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Fatigue of respiratory muscles is currently receiving much attention because of the critical role it may play in various pathologic conditions. This article attempts to provide physicians with some additional insights into the physiologic factors thought to underlie the development in general, and how these may be influenced by changing patterns of neural activity.
BACKGROUND: The Pulfrich stereoillusion occurs spontaneously in diseases inducing asymmetric visual pathway delays. Its influence on driving performance has never been investigated and was, therefore, assessed using a three-dimensional (3D) computer driving simulation. METHODS: A 3D driving scenery of a road with obstacles was visualised on an autostereoscopic 3D display. Seven normal subjects drove at a speed of 6 m/s using a steering wheel and three angles of view of the scenery (0 degrees, 45 degrees to left, and 90 degrees to left) with different interocular delays (25 ms on the right, 25 ms on the left, and no delay). One subject drove the scenery at an angle of 90 degrees without delay and with a delay of 8 ms, 16 ms, and 25 ms on the right and left, respectively, at speeds of 6 m/s, 12 m/s and 18 m/s. RESULTS: Stereo-illusion only influenced car position if the angle of view was 90 degrees (p<0.05). At this angle, increasing car speeds were associated with larger car displacements (delay on right p<0.001, on left p<0.01) and smaller delays with smaller car displacements (p<0.001). CONCLUSIONS: This study showed that Pulfrich phenomenon has an influence on car position only if the viewing angle is 90 degrees. No influence could be found if the driving direction corresponded to the visual axis of the driver. These findings are in agreement with reports of patients with spontaneous Pulfrich phenomenon who indicate that while driving, distances are only misjudged when looking sideways.
During long and monotonous driving at night, most drivers progressively show signs of visual fatigue and loss of vigilance. Their capacity to maintain adequate driving performance usually is affected and varies with the age of the driver. The main question is to know, on one hand, if occurrence of fatigue and drowsiness is accompanied by a modification in the driving performance of the driver and, on the other hand, if this relationship partially depends on the driver's age. Forty-six male drivers, divided into three age categories: 20-30, 40-50, and 60-70 years, performed a 350-km motorway driving session at night on a driving simulator. Driving errors were measured in terms of number of running-off-the-road incidents (RORI) and large speed deviations. The evolution of physiological vigilance level was evaluated using electroencephalography (EEG) recording. In older drivers, in comparison with young and middle-aged drivers, the degradation of driving performance was correlated to the evolution of lower frequency waking EEG (i.e., theta). Contrary to young and middle-aged drivers, the deterioration of the vigilance level attested by EEG correlated with the increase in gravity of all studied driving errors in older drivers. Thus, depending on the age category considered, only part of the driving errors would constitute a relevant indication as for the occurrence of a state of low arousal.
The benzodiazepine flunitrazepam is extensively prescribed to patients with insomnia in many countries, but has also become popular among alcohol- and drug abusers. Several reports indicate that it is used as a date rape drug and suggest that it may precipitate violent behavior. Furthermore, flunitrazepam is involved in many fatal intoxications in Sweden. This study was designed and conducted to explore the negative consequences of flunitrazepam abuse in Sweden, and to assess the trends in its use and abuse. The occurrence of flunitrazepam in cases referred to the Department of Forensic Chemistry in Linköping, Sweden 1992-1998, was investigated in detail. The detections were studied separately for different groups; medicolegal death investigations, drug abuse cases, driving under influence cases, and other medicolegal cases. These data were further compared with the sales, and seizures by the Swedish Customs and the Swedish Police. During 1992-1998, 641 fatalities occurred, where the cause of death was attributed to intoxication with flunitrazepam solely (130) or in combination with other drugs, or concomitant conditions (511). In 78% of all driving under influence cases, where flunitrazepam was detected, the analyses also disclosed the presence of illicit drugs. A similar association was seen in drug abuse cases. The seizures reported by the Swedish Customs revealed a substantial and increasing illegal trade. Cases, where flunitrazepam seemingly induced violent behavior were identified, and one of these is described in some detail. It is concluded that the abuse pattern and the toxicity of flunitrazepam should be kept in mind by forensic investigators and that this panorama also should be considered when decisions about the registration and classification of flunitrazepam are made in different countries.
Cyclodextrins are often used in order to increase the aqueous solubility of drug substances by complexation. In order to investigate the complexation reaction of ibuprofen and hydroxypropyl-beta-cyclodextrin, titration calorimetry was used as a direct method. The thermodynamic parameters of the complexation process (stability constant, K(11); complexation enthalpy, deltaH(c) degrees ) were obtained in two different buffer systems (citric acid/sodium-phosphate and phosphoric acid) at various pH values. Based on these data the relative contributions of the enthalpic and entropic terms of the Gibbs energy to the complexation process have been analyzed. In both buffers the enthalpic and entropic terms are of different sign and this case corresponds to a 'nonclassical' model of hydrophobic interaction. In citric buffer, the main driving force of complexation is the entropy, which increases from 60 to 67% while the pH of the solution increases from 3.2 to 8.0. However, for the phosphoric buffer the entropic term decreases from 60 to 45%, while the pH-value of the solution increases from 5.0 to 8.2, and the driving force of the complexation process changes from entropy to enthalpy. The experimental data of the present study are compared to results of other authors and discrepancies discussed in detail.
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OBJECTIVE: To determine the role of vehicle safety features, particularly vehicle size and weight, compared with other factors in parental decisions about choosing vehicles for teens to drive. METHODS: Written questionnaire to parents of teenagers attending drivers education training. RESULTS: The response rate to the survey was 62.6%. Two thirds reported that the teen would drive an existing family vehicle, 10.5% would buy an additional vehicle, and 20.3% would buy another vehicle as well as have the teen drive an existing family vehicle. Large size was important to only approximately 40% of families purchasing a car for the teen or families in which the teen would use an existing family vehicle. Gas mileage and other safety features were ranked as more important even in families in which a large car was available in the household. CONCLUSIONS: Families did not rank vehicle size and weight as important as other, less effective safety features in choosing cars for their teens. Information about vehicle crash-worthiness should be incorporated into drivers education and other programs reaching new teen drivers and their families.
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Continuous positive airway pressure (CPAP) improves idiopathic central sleep apnea (ICSA), but the mechanisms are not completely understood. It has been demonstrated that some ICSA patients have an increased CO2 drive, expressed by the hypercapnic ventilatory response (HCVR). The aim of our study was to evaluate whether CPAP can decrease the HCVR in successfully treated ICSA patients. Also the central apnea mean duration (CMD) was studied. Nine patients were evaluated. Their apnea-hypopnea index at baseline was high, but decreased from 50 +/- 5 to 8 +/- 3, during 5 +/- 1 cm H2O CPAP. After one month CPAP high values were still found for HCVR (2.69 +/- 0.23 L.min-1.mmHg-1 at baseline, 2.71 +/- 0.33 L.min-1.mmHg-1 after CPAP). Sleep quality was only improved by a decrease in the arousal index (from 29 +/- 12 to 6 +/- 1 a night) (p = 0.04). Daytime arterial O2 partial pressure (PaO2) increased from 73 +/- 4 mmHg to 85 +/- 3 mmHg (p = 0.02), whereas daytime arterial CO2 partial pressure (PaCO2) remained unchanged (from 41 +/- 1 mmHg to 40 +/- 1 mmHg). CMD was 21 +/- 6 s before and 13 +/- 1 s after CPAP (p = 0.05). The presence of hypersomnolence decreased from in 89% to in 33% of the patients. It is concluded that CPAP treatment can induce a subjective and objective improvement in ICSA patients, with improved sleep-related respiratory indices, daytime PaO2, but without a change in CO2 drive. High chemical drives seem to be the cause and not the consequence of sleep disordered breathing and persist after treatment.
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Borkenstein et al. (1974) study indicated that drivers with BACs of 0.05 to 0.09 per cent were twice as likely to crash as drivers with a zero BAC. Drivers with BACs from 0.10 to 0.14 per cent were ten times as likely to have a fatal crash in 1964. There have been numerous efforts during the history of motorized countries to control the consumption of alcohol and the problems associated with it through legislative mandate, it was not until the 1970s that acceptance of legal BAC (Blood Alcohol Concentration) limits laws became widespread. In particular, as more and more people drive automobiles, the number of traffic accidents involving drunken drivers has soared, and many of these are known to be related to the consumption of alcohol. Thus, legislators find themselves under increasing pressure to find a reasonable and fair solution to the question of alcohol impaired driving, as the scientific evidence about alcohol consumption level and psycho motor functions impairment came to clear. A landmark event in the development of policies regarding impaired driving was the establishment of the fact that consumption of alcohol does, in fact, increase the probability of traffic crashes. Legal limit laws specify a maximum permissible BAC limit for drivers. Currently, a BAC laws range from zero tolerance and 0.02 to 0.10% constitutes prima facie evidence in most countries for 'Driving under Influence of Alcohol.' This latter standard is too permissive, as driving skills deteriorate and crash involvement risk increases beginning at 0.02%. There are consequences attached to setting a BAC limit so high that a 72 kg man can drink five bottles of beer and still be under legal limit. In this sense high legal BAC limit may influence people to make bad estimates of their relative risk of injury or death while driving. Provided there is adequate political will, millions of lives could be saved in the coming years. This review is an attempt to examine in detail the available information about legal BAC limit laws, and issue of considerable interest to both policy makers and the public.
This article generalizes the results of a qualitative study, which suggested that localization of consequences in PSAs may have a impact on reducing the incidence of drunk driving among college students. The results of the current study suggest that this implication may be true. The results also suggest that frequency of binge drinking, gender, and age are factors that influence perceptions of drunk driving risk, and that PSAs need to take these factors into account in order to be effective.
Patients with obstructive pulmonary disease (OSA) have an increased rate of driving accidents, perhaps due to poor vigilance or impaired cognitive skills that influence their driving ability. The authors have assessed whether patients with OSA perform differently to control subjects on a steering simulator which allows the separate assessment of the two visual tasks required for steering a car, immediate positioning on road with reference to the road edges, and assessment of the curve of the oncoming road which allows faster driving. Twelve patients with OSA and 12 control subjects, matched for age, sex and driving experience, performed three 30-min drives with either all the oncoming road visible, only the near part of the road visible, or only the distant part of the road visible. Steering was assessed by measuring the SD around the theoretical perfect path (steering error) and the number of times the driver went "off road". Subjects identified the appearance of target numbers at the four corners of the screen as quickly as possible, thus making the test a divided attention task. Patients with OSA performed significantly less well on the three different road fields as measured by steering error (p<0.001), time to detect the target number (p<0.03), and off road events (p<0.03). The patients appeared to be particularly impaired on the two drives when only part of the road ahead was available to guide steering. This steering simulator, with its more realistic view of the road ahead, identifies impaired performance in patients with obstructive sleep apnoea. In addition it suggests that patients with obstructive sleep apnoea may be more disadvantaged compared to normal subjects when the view of the road ahead is limited (such as in fog).
Graduated licensing has been implemented in many U.S. states to reduce teenage driver crash involvement. The goal is to introduce teenagers gradually to driving before allowing full, unrestricted licensure. Tennessee, one of the states that introduced graduated licensing, implemented a program to influence both driving by teenagers during the learner stage and restrictions imposed by parents after licensure. In addition to a standard welcome letter, booklets and reminder cards were mailed to parents of teenagers who had just obtained their learner's permits. The booklets and cards were designed to assist parents in becoming more actively involved in their children's driving experiences. The effects of three different approaches (welcome letter only, letter plus booklet, and letter plus booklet plus reminder cards) on parental involvement, teenage crashes, and teenage citations were assessed based on telephone interviews with parents. Although the parents said the booklets and reminder cards were helpful and should continue to be sent to other parents, there were no discernible effects on teenage practice driving and reported parental involvement during the learner stage. Nor was there any measurable influence on restrictions imposed by parents after licensure. It is unknown whether the standard welcome letter affected parental involvement, but overall supervised driving exceeded the state requirements by a substantial margin.