Breathing continues automatically during sleep, although its patterns and underlying control mechanisms undergo noticeable changes compared to wakefulness. This continuous process ensures the body receives sufficient oxygen throughout the night. The way we breathe while asleep is a complex interplay between brain activity and physical airway dynamics. Understanding these shifts helps to distinguish between typical nocturnal breathing and patterns that might indicate an underlying issue.
The Mechanics of Normal Sleep Breathing
During sleep, the brainstem maintains involuntary control over respiration, regulating breathing rate and depth. This control ensures a continuous supply of oxygen to the body’s tissues. Respiratory muscles, including the diaphragm and intercostal muscles, receive signals from the brainstem to contract and relax, facilitating air movement into and out of the lungs.
Breathing patterns vary across different sleep stages. In Non-Rapid Eye Movement (NREM) sleep, the deeper stages of sleep, breathing becomes slower, more regular, and deeper than during wakefulness. As a person transitions into Rapid Eye Movement (REM) sleep, characterized by vivid dreaming and muscle relaxation, breathing can become faster, more irregular, and shallower. These fluctuations are normal physiological adjustments to the changing demands and states of the sleeping brain and body.
Common Variations in Sleep Breathing
Snoring is a common variation in sleep breathing, occurring when airflow through the upper airway is partially obstructed, causing tissues to vibrate. This vibration often involves the soft palate, uvula, and sometimes the base of the tongue. While occasional and light snoring is considered harmless, it indicates airway narrowing during sleep.
Mouth breathing during sleep is another common variation, often resulting from nasal congestion caused by allergies, colds, or anatomical factors like a deviated septum. When nasal passages are blocked, individuals breathe through their mouth to maintain airflow. This habit can lead to consequences like a dry mouth, sore throat upon waking, or increased susceptibility to dental issues. While not a disorder in itself, persistent mouth breathing can indicate underlying nasal obstruction.
Recognized Sleep-Related Breathing Disorders
Sleep-related breathing disorders involve abnormal breathing patterns during sleep that can disrupt sleep quality and oxygen levels. The most prevalent of these is Obstructive Sleep Apnea (OSA), which occurs when the upper airway repeatedly collapses or blocks during sleep. This physical obstruction, often involving soft tissues in the throat, prevents air from reaching the lungs despite ongoing efforts to breathe, leading to pauses lasting ten seconds or more. These blockages cause a drop in blood oxygen saturation and awakenings, though the individual may not recall them.
Central Sleep Apnea (CSA) presents differently, arising not from a physical blockage but from a failure of the brain to send signals to the muscles controlling breathing. In CSA, the respiratory effort itself stops for a period, as the diaphragm and chest muscles do not receive the command to contract. This can be influenced by conditions such as heart failure, stroke, or certain medications. Hypopnea is a related condition characterized by abnormally shallow breathing or a significant reduction in airflow, by at least 30%, lasting ten seconds or longer, resulting in a decrease in blood oxygen levels or an arousal from sleep.
When to Seek Medical Evaluation
A medical evaluation for sleep-related breathing issues may be beneficial if you experience loud, persistent snoring, particularly if it is accompanied by witnessed pauses in breathing, gasping, or choking sounds during sleep. These symptoms suggest obstructive sleep apnea. Frequent awakenings feeling breathless or experiencing excessive daytime sleepiness despite adequate sleep duration are also red flags.
Other symptoms include morning headaches, difficulty concentrating, irritability, or unexplained fatigue. A medical evaluation begins with a review of symptoms and medical history. To diagnose a sleep breathing disorder, a doctor might recommend a sleep study, known as polysomnography, which monitors brain waves, eye movements, muscle activity, heart rate, and breathing patterns overnight. This study provides detailed information about sleep quality and respiratory events.