra-tolerance +G(z) exposures, with reference to G-garment failure.

INTRODUCTION: +G(z) exposure above the tolerance threshold typically induces a sequence of symptoms/signs, with loss of: peripheral vision, central vision (black out), and consciousness (G-LOC). The aims of this study were to investigate: 1) whether G history influences latent time to, or sequence of, symptoms/signs upon G exposures exceeding the tolerance threshold; and 2) how pilots respond to a sudden loss of pressure in the anti-G garment (AGG) in flight-like scenarios. METHODS: There were 14 subjects who were exposed to rapid onset rate +G(z)-time profiles, with plateaus 1 and 2 G above the relaxed tolerance level, without initial pressurization of the AGG (NoAGG) and when losing AGG pressure after 10 (AGG_10) and 120 (AGG_120) s at the plateau. Simulated target-chase flights during which AGG pressure was released were performed by seven pilots; the pilot was instructed to behave as during real flight. RESULTS: Latent time to symptoms was shorter at +2 G than at +1 G, and shorter in AGG_10 and AGG_120 than in NoAGG. In AGG_120, 43 and 64% of the subjects experienced serious symptoms (black out, Almost LOC, G-LOC) at +1 and +2 G, respectively, compared to 21 and 54% in AGG 10 and 7 and 29% in NoAGG. The incidence of A-LOC/ G-LOC was higher in AGG_10 and especially in AGG_120 than in NoAGG. During the target chase, one pilot did not notice the pressure loss, one experienced G-LOC, and two A-LOC. DISCUSSION: The risk of serious consequences of G exposure exceeding the tolerance level appears to be greater when G-garment failure occurs after a prolonged than after a brief exposure.

Association of exercise-induced hyperinsulinaemic hypoglycaemia with MCT1-expressing insulinoma.

AIMS/HYPOTHESIS: Exercise-induced hyperinsulinism (EIHI) is a hypoglycaemic disorder characterised by inappropriate insulin secretion following anaerobic exercise or pyruvate load. Activating promoter mutations in the MCT1 gene (also known as SCLA16A1), coding for monocarboxylate transporter 1 (MCT1), were shown to associate with EIHI. Recently, transgenic Mct1 expression in pancreatic beta cells was shown to introduce EIHI symptoms in mice. To date, MCT1 has not been demonstrated in insulin-producing cells from an EIHI patient. METHODS: In vivo insulin secretion was studied during an exercise test before and after the resection of an insulinoma. The presence of MCT1 was analysed using immunohistochemistry followed by laser scanning microscopy, western blot analysis and real-time RT-PCR of MCT1. The presence of MCT1 protein was analysed in four additional insulinoma patients. RESULTS: Clinical testing revealed massive insulin secretion induced by anaerobic exercise preoperatively, but not postoperatively. MCT1 protein was not detected in the patient's normal islets. In contrast, immunoreactivity was clearly observed in the insulinoma tissue. Western blot analysis and real-time RT-PCR showed a four- to fivefold increase in MCT1 in the insulinoma tissue of the EIHI patient compared with human pancreatic islets. MCT1 protein was detected in three of four additional insulinomas. CONCLUSIONS/INTERPRETATION: We show for the first time that an MCT1-expressing insulinoma was associated with EIHI and that MCT1 might be present in most insulinomas. Our data suggest that MCT1 expression in human insulin-producing cells can lead to EIHI and warrant further studies on the role of MCT1 in human insulinoma patients.

[Experience of cytoflavin administration for treating acute carbon monoxide poisoning].

Results of an analysis of the efficiency of using cytoflavin, a drug possessing cytoprotective and antihypoxemic properties, in a group of 215 patients with a diagnosis of acute carbon monoxide poisoning in 2004-2010 are compared to analogous data for 215 patients with same diagnosis treated in 1999-2004 without cytoflavin administration. It is established that timely application of cytoflavin (against the standard treatment of CO poisoning) favored lower expressiveness of post-hypoxemic encephalopathythatis characteristic of the given pathology.

Cardiovascular consequences of high-performance aircraft maneuvers: implications for effective countermeasures and laboratory-based simulations.

The gravitational stress encountered by pilots of high-performance aircraft can cause dramatic shifts in blood volume and circulatory pressure, thus placing the cardiovascular system under significant stress, sometimes resulting in loss of consciousness due to cerebral under-perfusion. Since pilots experience both increased and decreased gravitational stress in high-risk environments, it is important not only to examine the cardiovascular effects of altered gravitational exposure, but also to create effective countermeasures that will increase pilot safety. In this review, we discuss the cardiovascular consequences of rapid changes in gravitational forces. We also examine the effectiveness of the countermeasures that have been developed to combat gravity-induced loss of consciousness. Finally, we examine those current laboratory-based techniques that simulate hyper-gravity and the "push-pull effect"; making it possible to investigate the cardiovascular mechanisms responsible for maintaining cerebral perfusion and consciousness.

New method of visual disturbances assessment in pilots during tests in the Polish human centrifuge.

OBJECTIVES: Visual disturbances are commonly accepted criteria for acceleration tolerance assessment. Researchers during centrifuge experiments use them as a safe criterion for cessation of acceleration exposure. Visual disturbances analysis is a non-invasive method of assessing retinal blood flow. Limitation of visual stimuli perception is a measure of physiological state of the experiment participants before hemodynamic changes, which reach a critical level manifested by G-induced loss of consciousness. Detection of these disturbances play an important role during the acceleration tolerance assessment. In this study, an attempt was made to answer the question on how many mistakes or incorrect reactions had to be identified to classify the ability of the pilot to fly on military jets. MATERIALS AND METHODS: A new computer-aided research apparatus of our own design was used to assess visual disturbances, being a criterion of +Gz tolerance. In the center of monitor screen, a line of 3 light points was projected. During the centrifuge test, green lateral lights randomly changed their shapes from circles to squares while central light, being a point of vision fixation, remained unchanged. To assess its efficacy, 14 volunteers participated in the tests with various stimuli exposure. The authors aimed at selecting parameters of stimuli and exposure so that the division of reactions presented in the table would correspond with the score scale appropriate for our goals. RESULTS: Preliminary tests showed that appropriately selected light intensity of the exposed stimuli enables the use of test results to assess the number of erroneous reactions, and consequently the level of pilots' concentration during centrifuge tests. CONCLUSIONS: It has been found that the chosen luminance range of the projected light points is correct as it allows to evaluate the reactions, which should be considered erroneous. Additionally, prolongation of the correct reaction time to the mean value of about 400 ms facilitates better differentiation of results. Proper results evaluation, depending on the number of errors, lack of reactions or prolonged reactions made the assessment easier with computer-aided methods.

G-induced loss of consciousness: retrospective survey results from 2259 military aircrew.

INTRODUCTION: Prevalence of G-induced loss of consciousness (G-LOC) in the United Kingdom Royal Air Force (RAF) was found to be 19.3% in 1987. With the introduction of the Typhoon, a fourth generation aircraft, the prevalence of G-LOC has been re-assessed to determine the effectiveness of current G tolerance training. METHOD: A survey was sent to 4018 RAF aircrew, irrespective of their current role. Information was requested on G-LOC, role and aircraft type, experience, and attitudes toward G-LOC prevention. RESULTS: Responses were received from 2259 (56.2%) individuals, 882 (39%) of whom were current fast jet aircrew. At least one episode of G-LOC was reported by 20.1% of all respondents. In front line aircraft, prevalence of G-LOC among the 882 fast jet aircrew who responded was 6%. In the whole group, G-LOC was reported most commonly in aircrew under training (70.9%), and was most prevalent in training aircraft (77.4% of G-LOC events). At the time of the G-LOC, 64% of aircrew had less than 100 h total flying time. G-LOC was reported most frequently between +5 to +5.9 Gz, and "push-pull" maneuvers were associated with 31.3% of G-LOC events. Pulling G was not considered a problem by 50.6% of respondents, although over 80% recognized the value of flying currency, use of an anti-G suit, and physical fitness, and 55.6% felt that centrifuge training would be valuable. DISCUSSION: The prevalence of G-LOC in the RAF has changed little since 1987, and there remains considerable scope for aircrew education, particularly with the introduction of the Typhoon.

Cyanotic breath-holding spell: a life-threatening complication after radical resection of a cervicomedullary ganglioglioma.

Cyanotic breath-holding spell is a benign and self-limiting disease of young children but occasionally associated with sudden, unexpected death. The authors report a rare case in a 2-year-old girl with a severe form that started after radical resection of a cervicomedullary ganglioglioma. She was admitted to our hospital because of delayed and unstable gait. Since magnetic resonance imaging showed a cervicomedullary tumor, she underwent a radical resection and histology showed the tumor to be a ganglioglioma. Postoperatively, the function of the lower cranial nerves and cerebellum deteriorated and hemiparesis on the left became apparent, but she returned to the preoperative state in a few months. In addition, mild sleep apnea (Ondine curse) and severe cyanotic breath-holding spells occurred. The former responded to medication but the latter failed and continued several times per day with a rapid onset and progression of hypoxemia, loss of consciousness, sweating and opisthotonos. Five months after the operation, the patient returned home with a portable oxygen saturation monitor equipped with an alarm. This case indicates that cyanotic breath-holding spell, as well as sleep apnea, is critical during the early postoperative period. This is the first report observing that such spells may occur as a complication of radical resection of a cervicomedullary tumor.

Psychostimulants and G tolerance in rhesus monkeys: effects of oral modafinil and injected caffeine.

INTRODUCTION: Caffeine and modafinil are psychostimulants that may be taken by fighter aircraft pilots to reduce fatigue. Fighter pilots are subjected to high positive G loads that reduce cerebral blood flow and consequently may induce G-LOC. The aim of the experiment was to determine whether these drugs may reduce tolerance to G stress. METHODS: Seven adult male rhesus monkeys participated in the experiment. Five were equipped with ECoG and ECG wires and underwent two G tests (A and B). Each experiment consisted of five centrifuge runs. Before the runs, the monkeys received no drug (control) or were given either 7.5 mg x kg(-1) caffeine IM or 64 mg x kg(-1) modafinil PO or the corresponding vehicles. The runs were performed up to +13 Gz with an onset rate of 0.1 G x s(-1) (test A) or 3 G x s(-1) (test B). The run was ended when the electrical activity of one ECoG channel had disappeared (i.e., G-LOC). RESULTS: In experiment A, drug administration had no significant effect. In experiment B, the injection of the caffeine-free solvent caused a delay in G-LOC compared with the control condition (no administration). Caffeine solvent also induced an increase in plasma osmolality. DISCUSSION: Modafinil administration has no significant effect on the G tolerance of rhesus monkeys. Regarding caffeine, the drug seems to have caused the reverse effect compared with the solvent. CONCLUSIONS: Caffeine and modafinil administration had no significant effect on the G-tolerance of rhesus monkeys when compared with controls. This result needs to be confirmed in humans.

Preventing G-induced loss of consciousness: 20 years of operational experience.

INTRODUCTION: Although anecdotal reports of G-induced loss of consciousness (G-LOC) in military aviation date back to before 1920, regular reporting did not begin until 1982. The effectiveness in the operational setting of G-LOC preventive measures, such as positive pressure breathing for G protection (PBG), has not been studied. METHODS: We use the term "crash" to represent an event where the aircraft was destroyed and "incident" to define those events where the crew reported a G-LOC episode and the aircraft was not damaged. Data on G-LOC crashes, incidents, and aircraft sorties (number of take-offs) were obtained from the USAF Safety Center database for FY 82-01. RESULTS: During FY 82-01, there were 29 G-LOC crashes while those aircraft at risk of G-LOC crashes flew a total of 13,959,816 sorties. Poisson regression showed a non-significant decrease in crashes with an incidence rate ratio (IRR) of 0.096 (CI 0.89-1.03) (4% per yr). G-LOC crashes decreased from 4.4 per million flight sorties (PMFS) to 1.6 after the implementation of anti-G-LOC training programs beginning in 1985. However, G-LOC crashes remained unchanged after implementation of PBG in 1995. In contrast, incidents showed an IRR of 1.04 (CI 1.02-1.06) for G-LOC incidents, an estimated increase of 5% per yr. DISCUSSION: The physical/mechanical limitations of PBG, risk homeostasis, and the possibility that G-LOC rates have reached their asymptotic minimum are all discussed as possible explanations for the failure of PBG to decrease G-LOC crashes.

An electromyographic assessment of the anti-G straining maneuver.

BACKGROUND: The anti-G straining maneuver (AGSM), used by aircrew to enhance their +Gz tolerance and to reduce the potential risk of G-induced loss of consciousness, has been recognized as an effective technique. The purpose of this study was to establish an objective tool to evaluate the effectiveness of an aircrew member's AGSM. METHODS: There were 20 healthy subjects who participated in the study, including 8 senior aviation physiological trainers and 12 trainees. The former were familiar with the anti-G maneuver and had experienced high +Gz exposure, the latter had never been exposed to any high +Gz stress before the study. The analytic method of electromyography (EMG) was used to investigate the physical characteristics of the L-1 AGSM. RESULTS: Comparison of the EMG data from the two groups indicated that the mean duration of a breathing cycle of the trainer group was significantly longer than that of the trainee group (p < 0.001). The buccinator was the muscle that had the most rapid firing rate in both groups (p < 0.001). The trainer group had a significantly faster firing rate of the buccinator than the trainee group (p = 0.03). In addition, the trainee group performed the AGSM with a firing sequence of muscles that was different from that of the trainer group. CONCLUSIONS: An automated and quantitative system based on EMG can be used during AGSM training to augment or replace the current subjective evaluation of the trainee's performance.