Sleep Apnea Treatment

What is sleep apnea

In the bibliographic review we find unequal official definitions for obstructive sleep apnea. The Spanish Society of Respiratory Disease (SSRD) defines the OSAHS as “a picture characterized by drowsiness, neuropsychiatric and cardiopulmonary side- effects arised from anatomical and functional impairment of the upper airway that leads to repeated episodes of obstruction during sleep itself, causing declines in the SaO2 and transient arousals that lead to a restless sleep. ”. The National Consensus on the apnea-hypopnea syndrome in 2005, defines OSAHS as “"a picture of excessive sleepiness, cognitive-behavioral disorders, respiratory, cardiac, metabolic or inflammatory side-effects to repeated obstruction of the upper airway during sleep”. These episodes are measured with the respiratory disturbance index (RDI). An IAR ≥5 associated with disease-related symptoms and unexplained by other causes confirms the diagnosis.

Since Guilleminault et al in 1973 introduced the term to define sleep apnea in patients with obstructive sleep apnea and excessive daytime sleepiness, the meanings used by the authors have been very different. In many cases, this overlapping of estimations reflected a confusion in diagnosis of OSAHS, which is not clinically discriminated from other asociated pathologies. Because of the similar symptomatics OSAHS has been associated with other diseases, as the syndrome of hypersomnia and periodic breathing, chronic snoring or the “mermaids curse”. Currently the apnea syndrome is considered as a clinical entity of its own and must be established against other differential diagnosis of sleep breathing disorders (SBD). In the literature coexist the terms OSA, OSAHS or SAS, all referring to the sleep apnea syndrome. The National Consensus on apnea hypopnea sleep syndrome, associated with the Spanish Society of Pneumology and Thoracic Surgery (SEPAR) and the Latin American Thoracic Association (ALAT), use the implication of SAHS, considering it as the most comprehensive and inclusive . This designation inserts hypopnea events (hypopneas), seen as a key in the clinical development of the disease and with the same clinical effects to those of the apneas. It also eliminates the term obstruction that limits and excludes the phenomena of central and mixed apneas.

Sleep apnea consists of repeated episodes of breathing pauses (apneas) during sleep as a result of anatomical or functional upper airway alternations affecting the permeability and impacting negatively their tendency to collapse hampering the normal functioning of the respiratory cycle. Apnea is defined as a temporary cessation of breathing for more than ten seconds. Subjects with SAHS suffer continuous episodes of cessation of airflow in which they stop breathing, what dues to hypoventilation, oxygen desaturation and respiratory effort in response to hypoxia and hypercapnia. These episodes of asphyxia may have a variable duration of a few seconds, reaching in some cases a level up to a minute long and recurrently occur hundreds of times overnight. The interruption of airflow is due to an obstruction of the upper airway. The occlusion occurs preferentially at the throat, which is the only region of the respiratory tract without rigid frame. This anatomical composition of soft tissue converts it into an area predestinated for potential collapse. During sleep (mainly in REM sleep), the muscle tone of the pharyngeal muscles decreases (hypotonia) and the equilibrium is lost, which normally coordinates the respiratory muscles, the diaphragm and the throat.

This relaxation during sleep, in some cases, and for reasons not yet fully tested, causing occlusion of the airway. This collapse of the pharynx causes interruptions in breathing, apneas and hypopneas associated with repeated awakenings during sleep,what has the immediate consequence that the normal sleep pattern interrupts. These continual interruptions in sleep, lead to a lack of sleep for the impossibility of reconciling a deep sleep, whose most evident manifestation is the daytime somnolence. Moreover the relationship of SDB with hypertension, cardiovascular disease, impaired quality of life and a higher incidence in the percentage of work and traffic accidents is prooved. The lack of deep sleep can also generate a compromise of the cognitive level manifested in disorders of behaviour and personality with impairment of cognitive and intellectual abilities, increased irritability, and depression. And if it is true that OSA can not be considered as a fatal disease in itself it accepts increased levels of mortality associated with the syndrome.

Apnea

Term introduced by Christian Guilleminault and William C. Dement, apnea is defined as a complete cessation of airflow for 10 seconds or longer. It can be obstructive if accompanied by respiratory efforts, central, in the absence of thoracoabdominal efforts, and neurological or mixed apnea, which combinates an initiating central component and end up with an obstruction component. This definition has limitations, because it does not address the levels of oxyhemoglobin desaturations, it does not quantify the presence of arousals (EEG arousals), variables, which are necessary to estimate sleep fragmentation and alterations in gas exchange. Therefore it is accepted that the cessation of the respiratory signal is considered complete or obstructive when there is a decreased flow of > 90%.

Hypopnea

The term was coined by Kart et al to refer to a partial reduction of airflow that courses oxygen desaturation, arousals and clinical implications similar to those of apneas. The concept of hypopnea raises serious difficulties to find a general definition and the definition still raises controversy because of the lack of unified criteria. The American Academy of Sleep Medicine defines a hypopnea as “a discernible reduction in respiratory signal together with decreased oxygen saturation of at least 3% and/or an electroencephalographic arousal. Generally speaking, following the recommendations of SEPAR , it is considered as hypopnea, if there exist a respiratory signal > 30% y < 90%reduction in combination with transient arousals (arousals) on electrocardiogram and/or O2 desaturation less than 3%. (According to the authors this value varies between 2-4%).

Unconscious arousals or arousals

The arousal is an Anglo-Saxon term understandable to the Castilian language equivalent to arousal or alertness. These are characteristical events of the clinical features of SAHS. They are defined as reactions of the body that result from sleep to waking in response to a sudden phenomenon. In the apneic phenomenons, the arousal is a reply to respiratory arrest. During sleep, the dilatoring muscles of the upper airway (geniohyoid, genioglossus, tensor veli ...), loose their tone and exert a dilating decreasing force insuffient to offset the negative pressure produced by the inspiratory muscles (intercostal and diaphragm). This process disrupts the air flow, causing hypoxemia with oxygen saturation levels decreased in the oxyhemoglobin. Neurological centers of the central system detect the blood oxygen desaturation, and issued by the immediate response, efferent pathways called "arousal". These transient awakenings return to the subject of the physiological conditions of wakefulness, recovering the phasic activity of the upper airway, causing "rattling noise", which put an end to the apnea, preventing the death of the patient, but interrupting and altering the sleep process, so that it avoids phases of deep and restful sleep. EEG repeated awakenings throughout the night, cause of daytime somnolence, alterations in mood, intellectual impairment, asthenia, fatigue and chronic fatigue. The American Sleep Disorders Association (ASDA) defined arousal as "the sudden appearance of alpha or theta rhythms on the EEG of at least 1.5 seconds without that it is specifically accompanied by increased electromyographic activity except in the REM period.

Respiratory efforts associated with arousals (RERA)

The organisms response to an episode of apnea, is an increase in respiratory effort to recover the permeability of the airways and replace the airflow. They correspond to periods of more than 10 seconds, which show a progressive increase in respiratory effort, ideally detected by recording esophageal pressure, ending with an arousal. The presence of these thoracic efforts distinguish between apnea / obstructive hypopnea, where there is respiratory effort or apnea / central hypopneas, defined by the absence of such efforts. The mixed apneas combine components of both.

Apnea/hypopnea Index (AHI)

The combined number of respiratory events of apneas and hypopneas per hour is called AHI. A less than five index is considered as normal but is not indicative enough to exclude the presence of OSAHS. It is necessary to combine this with the number of respiratory efforts associated with EEG arousals so that the assessment is accurate and does not show false negatives.

Respiratory disturbance index (RDI)

The amount of respiratory events of apneas and hypopneas per hour plus respiratory efforts (RERA) determines the respiratory disturbance index (RDI). All these parameters are needed to determine a diagnosis of OSAHS. The American Academy of Sleep Medicine has more recently defined OSA as the presence of an abnormal respiratory disturbance index (RDI), considering the sum of the AHI with the RERA. An RDI> 5 associated with relevant clinical signs and symptoms is diagnostically considered as OSAHS.