Patients with obesity hypoventilation syndrome (OHS) have a lower quality of life, more healthcare expenses, a greater risk of pulmonary hypertension, and a higher mortality compared to eucapnic patients with obstructive sleep apnea (OSA). Despite significant morbidity and mortality associated with OHS, it is often unrecognized and treatment is frequently delayed. The objective of this observational study was to determine the prevalence of OHS in patients with OSA seen at the sleep disorders clinic of a large public urban hospital serving predominantly minority population and to identify clinical--not mechanistic--predictors that should prompt clinicians to measure arterial blood gases. In the first stage, we randomly selected 180 patients referred to our sleep disorders clinic between 2000 and 2004 for suspicion of OSA. From this retrospective random sample we calculated the prevalence of OHS in patients with OSA and identified independent clinical predictors using logistic regression. In the second stage, we prospectively validated these predictors in a sample of 410 consecutive patients referred to the sleep disorders clinic for suspicion of OSA between 2005 and 2006. The prevalence of OHS in patients with OSA was 30% in the retrospective random sample and 20% in the prospective sample. Three variables independently predicted OHS in both samples: serum bicarbonate level (p < 0.001), apnea-hypopnea index (p = 0.006), and lowest oxygen saturation during sleep (p < 0.001). Due to the serious morbidity associated with OHS, we selected a highly sensitive threshold of serum bicarbonate level. A threshold of 27 mEq/l had a sensitivity of 92% and a specificity of 50%. Only 3% of patients with a serum bicarbonate level <27 mEq/l had hypercapnia compared to 50% with a serum bicarbonate > or =27 mEq/l. In conclusion, OHS is common in severe OSA. A normal serum bicarbonate level excludes hypercapnia and an elevated serum bicarbonate level should prompt clinicians to measure arterial blood gases.

; on behalf of the American Thoracic Society Assembly on Sleep and Respiratory Neurobiology THIS OFFICIAL CLINICAL PRACTICE GUIDELINE OF THE AMERICAN THORACIC SOCIETY WAS APPROVED MAY 2019 Background: The purpose of this guideline is to optimize evaluation and management of patients with obesity hypoventilation syndrome (OHS). Methods: A multidisciplinary panel identified and prioritized five clinical questions. The panel performed systematic reviews of available studies (up to July 2018) and followed the Grading of Recommendations, Assessment, Development, and Evaluation evidence-to-decision framework to develop recommendations. All panel members discussed and approved the recommendations. Recommendations: After considering the overall very low quality of the evidence, the panel made five conditional recommendations. We suggest that: 1) clinicians use a serum bicarbonate level ,27 mmol/L to exclude the diagnosis of OHS in obese patients with sleepdisordered breathing when suspicion for OHS is not very high (,20%) but to measure arterial blood gases in patients strongly suspected of having OHS, 2) stable ambulatory patients with OHS receive positive airway pressure (PAP), 3) continuous positive airway pressure (CPAP) rather than noninvasive ventilation be offered as the first-line treatment to stable ambulatory patients with OHS and coexistent severe obstructive sleep apnea, 4) patients hospitalized with respiratory failure and suspected of having OHS be discharged with noninvasive ventilation until they undergo outpatient diagnostic procedures and PAP titration in the sleep laboratory (ideally within 2-3 mo), and 5) patients with OHS use weight-loss interventions that produce sustained weight loss of 25% to 30% of body weight to achieve resolution of OHS (which is more likely to be obtained with bariatric surgery). Conclusions: Clinicians may use these recommendations, on the basis of the best available evidence, to guide management and improve outcomes among patients with OHS.

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Background Little information is available about the geo-economic variations in demographics, management, and outcomes of patients with acute respiratory distress syndrome (ARDS). We aimed to characterise the effect of these geo-economic variations in patients enrolled in the Large Observational Study to Understand the Global Impact of Severe Acute Respiratory Failure (LUNG SAFE). Methods LUNG SAFE was done during 4 consecutive weeks in winter, 2014, in a convenience sample of 459 intensivecare units in 50 countries across six continents. Inclusion criteria were admission to a participating intensive-care unit (including transfers) within the enrolment window and receipt of invasive or non-invasive ventilation. One of the trial's secondary aims was to characterise variations in the demographics, management, and outcome of patients with ARDS. We used the 2016 World Bank countries classification to define three major geo-economic groupings, namely European high-income countries (Europe-High), high-income countries in the rest of the world (rWORLD-High), and middle-income countries (Middle). We compared patient outcomes across these three groupings. LUNG SAFE is registered with ClinicalTrials.gov, number NCT02010073. Findings Of the 2813 patients enrolled in LUNG SAFE who fulfilled ARDS criteria on day 1 or 2, 1521 (54%) were recruited from Europe-High, 746 (27%) from rWORLD-High, and 546 (19%) from Middle countries. We noted significant geographical variations in demographics, risk factors for ARDS, and comorbid diseases. The proportion of patients with severe ARDS or with ratios of the partial pressure of arterial oxygen (PaO 2) to the fractional concentration of oxygen in inspired air (F I O 2) less than 150 was significantly lower in rWORLD-High countries than in the two other regions. Use of prone positioning and neuromuscular blockade was significantly more common in Europe-High countries than in the other two regions. Adjusted duration of invasive mechanical ventilation and length of stay in the intensive-care unit were significantly shorter in patients in rWORLD-High countries than in Europe-High or Middle countries. High gross national income per person was associated with increased survival in ARDS; hospital survival was significantly lower in Middle countries than in Europe-High or rWORLD-High countries. Interpretation Important geo-economic differences exist in the severity, clinician recognition, and management of ARDS, and in patients' outcomes. Income per person and outcomes in ARDS are independently associated.

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Obstructive sleep apnea (OSA) is independently associated with glucose intolerance and insulin resistance, and recent studies have shown that continuous positive airway pressure (CPAP) improves insulin sensitivity. The objective of this study was to describe the change in glycosylated hemoglobin (HbA1c) after treatment with CPAP in patients with type 2 diabetes mellitus and OSA. To test this hypothesis, we performed a retrospective analysis of 38 patients seen in the sleep clinic of an urban public teaching hospital. All patients had OSA and type 2 diabetes mellitus, and their diabetic medication regimen had remained unchanged during the period of CPAP therapy. Sixty-one percent were men, body mass index was 42+/-9.5 kg/m(2), and the Apnea-Hypopnea Index was 53+/-36 per hour. HbA1c before therapy with CPAP was 7.8+/-1.4% and decreased to 7.3+/-1.3% after 134+/-119 days of therapy (p<0.001). Treatment with CPAP leads to a clinically significant drop in HbA1c in patients with type 2 diabetes mellitus and severe OSA.

In obese patients without cardiopulmonary disease, oxygen levels decrease as BMI increases. This effect is associated with the obesity-related reduction in ERV and is independent of hypoventilation.