Literature Updates from December 2018

Comparison of apnoea–hypopnoea index and oxygen desaturation index when identifying obstructive sleep apnoea using type‐4 sleep studies.

Current gold-standard approaches for obstructive sleep apnea (OSA) detection and diagnosis are intrusive, have logistical and financial constraints and can affect the patient’s sleep quality. Type-4 devices have been increasingly used in the setting of resource limitations.


The authors aimed to investigate the correlation (Kappa coefficient) between flow based apnea-hypopnea index (AHIflow50%) and oxygen desaturation index 3% (ODI3%) when concurrently measured using a two-channel ApnealinkTM portable sleep study device in a sample of patients from the general population. They sought to determine if both indices can be used interchangeably.


296 out of an initial 772 patients that had both airflow and oxygen saturation recordings of at least 4 hours were included for analysis. The mean age was 53 years, mean body mass index (BMI) of 29 kg/m2, with 48% being male. Results yielded a median AHIflow50% of 5 (interquartile range 2,10) and median ODI3% of 9 (interquartile range 4,15). The authors found that the AHIflow50% based on airflow alone tended to underestimate obstructive sleep apnea compared to ODI3%. The concordance between AHIflow50% and ODI3% for the diagnosis of OSA and severity classification was 0.32 (moderately discordant), with variations when gender and BMI subgroups were analyzed (worse for increasing BMI and worse for females). The authors suggested caution when using ODI3% as the measure of choice for Type-4 portable sleep studies until further evidence emerges.”


DOI: 10.1111/jsr.12804

Risk factors for admission after shoulder arthroscopy

This retrospective review of all consecutive shoulder arthroscopy procedures performed during a 10 year period used a 2:1 control-case matching technique and univariate and multivariate analysis to identify variables associated with admission. Of the 5,598 arthroscopic procedures, 4.2% required admission. The most common reason for admission was respiratory monitoring, OSA increased the odds (OR 1.90) for admission after shoulder surgery. Increasing body mass index, increased age, COPD, diabetes and increased operative times were risk factors for admission. The absence of general anesthesia reduced the risk of admission.

Risk factors for opioid-induced respiratory depression in surgical patients: a systematic review and meta-analyses

This systematic review and meta-analysis included 12 observational studies. The incidence of postoperative opioid-induced respiratory depression (OIRD) was 5.0 cases per 1000 anesthetics. Eight-five percent of OIRD occurred within the first 24 hours after surgery. Risk factors for OIRD included pre-existing cardiac disease, pulmonary disease, and obstructive sleep apnea. The morphine equivalent daily dose of the postoperative opioids was higher in the OIRD than the control groups.

Hypercapnia impaired cognitive and memory functions in obese patients with obstructive sleep apnoea

In this prospective study, 39 obese patients (BMI ≥ 30) with moderate to severe OSA were enrolled. All patients underwent polysomnography, had an arterial blood gas and completed neurocognitive tests before treatment of OSA. Fifteen patients were found to be hypercapneic and considered to have obesity hypoventilation syndrome. These patients had deficits in logical memory and attention and increased reaction times when compared to non-hypercapneic patients with OSA.

Clinical Predictors of Pediatric Obstructive Sleep Apnea Syndrome

This is a retrospective study in from Taiwan in children with documented OSAS by PSG. The authors sought to determine which clinical signs would be most significant when building a logistic regression model for pediatric AHI. They propose a formula that takes the child BMI, the degree of snoring and nasal obstruction to estimate the AHI. The authors cautioned that their findings warrant further validation in different world regions and in different race populations.

Urine concentrations changes of cysteinyl leukotrienes in non-obese children with obstructive sleep apnea undergoing adenotonsillectomy.

In this study, the authors measure urinary levels of Cysteine Leukotrienes (CysLT) in children with documented severe OSAS by PSG before and after adenotonsillectomy. CysLT has been previously implicated in the development of adenotonsillar hypertrophy and pediatric OSAS. Children with residual OSAS were excluded. A total of 24 children were included for analysis. The authors suggest further studies in order to  determine CysLT as valid biomarker for the presence of OSA in children.

Sleep fragmentation delays wound healing in a mouse model of type 2 diabetes.

The delayed wound healing in obese, diabetic mice caused by SF is homologous to delayed wound healing in some patients with type 2 diabetes. The results support the interpretation that altered leptinergic signaling and inflammatory proteins contribute to delayed wound healing.

Optical probing of orexin/hypocretin receptor antagonists.

The present study investigated the function of Hypocretin (Hcrt or Orexin/OX) receptor antagonists in sleep modulation and memory function with optical methods in transgenic mice. The authors used Hcrt-IRES-Cre knock-in mice and AAV vectors expressing channelrhodopsin-2 (ChR2) to render Hcrt neurons sensitive to blue light stimulation.  Hcrt neurons were optogenetically stimulated and latencies to wakefulness were measured in the presence or absence of OX1/2R antagonists and Zolpidem.

Acute optogenetic stimulation of Hcrt neurons at different frequencies resulted in wakefulness. Treatment with dual OX1/2R antagonists (DORAs) DORA12 and MK6096, as well as selective OX2R antagonist MK1064 and Zolpidem, but not selective OX1R antagonist 1SORA1, significantly reduced the bout length of optogenetic stimulation-evoked wakefulness episode. DORAs and selective OX2R antagonists stabilize sleep and improve sleep-dependent cognitive processes even when challenged by optogenetic stimulation mimicking highly arousing stimuli.

Connectivity of sleep- and wake-promoting regions of the human hypothalamus observed during resting wakefulness

The findings of this study provide preliminary evidence relating a hypothalamic circuit investigated in animals to sleep–wake neuroimaging results in humans, with implications for our understanding of human sleep–wake regulation and the functional significance of anticorrelations.