Clinical Adult Literature Updates from September 2014

Safety and Efficacy of Drug-Induced Sleep Endoscopy Using a Probability Ramp Propofol Infusion System in Patients With Severe Obstructive Sleep Apnea

A propofol infusion strategy that requires limited experience with propofol dose selection and only 1 pump dosing change reliably produced airway obstruction in patients with severe sleep apnea.

Effects of Hyperoxia and Hypoxia on the Physiological Traits Responsible for Obstructive Sleep Apnoea

This study demonstrates that the beneficial effect of hyperoxia on OSA severity is primarily based on its ability to reduce Loop Gain. The effects of hypoxia may explain the disappearance of OSA and the emergence of central sleep apnoea in conditions such as high altitude.

Attitudes Regarding Perioperative Care of Patients With OSA: A Survey Study of Four Specialties in the United States

The authors performed a survey and asked questions about attitudes and practice patterns regarding OSA in the perioperative setting. Of 783 respondents, 94 % felt OSA was a risk factor for perioperative complications. Perioperative management guidelines for OSA are not available at most institutions.

Non-Invasive Respiratory Volume Monitoring to Detect Apnea in Post-Operative Patients: Case Series

The authors report on a novel, non-invasive respiratory volume monitor that provides a real time respiratory curve demonstrating lung volumes as well as a continuous, display of minute ventilation, tidal volume and respiratory rate. They discuss its potential use in OSA patients.

Incidence of Perioperative Sleep-Disordered Breathing in Patients Undergoing Major Surgery: A Prospective Cohort Study

Major surgery might have a modulating effect on nocturnal breathing patterns. The incidence and course of perioperative sleep-disordered breathing in individuals without a previous diagnosis of obstructive sleep apnea has not been investigated sufficiently so far.” They found in their study of 37 individuals without previous OSA diagnosis “that significant increase in the AHI occurred frequently after major surgical procedures in the late postoperative period. Sleep-disordered breathings in the late postoperative period deserve attention, as they potentially increase the risk of postoperative complications.

Sleep Apnoea is Associated With Major Cardiac Events in Peripheral Arterial Disease

84 patients (aged 67 ± 9 years) scheduled for sub-inguinal surgical revascularisation were enrolled for preoperative polysomnography. the primary predictors of MACCE were significant OSA (hazard ratio (HR) 5.1 (95% CI 1.9–13.9); p=0.001) and pre-existing coronary artery disease (HR 4.4 (95% CI 1.8–10.6); p=0.001).

Effect of Upper-Airway Stimulation for Obstructive Sleep Apnoea on Airway Dimensions

In this case series of 27 CPAP-intolerant patients with obstructive sleep apnea, the effect of upper airway stimulation (USA) using unilateral implantable hypoglossal nerve neurostimulator on airway dimensions was studied. Airway dimensions were studied while awake (n=15) and under drug-induced sedation (n=12). Authors found that UAS increased both retropalatal and retrolingual areas, and the effect was more in responders than the non-responders of UAS therapy. This finding could explain the beneficial effects of UAS therapy in select group of patients as seen by a reduction in the apnea-hypopnea index.

The Different Clinical Faces of Obstructive Sleep Apnoea: A Cluster Analysis

In this prospective cohort study of 822 patients with newly diagnosed moderate to sever obstructive sleep apnea (OSA) from the Icelandic Sleep Apnea Cohort, three clusters were identified based on the clinical presentation. Cluster classification included Cluster 1 as “disturbed sleep group” (32.7%), Cluster 2 as ‘‘minimally symptomatic group’’ (24.7%) and Cluster 3 as ‘‘excessive daytime sleepiness group’’ (42.6%). The probabilities of having comorbidities such as hypertension and cardiovascular disease were highest in cluster 2 but lowest in cluster 3. Authors postulate that this could be due to a potential “lag-time” between initial symptoms and diagnosis of OSA. Cluster 2 patients could be exposed to the harmful effects of untreated OSA longer as they are not symptomatic and less likely to seek treatment than the ones in cluster 3. However, the generalizability of these findings need to be established as this is a single center study, and long term follow-up will inform the effect on long term outcomes such as mortality.

Markers of Inflammation: Data From the MOSAIC Randomised Trial of CPAP for Minimally Symptomatic OSA

In this study, exploratory data on markers of systemic inflammation (interleukin 6 (IL-6), IL-10, C reactive protein, tumour necrosis factor, is reported. The Multi-centre Obstructive Sleep Apnoea Interventional Cardiovascular (MOSAIC) trial compared 6 months of CPAP therapy, versus no CPAP, in 391 patients with minimally symptomatic OSA, where an improvement in sleepiness and endothelial function was reported following treatment. The authors did not find any significant difference between the randomized groups in this report. These results suggest that a reduction in the levels of catecholamines could explain the improved endothelial function.