Combination of obstructive sleep apnoea and insomnia treated by continuous positive airway pressure with the SensAwake pressure relief technology to assist sleep: a randomised cross-over trial protocol.

INTRODUCTION: Obstructive sleep apnoea (OSA) is a common sleep breathing disorder affecting up to 17% of the middle-aged population. Continuous positive airway pressure (CPAP) is the primary treatment for patients with OSA, but acceptance and adherence to therapy is suboptimal in specific subgroups particularly those with insomnia or poor sleep quality (40%-80% of patients with OSA). Pressure intolerance, particularly during periods of wakefulness, inhibiting sleep onset or return to sleep, is one reason for poor CPAP adherence. AutoCPAPs continually monitor airflow changes and only increase the pressure when the upper airway requires it. Reducing the pressure during wakefulness-sleep transition and wakefulness-after-sleep-onset (WASO) may improve therapy comfort and potentially adherence without compromising therapy efficacy. We hypothesise that SensAwake, a pressure relief function that reduces CPAP pressure on the transition from sleep to wakefulness and on WASO, may improve objective sleep quality. METHODS AND ANALYSIS: This is a multicentre, randomised double-blind crossover clinical trial on patients with both OSA and insomnia. Insomnia is defined as Insomnia Severity Index >15 at screening. Baseline data, including actigraphy, are collected for 1 week before randomisation (1:1) to either conventional AutoCPAP or AutoCPAP with SensAwake for 4 weeks. After an evaluation visit, patients are switched to the other treatment arm for a further 4 weeks. Allowing for 20% dropout, 48 patients are required. If applicable, repeated measures analysis of variance will be used to assess differences in WASO measured by actigraphy (primary outcome), other actigraphy measures, AutoCPAP compliance, subjective questionnaire scores (Epworth Sleepiness Scale, Pittsburgh Sleep Quality Index, Short-Form 12 Health Survey) and 24 hours blood pressure (secondary outcomes). ETHICS AND DISSEMINATION: The protocol was approved by the regional Ethics Committee (CPP Sud-Est-V, IRB N°6705) on 9 December 2015, is registered on ClincalTrials.gov (NCT02721329) and started in June 2016 with expected publication of primary outcome results in 2018. TRIAL REGISTRATION NUMBER: NCT0272132; Pre-results.

Preferential superior surface motion in wear simulations of the Charité total disc replacement.

Laboratory wear simulations of the dual-bearing surface Charité total disc replacement (TDR) are complicated by the non-specificity of the device's center of rotation (CoR). Previous studies have suggested that articulation of the Charité preferentially occurs at the superior-bearing surface, although it is not clear how sensitive this phenomenon is to lubrication conditions or CoR location. In this study, a computational wear model is used to study the articulation kinematics and wear of the Charité TDR. Implant wear was found to be insensitive to the CoR location, although seemingly non-physiologic endplate motion can result. Articulation and wear were biased significantly to the superior-bearing surface, even in the presence of significant perturbations of loading and friction. The computational wear model provides novel insight into the mechanics and wear of the Charité TDR, allowing for better interpretation of in vivo results, and giving useful insight for designing future laboratory physical tests.

The effect of anterior-posterior shear on the wear of CHARITÉ total disc replacement.

STUDY DESIGN: An in vitro study of the wear rates of the CHARITÉ lumbar total disc replacement (TDR). OBJECTIVE: To investigate the effect of anterior-posterior shear on the in vitro wear rates of the CHARITÉ lumbar TDR. SUMMARY OF BACKGROUND DATA: Current standards prescribe only 4-degrees of freedom (DOF) inputs for evaluating the in vitro wear of TDRs, despite the functional spinal unit incorporating 6 DOF. Anterior-posterior shear has been highlighted as a significant load, particularly in the lumbar spine. A previous study investigated the effect of an anterior-posterior shear on the ProDisc-L, finding that wear rates were not significantly different from 4-DOF wear tests. METHODS: Six CHARITÉ lumbar discs were mounted in a 5 active DOF spine wear simulator and tested under 4-DOF (ISO18192) conditions. Six further CHARITÉ lumbar discs were tested under 5-DOF conditions, consisting of 4-DOF conditions plus an anterior-posterior shear displacement of +2/-1.5 mm. The displacement was decreased and then increased by a factor of 2 to investigate the effect of the magnitude of displacement. Micro-computed tomographic scans of the discs were taken before and after wear testing, and the height loss of the discs was calculated. These were compared with the same measurements taken from explanted CHARITÉ discs, micro-computed tomography scanned at another institution. RESULTS: Wear rates for 4 DOF (12.2 ± 1.0 mg/MC) were not significantly different from 4-DOF tests on the ProDisc-L. Wear rates were significantly increased (P < 0.01) for "standard" 5-DOF conditions (22.3 ± 2.0 mg/MC), decreased 5 DOF (24.3 ± 4.9 mg/MC), and increased 5 DOF (29.1 ± 7.6 mg/MC). The height loss of the explants and in vitro tested discs were not significantly different (P > 0.05). CONCLUSION: The addition of anterior-posterior shear to wear testing inputs of the CHARITÉ lumbar TDR increases the wear rate significantly, which is in direct contrast to the previous 5-DOF testing on the ProDisc. This study highlights the importance of clinically relevant testing regimens, and that test inputs may be different for dissimilar design philosophies.