Evaluation of zolpidem on alertness and psychomotor abilities among aviation ground personnel and pilots.

The use of hypnotics to optimize rest periods during sustained operations could be of help to military personnel. Zolpidem, an imidazopyridine hypnotic, was evaluated for its residual effects on daytime wakefulness in 12 subjects belonging to ground air force personnel and 12 navy fighter pilots. In this controlled double blind crossover study, each subject randomly received zolpidem 10 mg, flunitrazepam 1 mg or placebo, in three separate sessions, 1 week apart at 10 p.m. or 1 a.m., respectively. The absence of residual effects after zolpidem intake was attested by subjective assessments, psychomotor tests (including a simulated flight), and EEG analysis showed that this hypnotic could be considered for operational use.

Rapid decompression of a transport aircraft cabin: protection against hypoxia.

The hypoxic hazard after rapid decompression in transport aircraft was evaluated as a function of the current means of protection, including the role of the inhaled oxygen fraction (FIO2) prior to decompression. The decompressions were made in 2 s; the initial altitude was 8,000 ft and the final altitude was 16,000-45,000 ft. The physiological measurements were arterial oxygen saturation, heart rate, ventilatory frequency, and gaseous analysis in the mask. Results show that FIO2 prior to decompression is not very significant, but the delay before donning the oxygen system seems to be the most limiting factor against tolerance to hypoxia.

Cardiovascular responses of man exposed to +Gz accelerations in a centrifuge.

Cardiovascular investigations were conducted in male volunteer subjects exposed to +Gz accelerations. Some of them did not have any previous experience of the centrifuge. Electrocardiogram, blood pressure, heart rate, stroke volume, and cardiac output were recorded. Accelerations ranging from +1.5 Gz to +6 Gz were applied during periods of from 30 s to 20 min. Acceleration was achieved in 10-90 s. Heart rate markedly increased as a function of acceleration intensity, reaching 160 beats/s. Decreases in cardiac output (30-40%) and stroke volume were also observed. Protection by an anti-G suit reduces tachycardia. Accelerations induce various electrocardiographic disorders lasting several minutes after the stress has been stopped. These are sometimes the first symptoms of functional cardiovascular failure. The centrifuge turns out to be an excellent screening tool. However, when used for testing various aircrew equipment, strict monitoring of the subjects is required.

Characteristics in the atmosphere of long-range transport aircraft cabins.

In the long run, the fatigue in aircrews performing frequent, long-range flights is linked to factors connected to the aircraft, such as noise, temperature, cabin pressure, atmosphere quality, and flight characteristics. These are the factors inherent to the aircraft which we have investigated during six long-range flights without time zone changes in DC-8 and DC-10 aircraft of the U.T.A. Cie. The results show that none of the pollutants researched reach doses considered hazardous by FAR 25 or by French legislation. This fact is due to the effective ventilation in the cabins. In flight, thermal comfort is limited by a too-low hygrometry RH = 12%. Even in a modern aircraft, the noise level remains high, but acoustical energy is spread over the less detrimental frequencies.

[Adaptation of body plethysmography to the study of respiratory mechanics during muscular exercise (author's transl)]. / Adaptation de la pléthysmographie corporelle totale à l'étude de la mécanique ventilatoire pendant l'exercice musculaire.

A pressure-corrected integrated flow plethysmograph allowing the study of mechanical characteristics of the ventilatory system during muscular exercise is described. In order to limit the increase in temperature inside the body box during exercise, a forced convective flow passes through the box. Thermal exchanges induced by this flow have been studied. They are sufficient to allow muscular exercise during 15 minutes at a constant power of 100 W. It has been verified that this type of box allows measurement of the usual parameters of ventilatory mechanics: pulmonary volumes, compliance, resistance using the panting method. The measurement of resistance during spontaneous breathing inside the box is not possible.

[Hand blood flow at rest and during submaximal exercise in acute and chronic heat stress (author's transl)]. / Modifications du débit sanguin de la main et de la réactivité vasculaire avec l'acclimatation à la chaleur

Three groups of subjects, Europeans without any heat acclimation (called EE), Europeans after 3 weeks of acclimatization in India (EI), and Indians in their natural environment (II) were studied during exposure to an ambient temperature of 33 degrees C. Hand blood flow (Q), rectal temperature (Tre), mean cutaneous temperature (Tsk) were simultaneously recorded at rest and during 2 periods of muscular exercise (0.44 and 0.7 Vo2 max) of 35 mn duration. The results showed (1) at rest, Q was very high in EE, quite low in both EI and II; (2) at the onset of exercise, a hand vasoconstriction was observed in all cases; (3) during exercise, there was a progressive increase of Q until 200% maximum above rest values; (4) at the end of exercise, Q was proportional to the intensity of the exercise for each group and inversely proportional to the duration of heat exposure, the highest Q was observed in EE, the lowest in II and an intermediate value for EI close to the latter). These differences in hand blood flow could not be explained by differences in deep and/or superficial temperatures between subjects. Thus, during chronic heat exposure, there is, especially for an exercising man, a progressive modification of heat transport in the body: that is, a reduction of skin perfusion and a greater Tre-Tsk difference which are both adaptative responses. The value of hand blood flow as an estimation of whole superficial circulation is discussed.