Limitations of stroke volume estimation by non-invasive blood pressure monitoring in hypergravity.

Background: Altitude and gravity changes during aeromedical evacuations induce exacerbated cardiovascular responses in unstable patients. Non-invasive cardiac output monitoring is difficult to perform in this environment with limited access to the patient. We evaluated the feasibility and accuracy of stroke volume estimation by finger photoplethysmography (SVp) in hypergravity.

Single-beat versus multibeat real-time 3D echocardiography for assessing left ventricular volumes and ejection fraction: a comparison study with cardiac magnetic resonance.

Background: Real-time 3-dimensional echocardiography (RT3DE) is superior to 2D echocardiography in assessing left ventricular (LV) volumes and ejection fraction (EF), but its feasibility is limited by multibeat acquisition, which requires an optimal breath-hold and a regular heart rhythm. We sought to evaluate the accuracy and feasibility of single- and 2-beat RT3DE for LV volume and EF assessment.

Methods And Results: Sixty-six consecutive patients referred for cardiac magnetic resonance (CMR) underwent RT3DE and CMR on the same day.

Impact of longitudinal myocardial deformation on the prognosis of chronic heart failure patients.

Background: Longitudinal myocardial deformation indexes appear superior to left ventricular ejection fraction (LVEF) in assessing myocardial contractility. However, few studies have addressed the prognostic value of longitudinal motion markers (velocity, strain, and strain rate) in predicting outcome in heart failure patients.

Methods And Results: The study included 125 consecutive symptomatic heart failure patients (63+/-16 years, 77% male, LVEF=31+/-10%).

Heart rate variability in novice pilots during and after a multi-leg cross-country flight.

Background: A pilot's workload induces autonomic nervous system modulations which could be related to a decrease of vigilance that could impair safety. Kinetics during flight and recovery are not well known.

Objective: The aim of this study was to assess linear and nonlinear heart rate variability (HRV) modulations and vigilance during a high mental workload induced by a complex flight and subsequent recovery.

Short half-life hypnotics preserve physical fitness and altitude tolerance during military mountainous training.

Objective: We study the effect of short half-life hypnotics (zaleplon or zolpidem against placebo) on altitude tolerance in 12 nonacclimated male soldiers (age, 22.1 +/- 0.8 years; height, 177.

Heart rate and autonomic balance during stand tests before and after fighter combat missions.

Background: High workload during combat missions is a critical factor in the use of modern aircraft. Our objective was to evaluate the impact of piloting in war zones on the kinetics of the sympathovagal balance during recovery.

Methods: There were 40 military pilots who were monitored during operational flights in Afghanistan.

Energy expenditure during an ultraendurance alpine climbing race.

Objective: Accurate reports of energy expenditure (EE) during prolonged mountaineering activity are sparse. The purpose of this study was to estimate EE during a winter ultraendurance climbing race and individual mountaineering activities in Mont Blanc, France.

Methods: Seven days before the race, resting metabolic rate (RMR) and maximal oxygen consumption (Vo2(max)) were measured in 10 experienced male climbers (30.

Brief exposure to -2 Gz reduces cerebral oxygenation in response to stand test.

The aim of the present experiment was to determine whether a single 30 s of exposure to -2 Gz (foot-to-head inertial forces) as orthostatic stress results in altered brain oxygenation control in response to active standing. Cerebral oxygenation (oxy-Hb), cerebral blood volume (CBV), and mean arterial blood pressure at brain level (MAPbrain) were recorded in 12 subjects in supine and then in standing position (10 min), before and after -2 Gz centrifugation. The decrease in oxy-Hb (-5 +/- 9 vs.

Aerobatic flight effects on baroreflex sensitivity and sympathovagal balance in experienced pilots.

Background: Aerobatic flights subject pilots to accelerations and, therefore, to heavy physical workloads.

Objective: Our aim was to document changes in spontaneous baroreflex sensitivity and disturbances of sympathovagal balance after exposure to "push-pull" accelerations.

Methods: During 30-min flights, five aerobatic pilots performed five series of descending spirals: first, 30 s under negative (-3 Gz max), and then 30 s under positive (+4 Gz max) G loading, climbing between each series to regain altitude.

Cerebral oxygenation declines despite maintained orthostatic tolerance after brief exposure to gravitational stress.

We examined the effect of a single 120 s of exposure to +3Gz (head-to-foot inertial forces) centrifugation as orthostatic stress on cerebral oxygenation (oxy-Hb) and cerebral blood volume (CBV) changes in response to stand test, in order to relate the occurrence of altered cerebral oxygenation control to any increase in sympathetic activity. Frontal near-infrared spectroscopy and mean arterial blood pressure at brain level (MAPbrain) were recorded in 14 subjects in supine and then in standing (10 min) position, before and after +3Gz centrifugation. The decrease in oxy-Hb (-7 +/- 5 a.

EEG and ECG changes during simulator operation reflect mental workload and vigilance.

Background: Performing mission tasks in a simulator influences many neurophysiological measures. Quantitative assessments of electroencephalography (EEG) and electrocardiography (ECG) have made it possible to develop indicators of mental workload and to estimate relative physiological responses to cognitive requirements.

Objective: To evaluate the effects of mental workload without actual physical risk, we studied the cortical and cardiovascular changes that occurred during simulated flight.

EEG and ECG changes during selected flight sequences.

Background: Mental workload has become a critical factor in the design and use of modern aircraft. Because of the complexity of the human-machine system, it is necessary to determine workload, fatigue, and level of performance using noninvasive electrophysiological measures.

Objective: Our objective was to identify the electrophysiological indicators of mental workload during piloting tasks.

Analysis of heart rate variability after a ranger training course.

We studied the effects of prolonged physical activities on resting heart rate variability (HRV) during a training session attended by 23 cadets of the French military academy. This course lasts 1 month and is concluded by a 5-day field exercise simulation with physical and psychological stress. Data collection took place before (B) and immediately at the end (E) of the course.