Subsequent Nights Research Articles

Postsession Dreaming in Neurofeedback as an Indication of Nondeclarative Learning

Clients may report increased dreaming following neurofeedback sessions. Increased dreaming may not be strictly a side effect of training but may rather be a result of the nondeclarative learning accomplished in training. Research has demonstrated the connection between dreaming and consolidation of memory in both animals and human subjects. Rapid eye movement (REM) deprivation studies have shown the importance of REM sleep to the retention of newly learned skills. Other studies have shown that learning may increase the proportion of REM sleep on subsequent nights. More specifically, REM dreaming may be related to the consolidation of procedural, nondeclarative memory, the type of learning that occurs also during neurofeedback training. When a client reports increased nocturnal dreaming following a neurofeedback session, this may serve as a valuable early indication that their brain is responding to this type of training.

The influence of placebo administration on the first- night effect in patients with insomnia disorder

ObjectiveWe aimed to investigate the effects of placebo on the first-night effect (FNE) in insomniacs. MethodsIn sum, 36 patients with insomnia disorder who met the DSM-5 criteria were enrolled in this study. Sixteen patients with insomnia disorder were given two days of placebo intervention (placebo-administration group, PL). Twenty patients with insomnia disorder (drug-free group, DF) were not given any interventions. All participants underwent two consecutive nights of polysomnographic (PSG) testing in the sleep laboratory. Sleep diaries were recorded during one week at home before the PSG nights and on two subsequent nights. ResultsThe results demonstrated that compared with the DF group, sleep onset latency (SOL), time in bed (TIB) and wake after sleep onset (WASO) significantly increased and sleep efficiency (SE) significantly decreased in the first sleep lab night in the PL group (all p < 0.05). Moreover, compared with the second night, significant differences were observed in lower self-reported total sleep time (TST) and more subjective WASO during the first night in the PL group (all p < 0.05). However, no significant difference was found in the duration and percentage of N1, N2, N3 and REM between the two groups. ConclusionIn patients with insomnia disorder, placebo administration may increase the occurrence of worse sleep without causing a change in the duration and percentage of N1, N2, N3 and REM on the first sleep lab night. In some cases, a placebo may not serve as treatment but may result in a nocebo effect.

Sighting of Petaurista petaurista (Pallas, 1766) (Mammalia: Rodentia: Sciuridae) on limestone hills in Merapoh, Malaysia

Flying squirrels are poorly studied nocturnal mammals as their elusive and nocturnal behaviour makes it hard to observe them in the wild. Here, we describe sightings of Petaurista petaurista on a limestone hill and its foot at Merapoh, Pahang, Malaysia. This is the first report as the species is usually known to inhabit forest habitat. We observed the first squirrel resting on a steep limestone wall at night. During subsequent nights, three individuals were observed feeding on Ficus hispida and Terminalia catappa fruits on the foot of the hill in nearby trees. These sightings suggest that P. petaurista may use limestone hill habitat.

Differential Effects of REM Sleep on Emotional Processing: Initial Evidence for Increased Short-term Emotional Responses and Reduced Long-term Intrusive Memories

ABSTRACT Background: Rapid eye movement (REM) sleep has been postulated to facilitate emotional processing of negative stimuli. However, empirical evidence is mixed and the conditions under which higher amounts of REM sleep lead to decreased or increased emotional responses are unclear. We proposed that the time course between REM sleep and measurement of emotional responses is a crucial factor and hypothesized that more REM sleep will enhance emotional responses shortly after sleep, but will lead to decreased emotional responses in the long-term. Participants and Methods: Seventy-six healthy young women watched negative and neutral pictures before a polysomnographically-recorded nap including three different groups (1: no REM sleep, 2: REM sleep awakening, 3: REM sleep). Short-term emotional responses were measured using aversiveness ratings of negative pictures; aversiveness ratings of intrusive picture memories on the three subsequent evenings were used to measure long-term emotional responses. Results: For short-term emotional responses, no significant interaction indicating group differences was found. However, we found correlations between longer REM sleep duration and higher aversiveness ratings of negative pictures. In contrast, lower aversiveness of intrusive picture memories after two days was found in participants with a full REM sleep period compared to individuals without REM sleep. Correlational analyses also supported this pattern of results. Conclusions: Results suggest that REM sleep may increase reactivity to emotional stimuli in the short-term and this effect of REM sleep appears to facilitate emotional processing during subsequent nights leading to reduced intrusive picture memories in the long-term.

Microclimate Thermal Management Using Thermoelectric Air-Cooling Duct System Operated at Five Incremental Powers and its Effect on Sleep Adaptation of the Occupants

In this study, the microclimate of the test room was regulated using thermoelectric air duct cooling system (TE-AD) operated at input powers-240 W, 360 W, 480 W, 600 W, 720 W, and 840 W, on subsequent nights. Fifteen (15) healthy male volunteers were recruited to sleep under these test conditions and their sleep quality was assessed by studying objective measures such as sleep onset latency (SOL), mean skin temperature and heart rate as well as subjective parameters like predicted mean vote (PMV) and predicted percentage of dissatisfied (PPD). There was a consistent improvement on all studied parameters when the power of the system was increased from 240 W to 720 W. The mean sleep onset latency time was reduced from (M = 40.7 +/− 0.98 min) to (M = 18.33 +/− 1.18 min) when the operating power was increased from 240 W to 720 W, denoting an improvement in sleep quality. However, increasing the power further to 840 W resulted in deteriorating cooling performance of the TE-AD system leading to an increase in temperature of the test room and reduction in sleep comfort. Analysis of subjective indices of thermal comfort viz. PMV and PPD revealed that subjects are highly sensitive towards variations in microclimate achieved by changing the operating power of the TE-AD. This device was also found to be environmentally sustainable, with estimated reduction in CO2 emission calculated to be around 38% as compared to the conventional air-conditioning.

Cognitive Impairments during the Transition to Working at Night and on Subsequent Night Shifts.

Demands of modern society force many work operations into the night when the internal circadian timekeeping system is promoting sleep. The combination of disturbed daytime sleep and circadian misalignment, which is common in overnight shift work, decreases cognitive performance, yet how performance may differ across multiple consecutive nights of shift work is not fully understood. Therefore, the primary aim of this study was to use a simulated night-shift protocol to examine the cognitive performance and ratings of sleepiness and clear-headedness across the hours of a typical daytime shift, a first night shift with an afternoon nap and extended wakefulness, and 2 subsequent overnight shifts. We tested the hypothesis that cognitive performance would be worse on the first night shift as compared with the baseline and subsequent nighttime shifts and that performance during nighttime shifts would be reduced as compared with the baseline daytime shift. Fifteen healthy adults (6 men) were studied in the 6-day in-laboratory protocol. Results showed that working during the night increased subjective sleepiness and decreased clear-headedness and performance on the Psychomotor Vigilance Task (i.e., slower median, fastest and slowest reaction times, and increased attentional lapses), Stroop color word task (decreased number of correct responses and slower median reaction time), and calculation addition performance task (decreased number attempted and correct). Furthermore, we observed limited evidence of sleepiness, clear-headedness, or performance adaptation across subsequent nights of simulated night work. Our findings demonstrate that night-shift work, regardless of whether it is the first night shift with a nap and extended wakefulness or subsequent night shifts, decreases performance and clear-headedness as compared with the day shift.

Small logging roads do not restrict movements of forest rats in Bornean logged forests

AbstractSelective logging is driving the proliferation of roads throughout tropical rain forests, particularly narrow, unpaved logging roads. However, little is known about the extent of road edge effects or their influence on the movements of tropical understory animal species. Here, we used forest rats to address the following questions: (a) Does the occupancy of rats differ from road edges to forest interior within logged forests? (b) Do roads inhibit the movements of rats within these forests? We established trapping grids along a road edge‐to‐forest interior gradient at four roads and in three control sites within a logged forest in Sabah, Malaysia. To quantify the probability of road crossing, rats were captured, translocated across a road, and then recaptured on subsequent nights. We caught 216 individuals of eight species on 3,024 trap nights. Rat occupancy did not differ across the gradient from road edge to interior, and 48 percent of the 105 translocated individuals crossed the roads and were recaptured. This proportion was not significantly different from that of rats returning in control sites (38% of 60 individuals), suggesting that small roads were not barriers to rat movements within logged forests. Subadults were significantly more likely to return from translocation than adults in both road and control sites. Our results are encouraging for the ecology of small mammal communities in heavily logged forests, because small logging roads do not restrict the movements of rats and therefore are unlikely to create an edge effect or influence habitat selection.

The Impact of Shift Work on Sleep, Alertness and Performance in Healthcare Workers

Shift work is associated with impaired alertness and performance due to sleep loss and circadian misalignment. This study examined sleep between shift types (day, evening, night), and alertness and performance during day and night shifts in 52 intensive care workers. Sleep and wake duration between shifts were evaluated using wrist actigraphs and diaries. Subjective sleepiness (Karolinska Sleepiness Scale, KSS) and Psychomotor Vigilance Test (PVT) performance were examined during day shift, and on the first and subsequent night shifts (3rd, 4th or 5th). Circadian phase was assessed using urinary 6-sulphatoxymelatonin rhythms. Sleep was most restricted between consecutive night shifts (5.74 ± 1.30 h), consecutive day shifts (5.83 ± 0.92 h) and between evening and day shifts (5.20 ± 0.90 h). KSS and PVT mean reaction times were higher at the end of the first and subsequent night shift compared to day shift, with KSS highest at the end of the first night. On nights, working during the circadian acrophase of the urinary melatonin rhythm led to poorer outcomes on the KSS and PVT. In rotating shift workers, early day shifts can be associated with similar sleep restriction to night shifts, particularly when scheduled immediately following an evening shift. Alertness and performance remain most impaired during night shifts given the lack of circadian adaptation to night work. Although healthcare workers perceive themselves to be less alert on the first night shift compared to subsequent night shifts, objective performance is equally impaired on subsequent nights.

Insights into the feeding ecology of and threats to Sand Cat Felis margarita Loche, 1858 (Mammalia: Carnivora: Felidae) in the Kyzylkum Desert, Uzbekistan

Little is known about the ecology of the Sand Cat Felis margarita throughout its range in the deserts of northern Africa to central Asia. We present observations of the Sand Cat in the southern Kyzylkum Desert, Uzbekistan, potentially preying upon a large bird and returning to the kill on subsequent nights. This record contributes to the knowledge about the feeding ecology and varied diet of the Sand Cat and its opportunistic hunting strategy.

Comparison of home sleep apnea testing versus laboratory polysomnography for the diagnosis of obstructive sleep apnea in children

IntroductionObstructive sleep apnea (OSA) affects 1–5% of pediatric patients. Laboratory polysomnography is expensive, not always available, and is inconvenient for patients. Our study investigates the diagnostic ability of an unattended ambulatory monitor for the diagnosis of pediatric OSA. MethodsA prospective study was conducted in children, ages 2–17. Subjects completed in-lab polysomnography simultaneously with ambulatory monitoring. Caregivers attempted home studies on two subsequent nights to compare the home monitor and the laboratory polysomnogram (PSG). ResultsThirty-three subjects completed simultaneous laboratory polysomnogram with portable monitoring. Twenty patients completed home studies, with 16 completing 2 nights of monitoring. The measurement of AHI by the portable monitor was different than that obtained by the PSG with statistical significance for the comparisons of PSG vs. In-Lab (p = 0.0026), PSG vs. Home 1 (p = 0.033), and PSG vs. Home 2 (p = 0.033). The sensitivity of the portable monitor for diagnosing OSA was best for the In-lab use at 81%, but only 69% and 70% for the uses at home on the 2 nights respectively. Interestingly, the comparison of AHI and lowest oxygen saturation measurements from the home sleep test in children age 6 and older did not differ significantly from the PSG. ConclusionsThis pilot study demonstrated differences between home sleep testing and in-lab polysomnography for the diagnosis of pediatric sleep apnea. These differences were predominantly found to exist in younger children. Larger prospective studies are needed prior to widespread use, but home studies may alleviate issues of access to care and higher costs of laboratory polysomnography.

Photometry of the three eclipsing novalike variables EC 21178-5417, GS Pav and V345 Pav

As part of a project to better characterize comparatively bright, yet little studied cataclysmic variables time resolved photometry of the three eclipsing novalike variables EC 21178-5417, GS Pav und V345 Pav is presented. Previously known orbital periods are significantly improved and long-term ephemeris are derived. Variations of eclipse profiles, occurring on time scales of days to weeks, are analyzed. Out of eclipse the light curves are characterized by low scale flickering superposed on more gradual variations with amplitudes limited to a few tenths of a magnitude and profiles which at least in EC 21178-5417 and GS Pav roughly follow the same pattern in all observed cycles. Additionally, signs for variations on the time scale of some tens of minutes are seen in GS Pav, most clearly in two subsequent nights when in the first of these a signal with a period of 15.7 min was observed over several hours. In the second night variations with twice this period were seen. While no additional insight could be gained on quasi periodic oscillations (QPOs) and dwarf nova oscillations in EC 21178-5417, previously detected by Warner et al. (2003), and while such oscillations could not be found in V345 Pav, stacked power spectra of GS Pav clearly reveal the presence of QPOs over time intervals of several hours with periods varying between 200 s and 500 s in that system.

Subtle changes in the landmark panorama disrupt visual navigation in a nocturnal bull ant.

The ability of ants to navigate when the visual landmark information is altered has often been tested by creating large and artificial discrepancies in their visual environment. Here, we had an opportunity to slightly modify the natural visual environment around the nest of the nocturnal bull ant Myrmecia pyriformis We achieved this by felling three dead trees, two located along the typical route followed by the foragers of that particular nest and one in a direction perpendicular to their foraging direction. An image difference analysis showed that the change in the overall panorama following the removal of these trees was relatively little. We filmed the behaviour of ants close to the nest and tracked their entire paths, both before and after the trees were removed. We found that immediately after the trees were removed, ants walked slower and were less directed. Their foraging success decreased and they looked around more, including turning back to look towards the nest. We document how their behaviour changed over subsequent nights and discuss how the ants may detect and respond to a modified visual environment in the evening twilight period.This article is part of the themed issue 'Vision in dim light'.

A novel approach using actigraphy to quantify the level of disruption of sleep by in-home polysomnography: the MrOS Sleep Study: Sleep disruption by polysomnography

BackgroundThe “first-night effect” of polysomnography (PSG) has been previously studied; however, the ability to quantify the sleep disruption level has been confounded with the use of PSG on all nights. We used actigraphy to quantify disruption level and examined characteristics associated with disruption. MethodsTotally, 778 older men (76.2 ± 5.4 years) from a population-based study at six US centers underwent one night of in-home PSG. Actigraphy was performed on the PSG night and three subsequent nights. Actigraphically measured total sleep time (TST), sleep efficiency (SE), wake after sleep onset (WASO), and sleep onset latency (SOL) from the PSG night and subsequent nights were compared. Linear regression models were used to examine the association of characteristics and sleep disruption. ResultsOn average, sleep on the PSG night was worse than the following night (p < 0.05, TST 21 ± 85 min less, SE 2.3 ± 11.3% less, WASO 4.9 ± 51.8 min more, SOL 6.6 ± 56.2 min more). Sleep on the PSG night was significantly worse than that two and three nights later. Characteristics associated with greater sleep disruption on the PSG night included older age, higher apnea–hypopnea index, worse neuromuscular function, and more depressive symptoms. Minorities and men with excessive daytime sleepiness slept somewhat better on the PSG night. ConclusionsAmong older men, there was sleep disruption on the PSG night, which may lead to sleep time underestimation. The increase of sleep on the night after the PSG suggests that data from the second monitoring may overestimate sleep.

Effectiveness of a mobility monitoring system included in the nursing care process in order to enhance the sleep quality of nursing home residents with cognitive impairment

Sleep disturbances are common in nursing homes residents with dementia. In this study, the use of a mobility monitoring system accompanied with case conferences was investigated in order to improve sleep quality in nursing home residents with cognitive impairment. An open two-phase randomized controlled trial was conducted at three nursing homes between November 2014 and September 2015. Residents were randomly assigned to an intervention group using the monitoring system and a control group not using the system. A 10-week period of intensive use of the monitoring system and case conferences led by an advanced nurse practitioner (Phase I) was followed by three months of reduced use of the monitoring system and case conferences led by an internal registered nurse (Phase II). Data were collected before intervention started (T0), after Phase I (T1) and after Phase II (T2). The night shift nurse in charge rated the residents’ sleep quality on a four point scale over five subsequent nights. Data from 44 residents were included in the analysis with a linear mixed model. We observed a significant interaction between the time and groups with a more pronounced increase in sleep quality in the intervention group in T1, but a decrease in T2. Sleep quality in the control group stayed almost stable (F = 3.566, p = 0.034). Results indicate that the use of the mobility monitoring system can improve the assessment of night-time mobility and activity supporting nurses in planning and implementing care interventions such as repositioning, continence care and inspection rounds.

Night-to-night variation of pulse oximetry in children with sleep-disordered breathing

BackgroundSleep-disordered breathing is a common and serious feature of many paediatric conditions and is particularly a problem in children with Down syndrome. Overnight pulse oximetry is recommended as an initial...

Effect of Using Eye Mask on Sleep Quality in Cardiac Patients: A Randomized Controlled Trial.

Background:Patients in coronary care unit are at risk of sleep deprivation. Sleep deprivation can be associated with increased blood pressure and heart rate, raising the risk of developing cardiovascular problems among patients hospitalized in coronary care unit.Objectives:This study was carried out to examine the effect of eye mask on sleep quality in cardiac patients.Patients and Methods:In this randomized controlled trial, 60 patients who met the inclusion criteria were selected using a convenient sampling method and randomly allocated into the experimental and control groups. Patients in the control group received routine care. However, in the experimental group, patients received routine care and eye mask for three subsequent nights. In the both groups, the sleep quality was assessed using the Pittsburgh sleep quality index. Data were analyzed by the chi-square test, independent samples t-test, Mann-Whitney U, and Wilcoxon signed-rank tests.Results:After the study, the median scores of the subjective sleep quality, the sleep latency, the sleep duration, the habitual sleep efficiency, and the sleep disturbances domains, as well as the median score of overall Pittsburgh sleep quality index in the experimental group were significantly lower than those in the control group (P < 0.05). However, no significant differences were observed between the two groups in terms of the use of sleep medications and the daytime dysfunction domains (P > 0.05).Conclusions:Using eye mask can significantly improve the sleep quality in cardiac patients. Therefore, nurses are recommended to use eye mask in combination with current treatments for improving patients’ sleep quality.

Circadian Disruption Alters the Effects of Lipopolysaccharide Treatment on Circadian and Ultradian Locomotor Activity and Body Temperature Rhythms of Female Siberian Hamsters.

The effect of circadian rhythm (CR) disruption on immune function depends on the method by which CRs are disrupted. Behavioral and thermoregulatory responses induced by lipopolysaccharide (LPS) treatment were assessed in female Siberian hamsters in which circadian locomotor activity (LMA) rhythms were eliminated by exposure to a disruptive phase-shifting protocol (DPS) that sustains arrhythmicity even when hamsters are housed in a light-dark cycle. This noninvasive treatment avoids genome manipulations and neurological damage associated with other models of CR disruption. Circadian rhythmic (RHYTH) and arrhythmic (ARR) hamsters housed in a 16L:8D photocycle were injected with bacterial LPS near the onset of the light (zeitgeber time 1; ZT1) or dark (ZT16) phase. LPS injections at ZT16 and ZT1 elicited febrile responses in both RHYTH and ARR hamsters, but the effect was attenuated in the arrhythmic females. In ZT16, LPS inhibited LMA in the dark phase immediately after injection but not on subsequent nights in both chronotypes; in contrast, LPS at ZT1 elicited more enduring (~4 day) locomotor hypoactivity in ARR than in RHYTH hamsters. Power and period of dark-phase ultradian rhythms (URs) in LMA and Tb were markedly altered by LPS treatment, as was the power in the circadian waveform. Disrupted circadian rhythms in this model system attenuated responses to LPS in a trait- and ZT-specific manner; changes in UR period and power are novel components of the acute-phase response to infection that may affect energy conservation.

Modafinil Increases Awake EEG Activation and Improves Performance in Obstructive Sleep Apnea during Continuous Positive Airway Pressure Withdrawal.

We examined the changes in waking electroencephalography (EEG) biomarkers with modafinil during continuous positive airway pressure (CPAP) withdrawal in patients with obstructive sleep apnea (OSA) to investigate neurophysiological evidence for potential neurocognitive improvements. Randomized double-blind placebo-controlled crossover study. CPAP was used for the first night and then withdrawn for 2 subsequent nights. Each morning after the 2 CPAP withdrawal nights, patients received either 200 mg modafinil or placebo. After a 5-w washout, the procedure repeated with the crossover drug. University teaching hospital. Stable CPAP users (n = 23 men with OSA). Karolinska Drowsiness Test (KDT) (awake EEG measurement with eyes open and closed), Psychomotor Vigilance Task (PVT), and driving simulator Performance were assessed bihourly during the 3 testing days following CPAP treatment and CPAP withdrawal nights. Compared to placebo, modafinil significantly increased awake EEG activation (faster EEG frequency) with increased alpha/delta (A/D) ratio (P < 0.0001) and fast ratio = (alpha+beta)/(delta+theta) (P < 0.0001) across the 2 days of CPAP withdrawal. The A/D ratio significantly correlated with the driving simulator response time (P = 0.015), steering variation (P = 0.002), and PVT reaction time (P = 0.006). In contrast, individual EEG band power of alpha, beta, theta, and delta did not correlate with any neurocognitive performance. Modafinil administration during continuous positive airway pressure (CPAP) withdrawal increased awake EEG activation, which correlated to improved performance. This study provides supporting neurophysiological evidence that modafinil is a potential short-term treatment option during acute CPAP withdrawal.

Participation of irradiated Anopheles arabiensis males in swarms following field release in Sudan.

BackgroundThe success of the sterile insect technique (SIT) depends the release of large numbers of sterile males, which are able to compete for mates with the wild male population within the target area. Unfortunately, the processes of colonisation, mass production and irradiation may reduce the competitiveness of sterile males through genetic selection, loss of natural traits and somatic damage. In this context, the capacity of released sterile Anopheles arabiensis males to survive, disperse and participate in swarms at occurring at varying distances from the release site was studied using mark-release-recapture (MRR) techniques.MethodsIn order to assess their participation in swarms, irradiated and marked laboratory-reared male mosquitoes were released 50, 100 or 200 m from the known site of a large swarm on three consecutive nights. Males were collected from this large swarm on subsequent nights. Over the three days a total of 8,100 males were released. Mean distance travelled (MDT), daily probability of survival and estimated population size were calculated from the recapture data. An effect of male age at the time of release on these parameters was observed.ResultsFive per cent of the males released over three days were recaptured. In two-, three- and four-day-old males, MDT was 118, 178 and 170 m, and the daily survival probability 0.95, 0.90 and 0.75, respectively. From the recapture data on the first day following each release, the Lincoln index gives an estimation of 32,546 males in the natural population.DiscussionSterile An. arabiensis males released into the field were able to find and participate in existing swarms, and possibly even initiate swarms. The survival probability decreased with the age of male on release but the swarm participation and the distance travelled by older males seemed higher than for younger males. The inclusion of a pre-release period may thus be beneficial to male competitiveness and increase the attractiveness of adult sexing techniques, such as blood spiking.

P165 Ambulatory Management Of Suspected Pulmonary Embolism At A Districtgeneralhospital. A 2 Year Review

Background Studies have suggested that outpatient (OP) management of suspected pulmonary embolism (PE) is feasable. 1 At our DGH (popn 289400) in 2012 we found that over a 2 month period most suspected PE patients (suitable for ambulatory care) were being identified resulting in significant (17 nights) bed savings. 2 The aims of repeating our study were 1) to ascertain the proportion of patients who had a CTPA that were managed as OP and subsequent nights saved 2) to identify any further patients that could have been managed as OP and potential nights saved 3) a comparison with 2012 Methods RADIS was used to collect all CTPA’s performed between 1st Jan 2014 and 28th February 2014. Inclusion criteria: Ambulatory, normal heart rate, respiratory rate, blood pressure and oxygen saturations, any patient who was managed as an OP. Simpflified PESI Score 2 weeks, sPESI Score >1, clinical concern. Results For the above period 102 CTPA’s were performed (105 in 2012). Average time from request to CTPA was 4.7 h (0.5–24 h. 4.1 hrs in 2012) Figure 1 shows the excluded patients.9 patients were included;7 were female, average age 47 years (23–66 years). All had a sPESI score Conclusion The number of ambulatory patients investigated for PE has reduced from 2012 to 2014 which probably reflects an increased acute physician presence at our DGH but some bed savings (7 nights over our 2 month period) were still made. Over 2 years approximately 180 ambulatory patients have been investigated and managed for PE at our DGH with no adverse incidents to date. References Hogg K et al . Emerg Med J 2006;23:123–127 Benjamin JA et al . Thorax 2012;67:A123