Domiciliary Transcutaneous Electrical Stimulation in Obstructive Sleep Apnoea

Obstructive sleep apnoea is highly prevalent, with the obesity epidemic increasing the problem. The best treatment for uncomplicated and moderate-severe OSA remains CPAP therapy. However, long-term adherence to treatment with CPAP is poor and there are few alternatives. Electrical stimulation of the dilator muscles of the upper airway has been shown to reduce nocturnal apnoeas significantly using an invasive approach, hypoglossal nerve stimulation, as well as by non-invasive transcutaneous stimulation. Although non-invasive transcutaneous stimulation may not be as effective as CPAP therapy in many OSA patients it could be an important option to treat some of the large number of patients who fail CPAP and might also be of use in those whose OSA is not judged sufficiently severe to warrant CPAP.

The investigators propose a study to use a transcutaneous electrical stimulation device in selected patients with OSA who do not tolerate CPAP therapy following assessment of the upper airway. Participants will undergo a baseline sleep study (polysomnography/home-based respiratory polygraphy). Following minimisation for gender (male/female) and OSA severity (mild/moderate-severe) they will be randomised into active treatment arm (transcutaneous electrical stimulation) or usual care (ongoing CPAP therapy). Patients will be treated over a period of 3-months in the community, re-assessed (including polysomnography/home-based respiratory polygraphy) and the results will be compared against usual care, ongoing CPAP therapy. This study will help to prepare a definitive multi-centre randomized controlled trial using the non-invasive method of upper airway stimulation in OSA.

The primary aim of this study is to assess efficacy and generate an accurate sample size estimation, test the subjective willingness of patients to use and objectively determined compliance with the treatment over a long period, as well as to specify the drop-out rate. The improvement in sleep apnoea will be the primary outcome measures. The symptomatic response, feasibility of the method, including compliance, comfort, adverse events, will be the secondary outcome measure. An ad-hoc analysis will be performed in the responder group (improvement in the apnoea-hypopnea index (AHI) by >50% from baseline OR improvement in the 4% oxygen-desaturation index (ODI) >25% from baseline OR AHI/4%ODI <5/hour at follow up).

Inclusion criteria

• mild-moderate OSA (AHI 5-35/hour)
• difficulties with or failed CPAP and/or withdrawn from standard care (CPAP <4hours/night)
• Body mass index (BMI) 18.5-32 kg/m2
• No significant anatomical obstruction in the upper airway (e.g. normal sized tonsils).

Exclusion criteria

• No OSA (AHI <5/h)
• Severe obstructive sleep apnoea (AHI>35/hour)
• Exclusively postural sleep apnoea
• isolated Rapid-Eye-Movement (REM) sleep associated OSA
• Cachexia (BMI <18.5 kg/m2)
• Obesity (BMI >32 kg/m2)
• Hypercapnic respiratory failure (pCO2>6.5 kPa)
• Features of obesity hypoventilation syndrome (elevated bicarbonate, HCO3- >28mmol/L).
• enlarged tonsils (size 3-4)
• polyps and adenoids
• neuromuscular disease
• hypoglossal nerve palsy
• abnormal pulmonary function tests
• severe pulmonary hypertension
• valvular heart disease
• heart failure (New York Heart Association, NYHA III-IV)
• myocardial infarction and significant cardiac arrhythmias
• uncontrolled hypertension
• active psychiatric disease
• co-existing non-respiratory sleep disorder
• significant metal implants or cardiac/other pacemakers.
• facial hair that affects the correct placement of the hydrogel patch
• endoscopically identified contraindication to upper airway stimulation (multi-level obstruction)

These criteria are consistent with our experience from previous trials using transcutaneous electrical stimulation in OSA and likely to identify potential responders; these criteria are also similar to those from trials using hypoglossal nerve stimulation.