Apnea refers to a temporary cessation of breathing, a pause in the respiratory process. While many associate breathing pauses during sleep with a physical blockage in the airway, such as snoring, there is a distinct type of apnea where the airway remains unobstructed. This condition, known as clear airway apnea, highlights a different mechanism behind the breathing interruption.
Defining Clear Airway Apnea
Clear airway apnea, often referred to as central sleep apnea (CSA), involves a cessation of breathing where the airway is open and there is no physical obstruction. Unlike obstructive sleep apnea (OSA), where breathing attempts occur against a blocked airway, CSA is characterized by a lack of respiratory effort. This absence of effort stems from the brain’s temporary failure to send signals to the breathing muscles, indicating a malfunction in its respiratory control center.
Underlying Causes
One significant cause of clear airway apnea is the immaturity of the central nervous system, particularly observed in premature infants. This condition, often termed apnea of prematurity, arises because their brains have not fully developed the control mechanisms for consistent breathing.
Neurological conditions can also contribute to clear airway apnea. Disorders affecting the brainstem, which houses the respiratory control center, or conditions like stroke and traumatic brain injury, can impair the brain’s signaling to the breathing muscles. Certain medications, including opioids and benzodiazepines, can suppress the central nervous system, thereby reducing the brain’s drive to breathe and inducing clear airway apnea. In some instances, clear airway apnea can manifest as a symptom of other medical issues, such as heart failure, which can alter blood gas levels and affect the brain’s respiratory regulation.
Identifying Signs
The signs of clear airway apnea can vary depending on age, but they generally involve observable pauses in breathing. In infants, especially premature newborns, these pauses can last 20 seconds or longer and may be accompanied by a bluish tint to the skin around the lips or nose, a rapid heart rate, or a severe decrease in heart rate. Caregivers might also notice periods of absent breathing, followed by gasping or snorting as breathing resumes.
For adults, clear airway apnea episodes may be less overtly dramatic, but a bed partner might notice frequent pauses in breathing during sleep. Individuals with clear airway apnea may experience excessive daytime sleepiness, difficulty concentrating, or morning headaches due to fragmented sleep and reduced oxygen levels. While snoring is more common in obstructive sleep apnea, it can sometimes occur with clear airway apnea, or the person might wake up feeling short of breath.
Diagnosis and Treatment Approaches
Diagnosis of clear airway apnea involves an overnight sleep study, known as polysomnography. This test monitors brain waves, heart rate, oxygen levels, respiratory effort, and airflow during sleep. Sensors detect the absence of chest and abdominal movement despite an open airway, confirming a central event. In some cases, home sleep tests that monitor heart rate, blood oxygen, airflow, and breathing patterns may be used as an initial screening tool.
Treatment for clear airway apnea is individualized and often targets the underlying cause. For infants with apnea of prematurity, caffeine citrate is a common pharmacological treatment that stimulates the central nervous system and reduces apnea frequency.
Respiratory support, such as continuous positive airway pressure (CPAP) or bilevel positive airway pressure (BiPAP), can be used to stabilize breathing patterns, even though the airway is clear. In situations where an underlying medical condition, like heart failure, is contributing to the apnea, treating that specific condition can help manage the central apneic events.