Clinical Adult Literature Updates from May 2012

Continuous Positive Airway Pressure in Severe Obstructive Sleep Apnea Reduces Pain Sensitivity

This study is to evaluate effects of CPAP on pain sensitivity in severe OSA patients. Apnea-hypopnea index (AHI) decreased from 50.9 ± 14.5 to 1.4 ± 1.0 with CPAP, and sleep continuity improved. CPAP treatment reduces pain sensitivity in OSA patients.

Canadian Thoracic Society 2011 Guideline Update: Diagnosis and Treatment of Sleep Disordered Breathing

The CTS Sleep Disordered Breathing Committee posed specific questions for 8 areas. The recommendations regarding maximum assessment wait times, portable monitoring, treatment of asymptomatic adult OSA patients, treatment with conventional CPAP compared with automatic CPAP, and treatment of central sleep apnea syndrome in heart failure patients replace the recommendations in the 2006⁄2007 guidelines. The recommendations on bariatric surgery, complex sleep apnea and optimum positive airway pressure technologies are new topics, which were not covered in the 2006⁄2007 guidelines.

Risk for Hospital Readmission Following Bariatric Surgery

This is a prospective observational study of 24,662 patients undergoing primary RYGB and 26,002 patients undergoing primary AGB at 249 and 317 Bariatric Surgery Centers of Excellence, for three years. The readmission rate was 5.8% for RYGB and 1.2% for AGB patients 30 days after discharge. Readmission rates are low and mortality is very rare following bariatric surgery, but risk for both is significantly higher after RYGB. Predictors of readmission were disparate for the two procedures. Results do not support excluding patients with certain comorbidities since any reductions in overall readmission rates would be very small on the absolute risk scale.

Obesity and Obstructive Sleep Apnoea: Mechanisms for Increased Collapsibility of the Passive Pharyngeal Airway

In the pharyngeal airway region, excessive soft tissue for a given maxillomandibular enclosure size (upper airway anatomical imbalance) can increase tissue pressure surrounding the pharyngeal airway, thereby narrowing the airway. Lung volume reduction due to excessive central fat deposition may decrease longitudinal tracheal traction forces and pharyngeal wall tension, changing the ‘tube law’ in the pharyngeal airway (lung volume dependence of the upper airway). The lung volume dependence of pharyngeal airway patency appears to contribute more significantly to the development of OSA in morbidly obese, apnoeic patients.

Review of Interscalene Block for Postoperative Analgesia After Shoulder Surgery in Obese Patients

The ongoing debate on the relevance of obesity, for example in terms of OSA syndrome, obesity hypoventilation syndrome, and other related respiratory disturbances, in relation to the choice of analgesic techniques, especially interscalene block, patient-controlled intravenous analgesia and patient monitoring, demands large-scale, well-designed studies to resolve it. Nevertheless, obesity per se should not dissuade patients from undergoing shoulder surgery under interscalene block.

High STOP-Bang Score Indicates a High Probability of Obstructive Sleep Apnoea

The STOP-Bang questionnaire is used to screen patients for OSA. This study evaluated the association between STOP-Bang scores and the probability of OSA. In the surgical population, a STOP-Bang score of 5–8 identified patients with high probability of moderate/severe OSA. The STOP-Bang score can help the healthcare team to stratify patients for unrecognized OSA, practice perioperative precautions, or triage patients for diagnosis and treatment.

Clinical Predictors of Apnoea-Hypopnoea During Propofol Sedation in Patients Undergoing Spinal Anaesthesia

This study assessed the relationship between the occurrence of apnoea-hypopnoea during propofol sedation for spinal anaesthesia and two different predictive tests of sleep apnoea: the STOP-Bang score and the OSA score. Both assessment tools have some predictive value for the occurrence of apnoea-hypopnoea during propofol sedation in patients undergoing spinal anaesthesia.

Respiratory Event Detection by a Positive Airway Pressure Device

The purpose of this study was to compare the AED (Automatic Event Detection) algorithm used in PAP device with manually scored events on PSG. The AHI, AI, and HI by the two methods were highly correlated. An AHI < 10 events/hr by AED is likely to indicate efficacious treatment. However, high AHI values by AED may represent inadequate treatment especially if the reported events are apneas.

Obstructive Sleep Apnea Syndrome and Perioperative Complications: A Systematic Review of the Literature

In this systematic review, the authors describe the epidemiology and pathophysiology of an association between OSAS and perioperative complications. They also discuss the perioperative strategy to identify and manage these patients.

Noninvasive Ventilation in Mild Obesity Hypoventilation Syndrome: A Randomized Controlled Trial

In this RCT, the authors evaluated the impact of one month NIV (Non-Invasive Ventilation) on mild OHS (Obesity Hypoventilation Syndrome) compared with lifestyle change. NIV treatment significantly reduced daytime PaCO2 and apnea-hypopnea index. However, the use of NIV did not lead to significant improvement in daytime sleepiness, or inflammatory, cytokine, or metabolic markers.