Devices to detect apnoea
[Part 2: Questions; Duncan J]
Apnoea occurs in SUDEP and, in some cases, is likely to be the primary event, with a cardiac arrest being a secondary event consequent to the cessation of breathing. It is well-known that cessation of breathing, apnoea, occurs in many generalized and complex partial seizures, with associated lack of oxygen supply to the brain and heart. Apnoea may result from airway obstruction, reduced respiratory drive or a combination of these. If recognized in time, however, death from apnoea can be averted by prompt basic resuscitation.
Whilst monitoring of breathing is well-established in intensive care units, chronic monitoring in low intensity clinical, domiciliary and residential settings is not satisfactory. Existing devices that monitor respiration are based either on sensing airflow, movement, or concentrations of oxygen and carbon dioxide in the blood. The first approach uses detectors that are secured just under the patient’s nose and sense the movement of air into and out of the airways to detect breathing. These can be successfully used within a hospital, but difficulty keeping the device in place makes them impractical for day to day use.
Other breathing detectors sense movements associated with breathing. They can be either attached to a mattress and with an audible or visible alarm triggered after a delay following cessation of movement; or a sensor pad on the chest which triggers when breathing is interrupted. The main problems with this approach are the false alarms that may occur, the size of the devices and need for mains power which restricts the places in which they may be used.
Pulse oximetry uses infrared light that shines through skin with good blood flow such as the finger, toe, or ear lobe, and can measure the oxygen level in the blood. The equipment is bulky, needs a mains power supply and the probes often get displaced from the skin. Further, the detectable changes in blood oxygen and carbon dioxide levels occur after a delay following disruption of breathing and so, inevitably, lag behind the causative event.
There is an urgent need for a device that can reliably detect breathing and its cessation, and which is small and discrete enough for long-term use in domestic and residential settings, as well as in low-intensity clinical care areas.
Electronic engineers at Imperial College and neurologists at UCL in London have pioneered a miniaturized, wearable apnoea detection device and respiration monitor that is suitable for long-term use in low-intensity clinical, domiciliary or residential care and may alert carers to the cessation of breathing. The device is applied to the skin of the neck with adhesive and detects the noise of air flow in the trachea, and hence registering when a breath occurs. The device is light enough to be worn comfortably and unobtrusively and is designed to detect episodes of apnoea.
This device has been shown to reliably detect apnoea in the context of sleep apnoea (Rodriguez-Villegas et al., 2014) and a forthcoming trial will determine its ability to reliably identify episodes of apnoea associated with epileptic seizures, and hence raise the alarm when breathing is affected, this being a warning sign of a severe seizure that carries risk of SUDEP.
Professor of Neurology
Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology
National Hospital for Neurology and Neurosurgery, London, UK
How to cite:
Duncan J. Devices to detect apnoea. In: Hanna J, Panelli R, Jeffs T, Chapman D, editors. Continuing the global conversation [online]. SUDEP Action, SUDEP Aware & Epilepsy Australia; 2014 [retrieved day/month/year]. Available from: www.sudepglobalconversation.com.