摘要:

SUMMARY This review of experimental studies focuses on the disturbances of sleep that may occur in connection with irregular work hours and their relation to ensuing alertness. Three aspects of sleep are covered: the duration of sleep, the stages of sleep, and the continuity of sleep. A sleep curtailment as small as 2 h has clear negative effects on alertness. Sleep disturbed as frequently as every minute clearly affects alertness, but such procedures also affect the stages of sleep and decrease total sleep time. However, fragmentation rates of one per 10 minutes also induce sleepiness without affecting sleep content or duration. There is no clear evidence for slow‐wave sleep (SWS) being more important than other stages, but designs may not have been sensitive enough. In connection with fragmentation studies it is suggested, however, that the effects are stronger if more SWS is lost. In summary, the review suggests that the relatively mild disturbances of sleep in shift work may contribute to reduced alertness although there are probably other, more potent, fact

ISSN:0962-1105    

DOI:10.1111/j.1365-2869.1995.tb00224.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SUMMARY This review paper deals with the issue of shift rotation, i.e. the number of consecutive shifts of the same type and the order of change between shifts. To minimize the disturbances of the circadian system and the accumulation of sleep deficits, rapidly and clockwise‐rotating shift systems would seem to be preferable. Regarding consecutive night shifts, a week of night shifts seems to be the worst system with regard to performance and accidents. There is a lack of reliable data on the effects of permanent vs. rotating‐shift systems on alertness, performance and accidents. This is also true for the comparison of forward (delaying) and backward (advancing) rotating‐shift systems, although the former would seem to be associated with fewer problems. For both systems, controlled longitudinal studies are ne

ISSN:0962-1105    

DOI:10.1111/j.1365-2869.1995.tb00225.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SUMMARY Continuous positive airway pressure, like positive end‐expiratory pressure (PEEP), increases lung volume and pleural pressure and usually decreases venous return. The decrease in venous return has been ascribed to a simple increase in right atrial pressure. However, recent studies have demonstrated PEEP also changes the resistive and elastic properties of peripheral veins. PEEP elevates the upstream pressure driving venous return, increases venous resistance, and directly compresses the inferior vena cava. The dogma that PEEP decreases venous return by decreasing the pressure gradient driving blood from the systemic vessels to the heart appears to be unt

ISSN:0962-1105    

DOI:10.1111/j.1365-2869.1995.tb00185.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SUMMARY This review summarizes the effects on sleep duration and sleepiness of (1) the timing of shifts (start and finishing times) and (2) the scheduling of free time between shifts. The results from the few studies available show that sleep duration is clearly determined by the change over time between the night and the morning shift—no more than 5 or 6 hours of sleep is obtained before the morning shift if the shift starts at 06.00 hours or earlier. Therefore, it is suggested that the morning shift should not start before 07.00 hours. A late start of the morning shift will however, increase the sleepiness at the end of the night shift, as well as decrease the duration of the daysleep after the night shift. On the other hand, one may argue that the short daysleep after a night shift may be compensated for by an evening nap, whereas a short night sleep before a morning shift cannot (no time for nap). The review of studies concerning free time between shifts suggests that at least 16 hours is needed and that quick change‐overs should be avoided. The free time after a spell of night shifts should be at least 48 hours since the shiftworker needs two main sleep episodes to recover from night

ISSN:0962-1105    

DOI:10.1111/j.1365-2869.1995.tb00226.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SUMMARY All‐night polysomnographic recordings were made of clinically diagnosed sleep bruxists (n= 23) and non‐symptomatic controls (n= 6). The total duration of masseter contraction (MC) episodes during sleep was 11.6 minutes per night in bruxists and 6.6 in controls (P<0.01). The mean frequency of MC episodes was 11.0 per hour of sleep in bruxists and 6.4 in controls (P<0.05). The mean relative amplitude of MC episodes reflecting clenching strength was 0.81 in bruxists and 0.56 in controls (P<0.01). The percentage distribution of mixed and phasic MC episodes was 94% among bruxists and 88% in controls. The remaining activity was classified as tonic in both groups. The subclassification of rhythmic jaw movements (RJM), defined as three or more separate rhythmic contractions during MC episode were also evaluated. The frequency of those MC episodes with RJM was 3.6 per hour of sleep in bruxists and 1.1 in controls (P<0.001). The difference in the relative amplitude between the two study groups suggests that the amount of clenching force is the primary factor responsible for the harmful effects of sleep bruxism on the masticatory apparatus. The most significant difference was seen in those phasic and mixed MC episodes which also included the subclassification of rhythmic jaw movement. The result suggests that relative amplitude and rhythmicity of MC episodes can be used as a basis to confirm the diagnosis and to evaluate the treatment effects of suspected sleep bru

ISSN:0962-1105    

DOI:10.1111/j.1365-2869.1995.tb00150.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SUMMARY It is generally assumed that inspiration will enhance both superior and inferior vena cava (SVC and IVC) blood flows due to the decrease in right atrial pressure produced by the fall in intrathoracic pressure. However, inspiration can also increase abdominal pressure due to the descent of the diaphragm. Using a model of abdominal vascular zone conditions, analogous to pulmonary vascular zone conditions, the abdominal venous compartment can be viewed as either a capacitor (zone III abdomen) or as a collapsible Starling resistor (zone II abdomen). This dual nature of the abdominal venous bed can explain how an inspiratory increase in abdominal pressure can increase IVC flow with hypervolaemia, but increase IVC flow with hypovolaemia. Combined generalized increases in abdominal pressure and focal forces over the liver can be shown to be an essential element in the pathogenesis of a Kussmaul's sign. Increases in abdominal pressures produced by active diaphragmatic descent can increase the total IVC venous return by enhancing the splanchnic IVC flow under relatively hypervolaemic conditions, but decrease the total IVC venous return by impeding the non‐splanchnic IVC flow under hypo‐volaemic conditions. Results are presented which suggest that the concept of abdominal vascular zone conditions is useful to understand overall directions of changes in total and regional venous return during normal and obstructed breathing and may provide useful analysis of the haemodynamic events which occur in obstructive sleep a

ISSN:0962-1105    

DOI:10.1111/j.1365-2869.1995.tb00186.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SUMMARY Studies of overtime have pointed to fatigue as a potential factor producing, for example, a three‐fold increase in accident rate after 16 h of work, increases in back injuries, hospital outbreaks of bacterial infection, or nuclear‐power plant safety compromises. Fatigue has been measured more directly in studies of scheduled long workshifts, where performance decrements in both work‐related tasks and laboratory‐type behavioural tests have been observed, and significant loss of sleep and increases in subjective sleepiness have been reported. Analyses of accidents or injuries during scheduled extended workshifts, however, have produced equivocal results. Factors which could compound the fatiguing effects of extended workshifts, such as workload, noise, chemical exposure, or duties and responsibilities outside of the workplace, rarely have been studied systematically. It is concluded that extended workshift schedules should be instituted cautiously and evaluated carefully, with appropriate attention given to staffing levels, workload, job rotation, environmental exposures, emergency contingencies, rest breaks, commuting time, and social or domestic respons

ISSN:0962-1105    

DOI:10.1111/j.1365-2869.1995.tb00227.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SUMMARY Large decreases in inspiratory intrathoracic pressure (ITP) occur during obstructive apnoeas. The cardiac effects of apnoea‐associated decreased ITP come from the interaction of increased preload (venous return) on the right ventricle (RV) and increased afterload on the left ventricle (LV), and are modulated by the autonomic effects of shifts in blood volume and hypoxaemia. During obstructed breathing, venous return increases by as much as three‐fold during inspiration even though mean flow may change little. This leads to a substantial inspiratory increase in RV end‐diastolic and stroke volume. Because of ventricular interdependence, there is a decrease in LV diastolic compliance and corresponding decrease LV preload.Sustained decreases in ITP (Müller manoeuvre) inhibit LV ejection, and hence increase LV afterload. However, breathing against an obstructed airway (repetitive short Müller manoeuvre) is not necessarily modelled by the sustained manoeuvre. Animal studies indicate that with airway obstruction, for the first beat or two of inspiration the primary effect on the LV is a reduction in stroke volume related to a decrease in preload, and afterload, if anything, decreases. In fact, afterload only increases during early expiration when stroke volume increases. When obstructive and central apnoeas are paired for duration and blood‐gas alterations, there are increases in pulmonary blood volume with central apnoeas and in RV volume with obstructive apnoeas, consistent with the postulation that the primary effect of obstructive apnoeas is on venous return.In conclusion, the putative role of decreased ITP in increasing LV afterload under conditions appropriate to OSA is not well supported by experimental studies. However, effects with very large swings in ITP as might be seen under the most extreme forms of OSA, and differences in timing of the swings between diastole and systole have yet to be i

ISSN:0962-1105    

DOI:10.1111/j.1365-2869.1995.tb00187.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SUMMARY Plasma prolactin (PRL) concentration exhibits a sleep‐dependent pattern, with highest levels during sleep and lowest levels during the waking period. The syndrome of obstructive sleep apnoea (OSA) is associated with severe hypoxaemia and chronic sleep fragmentation, both of which could affect the sleep‐entrained PRL rhythm. Treatment with nasal continuous positive airway pressure (CPAP) immediately restores a normal sleep structure by successful abolition of the apnoeas. In the present study, seven OSA patients underwent two night studies, once when no treatment was given and once during the first night of CPAP treatment. Sleep was recorded polygraphically in all experiments. Plasma PRL was measured at 10 min intervals and secretory rates were calculated by a deconvolution procedure. CPAP treatment greatly reduced hypoxaemia and improved sleep quality. The secretory pulse amplitude and the total amount of PRL secreted during the night remained constant regardless of whether patients were treated or not. The only difference found was a lower pulse frequency in untreated OSA patients as compared to treated patients, which may be attributed either to hypoxaemia or to sleep disturbance or to the combined action of both. Treatment may be considered to normalize PRL release by restoring pulse frequency to values similar to those observed for normal sub

ISSN:0962-1105    

DOI:10.1111/j.1365-2869.1995.tb00151.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SUMMARY On‐site studies of shiftwork show considerable differences in sleepiness between workers. Variation between individuals depends on different sleeping, coping and living habits of the workers, on possible sleep disorders, but also on more ‘permanent’ inter‐individual factors that may influence sleepiness by changing either the circadian or homeostatic factors of sleep. The effects of circadian phase, age, sex, physical fitness, domestic and personality factors on shiftworkers' sleepiness and work‐related accidents are reviewed. It is concluded that only a minor part of the variation in sleepiness between individuals can be explained. The present knowledge is not sufficient to carry out reliable ‘selection’ of individuals suitable for shiftwork. However, preventive advice and medical surveillance focusing on individual differences in sleepiness

ISSN:0962-1105    

DOI:10.1111/j.1365-2869.1995.tb00228.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY