Ventilatory effects of low-dose paraoxon result from central muscarinic effects

Paraoxon induces respiratory toxicity. Atropine completely reversed parathion- and paraoxon-induced respiratory toxicity. The aim of this study was to assess the peripheral or central origin of ventilatory effects of low-dose paraoxon. Male Sprague-Dawley rats were given paraoxon 0.215 mg/kg subcutaneously and treated with either atropine (10 mg/kg sc) or ascending doses of methylatropine of 5.42 (equimolar to that of atropine), 54.2, and 542 mg/kg administered subcutaneously 30 min after paraoxon. Ventilation at rest was assessed using whole-body plethysmography and rat temperature using infra-red telemetry. Results are expressed as mean ± SE. Statistical analysis used two-way ANOVA for repeated measurements. Paraoxon induced a significant decrease in temperature 30 min after injection lasting the 90 min of the study period. This effect was partially corrected by atropine, but not by methylatropine whatever the dose. Paraoxon induced a decrease in respiratory rate resulting from an increase in expiratory time associated with an increase in tidal volume. Atropine completely reversed the ventilatory effects of low-dose paraoxon while the equimolar dose of methylatropine had no significant effects. The 54.2 and 542 mg/kg doses of methylatropine had no significant effects. Atropine crosses the blood-brain barrier and reverses peripheral and central muscarinic effects. In contrast, methylatropine does not cross the blood-brain barrier. Atropine completely reversed the ventilatory effects of low-dose paraoxon, while methylatropine had no significant effects at doses up to 100-fold the equimolar dose of atropine. We conclude that the ventilatory effects of low-dose paraoxon are mediated by disrupted muscarinic signaling in the central nervous system.     

Mental workload in air traffic control: an index constructed from field tests

BACKGROUND: Mental workload assessment is a recurrent issue in air traffic control (ATC). Studies of ATC have used either objective aspects, i.e., numbers and distribution of aircraft, or subjective factors, such as self-imposed performance and stress levels, with mixed results. This is partly due to the difficulty in bringing together comparable data pertaining to both air traffic, with its ever-changing distribution, and judgement or quickly fluctuating psychophysiological variables. METHODS: We propose a method of mental load estimation devised to take into account both objective traffic variables and the additional load imposed by subjective effects, including the seriousness of conflicts and the time-pressure for their resolution. First, we developed a traffic load index (TLI) to identify time boundaries during which additional load may occur. Then we quantified the additional load according to the air traffic situation. RESULTS: TLI was developed from analysis of 25 h of recordings of radar control sessions involving 25 professional air traffic controllers at a major airport. Results were then compared with a simple objective index (number of aircraft) and subjective workload ratings (NASA-TLX test). The whole population (intersubjects analysis) showed a better correlation between the TLI and the self-rated workload than for the number of aircraft alone. Among the controllers who rated more than one level of workload through the TLX-test, 77.8% showed better correlation between TLI and TLX than between N and TLX (intrasubjects analysis). CONCLUSION: Workload estimation should integrate both objective task variables and subjective evaluations associated with them.