Patrick McKeown explains what is sleep apnoea.
Apnoea is a Greek word meaning “without breath.”
There are three types of apnoea during sleep: central, obstructive and mixed. Mixed apnoea is a combination of central and obstructive sleep apnoea. It can be argued with some conviction that chronic hyperventilation offers an explanation for both types of sleep apnoea.
Central Sleep Apnoea
Central sleep apnoea affects approximately 5% of sufferers and results from the brain not sending the right signals to breathe. Excessive breathing volume during sleep causes a reduction in the partial pressure of carbon dioxide. This shifts the pH of the blood in an alkaline direction. To maintain the pH within normal levels, a natural bodily response is to hold the breath, allowing the pH to revert to normal. In other words, central apnoea occurs from breathing in excess of metabolic requirements.
Obstructive Sleep Apnoea
During your school days, you may remember reading about Joe the "fat boy" from the Pickwick papers written by Charles Dickens in 1837.
Joe ate in great quantities and was liable to fall asleep during any situation. His breathing was heavy, he snored and he was continuously sleepy. Originally described as the Pickwickian syndrome, his breathing was later labelled as obstructive sleep apnoea syndrome.
While obstructive sleep apnoea more often affects men with a neck size of 17 inches or larger, it can also affect children and adults who are not overweight. Children who breathe through their mouth are at risk of developing cranio-facial changes, such as undeveloped jaws, smaller airways, and narrow faces. It also increases the likelihood of the child developing lifelong sleep apnoea.
Obstructive sleep apnoea is the most common type of apnoea and is characterised by holding the breath from collapse of the upper airways during sleep. This holding of the breath, which prevents airflow to the lungs, may occur between five and fifty times per hour. Each breath hold can range from a few seconds to over one minute, causing one’s blood oxygen saturation to decline to as low as 50%.
After a period of holding the breath during sleep, the centre within the brain that controls breathing alerts the rest of the brain that the breath is being held and the individual partially wakes up. This is followed by gasping, a sharp intake of breath, and spluttering, which is often of great concern to sleep partners who in turn suffer from sleep deprivation. The sufferer is unaware that he or she is holding his or her breath, often feels that he or she slept well but wonders why he or she is so tired during the day.
All patients with sleep apnoea breathe extremely heavily while sleeping. A normal routine is thunderous snoring followed by complete cessation of the breath.
Imagine sucking air through a collapsible rubber tube. As one sucks air through the tube, the walls of the tube tend to collapse inwards from the pressure created by drawing air. During a gentle draw of air, pressure is minimal and the inner walls of the tube do not collapse. However, during a strong draw of air, the walls can collapse and the more effort one makes to suck air through the tube, the more the walls collapse.
An engineer looking at this problem might offer two solutions. The first is to widen the tube. The second is to reduce the airflow.
Widening a human airway through surgery is a last resort. While losing weight from around the neck region is helpful, a more plausible option is to reduce breathing volume.
Large breathing volume causes the airway walls to collapse, resulting in holding of the breath. During the cessation of the breath, the chest and diaphragm continue to try to draw air into the lungs. This results in jerking and heaving as the diaphragm presses downward. The greater the heaving of the chest and diaphragm, the more the airway walls are drawn inward. Eventually, the patient begins to breathe again.
Symptoms resulting from sleep apnoea include excessive daytime sleepiness, waking up tired, loud snoring, holding the breath during the night, loud snorts, gasps upon resumption of breathing, dry throat, dry mouth, and headaches in morning, problems with memory and concentration, heartburn or reflux, swelling of the legs, needing to urinate during the night, sweating during sleep, chest pain, and elevations in blood pressure. Of course, this loud snoring accompanied by loud snorts and gasps can also lead to marital problems.