A sleep study, or polysomnography, is a diagnostic tool for identifying sleep disorders by monitoring bodily functions. Within sleep-disordered breathing, Respiratory Effort-Related Arousal (RERA) is a specific disturbance that sleep studies detect.
Understanding RERA
A Respiratory Effort-Related Arousal (RERA) occurs when there is an increase in breathing effort during sleep that does not meet the full criteria for an apnea or hypopnea but still causes a brief awakening from sleep. This increased effort often results from a partial narrowing of the upper airway, forcing the individual to work harder to pull air into their lungs. This heightened respiratory activity leads to increased intrathoracic pressure swings, which ultimately triggers a brief arousal from sleep. The defining characteristic of a RERA is this arousal, which fragments sleep, rather than a significant reduction in airflow or a drop in oxygen levels that might characterize other breathing events.
Identifying RERA During a Sleep Study
During a polysomnogram (PSG), RERA events are detected using specialized sensors. Nasal pressure transducers identify inspiratory flow limitation, showing a flattening of the inspiratory waveform as the airway narrows. Respiratory effort belts record increasing breathing effort. An electroencephalogram (EEG) monitors brain activity to identify the brief arousal that marks the end of a RERA event.
To be scored as a RERA, a sequence of breaths must last for at least 10 seconds and be characterized by increasing inspiratory effort or a flattening of the nasal pressure waveform. This increased effort must directly lead to an arousal from sleep, without meeting the more stringent criteria for an apnea or hypopnea. Sleep technologists and physicians analyze these data to identify and quantify RERA events. The inclusion of RERA scoring provides a more complete assessment of sleep-disordered breathing, especially when other respiratory events are not prevalent.
The Impact of RERA on Sleep Quality
RERA is clinically significant because its repeated arousals cause sleep fragmentation, even without oxygen drops or airflow cessation. These frequent awakenings prevent continuous, restorative sleep, disrupting the normal sleep architecture. Common symptoms include excessive daytime sleepiness, chronic fatigue, and unrefreshing sleep. Individuals may also experience morning headaches, dry mouth, or difficulty concentrating.
Frequent RERAs are a feature of Upper Airway Resistance Syndrome (UARS), a condition within sleep-disordered breathing. These ongoing disruptions can significantly impair daily functioning, cognitive performance, and overall quality of life, highlighting the importance of identifying and addressing RERA in sleep evaluations.
RERA Compared to Apneas and Hypopneas
RERA events are distinct from obstructive apneas and hypopneas, though all three fall under the umbrella of sleep-disordered breathing. An apnea is defined as a complete or near-complete cessation of airflow for at least 10 seconds, typically accompanied by a drop in blood oxygen levels. A hypopnea, conversely, involves a significant reduction in airflow, usually 30% to 50% or more, lasting at least 10 seconds, which is associated with either an oxygen desaturation or an arousal from sleep.
The key distinction for RERA is that it involves increased respiratory effort and an arousal from sleep without meeting the specific airflow reduction or oxygen desaturation thresholds of apneas or hypopneas. While apneas and hypopneas signify more severe airflow limitations, RERA represents a milder form of obstruction that still causes sleep disruption due to the associated arousal. Understanding these differences is crucial for accurate diagnosis, as the Respiratory Disturbance Index (RDI) includes RERA events along with apneas and hypopneas, providing a more comprehensive measure of sleep-disordered breathing severity than the Apnea-Hypopnea Index (AHI) alone.