During the most restful sleep, some people snore unpleasantly loudly, which destroys the chance of dormancy for everyone who shares their bedroom. But even those who do not snore breathe harder when they nod than when they are awake. Why do people breathe so hard when they sleep?
The noise made when you breathe – whether you are awake or asleep – is caused by the vibration of air moving through the breathing tube, said dr. Timothy Morgenthaler, a pulmonologist and specialist in sleep medicine at the Mayo Clinic in Minnesota, said. How hard the breathing sounds depends on how narrow the breathing tube is and how fast air moves through it. “You could almost consider it a musical instrument,” he said.
As you inhale, the rapid air movement to your upper airway – the part of the respiratory system that extends from the mouth to the larynx – reduces the pressure in the entire airway, also known as the airway. This pressure change can cause the upper airway to collapse, impeding breathing. A reflex in the upper airway prevents it from collapsing and keeps your pipes open when you are awake. “Because it’s open, the flow through that airway is not turbulent, so the air moves without much noise,” Morgenthaler told WordsSideKick. But when you sleep, the reflex is not so strong. The upper airway tends to partially collapse, and breathing becomes louder.
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Sleep, especially during rapid eye movement (REM), also leads to lower muscle tone around the airway, Morgenthaler added. In other words, the muscles that support the airway relax and cause the breathing tube to contract. As the airway becomes narrower, the velocity of the air increases thereby. The air vibrates more and creates more sound.
The tightness also means that your breaths become fast and shallow. The average person takes about 14 breaths per minute while awake and 15 or 16 while sleeping, Morgenthaler said. Although you breathe more often while you sleep, you take in less oxygen and emit less carbon dioxide because your body’s need for ventilation is not as high as when you are awake. “We do not expect to go away and chase or harvest an animal,” he said.
If someone’s breathing tube becomes particularly narrow, they may start snoring. This usually happens when the airway reaches the diameter of a McDonald’s straw, which is slightly wider than ordinary straws, Morgenthaler said. When it is so small, the air in the airway not only vibrates but also tissues in the environment that cause snoring.
If someone’s airway narrows further during sleep, they may develop obstructive sleep apnea. The airway can become so narrow that breathing is impossible, and the person wakes up to gasp for air. Even in people without sleep apnea, the airway can reduce it to four times an hour. If it occurs more frequently, it becomes obstructive sleep apnea. Losing weight is often an effective treatment because excess fat around the airways can impede breathing. Morgenthaler also recommended that alcohol be skipped near bedtime because it relaxes the surrounding muscles. If that doesn’t help, the person may need a machine such as a continuous positive airway pressure (CPAP) to keep the airway open during sleep, he said.
Originally published on Live Science.