Sleep apnoea is a condition that interrupts your breathing when you are asleep. This is usually caused by an obstruction blocking the back of the throat so that the air cannot reach your lungs. The cessation of breathing automatically forces you to wake up in order to start breathing again. This can happen many times during the night, making it hard for your body to get enough oxygen, and preventing you from obtaining enough good quality sleep.
Obstructive Sleep Apnoea (OSA)
This is a common feature in middle aged, overweight men. OSA can range from being very mild to severe. Sleep apnoea is usually defined as cessation of air flow into the lungs which lasts for more than 10 seconds.
This definition however is rather artificial as some apnoeas which last for more than 10 seconds during sleep are perfectly normal. It is quite common for intervals between breaths to last for 10-20 seconds without there being any underlying sleep or respiratory disorder.
How Do one Know that he or she Has Sleep Apnoea?
A common situation in which breathing may stop for more than 10 seconds is when the stage of sleep changes. We can determine the severity of sleep apnoea by two indices. The apnoea index (AI) (the number of apnoeas occuring per hour), and the apnoea/hypopnoea index (AHI) (significant drop in oxygen saturation of 4% or more per hour due to the cessation of breathing). An AHI of less than 10 is not likely to be associated with clinical problems.
To determine whether you are suffering from sleep apnoea you must first undergo a specialist “sleep study”. This will usually involve a night in hospital where equipment will be used to monitor the quality of your sleep and the amount of oxygen your body is getting. This information will enable a specialist to diagnose whether or not you have sleep apnoea and decide on your best course of treatment. The ultimate investigation is polysomnography which will include:
- Electro-encephalography (EEG) – brain wave monitoring
- Electromyography (EMG) – muscle tone monitoring
- Recording thoracic-abdominal movements – chest and abdomen movements
- Recording oro-nasal flow – mouth and nose air flow
- Pulse oximetry – heart rate and blood oxygen level monitoring
- Electrocardiography(ECG) – heart monitoring
Obstructive Sleep Apnoea OSA is the most common form of sleep apnoea, This is when the airway is blocked but the respiratory effort continues.
But there is also a condition called Central Sleep Apnoea (CSA). This is a condition when the brain does not send the right signals to tell you to breathe when you are asleep causing a lack of reparatory activity. In other words the brain “forgets” to make you breathe. It can also be associated with weakness of the breathing muscles. CSA is less common than OSA, and needs to be investigated by a specialist. The assessment is often more complicated than for patients with OSA and the treatment has to be carefully matched to the patient’s requirements.
There is also a condition called Mixed Sleep Apnoea which is a combination of both OSA and CSA. The cause of Silent death in some patients are due to this.