Novel metrics of sleep-disordered breathing are associated with outcome after ischemic stroke

OBJECTIVE/BACKGROUND

Standard measures of sleep-disordered breathing (SDB) that rely on count data may not sufficiently capture SDB severity or reflect downstream consequences of SDB. We hypothesized that novel metrics derived from pulse rate, oxygen saturation, and nasal pressure would be associated with stroke outcomes.

PATIENTS/METHODS

Shortly after ischemic stroke, participants in a population-based study were offered ApneaLink Plus testing. Signal analysis was used to generate 166 metrics from the nasal pressure cannula and finger probe, categorized as: autonomic (based on pulse rate variability), oximetry-derived, nasal pressure-derived, and mixed oxygen and nasal pressure-derived measures. Three-month outcome assessments included functional and cognitive outcomes and stroke recurrence. Tobit regression and Cox proportional hazards models were used to examine associations between each sleep apnea metric and the three outcomes, unadjusted and adjusted for multiple potential confounders. Models were adjusted for multiple comparisons.

RESULTS

Of the 530 participants, the median age was 65 (IQR: 57, 73), 49 % were female, and 64 % were Mexican American. Without covariate adjustment, 23 of 166 variables were associated with functional outcome, 43 were associated with cognitive outcome, and 1 was associated with stroke recurrence. After adjustment, 7 mixed, oximetry, or nasal pressure-based metrics and 1 autonomic metric were associated with functional outcome, but none was associated with cognitive outcome or stroke recurrence.

CONCLUSIONS

Many novel metrics of SDB were associated with important stroke outcomes, and 8 novel metrics were associated with functional outcome in adjusted models. This raises hypotheses about pathways by which SDB may negatively impact stroke outcomes.

Lateralized neonatal EEG coherence during sleep predicts language outcome

BACKGROUND

Enriched language exposure may benefit infants in the neonatal intensive care unit. We hypothesized that changes in neonatal electroencephalogram (EEG) coherence during sleep, in response to maternal voice exposure, predict language development.

METHODS

Convalescent neonates underwent 12-h polysomnography. A recording of the mother's voice was randomized to continuous playback in the first or second 6 h. We calculated the imaginary coherence (ICOH-a measure of functional connectivity) between EEG leads. Spearman correlations were computed between ICOH and 18-month Bayley-III language scores.

RESULTS

Thirty-five neonates were included (N = 18 33-to-<35 weeks gestation; N = 17 ≥ 35 weeks). Predictive value of ICOH during neonatal non-rapid eye movement (NREM) sleep was left lateralized, and varied with gestational age and voice playback. ICOH in the left-hemispheric (C3-Cz; T3-Cz) channels across multiple EEG frequency bands was associated with 18-month language scores (rho = -0.34 to -0.48). The association was driven by neonates born at 33-34 weeks gestation, and a trend suggested a possible effect of maternal voice at some EEG frequencies. Right hemisphere ICOH (C4-Cz; T4-Cz) was not associated with language outcome.

CONCLUSIONS

Left-hemispheric EEG functional connectivity during neonatal NREM sleep shows early signs of physiologic asymmetry that may predict language development. We speculate that sleep analyses could have unique prognostic value.

IMPACT

During neonatal NREM sleep, EEG functional connectivity predicts future language development. Left temporal and central EEG coherence-specifically the imaginary component of coherence-is predictive, whereas the same analysis from the right hemisphere is not. These results appear to vary according to the infant's gestational age, and a trend suggests they may be enhanced by measuring functional connectivity during exposure to the mother's voice. These findings identify early evidence of physiologic differentiation within the cerebral hemispheres and raise the possibility that neonatal NREM sleep has a role to play in language development.

Maternal Voice and Infant Sleep in the Neonatal Intensive Care Unit

BACKGROUND

Approximately 10% of US newborns require a NICU. We evaluated whether the NICU acoustic environment affects neonatal sleep and whether exposure to the mother's voice can modulate that impact.

METHODS

In a level IV NICU with single-infant rooms, 47 neonates underwent 12-hour polysomnography. Their mothers were recorded reading children's books. Continuous maternal voice playback was randomized to either the first or second 6 hours of the polysomnogram. Regression models were used to examine sleep-wake stages, entropy, EEG power, and the probability of awakening in response to ambient noise during and without voice playback.

RESULTS

After epochs with elevated noise, the probability was higher with (versus without) maternal voice exposure of neonates staying asleep (P = .009). However, the 20 neonates born at ≥35 weeks' gestation, in contrast to those born at 33 to 34 weeks, showed an age-related increase in percent time awake (R ² = 0.52; P < .001), a decrease in overall sleep (R ² = 0.52; P < .001), a reduction in rapid eye movement sleep bouts per hour (R ² = 0.35; P = .003), and an increase in sleep-wake entropy (R ² = 0.52; P < .001) all confined solely to the 6 hours of maternal voice exposure. These associations remained significant (P = .02 to P < .001) after adjustment for neurologic examination scores and ambient noise.

CONCLUSIONS

Hospitalized newborns born at ≥35 weeks' gestation but not at 33 to 34 weeks' gestation show increasing wakefulness in response to their mother's voice. However, exposure to the mother's voice during sleep may also help protect newborns from awakening after bursts of loud hospital noise.

Neonatal Sleep-Wake Analyses Predict 18-month Neurodevelopmental Outcomes

Objectives

The neurological examination of critically ill neonates is largely limited to reflexive behavior. The exam often ignores sleep-wake physiology that may reflect brain integrity and influence long-term outcomes. We assessed whether polysomnography and concurrent cerebral near-infrared spectroscopy (NIRS) might improve prediction of 18-month neurodevelopmental outcomes.

Methods

Term newborns with suspected seizures underwent standardized neurologic examinations to generate Thompson scores and had 12-hour bedside polysomnography with concurrent cerebral NIRS. For each infant, the distribution of sleep-wake stages and electroencephalogram delta power were computed. NIRS-derived fractional tissue oxygen extraction (FTOE) was calculated across sleep-wake stages. At age 18-22 months, surviving participants were evaluated with Bayley Scales of Infant Development (Bayley-III), 3rd edition.

Results

Twenty-nine participants completed Bayley-III. Increased newborn time in quiet sleep predicted worse 18-month cognitive and motor scores (robust regression models, adjusted r2 = 0.22, p = .007, and 0.27, .004, respectively). Decreased 0.5-2 Hz electroencephalograph (EEG) power during quiet sleep predicted worse 18-month language and motor scores (adjusted r2 = 0.25, p = .0005, and 0.33, .001, respectively). Predictive values remained significant after adjustment for neonatal Thompson scores or exposure to phenobarbital. Similarly, an attenuated difference in FTOE, between neonatal wakefulness and quiet sleep, predicted worse 18-month cognitive, language, and motor scores in adjusted analyses (each p < .05).

Conclusions

These prospective, longitudinal data suggest that inefficient neonatal sleep-as quantified by increased time in quiet sleep, lower electroencephalogram delta power during that stage, and muted differences in FTOE between quiet sleep and wakefulness-may improve prediction of adverse long-term outcomes for newborns with neurological dysfunction.

Do respiratory cycle-related EEG changes or arousals from sleep predict neurobehavioral deficits and response to adenotonsillectomy in children?

STUDY OBJECTIVES

Pediatric obstructive sleep apnea (OSA) is associated with hyperactive behavior, cognitive deficits, psychiatric morbidity, and sleepiness, but objective polysomnographic measures of OSA presence or severity among children scheduled for adenotonsillectomy have not explained why. To assess whether sleep fragmentation might explain neurobehavioral outcomes, we prospectively assessed the predictive value of standard arousals and also respiratory cycle-related EEG changes (RCREC), thought to reflect inspiratory microarousals.

METHODS

Washtenaw County Adenotonsillectomy Cohort II participants included children (ages 3-12 years) scheduled for adenotonsillectomy, for any clinical indication. At enrollment and again 7.2 ± 0.9 (SD) months later, children had polysomnography, a multiple sleep latency test, parent-completed behavioral rating scales, cognitive testing, and psychiatric evaluation. The RCREC were computed as previously described for delta, theta, alpha, sigma, and beta EEG frequency bands.

RESULTS

Participants included 133 children, 109 with OSA (apnea-hypopnea index [AHI] ≥ 1.5, mean 8.3 ± 10.6) and 24 without OSA (AHI 0.9 ± 0.3). At baseline, the arousal index and RCREC showed no consistent, significant associations with neurobehavioral morbidities, among all subjects or the 109 with OSA. At follow-up, the arousal index, RCREC, and neurobehavioral measures all tended to improve, but neither baseline measure of sleep fragmentation effectively predicted outcomes (all p > 0.05, with only scattered exceptions, among all subjects or those with OSA).

CONCLUSION

Sleep fragmentation, as reflected by standard arousals or by RCREC, appears unlikely to explain neurobehavioral morbidity among children who undergo adenotonsillectomy.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, ID: NCT00233194.

The face of sleepiness: improvement in appearance after treatment of sleep apnea

STUDY OBJECTIVES

Anecdote but no formal evidence suggests that facial appearance improves after hypersomnolent patients with obstructive sleep apnea are treated. We investigated whether masked volunteer raters can identify post- rather than pre-treatment images as looking more alert, and whether impressions are predicted by any objective changes on highly precise 3-dimensional digital photogrammetry.

METHODS

Participants included 20 adults with obstructive sleep apnea on polysomnography and excessive sleepiness on Epworth Sleepiness Scales. Photogrammetry was performed before and after ≥ 2 months of adherent use of positive airway pressure. Twenty-two raters then assessed pre- and post-treatment facial images, paired side-by-side in random order.

RESULTS

Subjects included 14 men and 6 women, with mean age 45 ± 11 (SD) years and mean baseline apnea/hypopnea index of 26 ± 21. The 22 raters twice as often identified post-treatment rather than pre-treatment images to look more alert (p = 0.0053), more youthful (p = 0.026), more attractive (p = 0.0068), and more likely to reflect the treated state (p = 0.015). Photogrammetry documented post-treatment decreases in forehead surface volume and decreased infraorbital and cheek redness, but no narrowing of the interpalpebral fissure. Decreased deep NREM sleep at baseline, and pre- to post-treatment decrements in facial redness showed promise as predictors of improved subjective ratings for alertness.

CONCLUSIONS

Patients with obstructive sleep apnea are perceived to appear more alert, more youthful, and more attractive after adherent use of positive airway pressure. Objective changes in facial surface volume and color were identified. Post-treatment decrements in redness may inform subjective impressions of improved alertness.

Sleep-wake cycling and cerebral oxygen metabolism among critically ill neonates

Among adults, wakefulness and rapid eye movement (REM) sleep, compared to non-REM sleep, require higher overall brain metabolism, but in neonates analogous data are not available. Behavioral states with higher metabolic demand could increase vulnerability to hypoperfusion or hypoxia in the compromised neonatal brain. Using cerebral oximetry (near-infrared spectroscopy), and simultaneous polysomnography, we evaluated whether brain oxygen metabolism varies by sleep-wake state among critically ill newborns. For each of 10 infants, sleep-wake cycling was detectable and cerebral oximetry varied (P < .0001) across behavioral states, but the patterns differed among subjects. We conclude that cerebral oxygen metabolism varies with sleep-wake states in high-risk newborns. The direction and degree of these changes are variable and subject-specific in this initial sample, but could reflect or affect brain injury and vulnerability.

Quantitative sleep stage analyses as a window to neonatal neurologic function

OBJECTIVE

To test the hypothesis that neonatal sleep physiology reflects cerebral dysfunction, we compared neurologic examination scores to the proportions of recorded sleep/wake states, sleep depth, and sleep fragmentation in critically ill neonates.

METHODS

Newborn infants (≥35 weeks gestation) who required intensive care and were at risk for seizures were monitored with 8- to 12-hour polysomnograms (PSGs). For each infant, the distribution of sleep-wake states, entropy of the sequence of state transitions, and delta power from the EEG portion of the PSG were quantified. Standardized neurologic examination (Thompson) scores were calculated.

RESULTS

Twenty-eight infants participated (mean gestational age 39.0 ± 1.6 weeks). An increased fraction of quiet sleep correlated with worse neurologic examination scores (Spearman rho = 0.54, p = 0.003), but the proportion of active sleep did not (p > 0.1). Higher state entropy corresponded to better examination scores (rho = -0.43, p = 0.023). Decreased delta power during quiet sleep, but not the power at other frequencies, was also associated with worse examination scores (rho = -0.48, p = 0.009). These findings retained significance after adjustment for gestational age or postmenstrual age at the time of the PSG. Sleep stage transition probabilities were also related to examination scores.

CONCLUSIONS

Among critically ill neonates at risk for CNS dysfunction, several features of recorded sleep-including analyses of sleep stages, depth, and fragmentation-showed associations with neurologic examination scores. Quantitative PSG analyses may add useful objective information to the traditional neurologic assessment of critically ill neonates.

Limited short-term prognostic utility of cerebral NIRS during neonatal therapeutic hypothermia

OBJECTIVE

We evaluated the utility of amplitude-integrated EEG (aEEG) and regional oxygen saturation (rSO2) measured using near-infrared spectroscopy (NIRS) for short-term outcome prediction in neonates with hypoxic ischemic encephalopathy (HIE) treated with therapeutic hypothermia.

METHODS

Neonates with HIE were monitored with dual-channel aEEG, bilateral cerebral NIRS, and systemic NIRS throughout cooling and rewarming. The short-term outcome measure was a composite of neurologic examination and brain MRI scores at 7 to 10 days. Multiple regression models were developed to assess NIRS and aEEG recorded during the 6 hours before rewarming and the 6-hour rewarming period as predictors of short-term outcome.

RESULTS

Twenty-one infants, mean gestational age 38.8 ± 1.6 weeks, median 10-minute Apgar score 4 (range 0-8), and mean initial pH 6.92 ± 0.19, were enrolled. Before rewarming, the most parsimonious model included 4 parameters (adjusted R(2) = 0.59; p = 0.006): lower values of systemic rSO2 variability (p = 0.004), aEEG bandwidth variability (p = 0.019), and mean aEEG upper margin (p = 0.006), combined with higher mean aEEG bandwidth (worse discontinuity; p = 0.013), predicted worse short-term outcome. During rewarming, lower systemic rSO2 variability (p = 0.007) and depressed aEEG lower margin (p = 0.034) were associated with worse outcome (model-adjusted R(2) = 0.49; p = 0.005). Cerebral NIRS data did not contribute to either model.

CONCLUSIONS

During day 3 of cooling and during rewarming, loss of physiologic variability (by systemic NIRS) and invariant, discontinuous aEEG patterns predict poor short-term outcome in neonates with HIE. These parameters, but not cerebral NIRS, may be useful to identify infants suitable for studies of adjuvant neuroprotective therapies or modification of the duration of cooling and/or rewarming.

Do snoring sounds arouse the snorer?

STUDY OBJECTIVES

Respiratory cycle-related electroencephalographic (EEG) changes (RCREC), especially in delta and sigma frequencies, are thought to reflect subtle, breath-to-breath inspiratory microarousals that are exacerbated in association with increased work of breathing in obstructive sleep apnea (OSA). We wondered whether snoring sounds could create these microarousals, and investigated whether earplugs, anticipated to alter snoring perception, might affect RCREC.

DESIGN

Randomized controlled trial.

SETTING

An accredited, academic sleep laboratory.

PATIENTS

Adults (n = 400) referred for suspected OSA.

INTERVENTIONS

Subjects were randomly assigned to use earplugs or not during a night of diagnostic polysomnography.

RESULTS

Two hundred three of the participants were randomized to use earplugs. Earplug use was associated with lower RCREC in delta EEG frequencies (0.5-4.5 Hz), although not in other frequencies, after controlling for potential confounds (P = 0.048). This effect of earplug use was larger among men in comparison with women (interaction term P = 0.046), and possibly among nonobese subjects in comparison with obese subjects (P = 0.081). However, the effect of earplug use on delta RCREC did not differ significantly based on apnea severity or snoring prominence as rated by sleep technologists (P > 0.10 for each).

CONCLUSIONS

This randomized controlled trial is the first study to show that perception of snoring sounds, as modulated by earplugs, can influence the cortical EEG during sleep. However, the small magnitude of effect, lack of effect on RCREC in EEG frequencies other than delta, and absence of effect modulation by apnea severity or snoring prominence suggest that perception of snoring is not the main explanation for RCREC.

Respiratory cycle-related EEG changes: response to CPAP

STUDY OBJECTIVES

Respiratory cycle-related EEG changes (RCREC) quantify statistically significant synchrony between respiratory cycles and EEG spectral power, vary to some extent with work of breathing, and may help to predict sleepiness in patients with obstructive sleep apnea. This study was designed to assess the acute response of RCREC to relief of upper airway obstruction by positive airway pressure (PAP).

DESIGN

Comparison of RCREC between baseline diagnostic polysomnograms and PAP titration studies.

SETTING

Accredited academic sleep disorders center.

PATIENTS

Fifty adults referred for suspected sleep disordered breathing.

INTERVENTIONS

For each recording, the RCREC in specific physiologic EEG frequency ranges were computed as previously described for the last 3 h of sleep not occupied by apneic events.

RESULTS

The sample included 27 women; mean age was 47 ± 11 (SD) years; and median respiratory disturbance index at baseline was 24 (inter-quartile range 15-43). Decrements in RCREC, from baseline to PAP titration, reached 43%, 24%, 14%, 22%, and 31% for delta (P = 0.0004), theta (P = 0.01), alpha (P = 0.10), sigma (P = 0.08), and beta (P = 0.01) EEG frequency ranges, respectively. Within each specific sleep stage, these reductions from baseline to PAP studies in synchrony between EEG power and respiratory cycles still reached significance (P < 0.05) for one or more EEG frequency ranges and for all frequency ranges during REM sleep.

CONCLUSIONS

RCREC tends to diminish acutely with alleviation of upper airway obstruction by PAP. These data in combination with previous observations support the hypothesis that RCREC reflect numerous, subtle, brief, but consequential inspiratory microarousals.

What do plasma beta-endorphin levels reveal about endogenous opioid analgesic function?

Plasma levels of beta-endorphin (BE), an endogenous opioid analgesic, are often reported as they relate to acute and chronic pain outcomes. However, little is known about what resting plasma BE levels might reveal about functioning of the endogenous opioid antinociceptive system. This study directly examined associations between resting plasma BE and subsequent endogenous opioid analgesic responses to acute pain in 39 healthy controls and 37 individuals with chronic low back pain (LBP). Resting baseline levels of plasma BE were assessed. Next, participants received opioid blockade (8 mg naloxone i.v.) or placebo in a double-blind, randomized, crossover design. Participants then underwent two acute pain stimuli: finger pressure (FP) pain and ischaemic (ISC) forearm pain. Blockade effects (naloxone minus placebo pain ratings) were derived to index endogenous opioid analgesic function. In placebo condition analyses for both pain stimuli, higher resting BE levels were associated with subsequently greater reported pain intensity (p's < 0.05), with this effect occurring primarily in healthy controls (BE × Participant Type interactions, p's < 0.05). In blockade effect analyses across both pain tasks, higher resting plasma BE predicted less subsequent endogenous opioid analgesia (smaller blockade effects; p's < 0.05). For the ISC task, these links were significantly more prominent in LBP participants (BE × Participant Type Interactions, p's < 0.05). Results suggest that elevated resting plasma BE may be a potential biomarker for reduced endogenous opioid analgesic capacity, particularly among individuals with chronic pain. Potential clinical implications are discussed.

Engineering better sleep

Sleep medicine is a growing field with multidisciplinary origins in physiological monitoring techniques, on which it still largely depends. Collaborations between engineers and sleep specialists offer substantial opportunities to improve on current approaches to diagnosis and assessment of patients with sleep problems. Such collaborations could also prove key to improved fundamental understanding of the pathophysiology that underlies sleep disorders and their adverse impact on the brain, cardiovascular system, and optimal health.

Sleep stage dynamics differ between children with and without obstructive sleep apnea

STUDY OBJECTIVES

Analysis of sleep dynamics--distributions of contiguous sleep and sleep stage durations--reveal exponential distributions and potential clinical utility in adults. We sought to examine these polysomnographic variables for the first time in children, and in the context of childhood sleep disordered breathing (SDB).

DESIGN AND SETTING

Analysis of polysomnographic data available from the Washtenaw County Adenotonsillectomy Cohort.

PARTICIPANTS

Selected subjects were 48 children aged 5-12 years with SDB (pediatric apnea/hypopnea index > or = 1.5) who were scheduled for adenotonsillectomy and 20 control subjects of similar ages without SDB. Subjects were studied at enrollment and again one year later in almost all cases.

RESULTS

Durations of sleep and specific sleep stage bouts generally followed exponential distributions. At baseline, the number of sleep stage changes, proportion of total sleep time occupied by stage 1 sleep, proportion stage 2 sleep, mean stage 2 duration, and mean stage REM duration each distinguished subjects with and without SDB (P < 0.05), but only mean stage 2 duration did so independently after accounting for the other variables (P = 0.03). At one-year follow-up, changes in total sleep time, mean stage 2 duration, and mean stage REM duration distinguished SDB from control subjects, but again only changes in mean stage 2 duration did so independently (P = 0.01).

CONCLUSIONS

Durations of uninterrupted sleep and specific sleep stages appear to follow exponential distributions in children with or without SDB. Parameters that describe these distributions--particularly mean duration of stage 2 sleep periods--may provide useful additions to standard sleep stage analyses.

Respiratory cycle-related EEG changes during sleep reflect esophageal pressures

STUDY OBJECTIVES

Respiratory cycle-related EEG changes (RCREC) have been demonstrated during sleep by digital analysis and hypothesized to represent subtle inspiratory microarousals that may help to explain daytime sleepiness in patients with sleep-disordered breathing. We therefore examined for the first time associations between RCREC and esophageal pressure swings (deltaPes) that reflect work of breathing.

DESIGN

Retrospective analysis.

SETTING

Academic sleep laboratory.

PATIENTS

Forty adults referred for suspected sleep disordered breathing.

INTERVENTIONS

Polysomnography with esophageal pressure monitoring and automatic computation of deltaPes using a novel algorithm.

RESULTS

Computed deltaPes for nearly all respiratory cycles during sleep correlated well with visual scoring of selected respiratory cycle samples (Spearman rho = 0.86, P < 0.0001). The RCREC within the sigma EEG range (12.5-15.5 Hz) rather than that within other frequency ranges most often showed significant within-subject inverse correlations with deltaPes. In contrast, in between-subject comparisons, beta (15.5-30.5 Hz) and to a lesser extent theta (4.5-7.5 Hz) RCREC, rather than sigma RCREC, showed significant inverse associations with mean APes.

CONCLUSIONS

Variation within subjects of sigma RCREC with APes supports previous evidence that RCREC within this range may reflect microarousals exacerbated by increased work of breathing. Correlation of beta and theta, but not sigma RCREC with deltaPes in between-subject comparisons is more difficult to explain but suggests that ranges other than sigma also deserve further investigation for clinical utility.

Relationships among patient hostility, anger expression, depression, and the working alliance in a work hardening program

Hostility, anger expression, and depression may adversely affect the response of chronic pain patients to pain or functional restoration programs by hampering the development of good working alliances between patients and physical or occupational therapists. Measures of hostility, anger expression, and depression and the Working Alliance Inventory (WAI) were completed by 71 patients with chronic pain (stemming from work-related injuries) prior to starting a "work hardening" program. The physical or occupational therapist acting as any given patient's "program manager" completed the WAI, as well. Hostility and anger expression were correlated negatively only with patient ratings of the working alliance. Therapist ratings were predicted by the interaction of patient anger expression and depression, such that therapists reported their poorest alliances with patients who were both depressed and expressed anger. Results imply that hostility and the propensity to express anger may diminish a pain patient's capacity to foster a collaborative relationship with physical or occupational therapists, while therapists may readily become alienated from depressed and irritable patients.

Sleep stage dynamics in fibromyalgia patients and controls

OBJECTIVE

To determine whether previously described sleep stage dynamics, reflecting the mean duration of specific sleep stages, may have clinical utility in a sample of patients with fibromyalgia syndrome (FMS) and controls.

METHODS

Women with FMS (n=15, screened to exclude other sleep disorders) and age-matched women in good health (n=15) were studied with nocturnal polysomnography, multiple sleep latency tests, 2-week pain diaries, and a measure of current pain intensity.

RESULTS

The FMS subjects, in comparison to controls, did not show differences in several common polysomnographic measures, except for increased numbers of stage shifts (126+/-27 vs. 107+/-22, p=.042). Mean durations for episodes of total sleep, stage 1 sleep, stage 3/4 sleep, and rapid eye movement sleep failed to distinguish FMS and control subjects (Wilcoxon rank sum tests, p>.10 for each), but those for stage 2 sleep were shorter in the FMS subjects (p=.006), possibly because transitions to stage 3/4 sleep occurred more quickly (p=.036). Shorter stage 2 sleep durations predicted higher pain diary scores (Spearman rho=-.56, p=.0014) and current pain intensity (rho=-.71, p<0.0001).

CONCLUSIONS

Sleep stage dynamic, and, more specifically, shorter durations of sleep stage 2 periods, distinguish FMS and control female subjects and may predict pain levels experienced in FMS. Analysis of the lengths of individual sleep stages, in addition to the usual sleep stage amounts and percentages listed in standard polysomnogram reports, may have clinical utility.

EMG variance during polysomnography as an assessment for REM sleep behavior disorder

STUDY OBJECTIVES

In a previous study, we validated a polysomnographic assessment for REM sleep behavior disorder (RBD). The method proved to be reliable but required slow, labor-intensive visual scoring of surface electromyogram (EMG) activity. We therefore developed a computerized metric to assess EMG variance and compared the results to those previously published for visual scoring, bed partner-rated RBD symptom scores, and clinical assessments by sleep medicine specialists.

DESIGN

Retrospective validation of new computer algorithm.

SETTING

Sleep research laboratory

PARTICIPANTS

Twenty-three subjects: 17 with neurodegenerative disorders (9 with probable or possible RBD), and 6 controls.

INTERVENTIONS

N/A METHODS: We visually scored 2 consecutive nocturnal polysomnograms for each subject. A computer algorithm calculated the variance of the chin EMG during all 3-second mini-epochs, and compared variances during REM sleep to a threshold defined by variances during quiet NREM sleep. The percentage of all REM mini-epochs with variance above this threshold created a metric, which we refer to as the supra-threshold REM EMG activity metric (STREAM) for each subject.

RESULTS

The STREAM correlated highly with the visually-derived score for RBD severity (Spearman rho = 0.87, P < 0.0001). A clinical impression of probable or possible RBD was associated to a similar extent with both STREAM (Wilcoxon rank sum test, P = 0.009) and the visually-derived score (P = 0.018). An optimal STREAM cutoff identified probable or possible RBD with 100% sensitivity and 71% specificity. The RBD symptom score correlated with both STREAM (rho = 0.42, P = 0.046) and the visual score (rho = 0.42, P = 0.048).

CONCLUSIONS

These results suggest that a new, automated assessment for RBD may provide as much utility as a more time-consuming manual approach.

Subjective sleepiness and polysomnographic correlates in children scheduled for adenotonsillectomy vs other surgical care

STUDY OBJECTIVE

To compare a validated subjective measure of childhood sleepiness to an objective determination, assess the frequency of problematic sleepiness among children with suspected sleep-disordered breathing (SDB), and examine what standard or investigational polysomnographic measures of SDB predict subjective sleepiness.

DESIGN

Prospective, cross-sectional.

SETTING

University-based sleep disorders laboratory.

PARTICIPANTS

Washtenaw County Adenotonsillectomy Cohort.

INTERVENTION

Polysomnography followed by Multiple Sleep Latency Tests (MSLTs) in 103 children aged 5 to 12 years old: 77 were scheduled for clinically indicated adenotonsillectomy, usually for suspected SDB, and 26 for unrelated surgical care. Parents completed the previously validated, 4-item Pediatric Sleep Questionnaire-Sleepiness Subscale (PSQ-SS).

RESULTS

Thirty-three (43%) of the children scheduled for adenotonsillectomy had high PSQ-SS scores, in comparison with only 3 (12%) of the controls (p = .004). The PSQ-SS scores correlated inversely with mean sleep latencies on the MSLTs (rho = -0.23, p = .006). The obstructive apnea index, apnea-hypopnea index, and respiratory disturbance index (which included respiratory event-related arousals identified by esophageal pressure monitoring) each correlated similarly with PSQ-SS scores, as did investigational quantification of esophageal pressures and respiratory cycle-related electroencephalographic changes (each rho approximately 0.30, p < .02). A stepwise regression identified sigma-frequency respiratory cycle-related electroencephalographic changes as the strongest independent predictor of subjective sleepiness among all subjects and particularly among those without obstructive sleep apnea.

CONCLUSIONS

Sleepiness is a frequent problem among children with suspected SDB. Subjective sleepiness (PSQ-SS) reflects MSLT results to a limited extent, as in adults. Standard polysomnographic measures of SDB predict subjective sleepiness, but respiratory cycle-related electroencephalographic changes may offer additional clinical utility.

Altered cardiovascular/pain regulatory relationships in chronic pain

In healthy individuals, there is an inverse relationship between resting blood pressure (BP) and pain sensitivity. This study examined possible dysregulation of this adaptive relation in chronic pain patients, and tested whether the extent of this dysregulation is a function of pain duration. Continuous resting BP's were assessed for 5 min after a 5-min rest period in 121 chronic benign pain patients. Unlike the inverse relationship observed previously in normals, mean resting diastolic. BPs during the assessment period were correlated positively with ratings of pain severity. A Pain Duration x Systolic BP interaction emerged (p < .05) such that the magnitude of the BP-pain relation was greatest in patients with the longest duration of pain, r(38) = .50, p < .001. A hypothesized progressive alteration in endogenous pain regulatory systems in chronic pain patients was supported. A possible role of endogenous opioid dysfunction in accounting for these alterations is discussed.

Electroencephalographic Changes during Respiratory Cycles Predict Sleepiness in Sleep Apnea

Common polysomnographic measures of sleep-disordered breathing have shown a disappointing ability to predict important consequences such as excessive daytime sleepiness. Using novel analytic techniques, this study tested the hypothesis that numerous, brief disruptions in cortical activity could occur on a breath-to-breath basis during nonapneic sleep. Spectral analysis proved the existence of respiratory cycle-related electroencephalographic changes in each of 38 adult patients evaluated by polysomnography for sleep-disordered breathing. Furthermore, the tendency for sigma (13-15 Hz) electroencephalographic power to vary with the respiratory cycle predicted next-day sleepiness as measured by the multiple sleep latency test. The predictive value was enhanced when the analysis was limited to those 27 patients who had sleep-disordered breathing (more than 5 apneas or hypopneas per hour of sleep). In contrast, nocturnal rates of apneas and hypopneas, as well as minimal oxygen saturation, did not predict sleepiness as well. On average, sigma power increased notably during inspiration, whereas delta (1-4 Hz) power showed a simultaneous decrease. We conclude that electroencephalographic activity shows detectable changes during nonapneic respiratory cycles in adults evaluated for sleep-disordered breathing. Quantification of these changes, which may reflect numerous inspiratory microarousals, could prove useful in prediction of excessive daytime sleepiness.

Method for detection of respiratory cycle-related EEG changes in sleep-disordered breathing

STUDY OBJECTIVES

In sleep-disordered breathing (SDB), visual or computerized analysis of electroencephalogram (EEG) signals shows that disruption of sleep architecture occurs in association with apneas and hypopneas. We developed a new signal analysis algorithm to investigate whether brief changes in cortical activity can also occur with individual respiratory cycles.

DESIGN

Retrospective.

SETTING

University sleep laboratory.

PARTICIPANTS

A 6 year-old boy with SDB.

INTERVENTION

Polysomnography before and after clinically indicated adenotonsillectomy.

MEASUREMENTS

For the first 3 hours of nocturnal sleep, a computer algorithm divided nonapneic respiratory cycles into 4 segments and, for each, computed mean EEG powers within delta, theta, alpha, sigma, and beta frequency ranges. Differences between segment-specific EEG powers were tested by analysis of variance. Respiratory cycle-related EEG changes (RCREC) were quantified.

RESULTS

Preoperative RCREC were statistically significant in delta (P < .0001), theta (P < .001), and sigma (P < .0001) but not alpha or beta (P > .01) ranges. One year after the operation, RCREC in all ranges showed statistical significance (P < .01), but delta, theta, and sigma RCREC had decreased, whereas alpha and beta RCREC had increased. Preoperative RCREC also were demonstrated in a sequence of 101 breaths that contained no apneas or hypopneas (P < .0001). Several tested variations in the signal-analysis approach, including analysis of the entire nocturnal polysomnogram, did not meaningfully improve the significance of RCREC.

CONCLUSIONS

In this child with SDB, the EEG varied with respiratory cycles to a quantifiable extent that changed after adenotonsillectomy. We speculate that RCREC may reflect brief but extremely numerous microarousals.

Correlates of Respiratory Cycle-Related EEG Changes in Children with Sleep-Disordered Breathing

STUDY OBJECTIVES

To explore newly-identified respiratory cycle-related electroencephalographic changes (RCREC), which may represent microarousals, as correlates of neurobehavioral outcomes in children with sleep-disordered breathing (SDB).

DESIGN

Retrospective.

SETTING

University sleep laboratory.

PARTICIPANTS

Ten research subjects, aged 6 to 10 years, with and without SDB.

INTERVENTION

Polysomnography, Multiple Sleep Latency Tests, and tests of auditory attention before and after clinically-indicated tonsillectomy (n = 9) or hernia repair (n = 1, control).

MEASUREMENTS

For the first 3 hours of nocturnal sleep, a computer algorithm quantified the degree to which delta, theta, and alpha electroencephalographic power varied within non-apneic respiratory cycles. Correlations between the RCREC and standard objective measures of SDB, sleepiness, and attention were explored.

RESULTS

Five children had SDB (> 1 obstructive apnea per hour of sleep). Preoperative delta, theta, or alpha RCREC were statistically significant (P < .01) in all subjects except 1 without SDB and the 1 control. Theta RCREC correlated with rates of apneas and hypopneas (P = .01) and decreased after the apnea was treated. Postoperative changes in delta and theta RCREC predicted changes in Multiple Sleep Latency Test scores (rho = -0.84, P = .002; rho = -0.64, P = .05), whereas changes in rates of apneas and hypopneas did not (rho = -0.24, P = .50). Postoperative changes in attention tended to correlate with changes in delta RCREC (rho = -0.54, P = .11) more strongly than with changes in rates of apneic events (rho = -0.07, P = .84).

CONCLUSIONS

The RCREC may reflect brief but numerous microarousals that could help to explain neurobehavioral consequences of SDB.

Cognitive factors influence outcome following multidisciplinary chronic pain treatment: a replication and extension of a cross-lagged panel analysis

Reducing maladaptive cognitions is hypothesized to constitute an active therapeutic process in multidisciplinary pain programs featuring cognitive-behavioral interventions. A cross-lagged panel design was used to determine whether: a) early-treatment cognitive changes predicted late-treatment pain, interference, activity and mood changes, but not vice versa; b) three cognitive factors made unique contributions to outcome; c) substantial cognitive changes preceded substantial improvements in outcome. Sixty-five chronic pain patients, participating in a 4-week multidisciplinary program, completed measures of pain helplessness, catastrophizing, pain-related anxiety (process factors), pain severity, interference, activity level and depression (outcomes) at pre-, mid- and posttreatment. Results showed that early-treatment reductions in pain helplessness predicted late-treatment decreases in pain and interference, but not vice versa, and that early-treatment reductions in catastrophizing and pain-related anxiety predicted late-treatment improvements in pain severity, but not vice versa. Findings suggested that the three process factors predicted improvements mostly in common. However, little evidence was found that large early-treatment reductions in process variables preceded extensive improvements in pain. Findings replicate those of a recent report regarding cross-lagged effects, and offer support that cognitive changes may indeed influence late-treatment changes in outcomes.

Polyanionic polysaccharides reduce intra-abdominal adhesion and abscess formation in a rat peritonitis model

BACKGROUND

Intra-abdominal infection is complicated by adhesion and abscess formation. We have assessed the adhesion- and abscess-reducing capacity of various solution volumes and concentrations of two polyanionic polysaccharides, hyaluronan (HA) and carboxymethylcellulose (CMC), in a rat peritonitis model.

STUDY DESIGN

In 192 male Wistar rats a bacterial peritonitis was induced using cecal ligation and puncture. After 24 h the abdomen was reopened and the ligated cecum resected. Animals were randomized into three control groups, nine groups treated with various solution volumes (1 to 8 ml) containing different HA concentrations, and four groups treated with 1.7% CMC solution. Rats were killed at day 7, postoperatively, and adhesions were scored at five abdominal sites on a scale from 0 to 4. The presence and size of intra-abdominal abscesses were noted.

RESULTS

Fifty-four rats (28%) prematurely died. There was no significant difference in mortality between treatment groups and controls. Treatment with CMC (P < 0.001) and low (0.2 and 0.4%) concentrations of HA (P < 0.005) significantly reduced intra-abdominal adhesion formation. High volumes of 0.2 and 0.4% HA were most effective (P = 0.01). The effect of CMC was volume independent. The incidence of abdominal abscesses was also significantly reduced by treatment with either CMC (P < 0.001) or low concentrations of HA (P < 0.001). With regard to abscess formation the effect was independent of the volume administered for HA, while low volumes of CMC were most effective (P < 0.005).

CONCLUSION

Intraperitoneal treatment with either CMC or low-viscosity HA solution reduced intra-abdominal adhesion and abscess formation in a rat peritonitis model. The volume-induced reduction in adhesion formation suggests a hydroflotation effect of HA solution.

A fourth empirically derived cluster of chronic pain patients based on the multidimensional pain inventory: evidence for repression within the dysfunctional group

The authors proposed that chronic pain patients with repressive defenses are not represented in current 3-cluster solutions of the Multidimensional Pain Inventory (MPI; R. D. Kerns, D. C. Turk, & T. E. Rudy, 1985) and that such a group can be distinguished by using a measure of defensiveness together with subscales of the MPI. They expected these patients to be described both by high defensiveness and by elevated pain and disability but minimal emotional distress. For 178 pain patients, hierarchical cluster analyses were performed on the MPI and Balanced Inventory of Desirable Responding (D. L. Paulhus, 1984). A 3-cluster solution replicated past findings in identifying dysfunctional, interpersonally distressed, and adaptive coper groups. A 4-cluster solution fit the data better, with a repressor group described by high pain, low activity and low distress emerging from the dysfunctional group. Profile analysis of validation measures showed that repressors scored comparably with dysfunctional patients on somatic symptoms of depression, pain severity, and perceived disability but significantly higher on these factors than the adaptive copers. Repressors scored comparably with adaptive copers on cognitive-affective symptoms of depression, anxiety, and anger but significantly lower on these variables than dysfunctional patients. Repressors also reported greater pain severity and perceived disability relative to their reports of negative affect, whereas dysfunctional and adaptive coper groups exhibited no such disparities. Without a measure of defensiveness, the MPI may misclassify a distinct group of patients as dysfunctional, but who readily endorse physical symptoms yet report low levels of emotional distress.

A fourth empirically derived cluster of chronic pain patients based on the multidimensional pain inventory: evidence for repression within the dysfunctional group

The authors proposed that chronic pain patients with repressive defenses are not represented in current 3-cluster solutions of the Multidimensional Pain Inventory (MPI; R. D. Kerns, D. C. Turk, & T. E. Rudy, 1985) and that such a group can be distinguished by using a measure of defensiveness together with subscales of the MPI. They expected these patients to be described both by high defensiveness and by elevated pain and disability but minimal emotional distress. For 178 pain patients, hierarchical cluster analyses were performed on the MPI and Balanced Inventory of Desirable Responding (D. L. Paulhus, 1984). A 3-cluster solution replicated past findings in identifying dysfunctional, interpersonally distressed, and adaptive coper groups. A 4-cluster solution fit the data better, with a repressor group described by high pain, low activity and low distress emerging from the dysfunctional group. Profile analysis of validation measures showed that repressors scored comparably with dysfunctional patients on somatic symptoms of depression, pain severity, and perceived disability but significantly higher on these factors than the adaptive copers. Repressors scored comparably with adaptive copers on cognitive-affective symptoms of depression, anxiety, and anger but significantly lower on these variables than dysfunctional patients. Repressors also reported greater pain severity and perceived disability relative to their reports of negative affect, whereas dysfunctional and adaptive coper groups exhibited no such disparities. Without a measure of defensiveness, the MPI may misclassify a distinct group of patients as dysfunctional, but who readily endorse physical symptoms yet report low levels of emotional distress.

Protection to +12 Gz

BACKGROUND

The U.S. Air Force has developed +Gz-protective equipment that will provide most pilots protection to +9 Gz with minimal-to-no straining. This equipment includes a pressure breathing system called COMBAT EDGE (CE), which is currently operational, and the Advanced Technology Anti-G Suit (ATAGS), which is not yet operational. For future high-performance aircraft design it is important to know the upper limit of various protective equipment and techniques.

METHODS

Six subjects were randomly exposed to a 12-cell matrix composed of +Gz and the following combinations of protective equipment at three seat-back angles (13 degrees, 30 degrees and 55 degrees from the vertical): 1) the standard CSU-13B/P anti-G suit (STD); 2) the STD suit with CE; 3) the ATAGS; and 4) the ATAGS with CE. Relaxed, followed by straining +Gz tolerance was determined using 15-s rapid onset runs to a maximum of +12 Gz. A comprehensive battery of baseline and post-exposure medical surveillance studies was performed to evaluate the medical consequences of these high +Gz exposures.

RESULTS

All 6 subjects were able to achieve +12 Gz with various combinations of +Gz-protective equipment, seat-back angle, and various amounts of straining, from none to maximum. When the data were collapsed over all protective equipment there was a significant (p < 0.05) seat effect. Relaxed tolerance to ROR increased with seat-back angle from 13 degrees to 30 degrees to 55 degrees. There was also a significant protective equipment effect when the data were collapsed over all seat-back angles.

CONCLUSIONS

These data confirm that effortless protection to +9 Gz is available using ATAGS/CE with the 13 degree and 30 degree seat-back angle (F-15, F-16 and F-22) and to +10.5 Gz with a 55 degree seat-back angle. Moreover, with ATAGS/CE, and a moderate degree of straining, +12 Gz is definitely achievable at 55 degrees, even with reduced anti-G suit pressure at 55 degrees. With additional straining +12 GC is also achievable at the 13 degree and 30 degree seat-back angles.

Evaluation of sepramesh biosurgical composite in a rabbit hernia repair model

BACKGROUND

In cases such as incisional hernia repair, polypropylene mesh (PPM) can be exposed to the underlying viscera and cause adhesions to the mesh. In this study, a composite prosthesis that was designed to be less susceptible to adhesion formation than PPM was evaluated in a rabbit incisional hernia repair model.

MATERIALS AND METHODS

A 5 x 7-cm full-thickness defect was created in the abdominal wall of 30 female New Zealand White rabbits. Ten animals each were repaired with PPM, Bard Composix (PP/ePTFE), or Sepramesh biosurgical composite-a polypropylene mesh coated on one side with chemically modified sodium hyaluronate and carboxymethylcellulose (HA/CMC). The animals were sacrificed after 28 days and the overall performance, including adhesion formation and tissue integration by histology and mechanical testing, was evaluated.

RESULTS

In the Sepramesh group, there was a significant reduction in the percentage of surface area covered by adhesions and a significant increase in the percentage of animals with no adhesions compared to standard materials. The tissue integration strength and overall cellular response were similar in all groups. A partially remesothelialized peritoneal surface was often apparent overlying the Sepramesh implant.

CONCLUSIONS

Sepramesh biosurgical composite effectively repaired abdominal wall defects in rabbits and reduced adhesion development to the mesh compared to the use of a PPM and a PP/ePTFE composite.

Effects of inertial load and countermeasures on the distribution of pulmonary blood flow

We assessed the influence of cranial-to-caudal inertial force (+G(z)) and the countermeasures of anti-G suit and positive pressure breathing during G (PBG), specifically during +G(z), on regional pulmonary blood flow distribution. Unanesthetized swine were exposed randomly to 0 G(z) (resting), +3 G(z), +6 G(z), and +9 G(z), with and without anti-G suit and PBG with the use of the Air Force Research Laboratory centrifuge at Brooks Air Force Base (the gravitational force of the Earth, that is, the dorsal-to-ventral inertial force, was present for all runs). Fluorescent microspheres were injected into the pulmonary vasculature as a marker of regional pulmonary blood flow. Lungs were excised, dried, and diced into approximately 2-cm(3) pieces, and the fluorescence of each piece was measured. As +G(z) was increased from 0 to +3 G(z), blood flow shifted from cranial and hilar regions toward caudal and peripheral regions of the lung. This redistribution shifted back toward cranial and hilar regions as anti-G suit inflation pressure increased at +6 and +9 G(z). Perfusion heterogeneity increased with +G(z) stress and decreased at the higher anti-G suit pressures. The distribution of pulmonary blood flow was not affected by PBG. ANOVA indicated anatomic structure as the major determinant of pulmonary blood flow.

Efficacy of hyaluronic acid/nonsteroidal anti-inflammatory drug systems in preventing postsurgical tendon adhesions

Tendon adhesion is acknowledged to be a function of both an overwhelming inflammatory response at the surgical site and the loss of physical separation that is normally present between the tendons and the synovial sheath. Adhesions bind the flexor tendons to each other and to surrounding structures, interfering with their normal gliding function. The clinical result of adhesion formation following flexor tendon surgery is poor digital function. This study investigated the effect of intraoperative treatments of high viscosity absorbable gels made of various combinations of hyaluronic acid and nonsteroidal anti-inflammatory drugs, on adhesion formation in a leghorn chicken flexor tendon model. Forty-eight mature, white leghorn chickens were used to verify the surgical model and to test five different gel treatments. The gels were formed from: 2% sodium hyaluronate in phosphate buffered saline alone or combined with 1 mg/mL tolmetin sodium; 1 mg/mL naproxen sodium; 0.216 g/mL calcium acetate; or 0.216 g/mL calcium acetate plus 1 mg/mL naproxen sodium. The gels were applied by injecting 0.2 mL of the specified composition into the intrasheath space near the conclusion of the surgical procedure. Gross and histological evaluations were conducted to analyze the efficacy. All of the treatments significant reduced the extent and severity of postsurgical tendon adhesion in this animal model as compared with the control (no gel treatment) (p < 0.05). The combination of naproxen sodium and calcium acetate in a high viscosity sodium hyaluronate carrier was the most effective composition. The combination of a high viscosity gel and nonsteroidal anti-inflammatory drugs appears to maintain the natural separation between the tendons and their sheaths and decrease the tissue inflammatory response through mediating two of the major stimuli in adhesion formation.

Role of transforming growth factor beta-1 in peritonitis-induced adhesions

Peritonitis is a major cause of intra-abdominal adhesion formation. The overexpression of transforming growth factor beta-1 (TGF-Beta1), a potent mitogen, chemoattractant, and stimulant for collagen synthesis by fibroblasts, has been linked to tissue fibrosis at various sites throughout the body including peritoneal adhesion formation. Hence we hypothesized that the mechanism(s) involved in peritonitis-induced adhesion formation may be mediated through the upregulation of TGF-Beta1 expression. Peritonitis was induced in rats by cecal ligation and puncture, while a control group underwent sham operation. Adhesions were scored and harvested from both groups at 0, 6 and 12 hours and at 1, 2, 4, 7, and 28 days. Tissue expression of TGF-Beta1 mRNA was determined by quantitative reverse transcription-polymerase chain reaction and TGF-Beta1 protein was localized by immunohistochemical analysis. Serum and peritoneal fluid TGF-Beta1 concentrations were quantified by enzyme-linked immunosorbent assay. Compared with sham operation, peritonitis was associated with a significantly greater incidence of abdominal adhesions and a significant increase in the levels of TGF-Beta1 mRNA expression at days 2, 4, and 7. Immunostaining intensity of TGF-Beta1 in adhesions from the peritonitis group also steadily rose through day 7. In peritoneal fluid, the ratio of active:total TGF-Beta1 was significantly increased in the peritonitis group on days 1, 2, and 4 compared with the sham group. These results suggest that peritonitis is associated with the upregulation of TGF-Beta1, a mechanism that may exacerbate adhesion formation.

Repression predicts outcome following multidisciplinary treatment of chronic pain

This study examined whether repression predicts outcome following multidisciplinary treatment for chronic pain and whether links between anxiety and outcome are obscured by repressors. Ninety-three chronic pain patients completed a 4-week pain program. Lifting capacity, walking endurance, depression, pain severity, and activity were measured at pre- and posttreatment. Low-anxious, repressor, high-anxious, and defensive/high-anxious groups were formed from median splits of Anxiety Content (ACS) and Lie scales of the Minnesota Multiphasic Personality Inventory-2 (MMPI-2; Butcher, Dahlstrom, Graham, Tellegen, & Kaemmer, 1989). Significant ACS x Lie interactions were found for lifting capacity, depression, and pain severity changes. Planned comparisons showed that both repressors and high-anxious patients performed poorly on lifting capacity; repressors alone recovered poorly on depression and pain severity. Results imply that repression may interfere with the process and outcome of pain programs.

Validity of the pain anxiety symptoms scale (PASS): prediction of physical capacity variables

Anxious responses to pain may lead to avoidance of behavior expected to produce pain. McCracken et al. (1992) developed the Pain Anxiety Symptoms Scale (PASS) to assess anxiety related specifically to pain. Efforts to validate the scale, however, have been confined mostly to examining associations between the PASS and other self-report instruments. This study tested whether PASS scores were related to behavioral performance variables recorded by therapists during a physical capacity evaluation. Participants were 98 male patients with persistent pain referred to two industrial rehabilitation centers. PASS scores were correlated negatively with amount of weight lifted and carried, and results of hierarchical regressions showed that PASS scores accounted for additional variance in these variables when measures of trait anxiety, depression and pain severity were controlled. However, we did not replicate the findings of McCracken et al. (1992) that PASS scores accounted for variance in self-reported disability with trait anxiety, depression or pain severity controlled. Results extend the validity of the PASS and are consistent with models of fear of pain: patients with high PASS scores may avoid potentially painful physical exertion to reduce their fear.

Repression predicts outcome following multidisciplinary treatment of chronic pain

This study examined whether repression predicts outcome following multidisciplinary treatment for chronic pain and whether links between anxiety and outcome are obscured by repressors. Ninety-three chronic pain patients completed a 4-week pain program. Lifting capacity, walking endurance, depression, pain severity, and activity were measured at pre- and posttreatment. Low-anxious, repressor, high-anxious, and defensive/high-anxious groups were formed from median splits of Anxiety Content (ACS) and Lie scales of the Minnesota Multiphasic Personality Inventory-2 (MMPI-2; Butcher, Dahlstrom, Graham, Tellegen, & Kaemmer, 1989). Significant ACS x Lie interactions were found for lifting capacity, depression, and pain severity changes. Planned comparisons showed that both repressors and high-anxious patients performed poorly on lifting capacity; repressors alone recovered poorly on depression and pain severity. Results imply that repression may interfere with the process and outcome of pain programs.

Repressed anger and patterns of cardiovascular, self-report and behavioral responses: effects of harassment

We hypothesized that anger repressors would show discrepancies between self-reported anger and cardiovascular and behavioral responses only during harassment. Subjects (N=102) were assigned randomly to condition. In the nonharassment condition, subjects told stories about eight Thematic Apperception Test cards without any harassment. In the harassment condition, subjects told four stories without harassment, and then told four more stories with harassment. Words connoting aggressive behavior and angry/hostile affect were coded from story content. Subjects were classified into low anger expressor, anger repressor, high anger expressor, and defensive anger expressor categories based on median splits of the Anger-Out Subscale and Marlowe-Crowne Social Desirability Scale. Results showed that harassed anger repressors reported anger comparable to that of low anger expressors but less than high expressors, whereas their heart rate (HR) reactivity was comparable to high expressors, but greater than low anger expressors. Increases in anger words did not distinguish repressors from other groups. Repressed anger may represent a distinct anger management style characterized by a discrepancy between acknowledged anger and cardiovascular reactivity--effects that become fully manifest only during interpersonal provocation.

Effect of surgical adhesion reduction devices on the propagation of experimental intra-abdominal infection

HYPOTHESIS

The use of certain surgical adhesion reduction devices where there is a risk of concomitant bacterial contamination potentiates intra-abdominal infection.

DESIGN

Evaluation of adhesion reduction devices in an experimental model of intra-abdominal infection.

SETTING

Experimental animal model.

INTERVENTIONS

Adhesion reduction devices were administered at the time of bacterial challenge.

MAIN OUTCOME MEASURES

Animal mortality rate, abscess formation, and bacterial counts in peritoneal fluid and blood cultures.

RESULTS

The use of bioresorbable membrane adhesion reduction devices in the presence or absence of antibiotic therapy did not alter the disease process as compared with appropriate control groups. However, adhesion reduction gels prepared from sodium hyaluronate and carboxymethylcellulose chemically modified with carbodiimide or ferric ion complexed sodium hyaluronate increased the incidence of peritonitis in treated animals. Gel formulations containing diimide-modified carboxymethylcellulose did not have this effect.

CONCLUSIONS

The use of certain adhesion reduction devices resulted in the propagation of intra-abdominal infection in an experimental rat model. This outcome was dependent on the composition of the device employed. The use of adhesion reduction devices should be tested in appropriate models of infection where there is the risk of concomitant bacterial contamination.

Anger management style and the prediction of treatment outcome among male and female chronic pain patients

Anger is a prominent emotion experienced by chronic pain patients. Anecdotes suggest that anger predicts poor outcome following multidisciplinary pain programs, but no empirical evidence documents this link. We expected that patient anger expression or suppression would predict poor outcome following a pain program and that gender differences would emerge. Pre- to posttreatment measures of lifting capacity, walking endurance, depression, pain severity and activity level were collected from 101 chronic pain patients. An 'anger expression x gender' interaction was found such that anger expression among males was correlated negatively with lifting capacity improvements. 'Anger suppression x gender' interactions emerged such that anger suppression among males was correlated negatively with improvements in depression and general activities. These effects remained significant after controlling for trait anger. Thus, how anger is managed may exert unique influence on outcomes apart from the effects of mere anger proneness, at least among male pain patients.

Cognitive and physical capacity process variables predict long-term outcome after treatment of chronic pain

Cognitive-behavioral and physical therapies are incorporated into multidisciplinary chronic pain programs because changes in pain cognitions and physical capacity may represent therapeutic processes that facilitate favorable outcome. Decreases in depression, however, may explain treatment responses more parsimoniously. Measures of pain helplessness, lifting capacity, walking endurance, depression, pain severity, and activity level were collected from 94 chronic pain patients at pre- and posttreatment and at 3- to 6-month follow-up evaluations. Decreases in pain helplessness were linked to pain severity reduction, whereas walking endurance increases were related to improvements in activity levels and downtime even after controlling for effects of depression decreases. Thus, cognitive and physical capacity changes that occur through pain treatment may make unique contributions to long-term outcome.

Cognitive and physical capacity process variables predict long-term outcome after treatment of chronic pain

Cognitive-behavioral and physical therapies are incorporated into multidisciplinary chronic pain programs because changes in pain cognitions and physical capacity may represent therapeutic processes that facilitate favorable outcome. Decreases in depression, however, may explain treatment responses more parsimoniously. Measures of pain helplessness, lifting capacity, walking endurance, depression, pain severity, and activity level were collected from 94 chronic pain patients at pre- and posttreatment and at 3- to 6-month follow-up evaluations. Decreases in pain helplessness were linked to pain severity reduction, whereas walking endurance increases were related to improvements in activity levels and downtime even after controlling for effects of depression decreases. Thus, cognitive and physical capacity changes that occur through pain treatment may make unique contributions to long-term outcome.

Pulmonary blood flow redistribution by increased gravitational force

This study was undertaken to assess the influence of gravity on the distribution of pulmonary blood flow (PBF) using increased inertial force as a perturbation. PBF was studied in unanesthetized swine exposed to -Gx (dorsal-to-ventral direction, prone position), where G is the magnitude of the force of gravity at the surface of the Earth, on the Armstrong Laboratory Centrifuge at Brooks Air Force Base. PBF was measured using 15-micron fluorescent microspheres, a method with markedly enhanced spatial resolution. Each animal was exposed randomly to -1, -2, and -3 Gx. Pulmonary vascular pressures, cardiac output, heart rate, arterial blood gases, and PBF distribution were measured at each G level. Heterogeneity of PBF distribution as measured by the coefficient of variation of PBF distribution increased from 0.38 +/- 0.05 to 0.55 +/- 0.11 to 0.72 +/- 0.16 at -1, -2, and -3 Gx, respectively. At -1 Gx, PBF was greatest in the ventral and cranial and lowest in the dorsal and caudal regions of the lung. With increased -Gx, this gradient was augmented in both directions. Extrapolation of these values to 0 G predicts a slight dorsal (nondependent) region dominance of PBF and a coefficient of variation of 0.22 in microgravity. Analysis of variance revealed that a fixed component (vascular structure) accounted for 81% and nonstructure components (including gravity) accounted for the remaining 19% of the PBF variance across the entire experiment (all 3 gravitational levels). The results are inconsistent with the predictions of the zone model.

Reduction of postsurgical adhesion formation in the rabbit uterine horn model with use of hyaluronate/carboxymethylcellulose gel

OBJECTIVE

To assess the efficacy of a bioabsorbable gel for reducing primary postoperative adhesions.

DESIGN

A randomized, prospective, blinded study.

SETTING

Academic research environment.

ANIMALS

Forty-one New Zealand Rabbits.

INTERVENTION(S)

A chemically modified hyaluronate and carboxymethylcellulose (HA/CMC) gel formulation was applied to a bilateral uterine horn injury. Postoperative adhesions were assessed at a second-look laparoscopy.

MAIN OUTCOME MEASURE(S)

The uterine horn model was shown to be adhesiogenic, with 29 (70%) of 42 untreated uterine horns found to have adhesions. After gel treatment, 22 (55%) of 40 uterine horns were free of adhesions compared with 12 (30%) of 42 controls.

RESULT(S)

Animals treated with HA/CMC gel had significantly reduced postsurgical adhesion scores when compared with controls.

CONCLUSION(S)

Treatment of injured uterine horn with HA/CMC gel resulted in a significant reduction in postoperative surgical adhesions.

Anger management style and hostility: predicting symptom-specific physiological reactivity among chronic low back pain patients

It was hypothesized that anger management style (anger-in or anger-out) and hostility affect the aggravation of chronic low back pain (CLBP) through symptom-specific (i.e., lower paraspinal muscle) reactivity during stress. Subjects were 102 CLBP patients who performed mental arithmetic and an Anger Recall Interview (ARI) while trapezius and lower paraspinal EMG, SBP, DBP, and HR were recorded. Results showed anger-in x hostility and anger-out x gender interactions for lower paraspinal but not trapezius reactivity, and only during the ARI. Further analyses revealed that (1) hostility was related positively to lower paraspinal reactivity among high anger suppressors, (2) hostility was related negatively to lower paraspinal reactivity among low anger suppressors, and (3) anger expression was related positively to lower paraspinal reactivity only among men. Anger management style and hostility may contribute to the exacerbation of CLBP by influencing stress reactivity only in muscles near the site of pain or injury.