Exercise Effect on Mental Health in Isolating or Quarantining Adults

INTRODUCTION: In response to coronavirus disease 2019 (COVID-19), travelers are typically subject to quarantine, which is often associated with poorer mental health (MH). While the protective benefits of community-based exercise are widely recognized, the degree to which this extends to the confined setting is unknown. This systematic review aims to evaluate the effect of exercise on MH in isolating or quarantining adults.METHODS: A literature search of Ovid MEDLINE, APA PsycInfo, and the Cochrane Database of Systematic Reviews limited to January 2019-September 2021 inclusive yielded five eligible studies.RESULTS: Data comprised a total of 2755 college and university students, most of whom were confined. Depending on the scale used, 24.9-76.7% of respondents demonstrated impaired MH, which improved with physical activity (PA), especially when regular and moderate or vigorous. The frequency, duration, and participants of exercise increased as lockdown progressed. One study showed that while sleep, diet, and PA all have an impact on MH, PA was the factor most strongly correlated with MH.DISCUSSION: Physical fitness should be optimized before and maintained during quarantine while exercise space and equipment should be accessible. Importantly, the sustainability of persistent quarantine must be considered given the pervasiveness of COVID-19.Chu V, Newman DG. Exercise effect on mental health in isolating or quarantining adults. Aerosp Med Hum Perform. 2023; 94(9):686-695.

Student Drowsiness During Simulated Solo Flight

INTRODUCTION: Pilot fatigue is a significant concern in aviation, where efforts are directed at improving rosters, developing models, and improving countermeasures. Little attention has been given to in-flight detection of fatigue/drowsiness. The aims of this research were to determine whether drowsiness is an issue and explore whether infrared reflectance oculography could prove useful for continuous inflight monitoring.METHODS: Nine university-based pilot trainees wore activity monitors and completed diaries, prior to a simulated navigational exercise of approximately 4 h, during the secondary window of circadian low. During the flight they wore a head-mounted device. Oculographic data were collected and converted into a single number, using the Johns Drowsiness Scale (JDS), with increasing values indicating greater drowsiness (range 0.0 to 10.0).RESULTS: Peak JDS values reached 6.5. Values declined from shortly before top of descent, continuing until landing. Two of the nine participants (22.2%), reached drowsiness levels at or above a cautionary warning level, below which is considered safe for driving a motor vehicle.DISCUSSION: The results of this study revealed the timeline and levels of fatigue that might be experienced by student pilots; showing that drowsiness is a potential issue for student pilots operating in flying conditions similar to those in the simulation. Analysis indicated that pilots are likely to experience levels of drowsiness above a cautionary warning level when modeling predicted effectiveness below 90%, indicating a potential drowsiness issue for pilots. It was concluded that oculography is worthy of further investigation for use as an objective fatigue detection tool in aviation.Corbett MA, Newman DG. Student drowsiness during simulated solo flight. Aerosp Med Hum Perform. 2022; 93(4):354-361.

Transition Metal Synthetic Ferrimagnets: Tunable Media for All-Optical Switching Driven by Nanoscale Spin Current

All-optical switching of magnetization has great potential for use in future ultrafast and energy efficient nanoscale magnetic storage devices. So far, research has been almost exclusively focused on rare-earth based materials, which limits device tunability and scalability. Here, we show that a perpendicularly magnetized synthetic ferrimagnet composed of two distinct transition metal ferromagnetic layers, Ni₃Pt and Co, can exhibit helicity independent magnetization switching. Switching occurs between two equivalent remanent states with antiparallel alignment of the Ni₃Pt and Co magnetic moments and is observable over a broad temperature range. Time-resolved measurements indicate that the switching is driven by a spin-polarized current passing through the subnanometer Ir interlayer. The magnetic properties of this model system may be tuned continuously via subnanoscale changes in the constituent layer thicknesses as well as growth conditions, allowing the underlying mechanisms to be elucidated and paving the way to a new class of data storage devices.

Factors Contributing to Accidents During Aerobatic Flight Operations

INTRODUCTION: Aerobatic flight operations involve a higher level of risk than standard flight operations. Aerobatics imposes considerable stresses on both the aircraft and the pilot. The purpose of this study was to analyze civilian aerobatic aircraft accidents in Australia, with particular emphasis on the underlying accident causes and survival outcomes.METHODS: The accident and incident database of the Australian Transport Safety Bureau was searched for all events involving aerobatic flight for the period 19802010.RESULTS: A total of 51 accidents involving aircraft undertaking aerobatic operations were identified, with 71 aircraft occupants. Of the accidents, 27 (52.9) were fatal, resulting in a total of 36 fatalities. There were 24 nonfatal accidents. In terms of injury outcomes, there were 4 serious and 9 minor injuries, and 22 accidents in which no injuries were recorded. Fatal accidents were mainly due to loss of control by the pilot (44.4), in-flight structural failure of the airframe (25.9), and terrain impact (25.9). G-LOC was considered a possible cause in 11.1 of fatal accidents. Nonfatal accidents were mainly due to powerplant failure (41.7) and noncatastrophic airframe damage (25). Accidents involving aerobatic maneuvering have a significantly increased risk of a fatal outcome (odds ratio 26).DISCUSSION: The results of this study highlight the risks involved in aerobatic flight. Exceeding the operational limits of the maneuver and the design limits of the aircraft are major factors contributing to a fatal aerobatic aircraft accident. Improved awareness of G physiology and better operational decision-making while undertaking aerobatic flight may help prevent further accidents.Newman DG. Factors contributing to accidents during aerobatic flight operations. Aerosp Med Hum Perform. 2021; 92(8):612618.

Increasing Altitude and the Optokinetic Cervical Reflex

INTRODUCTION: When an aircraft banks pilots will reflexively tilt their heads in the opposite direction, known as the optokinetic cervical reflex (OKCR). This is elicited by the appearance of the horizon and is an attempt to keep the moving horizon stable on the pilots retina to help maintain spatial orientation. The appearance of the horizon and the visual environment changes at higher altitudes and there is little research studying the effects of this. Our hypothesis was that increasing altitude would alter the visual cues present and decrease the OKCR.METHODS: There were 16 subjects who flew two flights in a flight simulator while their head tilt, aircraft altitude, and angle of aircraft bank were recorded. The flights were at an altitude of under 1500 ft above ground and above 15,000 ft above ground.RESULTS: Aircraft bank caused head tilt in the opposite direction at both altitudes. A two-way ANOVA with Bonferroni post hoc tests showed that 86% of aircraft bank angles from 0 to 90 in either direction had a head tilt that was statistically significantly smaller at high altitude.DISCUSSION: This study shows that there appears to be a difference between the OKCR at low and high altitude. Pilots at higher altitude seem to exhibit a smaller head tilt for the same aircraft bank angle. More research is required to fully understand why there is a decrease in the OKCR at high altitude, as well as the actual consequences of the decreased reflex on pilot orientation.Stewart MA, Pingali S, Newman DG. Increasing altitude and the optokinetic cervical reflex. Aerosp Med Hum Perform. 2021; 92(5):319325.

Optically and Microwave-Induced Magnetization Precession in [Co/Pt]/NiFe Exchange Springs

Microwave and heat-assisted magnetic recordings are two competing technologies that have greatly increased the capacity of hard disk drives. The efficiency of the magnetic recording process can be further improved by employing non-collinear spin structures that combine perpendicular and in-plane magnetic anisotropy. Here, we investigate both microwave and optically excited magnetization dynamics in [Co/Pt]/NiFe exchange spring samples. The resulting canted magnetization within the nanoscale [Co/Pt]/NiFe interfacial region allows for optically stimulated magnetization precession to be observed for an extended magnetic field and frequency range. The results can be explained by formation of an imprinted domain structure, which locks the magnetization orientation and makes the structures more robust against external perturbations. Tuning the canted interfacial domain structure may provide greater control of optically excited magnetization reversal and optically generated spin currents, which are of paramount importance for future ultrafast magnetic recording and spintronic applications.

Coherent Transfer of Spin Angular Momentum by Evanescent Spin Waves within Antiferromagnetic NiO

Insulating antiferromagnets have recently emerged as efficient and robust conductors of spin current. Element-specific and phase-resolved x-ray ferromagnetic resonance has been used to probe the injection and transmission of ac spin current through thin epitaxial NiO(001) layers. The spin current is found to be mediated by coherent evanescent spin waves of GHz frequency, rather than propagating magnons of THz frequency, paving the way towards coherent control of the phase and amplitude of spin currents within an antiferromagnetic insulator at room temperature.

Preflight Risk Assessment for Improved Safety in Helicopter Emergency Medical Service Operations

INTRODUCTION: Adverse weather and poor visual cues are common elements in night-time Helicopter Emergency Medical Service (HEMS) operations contributing to spatial disorientation and fatal accidents. Pilots are required to make weather-related preflight risk assessments to accept or reject a flight. This study's aim was to develop predictive risk assessment tools based on historical accident data to assist the decision-making process.METHODS: We analyzed 32 single-pilot HEMS night-time visual flight rules fatal accidents to identify contributory risk factors. Logistic regression analysis was used to develop prediction nomograms for nonvisual meteorological conditions (non-VMC), cause and nonsurvivable accidents as dependent variables. Risk factors such as temperature dew point spread, elevation difference, and years of HEMS pilot experience, were entered as continuous variables. Flight crew composition, pilot DTE (domain task experience) and flight rule capability, primary missions, and temperature dew point spread were entered as categorical variables. A point scoring matrix transposed model probability to likelihood and consequence severity.RESULTS: The nomograms correctly predicted the likelihood of entering non-VMC, accident cause, and sustaining a nonsurvivable accident in 75%, 55%, and 94% of cases, respectively. Using data from a recent nonsurvivable HEMS accident, the nomogram estimated a 92% probability (Very Likely) of nonsurvivable accident if visual cues were lost.CONCLUSION: These nomograms can provide preflight information to predict the likelihood of adverse safety outcomes occurring during a planned HEMS mission. While further development work is needed, this approach has the potential to improve HEMS operational safety.Aherne BB, Zhang C, Chen WS, Newman DG. Preflight risk assessment for improved safety in Helicopter Emergency Medical Service operations. Aerosp Med Hum Perform. 2019; 90(9):792-799.

Systems Safety Risk Analysis of Fatal Night Helicopter Emergency Medical Service Accidents

INTRODUCTION: In the United States, the proportion of Helicopter Emergency Medical Service (HEMS) fatal accidents remained unchanged despite an overall decreasing accident rate. Previous research showed night HEMS operations influenced fatal outcomes. Pilots with <6 yr of HEMS domain task experience (low-DTE) had a higher likelihood of a night operational accident in conditions associated with adverse weather. This study sought to determine whether a difference existed between day and night fatal accident rates and identify influences contributing to night fatal HEMS accidents. Any risk factors identified will be used for a risk analysis to inform future operational safety of the night visual flight rule (VFR) HEMS transport system.METHODS: Historical accident data and industry hours were obtained. Both pilot DTE groups (low and high) and mission VFR and instrument flight rule (IFR) capability were identified using data from 32 night VFR operational fatal HEMS accidents. Accidents were stratified by loss of control and controlled flight into terrain, pilot DTE, and flight rule capability. The effectiveness of both DTE groups and both flight rule capabilities were measured using system safety risk analysis techniques.RESULTS: Night fatal accident rates were statistically different from daytime. Low-DTE pilots and the VFR capability combination had the highest likelihood of night operational nonsurvivable accident.CONCLUSION: Low-DTE pilots and the VFR capability were the least effective mission combination to avoid hazardous conditions at night and maintain spatial orientation, respectively. The analysis identified measures to reduce likelihood of night fatal operational accidents.Aherne BB, Zhang C, Chen WS, Newman DG. Systems safety risk analysis of fatal night Helicopter Emergency Medical Service accidents. Aerosp Med Hum Perform. 2019; 90(4):396-404.

Pilot Decision Making in Weather-Related Night Fatal Helicopter Emergency Medical Service Accidents

INTRODUCTION

In the United States, between 1995 and 2013, night-time visual flight rules (VFR) Helicopter Emergency Medical Service (HEMS) fatal accidents mostly encountered adverse weather, and pilots with <6 yr of HEMS experience showed higher likelihood of a night operational accident. One adverse weather indicator is cloud-ceiling likelihood indicated by temperature dew point spread (TDPS). This study investigated the relationship between TDPS and HEMS pilot years of experience. It was hypothesized pilots with <6 yr HEMS experience were associated with fatal outcomes encountered at lower TDPS.

METHODS

Between 1995 and 2013, 32 single pilot night VFR HEMS fatal accidents occurring in the United States, caused by controlled flight into terrain or loss of control, were analyzed. Using Federal Aviation Administration weather guidance, the 0-4°C TDPS was selected as an indicator of cloud ceiling. Each flight's TDPS was analyzed with pilots' HEMS domain task experience.

RESULTS

There were 27 flights which entered the 0-4°C TDPS range; 20 (74%) were significantly associated with adverse weather. A significant negative linear relationship was found between TDPS of each mission and years of pilot HEMS experience (r = -0.423, P = 0.028). Pilots with <6 yr of experience were significantly associated with fatal outcomes (P = 0.049).

CONCLUSION

Pilots' incremental years of HEMS experience were associated with a TDPS decrement. Fatal outcomes were over nine times higher for pilots with <6 yr of HEMS experience in night VFR operational accidents in those conditions. Interventions for <6-yr pilots are recommended during experience building to prevent likelihood of operational accidents.Aherne BB, Zhang C, Chen WS, Newman DG. Pilot decision making in weather-related night fatal helicopter emergency medical service accidents. Aerosp Med Hum Perform. 2018; 89(9):830-836.

The Differential Effect of Sustained Operations on Psychomotor Skills of Helicopter Pilots

INTRODUCTION

Flying a helicopter is a complex psychomotor skill requiring constant control inputs from pilots. A deterioration in psychomotor performance of a helicopter pilot may be detrimental to operational safety. The aim of this study was to test the hypothesis that psychomotor performance deteriorates over time during sustained operations and that the effect is more pronounced in the feet than the hands. The subjects were helicopter pilots conducting sustained multicrew offshore flight operations in a demanding environment. The remote flight operations involved constant workload in hot environmental conditions with complex operational tasking.

METHODS

Over a period of 6 d 10 helicopter pilots were tested. At the completion of daily flying duties, a helicopter-specific screen-based compensatory tracking task measuring tracking accuracy (over a 5-min period) tested both hands and feet. Data were compared over time and tested for statistical significance for both deterioration and differential effect.

RESULTS

A statistically significant deterioration of psychomotor performance was evident in the pilots over time for both hands and feet. There was also a statistically significant differential effect between the hands and the feet in terms of tracking accuracy. The hands recorded a 22.6% decrease in tracking accuracy, while the feet recorded a 39.9% decrease in tracking accuracy.

DISCUSSION

The differential effect may be due to prioritization of limb movement by the motor cortex due to factors such as workload-induced cognitive fatigue. This may result in a greater reduction in performance in the feet than the hands, posing a significant risk to operational safety.McMahon TW, Newman DG. The differential effect of sustained operations on psychomotor skills of helicopter pilots. Aerosp Med Hum Perform. 2018; 89(6):496-502.

G-Induced Visual Symptoms in a Military Helicopter Pilot

INTRODUCTION

Military helicopters are increasingly agile and capable of producing significant G forces experienced in the longitudinal (z) axis of the body in a head-to-foot direction (+Gz). Dehydration and fatigue can adversely affect a pilot's +Gz tolerance, leading to +Gz-induced symptomatology occurring at lower +Gz levels than expected. The potential for adverse consequences of +Gz exposure to affect flight safety in military helicopter operations needs to be recognized. This case report describes a helicopter pilot who experienced +Gz-induced visual impairment during low-level flight.

CASE STUDY

The incident occurred during a tropical training exercise, with an ambient temperature of around 35°C (95°F). As a result of the operational tempo and the environmental conditions, aircrew were generally fatigued and dehydrated. During a low-level steep turn, a Blackhawk pilot experienced significant visual deterioration. The +Gz level was estimated at +2.5 Gz. After completing the turn, the pilot's vision returned to normal, and the flight concluded without further incident.

DISCUSSION

This case highlights the potential dangers of +Gz exposure in tactical helicopters. Although the +Gz level was moderate, the pilot's +Gz tolerance was reduced by the combined effects of dehydration and fatigue. The dangers of such +Gz-induced visual impairment during low-level flight are clear. More awareness of +Gz physiology and +Gz tolerance-reducing factors in helicopter operations is needed.

Pilot Domain Task Experience in Night Fatal Helicopter Emergency Medical Service Accidents

INTRODUCTION

In the United States, accident and fatality rates in helicopter emergency medical service (HEMS) operations increase significantly under nighttime environmentally hazardous operational conditions. Other studies have found pilots' total flight hours unrelated to HEMS accident outcomes. Many factors affect pilots' decision making, including their experience. This study seeks to investigate whether pilot domain task experience (DTE) in HEMS plays a role against likelihood of accidents at night when hazardous operational conditions are entered.

METHODS

There were 32 flights with single pilot nighttime fatal HEMS accidents between 1995 and 2013 with findings of controlled flight into terrain (CFIT) and loss of control (LCTRL) due to spatial disorientation (SD) identified. The HEMS DTE of the pilots were compared with industry survey data.

RESULTS

Of the pilots, 56% had ≤2 yr of HEMS experience and 9% had >10 yr of HEMS experience. There were 21 (66%) accidents that occurred in non-visual flight rules (VFR) conditions despite all flights being required to be conducted under VFR. There was a statistically significant increase in accident rates in pilots with <2 and <4 yr HEMS DTE and a statistically significant decrease in accident rates in pilots with >10 yr HEMS DTE.

CONCLUSION

HEMS DTE plays a preventive role against the likelihood of a night operational accident. Pilots with limited HEMS DTE are more likely to make a poor assessment of hazardous conditions at night, and this will place HEMS flight crew at high risk in the VFR night domain.

Development of a Field-Deployable Psychomotor Vigilance Test to Monitor Helicopter Pilot Performance

INTRODUCTION

Flying a helicopter is a complex psychomotor skill. Fatigue is a serious threat to operational safety, particularly for sustained helicopter operations involving high levels of cognitive information processing and sustained time on task. As part of ongoing research into this issue, the object of this study was to develop a field-deployable helicopter-specific psychomotor vigilance test (PVT) for the purpose of daily performance monitoring of pilots.

METHODS

The PVT consists of a laptop computer, a hand-operated joystick, and a set of rudder pedals. Screen-based compensatory tracking task software includes a tracking ball (operated by the joystick) which moves randomly in all directions, and a second tracking ball which moves horizontally (operated by the rudder pedals). The 5-min test requires the pilot to keep both tracking balls centered.

RESULTS

This helicopter-specific PVT's portability and integrated data acquisition and storage system enables daily field monitoring of the performance of individual helicopter pilots. The inclusion of a simultaneous foot-operated tracking task ensures divided attention for helicopter pilots as the movement of both tracking balls requires simultaneous inputs.

DISCUSSION

This PVT is quick, economical, easy to use, and specific to the operational flying task. It can be used for performance monitoring purposes, and as a general research tool for investigating the psychomotor demands of helicopter operations. While reliability and validity testing is warranted, data acquired from this test could help further our understanding of the effect of various factors (such as fatigue) on helicopter pilot performance, with the potential of contributing to helicopter operational safety.

A Methodology to Determine the Psychomotor Performance of Helicopter Pilots During Flight Maneuvers

INTRODUCTION

Helicopter flying is a complex psychomotor task requiring continuous control inputs to maintain stable flight and conduct maneuvers. Flight safety is impaired when this psychomotor performance is compromised. A comprehensive understanding of the psychomotor performance of helicopter pilots, under various operational and physiological conditions, remains to be developed. The purpose of this study was to develop a flight simulator-based technique for capturing psychomotor performance data of helicopter pilots.

METHODS

Three helicopter pilots conducted six low-level flight sequences in a helicopter simulator. Accelerometers applied to each flight control recorded the frequency and magnitude of movements.

RESULTS

The mean (± SEM) number of control inputs per flight was 2450 (± 136). The mean (± SEM) number of control inputs per second was 1.96 (± 0.15). The mean (± SEM) force applied was 0.44 G (± 0.05 G). No significant differences were found between pilots in terms of flight completion times or number of movements per second. The number of control inputs made by the hands was significantly greater than the number of foot movements. The left hand control input forces were significantly greater than all other input forces.

DISCUSSION

This study shows that the use of accelerometers in flight simulators is an effective technique for capturing accurate, reliable data on the psychomotor performance of helicopter pilots. This technique can be applied in future studies to a wider range of operational and physiological conditions and mission types in order to develop a greater awareness and understanding of the psychomotor performance demands on helicopter pilots.

Survival outcomes in low-level ejections from high performance aircraft

INTRODUCTION

The modern ejection seat has evolved to a high standard of sophistication, significantly expanding the safe ejection envelope. Low-level ejections are at the margins of this envelope and the outcome depends on numerous factors, including aircraft attitude, airspeed, and vertical rate of descent. The purpose of this study was to analyze all published ejection injury studies, with particular emphasis on altitude at the time of ejection, to determine if low-level ejections have an overall higher fatality rate.

METHODS

The aeromedical literature was reviewed for all studies relating to ejection outcomes in which the ejection altitude was recorded. Used in this analysis were 10 studies covering the period 1952-1997. Low-level ejections were defined as ejection below 500 ft (152 m) above ground level.

RESULTS

There were 562 low-level ejections identified. Out of this number, there were 274 fatalities, giving a low-level ejection survival rate of 51.2%. There were 2607 ejections that occurred above 500 ft (152 m), with a survival rate of 91.4%. There was a significant difference between ejection survival rates below and above 500 ft (152 m). Low-level ejections have a significantly increased risk of a fatal outcome (Odds Ratio 10.07).

CONCLUSIONS

Ejecting from an aircraft below 500 ft (152 m) has a lower survival rate compared with the survival rate for all ejections. This is due to many factors, including the nature of the emergency, aircraft operating parameters at the time, and the inherent dangers of low-level operations. Low-level emergencies are time-critical events in which an early decision to eject can improve the chances of a successful outcome.

Flying experience and cardiovascular response to rapid head-up tilt in fighter pilots

INTRODUCTION

Fighter pilots report G tolerance increases with regular exposure. Our previous work has shown that the cardiovascular system of +Gz-adapted fighter pilots responds differently to orthostatic challenges than that of non-pilots. A +Gz training effect in pilots after repetitive +Gz exposure has also been shown. Individual pilot factors such as flying experience may have a role in +Gz adaptation. In this study, we investigated the relationship between flying hours (a marker of cumulative +Gz exposure) and mean arterial blood pressure (MAP) response to head-up tilt (HUT; a marker of enhanced cardiovascular performance).

METHODS

There were 14 male fighter pilots who participated: 9 had over 1000 h jet flying experience and 5 had less than 500 h. Subjects underwent rapid (approximately 4 s) +75 degrees HUT. Beat-to-beat MAP was measured noninvasively. For each subject, change in MAP from resting values was obtained for the first 30 heart beats of the HUT period. MAP responses to tilt were compared between the experienced and less experienced pilots, and the averages of the MAP deviation values were plotted against flying hours.

RESULTS

There was a strong correlation (r = 0.87, P < 0.01) between the MAP response to tilt and jet flying hours. Comparison of the MAP responses to tilt indicates that the experienced pilots increased MAP more (+8 +/- 1.7 vs 5 +/- 1.5 mmHg) and maintained MAP at a higher level during the HUT than the less experienced pilots.

CONCLUSION

The results suggest that flying experience in the high +Gz environment is strongly correlated with enhanced cardiovascular performance under conditions of accelerative stress.

Cardiovascular training effects in fighter pilots induced by occupational high G exposure

INTRODUCTION

A fundamental difference in the cardiovascular response to acceleration between a group of fighter pilots (FP) and a group of non-pilots (NP) has been demonstrated previously. This study investigated the longitudinal effects of repetitive occupational +Gz exposure on the cardiovascular response to acceleration.

METHODS

There were 6 FP and 6 NP subjects who underwent rapid +75 degrees head-up tilt (HUT) on two separate occasions. The FP group were tested after a non-flying period of 5 wk (Test 1), and tested again after a period of repetitive exposure to high +Gz missions (Test 2). The NP group did not fly at all between Test 1 and Test 2. Mean arterial pressure (MAP), heart rate (HR), stroke volume (SV), and total peripheral resistance (TPR) were all determined non-invasively. SV was determined using impedance cardiography and calculated via the Kubicek equation. For each variable, resting values and the response to tilt for both HUT tests within and between each group were compared.

RESULTS

In the FP group, resting MAP was higher (86 mmHg) in Test 2 compared with Test 1 (78 mmHg). Between groups, FP resting MAP was only different from the NP resting MAP in Test 2. The FP HR response to HUT increased significantly between the two tests.

CONCLUSIONS

These findings suggest a +Gz-induced cardiovascular training effect in the FP group. Repetitive exposure to +Gz results in an increased resting MAP and an elevated HR response to tilt, which may provide benefits to operational fighter pilots.

Squat-stand test response following 10 consecutive episodes of head-up tilt

INTRODUCTION

The cardiovascular system is adaptable to multiple exposures to gravity over several days, and to repeated exposures in a single day. This study aimed to investigate if the cardiovascular adaptation observed following 10 +75 degrees head-up tilts (HUT) would improve the responses to the squat-stand test (SST).

METHODS

There were 16 subjects who were randomly allocated into either a tilting group that underwent 10 +75 degrees HUTs in 70 min (Tilting) or a control group that underwent 70 min of rest (Control). Before and after HUT or rest, subjects performed a SST (SST1 and SST2, respectively). Heart rate (HR), BP [systolic (SBP), diastolic (DBP), mean (MAP)], total peripheral resistance (TPR), stroke volume (SV), and cardiac output (CO) were determined during both SSTs. The final 30 s of squat and the first 30 s of stand (divided into three 10-s blocks termed Stand10, Stand20, and Stand30) were compared between SST1 and SST2.

RESULTS

In the Tilting condition, during the squat phase of SST2, the following were significantly elevated: SBP (131 +/- 9 to 140 +/- 7.2 mmHg) and MAP (94 +/- 8.7 to 105 +/- 10.2 mmHg); DBP (76 +/- 9.4 to 87 +/- 11.9 mmHg); TPR (1197 +/- 524.6 to 229 +/- 610.5 dyn x s(-1) x cm(-5)) and HR were significantly decreased (78 +/- 6.9 to 73 +/- 7.5 bpm) compared with SST1. At Stand10, DBP and MAP were significantly increased (59 +/- 9.5 to 69 +/- 15.7 mmHg and 74 +/- 8.9 to 84 +/- 14.7 mmHg, respectively); at Stand20, SBP was increased (121 +/- 17 to 128 +/- 22 mmHg); and at Stand30 the following were increased: DBP (64 +/- 8.8 to 75 +/- 16.1 mmHg); SBP (127 +/- 9.2 to 139 +/- 15.8 mmHg); and MAP (79 +/- 8 to 90 +/- 14.9 mmHg). There were no differences observed between SST1 and SST2 in the Control group.

DISCUSSION

Cardiovascular responses to the SST can be improved with 10 consecutive +75 degrees HUTs. This is predominantly due to an increase in DBP, indicative of a change in vascular resistance.

Acute cardiovascular adaptation to 10 consecutive episodes of head-up tilt

BACKGROUND

The cardiovascular system is highly adaptable to sustained +Gz acceleration. Little is known as to whether the cardiovascular system can adapt to acute, repetitive +Gz exposures. This study tested the hypothesis that the cardiovascular system would adapt to repeated orthostatic challenges in a single session.

METHODS

Over a 70-min period, 14 subjects were exposed to 10 +75 degrees head-up tilts (HUT). Each tilt involved a 5-min supine period followed by a 2-min HUT. Heart rate (HR), systolic BP (SBP), diastolic BP (DBP), mean arterial pressure (MAP), total peripheral resistance (TPR), stroke volume (SV), and cardiac output (CO) were determined non-invasively. Cardiovascular responses to HUT10 for the final 30 s of the supine period and the first 30 s of the tilt period were compared with those of HUT1. Integrated cardiac baroreflex sensitivity (BRS) was assessed using the Valsalva maneuver.

RESULTS

MAP and DBP increased in both supine (MAP p = 0.009, DBP p = 0.002) and tilt periods (MAP p = 0.003, DBP p = 0.009) for HUT10 compared with HUT1. TPR increased during the tilt period only (p = 0.001) during HUT10 compared with HUT1. CO and SV were decreased during the supine period at HUT10 relative to HUT1; however, there were no differences in the tilt period at HUT10 for either CO or SV. There was no change in the response of BRS, HR, or SBP from HUT1 to HUT10.

CONCLUSIONS

This study indicates that 10 repetitive HUTs can elicit changes in the cardiovascular responses to orthostasis, reflected by an increased vascular resistance.

G-induced visual and cognitive disturbances in a survey of 65 operational fighter pilots

INTRODUCTION

Only one previous study has assessed almost loss of consciousness (A-LOC) in operational fighter pilots, reporting an incidence rate of 14%. Research also indicates that 8-13% of pilots have experienced G-induced loss of consciousness (G-LOC). A-LOC can be as insidious as G-LOC due to the associated altered state of awareness and relative incapacitation time, making it a significant risk factor in the high +Gz environment. Royal Australian Air Force (RAAF) pilots currently fly the F/A-18 and Hawk 127, producing +Gz accelerations up to +7.5 Gz, which places these pilots at risk of both A-LOC and G-LOC.

METHODS

A survey was administered to 100 active RAAF fighter pilots requesting information on G-induced visual and cognitive disturbances, A-LOC symptoms, and G-LOC. Details regarding type of aircraft, flying maneuvers performed and mission outcome were also sought.

RESULTS

There were 65 RAAF fighter pilots who completed the survey (age 20-53 yr, height 168-193 cm, weight 64-110 kg, jet hours 30-5700 h). Of these pilots, 98% indicated they had experienced at least one visual or cognitive disturbance in the high G environment: gray-out 98%; black-out 29%; and A-LOC symptoms 52%, including abnormal sensation in limbs, disorientation, and confusion. There were 9% who indicated they had experienced G-LOC (50% were the pilot flying the aircraft).

DISCUSSION

These findings indicate that RAAF fighter pilots are experiencing a similar rate of visual disturbances and G-LOC when compared with other air forces. However, RAAF pilots reported a much higher incidence of A-LOC compared with the only other study of operational fighter pilots.

Muscle oxidative capacity is a better predictor of insulin sensitivity than lipid status

We determined whole-body insulin sensitivity, long-chain fatty acyl coenzyme A (LCACoA) content, skeletal muscle triglyceride (TG(m)) concentration, fatty acid transporter protein content, and oxidative enzyme activity in eight patients with type 2 diabetes (TYPE 2); six healthy control subjects matched for age (OLD), body mass index, percentage of body fat, and maximum pulmonary O(2) uptake; nine well-trained athletes (TRAINED); and four age-matched controls (YOUNG). Muscle biopsies from the vastus lateralis were taken before and after a 2-h euglycemic-hyperinsulinemic clamp. Oxidative enzyme activities, fatty acid transporters (FAT/CD36 and FABPpm), and TG(m) were measured from basal muscle samples, and total LCACoA content was determined before and after insulin stimulation. Whole-body insulin-stimulated glucose uptake was lower in TYPE 2 (P < 0.05) than in OLD, YOUNG, and TRAINED. TG(m) was elevated in TYPE 2 compared with all other groups (P < 0.05). However, both basal and insulin-stimulated skeletal muscle LCACoA content were similar. Basal citrate synthase activity was higher in TRAINED (P < 0.01), whereas beta-hydroxyacyl CoA dehydrogenase activity was higher in TRAINED compared with TYPE 2 and OLD. There was a significant relationship between the oxidative capacity of skeletal muscle and insulin sensitivity (citrate synthase, r = 0.71, P < 0.001; beta-hydroxyacyl CoA dehydrogenase, r = 0.61, P = 0.001). No differences were found in FAT/CD36 protein content between groups. In contrast, FABPpm protein was lower in OLD compared with TYPE 2 and YOUNG (P < 0.05). In conclusion, despite markedly elevated skeletal muscle TG(m) in type 2 diabetic patients and strikingly different levels of whole-body glucose disposal, both basal and insulin-stimulated LCACoA content were similar across groups. Furthermore, skeletal muscle oxidative capacity was a better predictor of insulin sensitivity than either TG(m) concentration or long-chain fatty acyl CoA content.

A comparative assessment of two techniques for investigating initial cardiovascular reflexes under acute orthostatic stress

The physiological differences between active and passive changes in posture have been previously established. This study determined the extent of the differences in the initial cardiovascular responses to the passive head-up tilt (HUT) and the active squat-stand test (SST). Eleven females and 13 males underwent one +75 degrees HUT and one SST. Beat-to-beat diastolic blood pressure (DBP), systolic blood pressure (SBP), mean arterial pressure (MAP) and heart rate (HR) were determined non-invasively. Data were recorded 10 s prior to (control) and 30 s after tilt or stand (event). Blood pressure and HR responses were analysed by calculating the deviation from control at 10 s (T10), 20 s (T20) and 30 s (T30) after the onset of each test. The DBP response (reflecting changes in systemic vascular resistance) at T10 was -10 (2) mmHg [mean (SEM)] for the HUT and -25 (2) mmHg for the SST ( P<0.01). DBP returned to control levels by T30 for the HUT, but remained depressed for the SST. MAP responses directly reflected these changes in DBP. HR significantly increased from control values ( P<0.001) for the HUT [+14 (1) bpm] and the SST [+16 (1) bpm], and remained elevated for the entire 30-s period for both tests. This study demonstrates that although the magnitude of the initial blood pressure decrease is greater for the active SST compared with the passive HUT, the reflex compensatory response is no different, making the SST a greater challenge for the cardiovascular reflexes.

The effect of caffeine on the cardiovascular responses to head-up tilt

BACKGROUND

Both caffeine and orthostasis have known cardiovascular effects. The possible interaction between these factors remains unknown. This study aimed to determine the effect of caffeine consumption on cardiovascular responses to head-up tilt.

METHODS

Sixteen subjects underwent three +75 degree head-up tilts: i) control, ii) acute, after a dose of 5 mg x kg(-1) body mass of caffeine or placebo, and iii) chronic, following 7 d of caffeine or placebo consumption at a daily dose of 5 mg x kg(-1) body mass. Heart rate (HR), systolic BP (SBP), diastolic BP (DBP), and mean arterial pressure (MAP) were measured using a Portapres BP monitor.

RESULTS

The overall pattern of heart rate (HR) response in both caffeine and placebo groups showed a significant increase in HR after tilting for each tilt. Acute caffeine consumption significantly decreased resting HR (p < 0.05). After chronic consumption, resting HR was no longer significantly different. In the control condition, the overall pattern of response to tilt for SBP, DBP, and MAP showed no significant differences in either group. An acute dose of caffeine caused a significant fall (p < 0.05) in all BP variables in response to tilt. This effect was also seen after chronic caffeine consumption in SBP and MAP, but not in DBP.

CONCLUSIONS

The results of this study indicate that both acute and chronic consumption of caffeine can lead to impaired cardiovascular function after exposure to an orthostatic challenge. This impaired function, reflected in a decreased resting HR and an inability to maintain MAP, is potentially due to impaired baroreflex function.

Central serous retinopathy with permanent visual deficit in a commercial air transport pilot: a case report

This report describes a case of central serous retinopathy (CSR) in the right eye of a commercial air transport pilot which resulted in a permanent reduction in visual acuity and the loss of his license. The previously fit and well pilot developed sudden loss of central vision, which resolved spontaneously. He then went on to experience recurrent episodes of fluctuating visual acuity (down to 6/60) and visual dysfunction in the right eye. His left eye remained unaffected. Eventually his condition stabilized, and he was left with a permanent reduction in right visual acuity (6/36) with intact peripheral visual fields and a completely normal left eye. After a period of grounding of 12 mo, he sought to have his license reinstated. He was considered to be a functionally monocular pilot, and as such was granted a conditional Class 1 medical category. The aeromedical disposition of this pilot and the issues involved in determining the fitness to fly of pilots with permanent visual defects arising from CSR are discussed.

The effect of low-level normobaric hypoxia on orthostatic responses

BACKGROUND

Altitude-induced hypoxia is believed to decrease tolerance to orthostasis. This preliminary investigation assesses the interaction between low-level normobaric hypoxia and the cardiovascular responses to orthostasis.

HYPOTHESIS

We hypothesize that low-level hypoxia at simulated altitudes up to 3350 m adversely affects cardiovascular responses to orthostasis.

METHODS

Six women and eight men underwent + 75 degrees head-up tilt (HUT) at 3 simulated altitudes (115 m (377 ft), 1680 m (5500 ft) and 3350 m (11,000 ft)). Minute ventilation (VE), tidal volume (VT), breathing frequency (f), heart rate (HR), and arterial blood pressure (BP) were measured non-invasively. Ventilatory parameters (VE, VT, and f) were measured during the control period to assess the respiratory response to hypoxia. Cardiovascular variables (HR and BP) during HUT were compared and analyzed by calculating the deviation from control (pre-tilt) values.

RESULTS

Respiratory data showed no significant hypoxic ventilatory response. The average HR deviation significantly decreased (p < 0.05) with HUT from 13 +/- 2 bpm (115 m) to 9 +/- 2 bpm (3350 m). The pattern of mean arterial BP deviation with HUT was similar across the three altitudes (-6.6 +/- 2.9 mm Hg at 115 m to -6.8 +/- 2.4 mm Hg at 3350 m), with no significant differences.

CONCLUSIONS

Changes in HR and arterial BP are fundamental aspects of the cardiovascular response to orthostatic stress. Although there were no significant changes in the BP response to orthostasis with hypoxia, the HR changes seen in this study suggest that the ability to modulate HR under orthostatic stress is reduced with exposure to low-level normobaric hypoxia.

The effect of baroreflex adaptation on the dynamic cardiovascular response to head-up tilt

BACKGROUND

Baroreflex adaptation to repetitive +Gz has been reported previously. The underlying mechanism may involve different responses of stroke volume (SV) and total peripheral resistance (TPR) to +Gz.

HYPOTHESIS

The previously observed enhanced mean arterial pressure (MAP) regulation in fighter pilots (FP) is mediated by increases in SV and/or TPR.

METHODS

There were 8 pilots and 12 non-pilots who underwent head-up tilt. SV was determined using impedance cardiography.

RESULTS

MAP increased significantly in FP, due to heart rate (HR) and TPR increasing more and SV decreasing less.

CONCLUSION

Baroreflex adaptation results in better performance of HR, SV and TPR in response to +Gz.

Acquired left bundle branch block in an asymptomatic fighter pilot: a case report

This report describes a case of acquired left bundle branch block (LBBB) in an asymptomatic F/A-18 fighter pilot of the Royal Australian Air Force. The previously fit and healthy pilot was found to have LBBB on routine electrocardiographic screening prior to his annual aircrew medical. He was completely asymptomatic, and the only potential etiological factor was a short-lived acute gastrointestinal infectious illness some 4 mo previously. The pilot was extensively investigated with the full range of available diagnostic procedures, including coronary angiography and cardiac biopsy. No cause was determined for his LBBB pattern, and he was assessed as having normal cardiovascular function. The aeromedical disposition of this aviator and the issues involved in determining fitness to fly in such a case are discussed. The importance of thorough clinical investigation and appropriate follow-up are highlighted.

The non-invasive assessment of stroke volume and cardiac output by impedance cardiography: a review

Impedance cardiography (IC) is an inexpensive, reliable and noninvasive technique for determining stroke volume (SV) and cardiac output (CO). It relies on the measurement of phasic changes in transthoracic electrical resistivity, related to ejection of blood into the ascending aorta with each heart beat. Because of its non-invasive nature, IC is becoming increasingly used in clinical settings, as well as in many areas of physiological research. This paper discusses IC in terms of its theoretical basis, the components of the impedance signal and how impedance data is mathematically processed. One of the major controversies surrounding IC concerns how well it compares with conventional methods of determining SV and CO, such as thermodilution. A literature review of such comparative studies demonstrated that the controversy is far from settled, but that IC is generally agreed to be capable of accurately monitoring trends in cardiovascular dynamics. The question of accuracy of IC in terms of absolute values of SV and CO remains to be determined. The methodological limitations, accuracy, reliability and reproducibility of IC are examined, as are some of the methods developed to improve these aspects of the technique. The application and utility of IC in aerospace medicine research is also addressed.

Patterns of physical conditioning in Royal Australian Air Force F/A-18 pilots and the implications for +Gz tolerance

BACKGROUND

The role of physical conditioning in tolerance to +Gz remains the subject of debate, particularly in relation to the relative merits of aerobic vs. anaerobic conditioning. The purpose of this study was to document the patterns of physical conditioning in Royal Australian Air Force (RAAF) fighter pilots and to relate these findings to the question of +Gz tolerance.

METHODS

A questionnaire was used to determine the physical conditioning activities of RAAF F/A-18 pilots. Aerobic fitness levels (VO2max) were determined in a sample of eight pilots using a progressive cycle ergometer protocol.

RESULTS

Of the 42 F/A-18 pilots who completed the questionnaire, 86% reported regular physical conditioning, mostly three times per week. Aerobic activities were the most common (83%), with running the most popular activity (55%). Anaerobic activities were reported by 26% of respondents. Most respondents reported doing more than one activity, with an average weekly training volume of 129+/-77 min. The ergometer test results revealed a mean VO2max of 50+/-6 ml O2 x kg x min(-1).

CONCLUSION

The high rates of participation in regular physical activity suggest that physical fitness is perceived as important by the fighter pilot operating in the high +Gz environment. The fighter pilots in this study participated in aerobic activities at a much higher rate than anaerobic activities. The aerobic fitness levels measured suggest that the pilots have good but not exceptionally high levels of aerobic power that are unlikely to influence +Gz tolerance.

Analysis of the Gz environment during air combat maneuvering in the F/A-18 fighter aircraft

BACKGROUND

The F/A-18 Hornet is a high performance fighter aircraft that equips four squadrons of the Royal Australian Air Force (RAAF). The F/A-18 pilot is regularly subjected to high accelerative forces, particularly during air combat maneuvering (ACM). Anecdotal and experimental evidence suggests that cardiovascular adaptation to repetitive Gz can occur.

HYPOTHESIS

The purpose of this study was to document the nature and characteristics of the Gz environment to which the pilot is exposed during air combat maneuvering in the F/A-18 fighter aircraft, in terms of its potential to act as a baroreflex training stimulus. The study also aimed to show that onboard data acquisition systems can provide physiologically useful information.

METHODS

Two air combat maneuvering sorties were flown. Gz data were downloaded from the F/A-18's onboard computer system for analysis.

RESULTS

ACM engagements in the F/A-18 consist of multiple, frequently repetitive excursions to high +Gz levels. Both sorties involved high peak +Gz levels (+7.21 and +7.09), with many excursions (37 and 61) through a +2 Gz threshold. Approximately 20% of each sortie was spent at or above +2 Gz.

CONCLUSIONS

This study confirms the physiologically challenging nature of ACM, involving force environment changes of high intensity and frequency. In addition, it indicates the general nature of the training stimulus applied to the arterial baroreflexes which is responsible for the development of cardiovascular adaptation to +Gz seen in previous studies. It also shows that onboard data acquisition systems can provide physiologically useful information, but are limited by low sampling rates.

Evidence of baroreflex adaptation to repetitive +Gz in fighter pilots

BACKGROUND

The arterial baroreflex acts to maintain arterial pressure in the face of an orthostatic challenge. The high +Gz loads experienced by fighter pilots represent an extreme form of orthostatic challenge. G-induced loss of consciousness (G-LOC) represents a failure of the baroreflex system to maintain the appropriate level of cerebral perfusion. The anecdotal experience of fighter pilots is that their cardiovascular systems adapt to frequent exposure to high +Gz levels.

HYPOTHESIS

The purpose of this study was to demonstrate that the baroreflex-mediated cardiovascular response of a group of 8 fighter pilots to a mild accelerative stimulus differs from that of a group of 12 non-pilots.

METHODS

Arterial pressures and heart rate responses to rapid head-up tilting to +75 degrees were compared between the two groups. Five variables were examined: systolic, diastolic, mean arterial and pulse pressures, and heart rate.

RESULTS

The cardiovascular responses of the groups were fundamentally different. In response to tilt, the non-pilots showed little change in systolic and mean arterial pressures, diastolic pressure increased slightly and pulse pressure decreased significantly. In the pilot group, however, significant increases were observed in systolic, diastolic and mean arterial pressures (p < 0.05), whereas pulse pressure did not change. Between groups there were significant differences observed in terms of arterial pressures (p < 0.05), but not heart rate.

CONCLUSION

The baroreflex of a fighter pilot is capable of adapting to +Gz, becoming a more sensitive and effective BP control system as a result. This adaptation affords the pilot greater protection against G-LOC.

Characteristics at four months follow-up of infants born small for gestational age: a controlled study

This prospective study compared 65 small-for-gestational-age (SGA) (birth weight < 3rd centile) and 71 control infants at a corrected age of 4 months. It was hypothesised that differences would exist in growth, development, temperament and minor neurological signs and that these would be predicted by type (proportional/disproportional) of growth restriction at birth and maternal mood disturbance at birth or at 4 months. Infants had a Griffith's developmental test and neuromotor assessment. Maternal mood and infant temperament were surveyed. Few differences were found between SGA and control infants. SGA infants showed catch-up growth with 63% being above the third percentile and 43% being above the tenth percentile for weight. SGA infants had lower Griffith's GQ scores (97 vs. 102, P = 0.02) and they were rated in temperament as more manageable than controls. There were no differences in subtle neuromotor signs. Neither type of SGA nor maternal mood disturbance at birth had prognostic significance for infant catch up growth, neuromotor scores, or temperament though level of maternal stress and anxiety at 4 months were related to lower GQ scores in SGA infants.

Head positioning for high +Gz loads: an analysis of the techniques used by F/A-18 pilots

A study was undertaken among Royal Australian Air Force fighter pilots to determine whether, as an occupational group, they had developed any particular protective head positioning strategies in order to minimize their risk of sustaining a +Gz-induced neck injury during air combat maneuvering. There were 42 F/A-18 Hornet pilots who responded to an anonymous questionnaire which asked about head positioning strategies. Of these, 29 pilots reported using a protective strategy. Several pilots reported using several different techniques. The most popular strategy reported was positioning the head prior to the application of +Gz (13 respondents). Eleven pilots reported using aircraft structures to wedge or brace their heads against. The results of this study show that fighter pilots who are regularly exposed to high +Gz forces develop an individualized approach to protecting their cervical spines from +Gz-induced injury.

+GZ-induced neck injuries in Royal Australian Air Force fighter pilots

+GZ-induced neck injuries are a relatively common occurrence in pilots of high performance fighter aircraft. We surveyed 52 fighter pilots from the Royal Australian Air Force Base at Williamtown via an anonymous questionnaire in order to determine the prevalence and operational significance of these injuries. The pilots flew either the F/A-18 Hornet or the MB326H Macchi. Of the respondents, 44 reported having had a neck injury under +GZ. A higher rate was reported in pilots of the F/A-18. Most of these injuries were simple muscle sprains. There were 20 pilots who reported their neck injury as having interfered with mission completion. Only 12 pilots reported doing any regular neck strengthening exercises, while 33 pilots reported doing preflight neck stretches immediately prior to high +GZ exposure. There were 14 pilots who sought medical attention for their injury, with 9 being taken off flight status for an average of 2 weeks. Air combat maneuvering sorties and the "check six" head position were identified as causal factors by most pilots. This study demonstrates the operational significance of these injuries, and highlights the need for more research into this important aerospace medicine issue.