RENEW OR SUBSCRIBE TO PPM
Subscription is FREE for qualified healthcare professionals in the US.
6 Articles in Volume 1, Issue #6
Accurate Diagnosis
Getting Off the Pain Roller Coaster
Getting to the Point
Opioid Rotation: Mechanisms, Concepts, and Benefits
The Neural Plasticity Model of Fibromyalgia Theory, Assessment, and Treatment: Part 4
The Pain and Sleep Relationship

The Pain and Sleep Relationship

CPAP and oral appliances offer hope for many pain patients who have sleep disorders.

Obstructive sleep apnea syndrome (OSAS) is a common yet underrecognized disorder. It is the most prevalent sleep disturbance observed at sleep disorder centers — of the approximately 75,000 patients seen annually in these centers, roughly 75 percent are diagnosed with OSAS.1,2 In the general population, OSAS affects approximately four percent of middle-aged adults and up to 50 percent of elderly persons.3,4 Projections of the prevalence of OSAS in the US range from seven to 18 million people.2

OSAS is a potentially life-threatening condition characterized by repeated collapse of the upper airway during sleep and cessation of breathing. The spectrum and severity of clinical presentations of OSAS are extremely variable.

In addition to its potential effect on mortality, OSAS can have a profound impact on quality of life. Many patients who suffer from OSAS experience pain, which further disturbs sleep. It is therefore important for caregivers who manage pain to be aware of the causes and treatment of OSAS.

Pathophysiology

Despite the prevalence of sleep apnea, the pathogenetic mechanisms of this disorder are not completely understood. Most of the data on the mechanisms of OSAS are derived from studies during non-rapid eye movement (NREM) sleep.

OSAS has been associated with anatomic compromise resulting from neoplasia (benign or malignant), metabolic abnormalities, and traumatic compromise. Inflammatory disorders may cause diffuse enlargement of structure such as the tongue and pharyngeal lymphoid tissues (as in tonsillitis), resulting in a compromise of the airway. However, in the majority of patients with OSAS, no specific focus of upper airway pathology can be identified.

Numerous mechanical factors may also influence upper airway closure and predispose a person to OSAS. These include upper airway caliber and compliance, load compensation, surface adhesive forces, pharyngeal luminal pressure, and thoracic caudal traction.

Associated Conditions

OSAS may occur in association with another primary sleep disorder called restless leg syndrome (RLS). RLS is characterized by intense pain or discomfort, mostly in the legs, during the evening when at rest. It is an akathisia and is often described as a “creepy sensation.” Patients with RLS note a strong urge to keep moving their legs or to get up and walk around to relieve the pain. RLS may significantly interfere with the onset of sleep.

Periodic limb movement disorder (PLMD) may accompany RLS or occur independently. This idiopathic condition is characterized by episodes of stereotypic rhythmic movement, usually of the legs, although other muscle groups (including the arms) may be involved. The patient’s bed partner typically perceives these episodes as kicks that occur in cycles of 20 to 40 seconds. Hundreds of limb movements may occur during a single night, but most of the time they do not awaken the affected person. They may, however, produce many brief arousals that disrupt sleep and decrease the amount of time spent in the deeper stages of sleep. The delayed sleep onset related to RLS and the sleep disruption from PLMD may cause daytime sleepiness.

RLS is primarily a clinical diagnosis. PLMD may be suspected based on information obtained from a bed partner. If necessary, the diagnosis can be confirmed by electromyography of limb-muscle activity during nighttime monitoring in a sleep laboratory.

There are no known causes of RLS. Caffeine and alcohol ingestion can aggravate and increase the frequency of RLS symptoms. Possible causes of RLS and PLMD include diabetes, Parkinson’s disease, rheumatoid arthritis, thyroid disease, iron and/or vitamin deficiency, and kidney dysfunction.

Like RLS, PLMD has no known causes. PLMD occurs only during sleep and involves unilateral or bilateral movements of limb muscles. The condition may be metabolic, vascular, or neurologic in origin. In addition to occurring commonly in patients with RLS, PLMD may occur in persons with OSAS.

Many persons with RLS and/or PLMD endure associated pain and other symptoms for years before seeking medical care, by which time they are in their 50s or 60s. Perhaps for this reason RLS and PLMD are associated primarily with geriatric patients; however, it is important to be aware that these primary sleep disorders can occur at any age.

Treatment should begin by examining the patient’s lifestyle and looking for opportunities to initiate lifestyle modification, particularly with regard to substances known to exacerbate symptoms (i.e., caffeine and alcohol). Because sleep loss can worsen symptoms, attention should be given to optimizing sleep habits.

For patients in whom changes in diet, drinking patterns, and sleep habits fail to reduce the symptoms of RLS and PLMD, drug therapy is indicated. Drug therapy is also indicated if there is pain associated with RLS or PLMD. There are four general classes of drugs used to treat RLS (and associated PLMD): dopaminergic agents, benzodiazepines, opioids, and anticonvulsants. Use of any agent should be viewed as a therapeutic trial; if symptom resolution does not occur within approximately one month, then a switch to another class of agents is a good idea.

Snoring and Sleep Apnea

Many people who snore or have OSAS mouth-breathe during sleep. Although this has not been systematically investigated, increased nasal or nasopharyngeal resistance might explain it.

Clinical studies have confirmed that nasal obstruction exacerbates a tendency toward OSAS.5 The larynx — the other high-resistance structure in the upper airway — can be the site of OSAS when compromised by space-occupying lesions or abductor paralysis.

Nonsurgical Management

Nonsurgical approaches to the management of OSAS include behavioral modification, drug therapy, continuous positive airway pressure (CPAP), and use of mechanical devices. Behavioral modifications include avoidance of alcohol and sedative medications, alteration of sleep position, avoidance of sleep deprivation, and weight loss. Drug therapy for OSAS is of limited clinical value, with the exception of thyroxine replacement in patients with hypothyroidism.14

Nonsurgical approaches to the management of OSAS include behavioral modification, drug therapy, continuous positive airway pressure (CPAP), and use of mechanical devices.

Continuous Positive Airway Pressure

Nasal CPAP is the initial treatment of choice for OSAS in adults and can reduce mortality and morbidity associated with OSAS.6 CPAP allows progressive restoration of air flow, as the pressure applied exceeds the airway opening pressure. CPAP works by pneumatically splinting the collapsible upper airway.

Because body position and sleep stages vary throughout the night, the CPAP mask pressure often does not remain constant. To address this problem, many sleep clinicians select a sufficiently high pressure setting to ensure that respiratory disturbances are reliably inhibited even in the least favorable situations. Unfortunately, this necessitates a needlessly high mask pressure for periods during which it is not required. Furthermore, the high mask pressure may make CPAP uncomfortable. Variable patient compliance remains a significant problem. Studies have found that up to 25 percent of patients discontinue CPAP therapy.7,8

A recently introduced CPAP device† offers the option to automatically adjust mask pressure to the lowest effective setting according to the varying requirements during the night. Self-adjusting nasal CPAP demonstrates similar reliability as conventional nasal CPAP in suppression of respiratory disturbances.9

Airway dryness may also contribute to CPAP discomfort. The high flow rates used during CPAP may overwhelm the capacity of the nasal mucosa to heat and humidify inspired air. Compounding this problem is a phenomenon known as mouth leak which occurs during approximately one-third of total sleep time in people who suffer from dryness of the nose and throat.10 During mouth leak, a portion of air bypasses the nasal membranes and exits via the mouth. Normally, expiratory air releases heat and water back into the nasal mucosa by condensing on the cooled mucosal surface. Leaked air is not conditioned in this way, and results in intensification of the excessive dryness experienced during the use of CPAP. To compensate for the decreased heat and humidification caused by mouth leak, blood vessels in the nose dilate; however, their capacity to do so may be overwhelmed by the high flow rates produced by CPAP. As the patient continues to mouth leak, further moisture is lost and blood vessels continue to dilate, thereby narrowing the airway.11 The net result of this process is increased nasal resistance and nasal congestion.12

Several recently introduced devices offer heated humidification, either as a stand-alone unit‡ that can be used in conjunction with any CPAP machine, or as an integrated CPAP system and heated humidifier‡†. The provision of heated and humidified air allows for a decrease in nasal resistance and alleviation of dryness and congestion experienced by patients with mouth leak.

Several pre-existing conditions may contraindicate the use of CPAP therapy for some patients. These include: bullous lung disease, pneumothorax, hypotension associated with intravascular volume depletion, cardiac arrhythmias, history of head trauma, and seizure disorders. When considering the use of CPAP in patients with any of these conditions, the clinician should weigh carefully the potential risks versus the potential benefits.

Oral Appliances

Another therapeutic option for patients with OSAS is the use of oral appliances. An oral appliance is a small device, similar to an orthodontic retainer or an athletic mouth guard. It is worn in the mouth during sleep to prevent the soft throat tissues from collapsing and obstructing the airway. Oral appliances relieve OSAS and snoring by realigning the jaw and/or tongue in relation to the head. Although oral appliances do not work on everybody, a well-made, well-fitted appliance may reduce or eliminate snoring, and may significantly relieve the symptoms of OSAS.

Oral appliances can be categorized generally into three types based on design. The first type mechanically lifts the soft palate. The effectiveness of this appliance type is presumed to be due to a prevention of collapse at the velopharyngeal level. The second type positions the tongue anteriorly while the mandible retains its customary relation to the maxilla. Some oral appliances of this type use a suction cup; others are designed to work through nocturnal neuromuscular training. Most oral appliances are of the third type — mandibular advancement appliances — which, as the name implies, advance the mandible. Because the mandible is the attachment for the genioglossus and other tongue muscles, the tongue moves anteriorly, as it does with the second type. The mechanism of action of the second and third of these oral appliance designs is to enlarge the hypopharyngeal airway by moving the base of the tongue farther from contact with the posterior wall of the pharynx, thereby reducing the likelihood of collapse from inspiration.

A position paper of the American Sleep Disorders Association states that oral appliances can be effective for patients with mild-to-moderate sleep apnea as well as for individuals who snore but do not have OSAS.13 Determination of the severity of OSAS depends on a number of factors, including degree of blood oxygen desaturation, duration of apneas, sleep efficiency, and severity of excessive daytime somnolence. Oral appliance therapy is a primary treatment for patients with mild-to-moderate disease and a secondary treatment for those with moderate-to-severe disease who cannot tolerate CPAP.13

Early use of an oral appliance may be indicated if a clinician believes that a patient will be poorly compliant with CPAP therapy. This can be the situation if a patient is claustrophobic, travels frequently, has preexisting sinus or nasal problems, or is reluctant to be dependent on a machine.

Pain and Sleep

Pain has long been recognized as accompanying sleep disorders, but the relationship between pain and sleep disorders is complex. The experience of pain affects one’s ability to obtain a restful night’s sleep. Certain conditions that cause pain have identifiable effects on sleep patterns. Furthermore, sleeplessness affects pain perception, potentially resulting in a vicious cycle.

Currently, there is no consensus in the medical community about how to treat the two problems when both are present. The consequences of sleeplessness can include impaired performance, decreased productivity, increased absenteeism from work, disability, elevated health care costs, and dangerous driving. Therefore, treatment is important.

Diagnosing the cause of sleeplessness is the first step toward optimal management of the patient with a sleep disorder and associated pain. Treatment should be matched to the cause when possible. If an underlying or accompanying medical disorder is identified, treating it is important. Quality of life suffers when pain and nonrestorative sleep become chronic.

Conclusion

The consequences of OSAS and other sleep disorders can be significant for those affected as well as bed partners and family members. Most patients will eventually seek treatment if symptoms are unrelenting and/or progressive. Optimal management depends on accurate diagnosis, and institution of the appropriate therapeutic modalities. If pain is a significant component of the sleep disorder, then it should be treated.

Tackling the pain/sleep relationship can be accomplished through an enhanced understanding of the pathophysiology of OSAS. New and improved therapeutic modalities in the areas of CPAP and oral appliances may be the most appropriate treatment for pain patients with sleep disorders.

Last updated on: December 28, 2011
close X
SHOW MAIN MENU
SHOW SUB MENU