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STUDY OBJECTIVES: Obstructive sleep apnea (OSA) is characterized by multiple “endotypic traits,” including pharyngeal collapsibility, muscle compensation, loop gain, and arousal threshold. Here, we examined (1) within-night repeatability, (2) long-term consistency, and (3) influences of body position and sleep state, of endotypic traits estimated from in-home polysomnography in mild-to-severe OSA (apnea-hypopnea index, AHI > 5 events/h). METHODS: Within-night repeatability was assessed using Multi-Ethnic Study of Atherosclerosis (MESA): Traits derived separately from “odd” and “even” 30-min periods were correlated and regression (error vs. N windows available) provided a recommended amount of data for acceptable repeatability (R(threshold) = 0.7). Long-term consistency was assessed using the Osteoporotic Fractures in Men Study (MrOS) at two time points 6.5 ± 0.7 years apart, before and after accounting for across-year body position and sleep state differences. Within-night dependence of traits on position and state (MESA plus MrOS data) was estimated using bootstrapping. RESULTS: Within-night repeatability for traits ranged from R = 0.62–0.79 and improved to R = 0.69–0.83 when recommended amounts of data were available (20–35 7-min windows, available in 94%–98% of participants); repeatability was similar for collapsibility, loop gain, and arousal threshold (R = 0.79–0.83), but lower for compensation (R = 0.69). Long-term consistency was modest (R = 0.30–0.61) and improved (R = 0.36–0.63) after accounting for position and state differences. Position/state analysis revealed reduced loop gain in REM and reduced collapsibility in N3. CONCLUSIONS: Endotypic traits can be obtained with acceptable repeatability. Long-term consistency was modest but improved after accounting for position and state changes. These data support the use of endotypic assessments in large-scale epidemiological studies. CLINICAL TRIAL INFORMATION: The data used in the manuscript are from observational cohort studies and are not a part of the clinical trial.

Rationale: Patients managed at a long-term acute-care hospital (LTACH) for weaning from prolonged mechanical ventilation are at risk for profound muscle weakness and disability. Objectives: To investigate effects of prolonged ventilation on survival, muscle function, and its impact on quality of life at 6 and 12 months after LTACH discharge. Methods: This was a prospective, longitudinal study conducted in 315 patients being weaned from prolonged ventilation at an LTACH. Measurements and Main Results: At discharge, 53.7% of patients were detached from the ventilator and 1-year survival was 66.9%. On enrollment, maximum inspiratory pressure (Pi(max)) was 41.3 (95% confidence interval, 39.4–43.2) cm H(2)O (53.1% predicted), whereas handgrip strength was 16.4 (95% confidence interval, 14.4–18.7) kPa (21.5% predicted). At discharge, Pi(max) did not change, whereas handgrip strength increased by 34.8% (P

The objective of this study was to describe trends in the prevalence of opioids in driver fatalities and examine geographic variation in opioid-involved crashes at a county level. Using comprehensive toxicological data from the Office of the Chief Medical Examiner in Maryland, we examined the prevalence of opioids in all motor vehicle crash fatalities in Maryland between 2006-2017 and tested for trends to assess the statistical significance of changes in the prevalence of prescription opioids detected in these drivers over time. Opioid-involved crash deaths accounted for 10.0% of all driver deaths during the study period. The prevalence of opioids detected in fatally injured drivers increased from 8.3% in 2006 to 14.1% in 2017, (Z = -1.9, p .05). The trends in opioid deaths do not follow broader trends in motor vehicle crash deaths; opioid-involved crashes appear to be increasing while overall motor vehicle crashes appear to be decreasing over the same period. To determine if the increase in opioid-involved crash deaths was the result of changes in pain management related to injuries sustained from the crash, we analyzed a subgroup of cases where death occurred at the scene of the crash. Within this group, there was no statistically significant increase in opioid-involved crashes during the study period. Opioid prevalence was higher in middle aged, and white drivers, and in crashes occurring in rural counties. Geographic distribution of opioid-involved crash deaths reflect broader patterns of opioid deaths overdose across the state. Irrespective of the timing of the deaths, of the drivers testing positive for opioids, 28% had elevated blood alcohol concentrations (‡ 0.01 g/dL), and 45% tested positive for other drugs.

Importance One mechanism for teenagers’ elevated crash risk during independent driving may be inadequate learner driving experience. Objective To determine how learner driver experience was associated with crash risk during the first year of independent driving. Design, Setting, and Participants Youth aged 15.5 to 16.1 years at recruitment were eligible to participate. Participants’ vehicles were instrumented with sensors, and driving was recorded during the learner period through 1 year of independent driving. Data were collected from January 2011 through August 2014 in southwestern Virginia. Exposures The amount, consistency and variety of practice, driving errors, and kinematic risky driving (KRD) rates during the learner period were recorded. Surveys, including one on sensation-seeking personality traits, were assessed at baseline. Main Outcomes and Measures Cox proportional hazard regressions examined associations between individual characteristics and learner driving experience with driving time to first crash and all crashes in the first year of independent driving. So that hazard ratios (HRs) can be directly comparable, units of measurement were standardized to the interquartile range. Results Of 298 individuals who responded to recruitment, 90 fulfilled the criteria and 82 completed the study (of whom 75 were white [91%] and 44 were girls [54%]). Teenage participants drove a mean (SD) of 1259.2 (939.7) miles over 89 days during the learner period. There were 49 property-damage crashes and/or police-reportable crashes during independent driving. Factors associated with driving time to first crash included higher sensation-seeking personality scale scores (HR, 1.67 [95% CI, 1.08-2.57] per 0.75-unit increase), learner driving KRD rates (HR, 1.27 [95% CI, 1.12-1.43] per 9.24-unit increase), and learner driving errors (HR, 0.44 [95% CI, 0.22-0.86] per increase of 6.48 errors). Similar results were obtained for all crashes in the first year, with the addition of consistency of learner driving practice (HR, 0.61 [95% CI, 0.38-0.99] per 0.23-unit increase). Conclusions and Relevance Individual characteristics and learner driving experiences were associated with crash risk during independent driving. As expected, there was an association between sensation seeking and crashes. Elevated KRD rates during the learner period may reflect risky driving behavior among novices or tolerance to abrupt maneuvers by parents who supervise driving. Consistent practice throughout the learner period could reduce teenage crash risk, which is supported by learning theories indicating distributed practice is effective for developing expertise. Errors during practice may constitute learning events that reinforce safer driving. Physicians could encourage parents to provide opportunities for regular practice driving and monitor their teenager’s KRD rates during the learner period using in-vehicle or smartphone-based technology.

More than a million polysomnograms (PSGs) are performed annually in the United States to diagnose obstructive sleep apnea (OSA). Third-party payers now advocate a home sleep test (HST), rather than an in-laboratory PSG, as the diagnostic study for OSA regardless of clinical probability, but the economic benefit of this approach is not known.We determined the diagnostic performance of OSA prediction tools including the newly developed OSUNet, based on an artificial neural network, and performed a cost-minimization analysis when the prediction tools are used to identify patients who should undergo HST.The OSUNet was trained to predict the presence of OSA in a derivation group of patients who underwent an in-laboratory PSG (n = 383). Validation group 1 consisted of in-laboratory PSG patients (n = 149). The network was trained further in 33 patients who underwent HST and then was validated in a separate group of 100 HST patients (validation group 2). Likelihood ratios (LRs) were compared with two previously published prediction tools. The total costs from the use of the three prediction tools and the third-party approach within a clinical algorithm were compared.The OSUNet had a higher +LR in all groups compared with the STOP-BANG and the modified neck circumference (MNC) prediction tools. The +LRs for STOP-BANG, MNC, and OSUNet in validation group 1 were 1.1 (1.0-1.2), 1.3 (1.1-1.5), and 2.1 (1.4-3.1); and in validation group 2 they were 1.4 (1.1-1.7), 1.7 (1.3-2.2), and 3.4 (1.8-6.1), respectively. With an OSA prevalence less than 52%, the use of all three clinical prediction tools resulted in cost savings compared with the third-party approach.The routine requirement of an HST to diagnose OSA regardless of clinical probability is more costly compared with the use of OSA clinical prediction tools that identify patients who should undergo this procedure when OSA is expected to be present in less than half of the population. With OSA prevalence less than 40%, the OSUNet offers the greatest savings, which are substantial when the number of sleep studies done annually is considered.

Respiratory pathogens are frequently isolated from the airways of patients with chronic obstructive pulmonary disease (COPD) in the absence of an exacerbation. This bacterial "colonization" by potential pathogens is associated with host inflammatory and immune responses, which could increase respiratory symptoms.To study whether bacterial colonization impacts daily respiratory symptoms in COPD.In a longitudinal prospective observational study of COPD, patients recorded daily symptoms electronically on the Breathlessness, Cough, and Sputum Scale (BCSS). Sputum cultures and quantitative polymerase chain reaction (PCR) were performed every 2 weeks. The relationship of BCSS and bacterial colonization was analyzed with generalized linear mixed effects models, after controlling for exacerbations, weather conditions, lung function, and demographic variables.A total of 41 patients recorded daily symptoms for 12,527 days. The average BCSS score was higher during the periods of colonization, determined by sputum culture with one or more of the following pathogens: nontypeable Haemophilus influenzae, Moraxella catarrhalis, Streptococcus pneumoniae, and Pseudomonas aeruginosa, compared to periods without colonization (5.28 vs. 4.46; P = 0.008) after controlling for confounding variables. The finding did not change when colonization was defined by quantitative PCR (average BCSS, 4.77 vs. 4.25; P = 0.006). Sputum IL-8 levels were elevated with bacterial colonization.Even in the absence of clinical exacerbation, colonization by bacterial pathogens in COPD was associated with a clinically significant moderate increase in daily symptoms, likely mediated by increased airway inflammation. Novel therapies that decrease bacterial colonization in COPD could improve daily symptoms and quality of life.

An increasing number of countries are requiring an extended learner permit prior to independent driving. The question of when drivers begin the learner permit period, and how long they hold the permit before advancing to independent licensure has received little research attention. Licensure timing is likely to be related to "push" and "pull" factors which may encourage or inhibit the process. To examine this question, we recruited a sample of 90 novice drivers (49 females and 41 males, average age of 15.6 years) soon after they obtained a learner permit and instrumented their vehicles to collect a range of driving data. Participants completed a series of surveys at recruitment related to factors that may influence licensure timing. Two distinct findings emerged from the time-to-event analysis that tested these push and pull factors in relation to licensure timing. The first can be conceptualized as teens' motivation to drive (push), reflected in a younger age when obtaining a learner permit and extensive pre-permit driving experience. The second finding was teens' perceptions of their parents' knowledge of their activities (pull); a proxy for a parents' attentiveness to their teens' lives. Teens who reported higher levels of their parents' knowledge of their activities took longer to advance to independent driving. These findings suggest time-to-licensure may be related to teens' internal motivation to drive, and the ability of parents to facilitate or impede early licensure.

Objective: To evaluate a conceptual framework portraying the factors underlying the intentions of medical stu- dents to train abroad. Methods: Eligible subjects were students in the pre-final and final years of medical studies in Lebanon. A survey ques- tionnaire based on the conceptual framework inquired about demographic and educational characteristics, influencing fac- tors, and intentions to train abroad. We assessed each of the factors for its frequency, distribution, and association with the intention to train abroad. Results: Of 576 eligible students, 425 (74%) participated. The frequency of the framework factors varied from 16% to 94% and was the highest for factors related to training and professional career. The factors independently associated with the intention to train abroad related to residency training, concern with professional career and political conditions. The intention to train abroad was also associated with thinking that the general public considers doctors trained abroad as more qualified (OR=6.3; 95% CI=1.2-33.2); receiving information about abroad training from doctors trained or training abroad (OR= 9.7; 95% CI=1.7-56.6); having relatives or friends living abroad (OR=6.9; 95% CI=1.4-35.7); and witnessing resi- dents traveling to retrain abroad (OR=22.2; 95% CI=4.5-111.1).

Animal models have shown a quantal slowing of respiratory pattern when exposed to opioid agonist, in a pattern similar to that observed in central sleep apnea. We postulated that opioid-induced hypoventilation is more likely to be associated with sleep apnea rather than hypoventilation alone. Since we did not have a direct measure of hypoventilation we used hypoxemia as an indirect measure reasoning that significant hypoventilation would not occur in the absence of hypoxemia.We conducted a retrospective analysis of 98 consecutive patients on chronic opioid medications who were referred for overnight polysomnography. All patients on chronic opioids seen in the chronic pain clinic were referred for a sleep study regardless of whether they had sleep symptoms or not. Sleep-related hypoxemia was defined as arterial oxyhemoglobin saturation of less than 90% for more than 5 min with a nadir ofor=85%, or greater than 30% of total sleep time at an oxyhemoglobin saturation of less than 90%.Of the 98 patients, 36% (95% CI 26-46%) had obstructive sleep apnea, 24%, (95% CI 16-33%) had central sleep apnea, 21% (95% CI 14-31%) had combined obstructive and central sleep apnea, in 4% (95% CI 0-10%) sleep apnea was classified as indeterminate, and 15% (95% CI 9-24%) had no sleep apnea. Opioids were potentially responsible for hypoxemia during wakefulness in 10% of patients (95% CI 5-18%) and for hypoxemia during sleep not clearly associated with apneas/hypopneas in 8% of patients (95% CI 4-15%). Two patients (2%, 95% CI 0-7%) had sleep-related hypoxemia in the absence of sleep apnea or hypoxemia during wakefulness.Patients on chronic opiate therapy for chronic pain have an extremely high prevalence of sleep apnea and nocturnal hypoxemia. Hypoxemia can occur during quiet wakefulness in patients on chronic opioid medications with and without sleep apnea. In patients on chronic opioid therapy, isolated nocturnal hypoxemia without coexisting sleep apnea or daytime hypoxemia is very uncommon.

Objectives Three cases are presented in which patients were using opioids as required for nonmalignant pain management and significant central sleep apnea developed. Patients in the first two cases had no evidence of sleep-related breathing disorders on polysomnography until they ingested an opioid for treatment of chronic pain during the night and severe central sleep apnea developed. The patient in our third case had established obstructive sleep apnea but experienced a significant number of central events after the ingestion of an opioid analgesic, leading to worsening severity of his underlying sleep-related breathing disorder. Conclusion The short-term ingestion of opioid analgesics can precipitate central sleep apnea in patients with chronic pain receiving long-term opiate therapy who otherwise show no evidence of central sleep apnea and have no cardiac or neurologic disease that would predispose them to central sleep apnea.

Objective. To assess the relation between medications prescribed for chronic pain and sleep apnea. Design. An observational study of chronic pain patients on opioid therapy who received overnight polysomnographies. Generalized linear models determined whether a dose relation exists between methadone, nonmethadone opioids, and benzodiazepines and the indices measuring sleep apnea. Setting. A private clinic specializing in the treatment of chronic pain. Patients. Polysomnography was sought for all consecutive (392) patients on around-the-clock opi- oid therapy for at least 6 months with a stable dose for at least 4 weeks. Of these, 147 polysomnog- raphies were completed (189 patients declined, 56 were directed to other sleep laboratories by insurance companies, and data were incomplete for seven patients). Available data were analyzed on 140 patients. Outcome Measures. The apnea-hypopnea index to assess overall severity of sleep apnea and the central apnea index to assess central sleep apnea. Results. The apnea-hypopnea index was abnormal ( ≥ 5 per hour) in 75% of patients (39% had obstructive sleep apnea, 4% had sleep apnea of indeterminate type, 24% had central sleep apnea, and 8% had both central and obstructive sleep apnea); 25% had no sleep apnea. We found a direct relation between the apnea-hypopnea index and the daily dosage of methadone ( P = 0.002) but not to other around-the-clock opioids. We found a direct relation between the central apnea index and the daily dosage of methadone ( P = 0.008) and also with benzodiazepines ( P = 0.004). Conclusions. Sleep-disordered breathing was common in chronic pain patients on opioids. The dose-response relation of sleep apnea to methadone and benzodiazepines calls for increased vigilance.

Mathematical formulas have been less than adequate in assessing the optimal continuous positive airway pressure (CPAP) level in patients with obstructive sleep apnea (OSA). The objectives of the study were (1) to develop an artificial neural network (ANN) using demographic and anthropometric information to predict optimal CPAP level based on an overnight titration study and (2) to compare the predicted pressures derived from the ANN to the pressures computed from a previously described regression equation.A general regression neural network was used to develop the predictive model. The derivation cohort included 311 consecutive patients who underwent CPAP titration at a University-affiliated Sleep Center. The model was validated subsequently on 98 participants from a private sleep laboratory.The correlation coefficients between the optimal pressure determined by the titration study and the predicted pressure by the ANN were 0.86 (95% confidence interval [CI] 0.83-0.88; p0.001) for the derivation cohort and 0.85 (95% CI 0.78-0.9; p0.001) for the validation cohort, respectively. Whereas there was no significant difference between the optimal pressure obtained during overnight polysomnography and the predicted pressure estimated by the ANN (p=0.4), the estimated pressure derived from the regression equation underestimated the optimal pressure in both the derivation and the validation group, respectively.The optimal CPAP level predicted by the ANN provides a more accurate assessment of the pressure derived from the historic regression equation.

There are data about the relationship between morphologic findings on high-resolution computed tomography (HRCT) and the number of acid-fast bacilli (AFB) on sputum smears in patients with pulmonary tuberculosis (PTB). It was also shown that existence of cavities and airspace consolidation might be related to smear positivity in PTB patients. However, there is no study suggesting a relationship between AFB on sputum smears and radiologic extent of disease based on HRCT findings.In this study, we investigated a relationship between the degree of smear positivity and radiologic extent of disease based on HRCT findings and, the degree of smear positivity and different pulmonary parenchymal changes on HRCTs of the PTB patients.Sixty-one male patients with PTB (mean age: 22+/-3.2) were included into the study. HRCT images were assessed for patterns, distribution, and profusion of pulmonary abnormalities. Dividing the lungs into 3 zones, profusion of abnormalities was assessed. A profusion score was given. Patients were divided as smear positive and smear negative and compared for the scores of HRCT findings. Smear-positive patients were divided into 4 groups as per grading of the sputum AFB smear: group I (sputum 1+), group II (sputum 2+), group III (sputum 3+), and group IV (sputum 4+). Correlations were investigated between the degree of smear positivity and the scores of HRCT findings.A significant correlation between radiologic extent of the disease based on HRCT and the degree of smear positivity was found (r=0.63, P=0.0001). There were also significant correlations between the degree of smear positivity and the scores of different HRCT findings. Nodule, cavity, and bronchial lesions are the most important contributors of the predictive properties of the total score. There was significant differences for the scores of HRCT findings between smear-positive and smear-negative patients.Our study suggests that radiologic extent of disease based on HRCT findings in patients with PTB correlated with the degree of smear positivity. Different HRCT findings such as nodule, cavitation, ground-glass opacity, consolidation, and bronchial lesion are significantly associated with smear-positive PTB. Particularly, nodules, cavities, and bronchial lesions might be predictors of smear positivity in patients with PTB. This study also suggests that the thickness of cavity wall and the distance of cavity from central airways might be related to the degree of smear positivity.

Scientific Organisation in the United States, China and Japan

Current recommendations for management of obese patients post-extubation are based on clinical experience and expert opinions. It was hypothesised that the application of noninvasive ventilation (NIV) during the first 48 h after extubation in severely obese patients would reduce post-extubation failure and avert the need for reintubation. Following protocol-driven weaning trials, 62 consecutive severely obese patients (body mass index > or =35 kg x m(-2)) were assigned to NIV via nasal mask immediately post-extubation and compared with 62 historically matched controls who were treated with conventional therapy. The primary end-point was the incidence of respiratory failure in the first 48 h post-extubation. Compared with conventional therapy, the institution of NIV resulted in 16% (95% confidence interval 2.9-29.3%) absolute risk reduction in the rate of respiratory failure. There was a significant difference in the intensive care unit and lengths of hospital stay between the two groups. Subgroup analysis of hypercapnic patients showed reduced hospital mortality in the NIV group compared with the control group. In conclusion, noninvasive ventilation may be effective in averting respiratory failure in severely obese patients when applied during the first 48 h post-extubation. In selected patients with chronic hypercarbia, early application of noninvasive ventilation may confer a survival benefit.

BACKGROUND: Residency training programs use the night float system increasingly to meet the new resident work hour regulations. OBJECTIVE: To assess and compare residents’, attendings’, and nurses’ perceptions of the night float system. DESIGN: A survey study. PARTICIPANTS: One hundred and seven residents, 48 attendings, and 69 nurses in a university-based multicenter internal medicine residency program. MEASUREMENTS: Perceived impact on patient care, resident training, and resident performance. RESULTS: The overall response rate was 75%. In general, more residents than both attendings and nurses had positive opinions regarding the night float system, particularly in relation to patient care. Only a small proportion of residents and attendings thought positively about the night float’s impact on training quality (29.9%; 18.2%), daily feedback (23.0%; 9.1%), and end of rotation evaluation (21.8%; 6.1%). Less than half of the nurses had positive perceptions of the night residents’ performance in terms of promptness (40.9%), physical availability (38.6%), familiarity with the patients’ cases, and management plans (15.9%), communication of management plans to nurses (36.4%), professional respect and trust (43.2%), and teamwork (45.5%). CONCLUSIONS: Residents had more positive perceptions than attendings and nurses. Nurses, in particular, had negative perceptions of resident performance in the setting of the night float system.

Increased oxidative stress in obstructive sleep apnoea is thought to contribute to endothelial dysfunction. The objective of this study was to test the hypothesis that inhibition of xanthine oxidase by allopurinol can improve endothelial function in patients with obstructive sleep apnoea. A randomised double-blind placebo-controlled crossover study was performed on 12 patients with moderate-to-severe obstructive sleep apnoea, comparing 300 mg allopurinol daily for 2 weeks with placebo. Endothelial function was assessed using hyperaemia-induced flow-mediated vasodilation (FMD) at baseline and following treatment. Plasma malondialdehyde levels were compared in order to assess significant changes in oxidative stress. Baseline FMD correlated significantly with the severity of sleep apnoea and the time spent with an arterial oxygen saturation of

Background: The prevalence of obesity is increasing, and there is evidence that obesity, in particular abdominal obesity as a marker of insulin resistance, is negatively associated with pulmonary function. The mechanism for this association and the best marker of abdominal adiposity in relation to pulmonary function is not known. Study objective: We assessed the association between pulmonary function and weight, body mass index (BMI), waist circumference, waist/hip ratio, and abdominal height as markers of adiposity and body fat distribution. We used multiple linear regression to analyze the association of pulmonary function (ie, FEV1 and FVC) [with maneuvers performed in the sitting position] with overall adiposity markers (ie, weight and BMI) and abdominal adiposity markers, stratified by gender, and adjusted for height, age, race, smoking, and other covariates. Setting and participants: A random sample of individuals (n 2,153) from the general population living in western New York state, 35 to 79 years of age. Results: In women, abdominal height and waist circumference were negatively associated with FEV1 percent predicted, while all five adiposity markers were negatively associated with FVC percent predicted. In men, all overall and abdominal adiposity markers were inversely associated with FEV1 percent predicted and FVC percent predicted. Conclusion: These results suggest that abdominal adiposity is a better predictor of pulmonary function than weight or BMI, and investigators should consider it when investigating the determinants of pulmonary function. (CHEST 2006; 129:853–862)

The primary aim of this study was to determine the prevalence of positional obstructive sleep apnea using a functional definition. Positional sleep apnea was defined as a total apnea-hypopnea index (AHI)or = 5 with a50% reduction in the AHI between the supine and nonsupine postures, and an AHI that normalizes (AHI5) in the nonsupine posture. A secondary aim was to determine if positional sleep apnea can be diagnosed accurately during a split-night study.Retrospective chart review.Two sleep centers in Buffalo, NY, one a Veterans Affairs Western New York Healthcare System Sleep Center (VAWNY) and the other a freestanding ambulatory center (Associated Sleep Center [ASC]).Three hundred twenty-six patients from the VAWNY, including 57 patients who underwent a split-night study and 242 patients from the ASC who underwent polysomnography.None.Patient characteristics and sleep study results.Positional sleep apnea was seen in 49 of 99 patients (49.5%) with mild sleep apnea (AHI, 5 to 15/h), 14 of 72 patients (19.4%) with moderate sleep apnea (AHI, 15 to 30/h), and 5 of 77 patients (6.5%) with severe sleep apnea (AHI30/h). Sufficient sleep (15 min) in both postures was not seen in 104 of 269 patients (38.7%) and 80 of 242 overnight studies (33.1%) at the VAWNY and ASC, respectively, and was not seen in 47 of 57 split-night studies (82.5%). The percentage of studies with insufficient sleep in both postures was significantly greater for split-night studies (p0.0001).Positional sleep apnea is common particularly in patients with mild disease. Positional sleep apnea cannot usually be assessed during a split-night study.

The effects of [+/-]-2,5-dimethoxy-4-iodoaminophentamine, a serotonin(2A/2C) receptor agonist, on pharyngeal airflow mechanics were examined in isoflurane-anesthetized lean and obese Zucker rats. The pharyngeal pressure associated with flow limitation, maximum inspiratory flow, oronasal resistance, genioglossus muscle activity, and arterial blood pressure (BP) were measured before and after the intravenous administration of the agonist. A robust activation of the genioglossus muscle in all lean and obese rats was associated with decreased upper airway (UA) collapsibility (p0.05), unchanged maximum flow, and increased oronasal resistance (p0.05) in both groups. The changes in UA mechanics and BP after the drug were similar in lean and obese rats. The serotonin agonist had no effect on UA mechanics in a group of paralyzed (pancuronium bromide) rats, despite similar elevations in BP. There was a smaller decrease (p0.05) in UA collapsibility that was also associated with increased upstream resistance when the drug was administered after bilateral hypoglossal nerve transection. We conclude that systemic administration of a serotonin(2A/2C) receptor agonist improves UA collapsibility predominantly, but not exclusively, via stimulation of the hypoglossal nerves and also increases upstream resistance, at least in part, through activation of nonhypoglossal motoneuronal pools innervating the UA muscles.

Background and Purpose. Individuals with cystic fibrosis (CF) have large amounts of infected mucus in their lungs, which causes irreversible lung tissue damage. Although patient-administered positive expiratory pressure (PEP) breathing has been promoted as an effective therapeutic modality for removing mucus and improving ventilation distribution in these patients, the effects of PEP on ventilation distribution and gas mixing have not been documented. Therefore, this preliminary investigation described responses in distribution of ventilation and gas mixing to PEP breathing for patients with moderate to severe CF lung disease. Subjects and Methods. The effects of PEP breathing on ventilation distribution, gas mixing, lung volumes, expiratory airflow, percentage of arterial blood oxyhemoglobin saturation (Spo2), and sputum volume were studied in 5 patients with CF (mean age=18 years, SD=4, range=13–22) after no-PEP, low-PEP (10–20 cm H2O), and high-PEP (>20 cm H2O) breathing conditions. Single-breath inert gas studies and lung function tests were performed before, immediately after, and 45 minutes after intervention. Single-breath tests assess ventilation distribution homogeneity and gas mixing by observing the extent to which an inspired test gas mixes with gas already residing in the lung. Results. Improvements in gas mixing were observed in all PEP conditions. By 45 minutes after intervention, the no-PEP group improved by 5%, the low-PEP group improved by 15%, and the high-PEP group improved by 23%. Slow vital capacity increased by 1% for no PEP, by 9% for low PEP, and by 13% for high PEP 45 minutes after intervention. Residual volume decreased by 13% after no PEP, by 20% after low PEP, and by 30% after high PEP. Immediate improvements in forced expiratory flow during the middle half of the forced vital capacity maneuver (FEF25%–75%) were sustained following high PEP but not following low PEP. Discussion and Conclusion. This study demonstrated the physiologic basis for the efficacy of PEP therapy. The results confirm that low PEP and high PEP improve gas mixing in individuals with CF, and these improvements were associated with increased lung function, sputum expectoration, and SpO2. The authors propose that improvements in gas mixing may lead to increases in oxygenation and thus functional exercise capacity.

Previous studies of immune response to Haemophilus influenzae after exacerbations of chronic obstructive pulmonary disease (COPD) have yielded contradictory results. Using homologous (infecting) strains and immunoassays to surface-exposed epitopes, we tested the hypothesis that adults with COPD make new antibodies to strain-specific, surface-exposed epitopes on H. influenzae after exacerbations. We collected clinical information, sputum, and serum monthly and during exacerbations from 81 patients with COPD over 56 months. Serum antibodies to H. influenzae after exacerbations associated with H. influenzae in sputum were detected with whole bacterial cell ELISA and bactericidal assays. An immune response to homologous H. influenzae occurred after 22 of 36 (61.1%) exacerbations with newly acquired strains compared with 7 of 33 (21.2%) exacerbations with preexisting strains (odds ratio [OR] = 4.4; 95%, 1.8 to 10.8; p = 0.001). An absence of an immune response was strongly associated with complement sensitivity (OR = 0.03; 95% confidence interval, 0.003 to 0.22; p = 0.001). New bactericidal antibodies developed after exacerbations were highly strain specific, showing bactericidal activity for only 11 of 90 (12.2%) heterologous strains. Development of an immune response to H. influenzae supports its role in causing exacerbations. The strain specificity of the immune response likely represents a mechanism of recurrent exacerbations.

s: To compare the relative usefulness of the different indexes derived from pulse oximetry in the diagnosis of obstructive sleep apnea (OSA), and to determine if a combination of these indexes improves the prediction of the apnea-hypopnea index (AHI) measured by polysomnography.Prediction model developed from 224 patients, validated prospectively in 101 patients from the same center (group 1) and in 191 patients from a different sleep center (group 2).Two independent sleep clinics run by university sleep specialists.Patients who underwent polysomnography for suspicion of OSA.The following indexes were calculated from pulse oximetry recordings performed simultaneously during polysomnography: (1) Delta index, the average of the absolute differences of oxygen saturation between successive 12-s intervals; (2) desaturation events per hour to 2%, 3%, and 4% levels; and (3) cumulative time spent below 90%, 88%, 86%, 84%, 82%, and 80% saturation.The best predictor was the Delta index, although desaturation events provided similar levels of diagnostic accuracy. An aggregation of multivariate models using combination of indexes reduced the prediction error (r(2) = 0.70) significantly (p0.05) compared to using the Delta index alone (r(2) = 0.60). The proportion of subjects from the validation groups within 95% confidence interval (CI) of the derivation group was 90% (95% CI, 83 to 95%) and 91% (95% CI, 86 to 95%) for groups 1 and 2, respectively. The overall likelihood ratios for the aggregated model in all patient groups were 4.2 (95% CI, 3.3 to 15.3), 3.4 (95% CI, 2.7 to 4.3), 3.0 (95% CI, 2.2 to 4.1), and 6.7 (95% CI, 4.9 to 9.2) for normal (AHI5/h), mild (AHI 5 to15/h), moderate (AHI 15 to30/h), and severe (AHIor = 30/h) disease, respectively.The Delta index and oxygen desaturation indexes provided similar levels of diagnostic accuracy. The combination of indexes improved the precision of the predicted AHI and may offer a potentially simpler alternative to polysomnography.

Study objectives Pulmonary function is dependent not only on smoking, but also on nutritional status. Since an increased RBC distribution width (RDW) has been associated with nutritional deficiencies, we postulated that RDW has an inverse relation to pulmonary function. The purpose of this study was to test this hypothesis. Design and setting A cross-sectional study was conducted of a random sample of the general population in western New York. Participants A total of 1,616 subjects of both genders who were aged 35 to 79 years and were free of respiratory disease. Interventions None. Measurements Pulmonary function was assessed from FEV1, FVC, height, body weight, total pack-years of smoking, smoking status, hemoglobin concentration, and hematologic indexes, eosinophil count, education, and blood levels of retinol, β-cryptoxanthin, and vitamin E. Results We found a direct relation between RDW and the number of pack-years of smoking and smoking status, and an inverse relation between FEV1 and FVC with RDW, even when potentially confounding variables such as smoking were taken into account. When the variability of FEV1 due to smoking was used for comparison, an additional 27% of that variability in FEV1 was explained by variations in antioxidant vitamin levels, and another 24% by RDW. Conclusions The results confirmed our hypothesis that there is an inverse relation between RDW and pulmonary function, and raise the possibility that RDW may be a biomarker for as-yet unidentified nutrients that affect pulmonary function.

The purpose of this work was to study the impact of a patient-self-completed history questionnaire upon the quality of the information in the medical record, resource utilization, patient satisfaction, and physician satisfaction. A controlled trial was performed in a primary care clinic of a public supported, urban, university hospital. The patients were mainly poor, minority, urban individuals visiting the clinic for their first primary care visit. The providers were attending physicians, nurse practitioners, and medical residents associated with the Department of Medicine teaching program. A self-administered history questionnaire was given to approximately half the new patients in a randomized, prospective manner. The physicians completed an assessment form on all new patients estimating the time spent, complexity of the case, and listing studies requested. If a history questionnaire was completed by the patient, the physician completed an assessment irrespective of whether it helped or hindered the evaluation of the patient. After the visit, nurses called the patient by telephone and asked questions concerning the patient's satisfaction. The patients' records were reviewed for the initial history papers. There were 127 patients receiving the history questionnaire and 114 controls. The presence of the history questionnaire in the medical record added to both the quantity and the quality of the information present. Of the provider responses, 87% (95% confidence interval: 78-93%) wanted all new patients to complete the questionnaire. Of the patients who received the questionnaire, all who were asked felt that all their issues were addressed, compared with only 83% in the control group (P = .015). No increases in physician time or in utilization of medical resources were found. The implementation of a self-administered history questionnaire in an urban primary care clinic resulted in improved chart quality and improved satisfaction of physicians and patients.

Background: Less than one third of patients with fatal pulmonary embolism (PE) are identified prior to autopsy. Objective: To determine whether the clinical syndromes of acute PE are effective at identifying patients who die of this condition. Method: Seven hundred seventy-eight autopsy reports at the Buffalo General Hospital from 1991 to 1996 inclusive were reviewed. Inpatient medical records of 67 patients who were identified as having PE as the primary or major cause of death then were analyzed. Results: Thirty patients (45% [95% confidence interval, 33 to 57%]) had received a diagnosis of PE prior to death, which was marginally higher than the number previously reported (p < 0.05). The diagnosis of PE was significantly lower (13%; p < 0.01) in patients with COPD or coronary artery disease (33%; p < 0.01). In contrast to the prospective investigation of PE diagnosis data, only a minority of patients (6%) presented with pleuritic pain or hemoptysis, while a significantly larger proportion (24%; p < 0.01) of our patients experienced circulatory collapse. Only 55% were identified as having PE from the following clinical syndromes of PE: isolated dyspnea; pleuritic pain and/or hemoptysis; and circulatory collapse. Among the 30 patients suspected of having PE, only 14 (47%) received IV heparin in therapeutic doses, despite clinical suspicion. Conclusion: Our results show a modest increase in the correct antemortem diagnosis of fatal PE. The current clinical syndromes used as markers for suspecting PE are not sufficient to detect patients who ultimately die of PE. Physicians should maintain a higher index of suspicion since fatal PE does not always present as one of the three clinical syndromes of PE. Once PE is suspected, heparin therapy should be started early. (CHEST 2001; 120:791–795)

Reduced pulmonary function and indicators of airway obstruction have been shown to be strong predictors of mortality in numerous epidemiologic studies (1—3). Interestingly, even mild reductions in pulmonary function in nonsmokers have been linked to increased mortality (4). Although smoking is the major risk factor for chronic obstructive pulmonary disease (COPD), several issues remain to be resolved (5). For example, why do only 10-20 percent of smokers develop COPD (6)? The balance between the negative effects resulting from exposure to oxidants, for example, from cigarette smoke and air pollutants, and the defense by antioxidants has been suggested to play a role in both the pathogenesis of airway obstruction and the link between reduced pulmonary function and mortality (7-12). In particular, the role of antioxidant vitamins in protection against lung disease has attracted considerable clinical and epidemiologic interest because diseases associated with airway obstruction, such as COPD and asthma, present immense public health problems (13-15). This subject, however, has not been reviewed systematically. The present article is a qualitative systematic review of the epidemiologic and other evidence that deals with the association of antioxidant vitamins with pulmonary function and airway obstruction (16-18).

Study objectives: The etiologic role of bacterial pathogens isolated from sputum culture in 40 to 50% of acute exacerbations of chronic bronchitis (AECB) is controversial. If bacterial pathogens cause these AECB, they should be associated with greater neutrophilic airway inflammation than pathogen-negative exacerbations. Design: This hypothesis was tested by comparing levels of interleukin (IL)-8, tumor necrosis factor (TNF)-a, and neutrophil elastase (NE) in 81 sputum samples obtained from 45 patients with AECB. Four groups were compared. In the first three groups, nontypeable Haemophilus influenzae (n 5 20), Haemophilus parainfluenzae (n 5 27), and Moraxella catarrhalis (n 5 14) were isolated as sole pathogens, respectively. In the fourth group, only normal flora was isolated (n 5 20). Paired samples, obtained from individual patients at different times, that differed in their culture results were also compared. Setting: An outpatient research clinic at a Veterans Affairs Medical Center. Patients: These patients were participating in a prospective, longitudinal study of the dynamics of bacterial infection in chronic bronchitis, for which they were seen in the study clinic on a monthly basis as well as when they were experiencing symptoms suggestive of AECB. Interventions: None. Measurements and results: H influenzae exacerbations were associated with significantly higher sputum IL-8, TNF-a, and NE. M catarrhalis exacerbations demonstrated significantly higher sputum TNF-a and NE when compared to pathogen-negative exacerbations. H parainfluenzaeassociated exacerbations had an inflammatory profile similar to pathogen-negative exacerbations. Sputum elastase level distinguished bacterial from nonbacterial AECB and correlated with clinical severity of the AECB. Conclusions: Increased airway inflammation associated with isolation of H influenzae and M catarrhalis supports an etiologic role of these pathogens in AECB. (CHEST 2000; 118:1557‐1565)

Study objectives Results from several studies havedescribed a relationship between pulmonary function and both all-causeand cause-specific mortality. The purpose of this study was toinvestigate the predictive value of pulmonary function by gender after29 years of follow-up. Design Prospective study with29-year follow-up of the Buffalo Health Study cohort. Participants Randomly selected sample of 554 men and 641women, aged 20 to 89 years, from all listed households of the city of, Buffalo, NY. Measurements and results Baselinemeasurements were performed in 1960 to 1961. Pulmonary function wasassessed based on FEV 1 expressed as the normal percentpredicted (FEV 1 % pred). FEV 1 % pred adjusted byage, body mass index, systolic BP, education, and smoking status wasinversely related to all-cause mortality in both men and women(p 25years, we observed a statistically significant negative associationbetween FEV 1 % pred and all-cause mortality. FEV 1 % pred was also inversely related to ischemic heartdisease (IHD) mortality. When participants were divided into quintilesof FEV 1 % pred, participants in the lowest quintile of, FEV 1 % pred experienced significantly higher all-causemortality compared with participants in the highest quintile of, FEV 1 % pred. For the entire follow-up period, the adjustedhazard ratios for all-cause mortality were 2.24 (95% confidenceinterval [CI], 1.60 to 3.13) for men and 1.81 (95% CI, 1.24 to 2.63)for women, respectively. Hazard ratios for death from IHD in the lowestquintile of FEV 1 % pred were 2.11 (95% CI, 1.20 to 3.71)and 1.96 (95% CI, 0.99 to 3.88) for men and women, respectively. Conclusions These results suggest that pulmonary functionis a long-term predictor for overall survival rates in both genders and could be used as a tool in general healthassessment.

Objective: To evaluate the predictive accuracy of the severity of illness scoring systems in a single institution. Design: A prospective study conducted by collecting data on consecutive patients admitted to the medical intensive care unit over 20 months. Surgical and coronary care admissions were excluded. Setting: Veterans Affairs Medical Center at Buffalo, New York. Patients and participants: Data collected on 302 unique, consecutive patients admitted to the medical intensive care unit. Interventions: None. Measurements and results: Data required to calculate the patients' predicted mortality by the Mortality Probability Model (MPM) II, Acute Physiology and Chronic Health Evaluation (APACHE) II and Simplified Acute Physiology Score (SAPS) II scoring systems were collected. The probability of mortality for the cohort of patients was analyzed using confidence interval analyses, receiver operator characteristic (ROC) curves, two by two contingency tables and the Lemeshow–Hosmer chi-square statistic. Predicted mortality for all three scoring systems lay within the 95 % confidence interval for actual mortality. For the MPM II, SAPS II and APACHE II, the c-index (equivalent to the area under the ROC curve) was 0.695 ± 0.0307 SE, 0.702 ± 0.063 SE and 0.672 ± 0.0306 SE, respectively, which were not statistically different from each other but were lower than values obtained in previous studies. Conclusion: Although the overall mortality was consistent with the predicted mortality, the poor fit of the data to the model impairs the validity of the result. The observed outcoume could be due to erratic quality of care, or differences between the study population and the patient population in the original studies. The data cannot be used to distinguish between these possibilities. To increase predictive accuracy when studying individual intensive care units and enhance quality of care assessments it may be necessary to adapt the model to the patient population.

The recent outbreaks of multidrug-resistant strains of M. tuberculosis in health care facilities has increased concern over its transmission in health care facilities. Isolation has been recommended for all patients suspected to have tuberculosis even though the feasibility and the cost of this recommendation can be substantial. We have developed a classification tree using clinical and radiographic data from 277 isolation episodes in patients admitted between August 1992 and March 1994 who required isolation for suspicion of tuberculosis. The classification tree was developed with a sensitivity and negative predictive value of 100% by binary recursive partitioning to predict those patients who are unlikely to require isolation. The predictor variables were upper zone disease on chest radiograph, a history of fever, weight loss, and CD4 count. The tree was validated in a separate cohort of 286 isolation episodes between April 1994 and December 1995. In this validation cohort, no erroneous prediction was made of not isolating a patient with active pulmonary tuberculosis. The classification tree had a sensitivity of 100% (95% confidence interval [CI]: 92.5 to 100%), a specificity of 48.1% (95% CI: 43.8 to 52.4%), and a negative predictive value of 100% (95% CI: 98.5 to 100%). We estimate that the use of the tree could have reduced the number of patients requiring isolation by more than 40% without increasing the risk of cross infection.

Study objective To evaluate the predictive ability of three scoring systems, acute physiology and chronic health evaluation (APACHE II), simplified acute physiology score (SAPS II), and mortality probability models (MPM II) in critically ill obstetric patients compared to a control group of nonobstetric female patients of similar age group (range, 17 to 41 years). Design A retrospective medical chart review of obstetric and nonobstetric female patients between 17 and 41 years of age. Setting Two university hospitals. Patients Ninety-three obstetric patients and 96 nonobstetric female patients were identified from 12, 740 consecutive ICU admissions. Results The actual mortality of the obstetric and the nonobstetric group was 10.8% (95% confidence interval [CI], 5.3 to 19.0%) and 12.5% (95% CI, 6.6 to 21.0%), respectively. The observed mortality was not statistically different from the mortality predicted by APACHE II, SAPS II, and MPM II (14.7%, 7.8%, and 9.1% for the obstetric group and 10.9%, 9.0%, and 9.9% for the nonobstetric group). Predictive accuracy was assessed by the c-index, which is equivalent to the area under the receiver operator characteristic (ROC) curve. There were no significant differences in the c-index for APACHE II, SAPS II, and MPM II within or between the obstetric group ([mean±SE], 0.93±0.02, 0.90±0.04, and 0.91±0.04, respectively) and the nonobstetric group (0.97±0.02, 0.95±0.03, and 0.96±0.02, respectively). Conclusions We conclude that APACHE II, SAPS II, and MPM II assess the ICU outcome of critically ill obstetric patients as accurately as nonobstetric critically ill female patients of similar age group.

Importance Patients requiring prolonged mechanical ventilation (>21 days) are commonly weaned at long-term acute care hospitals (LTACHs). The most effective method of weaning such patients has not been investigated. Objective To compare weaning duration with pressure support vs unassisted breathing through a tracheostomy collar in patients transferred to an LTACH for weaning from prolonged ventilation. Design, Setting, and Participants Between 2000 and 2010, a randomized study was conducted in tracheotomized patients transferred to a single LTACH for weaning from prolonged ventilation. Of 500 patients who underwent a 5-day screening procedure, 316 did not tolerate the procedure and were randomly assigned to receive weaning with pressure support (n = 155) or a tracheostomy collar (n = 161). Survival at 6- and 12-month time points was also determined. Main Outcome Measure Primary outcome was weaning duration. Secondary outcome was survival at 6 and 12 months after enrollment. Results Of 316 patients, 4 were withdrawn and not included in analysis. Of 152 patients in the pressure-support group, 68 (44.7%) were weaned; 22 (14.5%) died. Of 160 patients in the tracheostomy collar group, 85 (53.1%) were weaned; 16 (10.0%) died. Median weaning time was shorter with tracheostomy collar use (15 days; interquartile range [IQR], 8-25) than with pressure support (19 days; IQR, 12-31), P = .004. The hazard ratio (HR) for successful weaning rate was higher with tracheostomy collar use than with pressure support (HR, 1.43; 95% CI, 1.03-1.98; P = .033) after adjusting for baseline clinical covariates. Use of the tracheostomy collar achieved faster weaning than did pressure support among patients who did not tolerate the screening procedure between 12 and 120 hours (HR, 3.33; 95% CI, 1.44-7.70; P = .005), whereas weaning time was equivalent with the 2 methods in patients who did not tolerate the screening procedure within 0 to 12 hours. Mortality was equivalent in the pressure-support and tracheostomy collar groups at 6 months (55.92% vs 51.25%; 4.67% difference, 95% CI, −6.4% to 15.7%) and at 12 months (66.45% vs 60.00%; 6.45% difference, 95% CI, −4.2% to 17.1%). Conclusion and Relevance Among patients requiring prolonged mechanical ventilation and treated at a single long-term care facility, unassisted breathing through a tracheostomy, compared with pressure support, resulted in shorter median weaning time, although weaning mode had no effect on survival at 6 and 12 months. Trial Registration clinicaltrials.gov Identifier: NCT01541462

The length of time that blood remains in the pulmonary capillary is an important variable in gas exchange. We have investigated the distribution of capillary transit times in isolated rabbit lungs perfused with a bicarbonate-free buffer. The time course of gas exchange was monitored by enclosing the lungs in a plethysmograph. A bolus of buffer containing dissolved acetylene was injected into the perfusion system. Exchange of this inert gas occurred as soon as the bolus reached the capillary bed, thereby describing the input function into the bed. A separate bolus injection of bicarbonate solution resulted in production and excretion of CO2 as long as the bolus remained in the capillary bed. The rate of CO2 production was adjusted by partial inhibition of endothelial carbonic anhydrase. The distribution of capillary transit times was computed from a model of CO2 production in the capillary bed and the observed rates and volumes of acetylene and carbon dioxide excretion. The recovered distributions indicate that there is a fairly wide distribution of capillary transit times (relative dispersion, 0.45) around the mean value of 1.71 s (+/- 0.53 [SD]). Only 10% of capillary transit times are less than one half of mean transit time. It is likely that gas exchange reaches equilibrium in the capillary bed except possibly during strenuous exercise or exposure to high altitude or in disease.

Limited configuration-interaction calculations beyond Hartree-Fock are reported for an ab initio derived eight-band effective Hamiltonian for ${\mathrm{La}}_{2}$${\mathrm{CuO}}_{4}$. These results clearly implicate two important types of configurations, as well as the role of apical-O ${\mathrm{p}}_{\mathrm{z}}$ states, in the nature and dispersion of quasiparticle states associated with one hole doped into the parent insulator. The two types of configurations are spatially inhomogeneous ``spin bags'' centered about a flipped spin relative to the host antiferromagnetic order, and ``doped N\'eel'' configurations that leave the host spin order intact. Taken together these complementary parts are suggestive of the local singlet of Zhang and Rice. It is, however, the latter doped N\'eel configurations that carry those apical-O ${\mathit{p}}_{\mathit{z}}$ components that are primarily responsible for very shallow quasiparticle dispersion from k=(\ensuremath{\pi}/2,\ensuremath{\pi}/2), where the first holes are doped, towards (\ensuremath{\pi},0).

Transmural pulmonary arterial pressure (Ppa), diameter (D), and length (L) of a segment of the main pulmonary artery (MPA) were measured simultaneously in anesthetized open-chest dogs. The instantaneous volume was calculated from D and L. Pulmonary arterial elasticity for diameter (EpD) was calculated as the ratio of the amplitude of Ppa to D oscillation normalized by the mean D. Similar indexes were calculated for L (EpL) and V (Epv). Compliance per unit length was calculated from the dimensions and elasticity of the MPA. Under control conditions with 5 cmH2O positive end-expiratory pressure, EpD, EpL, and Epv at cardiac frequency were 175 +/- 27, 147 +/- 27, and 55 +/- 7 cmH2O, respectively. EpD increased with positive end-expiratory pressure, but EpL decreased and Epv was unaffected. EpD, EpL, Epv, and compliance per unit length were not significantly different between the start of inspiration and the start of expiration. In addition, there were no significant phase differences between the oscillations of Ppa and V at respiratory frequency. We conclude that the previously reported time variation of pulmonary arterial compliance during the ventilatory cycle is not due to time-varying properties of the MPA.

The purpose of the study was to determine if the adverse effect of body position on obstructive sleep apnea (OSA) is worsened during rapid eye movement (REM) sleep and if patients with OSA decrease the time spent supine during REM sleep.Overnight polysomnography from 80 sequential patients referred to Buffalo VA Sleep Lab for suspected OSA were analyzed with 20 patients in each of the following groups: normal with apnea-hypopnea indices (AHI)5/h, mild (AHI, 5-15/h), moderate (AHI, 15-30/h), and severe (AHI,30/h). We used extended Cox models with the Anderson-Gill modification for multiple events with two time varying covariates: sleep stage and body position. Generalized estimating equations with logit link were used to take into account correlated data within each patient for the relation between sleep stage and body position.The hazard ratios for events in REM vs non-REM sleep was significant for the normal, mild, and moderate groups only: 1.71 (95% CI 1.4-2.08), 1.45 (95% CI 1.22-1.73), 1.28 (95% CI 1.1-1.5), respectively. The hazard ratio for events in the supine vs non-supine position was significant for the mild and moderate groups only: 1.25 (95% CI 1.02-1.52) and 1.24 (95% CI 1.04-1.47), respectively. The addition of an interaction effect between sleep stage and body position was not statistically significant for any group. The odds ratios of sleeping in supine position for REM vs non-REM sleep were 0.47 (95% CI 0.27-0.82) for moderate OSA group and 0.54 (95% CI 0.3-0.95) for severe OSA.In summary, we found significant effects of both sleep stage and body position in mild and moderate but not severe OSA. Patients with moderate and severe OSA were less likely to spend time in the supine position during REM compared with non-rapid eye movement sleep.

Autotitrating continuous positive airway pressure (auto-CPAP) devices now have a smart card (a pocket-sized card with embedded integrated circuits which records data from the CPAP machine such as CPAP usage, CPAP pressure, large leak, etc.) which can estimate the Apnea–Hypopnea Index (AHI) on therapy. The aim of this study was to determine the accuracy of auto-CPAP in estimating the residual AHI in patients with obstructive sleep apnea (OSA) who were treated with auto-CPAP without a CPAP titration study. We studied 99 patients with OSA from April 2005 to May 2007 who underwent a repeat sleep study using auto-CPAP. The estimated AHI from auto-CPAP was compared with the AHI from an overnight polysomnogram (PSG) on auto-CPAP using Bland–Altman plot and likelihood ratio analyses. A PSG AHI cutoff of five events per hour was used to differentiate patients optimally treated with auto-CPAP from those with residual OSA on therapy. Bland and Altman analysis showed good agreement between auto-CPAP AHI and PSG AHI. There was no significant bias when smart card estimates of AHI at home were compared to smart card estimates obtained in the sleep laboratory. An auto-CPAP cutoff for the AHI of six events per hour was shown to be optimal for differentiating patients with and without residual OSA with a sensitivity of 0.92 (95% confidence interval (CI) 0.76 to 0.98) and specificity of 0.90 (95% CI 0.82 to 0.95) with a positive likelihood ratio (LR) of 9.6 (95% CI 5.1 to 21.5) and a negative likelihood ratio of 0.085 (95% CI 0.02 to 0.25). Auto-CPAP AHI of eight events per hour yielded the optimal sensitivity (0.94, 95% CI 0.73 to 0.99) and specificity (0.90, 95% CI 0.82 to 0.95) with a positive LR of 9.6 (95% CI 5.23 to 20.31) and a negative LR of 0.065 (95% CI 0.004 to 0.279) to identify patients with a PSG AHI of ≥ 10 events per hour. Auto-CPAP estimate of AHI may be used to estimate residual AHI in patients with OSA of varying severity treated with auto-CPAP.

This study compares the independent effects of flow (Qpa) and transmural pressure (Ppa) on the diameter (D) and length of a segment (L) of the main pulmonary artery (MPA) in anesthetized open-chested dogs. Qpa was increased by a shunt from the left lower lobe pulmonary artery to an external jugular vein. Ppa was increased with positive end-expiratory pressure (n = 5), or with a femoral arteriovenous shunt (n = 5). Mean Ppa, Qpa, D and L were calculated by averaging over a single cardiac cycle selected at end expiration of successive breaths. The independent effects of Ppa and Qpa on MPA dimensions were determined by multiple linear regression. The effects of Ppa delta D%/delta P% = 0.153 +/- 0.03 SE) and Qpa (delta D%/delta Q% = 0.021 +/- 0.004 SE) on D were similar in both groups of dogs. Changes of L (delta L%/delta Ppa% = 0.168 +/- 0.042 SE and delta Qpa% = 0.033 +/- 0.006 SE, n = 5) were similar to the corresponding changes of D. We conclude that the effects of flow are small relative to pressure and that flow not only causes vasodilatation but also vasoelongation of the MPA.