Sleep Related Respiratory Disorders:
A Review For The Primary Care Physician

Mitchell S. Rothstein, M.D., Pulmonary and Critical Care Associates, Board Certified Sleep Specialist, Director, Sleep Centers of America
 

Sleep related respiratory disorders include a continuum of conditions ranging from primary snoring through sleep apnea/hypopnea syndrome (OSAH). They are omnipresent in our society and are gaining recognition for their effects on quality of life as well as their direct relationship with well-accepted diseases such as hypertension, stroke and congestive heart failure.¹ OSAH is characterized by repetitive episodes of upper airway obstruction that occur during sleep and are usually associated with reductions in blood oxygen saturation and frequently associated with cortical electroencephalogram (EEG) arousal activity. The term Pickwickian syndrome was originally applied to those patients who had sleepiness, obesity, and evidence of right heart failure. Some of these patients probably had central alveolar hypoventilation syndrome or obesity hypoventilation syndrome rather than typical OSAH, as we now know it.

Epidemiology

Two percent of women and four percent of men meet the minimal diagnostic criterion for OSAH. Risk factors include obesity which is an important factor also contributing to the severity of OSAH. A snoring, hypertensive male with a short, fat neck and a collar size of 17 inches or greater is the prototypical patient profile. An upper airway exam revealing a thick tongue, ptosis of the soft palate with redundant tissues and an elongate, often edematous uvula, large tonsils, retrognathia, and a high arched hard palate are also suggestive, especially in combination with obvious evidence of nasal obstruction such as hypertrophied turbinates, polyps or septal deflection.

Pathophysiology

The physiologic consequences of OSAH can be divided into two groups, cognitive and cardiovascular. Repeated arousals with episodes of upper airway obstruction lead to severe sleep fragmentation causing excessive daytime sleepiness, cognitive impairment, memory loss and probably depression with personality changes over the long haul.

Cardiovascular consequences secondary to autonomic override from acidosis, hypoxemia and hypercapnia include the development of systemic and pulmonary hypertension, cardiac dysrhythmias ranging from sinus arrest to ventricular tachycardia as well as complete heart block.

OSAH is found in 38% of patients with hypertension compared with 4% of normotensive patients and OSAH is now an independent risk factor for the development of hypertension. ^2,3 Ten to twenty percent of OSAH patients have pulmonary hypertension. ⁴ Pulmonary hypertension is most likely to develop in OSAH patients who have daytime oxygen desaturation. Patients with pulmonary hypertension tend to be drowsier, have lower FEV-1s and lower oxygen saturations with a higher respiratory disturbance index. ⁵

Cardiac arrhythmias are common accompaniments of OSAH. During the apneic phase bradyarrhythmias are more common with tachyarrhythmias accompanying the hyperpneic phase developing the classic tachy-brady syndrome. Untreated OSAH is associated with an increased risk of cardiac mortality in patients with underlying CAD. ⁶

The most obvious pathogenic factor is local obstruction of the upper airway by soft tissue collapse; other factors are also important including neural influences and hormonal affects. Some obese and non-obese individuals with small airway spaces do not have OSAH indicating that more than just anatomy is important. During sleep in individuals predisposed to OSAH the upper airway collapses at the end of expiration and maintains its closed position during the inspiratory phase, in part, because of negative suction effects exerted at the level of the upper airway either retropalatal, retroglossal, or at both locations. Genetics also play a role as demonstrated by the familial predisposition of OSAH through predetermined neural control of the upper airway dilators and the shape of the posterior airspace.

There are significant differences in the size of upper airway soft tissues between normals, snorers, and OSAH patients. ⁷ Skeletal abnormalities primarily retrognathia, congenital craniofacial abnormalities and mandibular hypoplasia with micrognathia as seen in the Pierre Robin Syndrome are classic.

Diagnosis

The gold standard for diagnosis remains all night polysomnography, which includes sleep staging, respiratory measures, oxygen saturation, position monitoring, electrocardiography, limb movement monitoring and video recording. Results are analyzed in terms of respiratory events, arousal activity, sleep fragmentation and desaturation events. Typically patients with OSAH can be divided along lines of severity, which seem to correlate with physiologic consequences (i.e., excessive daytime sleepiness and cardiovascular sequela). Characteristically these patients have decreased slow wave sleep as well as decreased REM sleep with increased fragmentation. OSAH may be positional or sleep staged dependent. Patients of sufficient severity demonstrated early in the study can undergo baseline analysis during the first two hours and experience CPAP application during the final three hours or more of this study and be titrated to an effective pressure to relieve respiratory events and improve sleep continuity. Portable monitoring devices can be useful in evaluating patients who are unable to undergo in-lab polysomnography or patients with severe clinical presentations to whom the lab is unavailable for immediate diagnosis.

The differential diagnosis includes upper airway resistance syndrome, central sleep apnea syndrome, central alveolar hypoventilation syndrome and primary snoring. Central sleep apnea syndrome is characterized by cessation or decrease in ventilatory effort during sleep usually associated with oxygen desaturation. Central alveolar hypoventilation is characterized by ventilatory impairment resulting in arterial oxygen desaturation worsened by sleep, which occurs in patients with normal lung mechanics. Primary snoring is characterized by upper airway breathing noises without evidence of apnea, hypoventilation or arousals. Upper airways resistance is characterized by excessive daytime sleepiness, repetitive arousals greater than 10 per hour and sleep fragmentation with or without snoring and with or without oxygen desaturation.

Treatment

Therapeutic intervention in sleep related respiratory disorders is based on findings from nocturnal polysomnography, severity and patient acceptance. The apnea hypopnea index (AHI) provides an overall index of the frequency of respiratory disturbance per hour with an acceptable range of less than or equal to five. The arousal index may be of even greater significance and indicates the number of transient interruptions of sleep continuity per hour. Dividing severity of disease roughly based on the AHI into mild, moderate and severe classifications can be used to stratify some treatment plans.

All patients with OSAH should be advised to lose weight, since weight loss is the only known cure for some patients with OSAH. Generally a 10 to 15% decrease in body weight is needed to significantly decrease the AHI although this amount of weight loss is probably not adequate to cure OSAH in most patients. Other behavioral measures include avoidance of alcohol and sedating medications. Sleep deprivation is known to worsen OSAH and should be avoided if possible. Prompt treatment of colds and use of nasal decongestants and antihistamines are also important adjuvant measures in patients with nasal obstruction. Smoking cessation reduces upper airway irritation and edema, which can worsen OSAH. Head of bed elevation and positional therapy may be beneficial in selected patients.

Nasal continuous positive airway pressure (CPAP) is the most effective treatment of OSAH. CPAP works by splinting the upper airway and preventing collapse of soft tissue. This effectively eliminates apneas and hypopneas and decreases recurrent arousal from sleep as well as normalizing oxygen saturation. Most non-randomized studies show that CPAP reduces excessive daytime sleepiness (EDS) and improves mood, depression and quality of life evaluations. Recent studies have assessed the effectiveness of CPAP in patients with moderate OSAH; CPAP improves daytime sleepiness, mood, vigilance and attention. ⁸ In mild OSAH improved subjective reports of daytime sleepiness, depression and social function have been reported. ⁹

Side effects include dry mouth, rhinitis, and sinus congestion. The congestion can be particularly severe in patients with underlying sinus disease. In general, these side effects are effectively treated with humidification and use of nasal steroid sprays and/or antihistamines. Pressure sores from poor mask fits and allergic reactions can be addressed with a variety of mask types and refitting. The usual compliance rates of 50 to 70% reported after three months of therapy, may be improving with an increasing variety of mask types, interfaces and increasingly patient friendly auto-titrating/pressure generators. ¹⁰ Attentive medical follow up with increasing patient contacts also seem to trend towards increasing compliance rates.

Oral or dental appliances are being increasingly used in the management of OSAH and over 50 types of devices are now available. Oral appliances generally fall into two broad categories: tongue-retaining devices, which move the tongue forward, and mandibular advancement devices, which move the mandible forward. Both types increase the oral pharyngeal airspace and reduce the likelihood that soft tissues will collapse. Mandibular advancement devices also appear to put tension on the soft palate decreasing the likelihood of collapse. ¹¹

These devices appear to be most effective in primary snoring, upper airway resistance syndrome and mild to moderate OSAH. Major side effects include dental misalignment and aggravation of temporal mandibular joint disease.

For these reasons, dentists with an interest in treating patients with SRRD should follow patients who use oral devices. Still lacking are data demonstrating that oral devices are as effective as nasal CPAP. We consider oral appliances as first line therapy in primary snoring and in patients who refuse to try or fail to respond to CPAP in mild to moderate disease. We recommend follow up polysomnography to objectively document improvement in sleep architecture and reduction in the AHI.

Surgical intervention is indicated in patients who have surgically correctable abnormalities that are causing OSAH. Adeno-tonsillar hypertrophy is the most common correctable abnormality particularly in young adults. While nasal obstruction can also contribute to snoring and OSAH, correction of nasal obstruction does not generally resolve the OSAH because the site of collapse is in the oral or nasopharynx not the nasal cavity. Correction of severe nasal obstruction, however, is often indicated in an attempt to improve tolerance to CPAP. In general, a surgical approach in OSAH is recommended only for patients in whom non-invasive treatments have been unsuccessful or rejected. A stepwise approach to therapy appears to be associated with a higher success rate (defined as a 50% reduction in the AHI and final AHI less than 20). The area of pharyngeal collapse whether retrolingual or retropalatal is identified via a Muller Maneuver. The first stage procedure is then performed. Patients with retropalatal collapse undergo uvulopalatopharyngoplasty (UPPP). Patients with retropalatal and retrolingual collapse undergo UPPP combined with Genioglossal advancement with hyoid myotomy and suspension (GAHM). Patients with retrolingual collapse undergo GAHM. Response rates of 80%, 57% and 67% respectively for each procedure have been reported. ¹² If patients do not respond to an initial procedure, as noted above, then maxillomandibular advancement and osteotomy is performed. These are highly specialized procedures requiring a great deal of experience and expertise. Newer procedures such as somnoplasty and tongue base suspension are being used in various settings in an attempt to identify their success rates and identify a patient profile to apply them to. Tracheostomy remains the ultimate curative surgical intervention with a 100% surgical success rate but significantly less than jubilant patient acceptance.

Conclusion

OSAH is an important medical disorder that warrants active investigation by means of clinical evaluation and polysomnography studies. Treatment is essential not only to improve symptoms that include sleepiness but also to prevent the development of cardiovascular complications and relieve ongoing cognitive impairment. Effective treatment exists and includes behavioral, medical and surgical approaches. These can result in dramatic improvement in patient well-being.

References

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Jacksonville Medicine / March, 2001