Dentistry's Role in the Recognition and Treatment of Sleep-Breathing Disorders: The Need for Cooperation with the Medical Community
While the dentist can identify and help treat patients with sleep-breathing disorders, these conditions are potentially life-threatening diseases that are the domain of the medical profession.Laurence I. Barsh, DMD
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While oral appliance therapy for the treatment of sleep-disordered breathing can be an exciting and rewarding adjunct to the practice of dentistry, it is essential that dentists realize that snoring and obstructive sleep apnea are medical and not dental problems. Sleep-disordered breathing and its sequelae are diseases that should remain in the purview of the medical community. While the dentist can identify patients with sleep-breathing disorders and participate in their treatment, it is essential to emphasize that sleep-breathing disorders are potentially life-threatening diseases whose diagnosis and treatment are the domain of the medical profession. Accepting dentistry's position as part of a treatment team, ongoing review of scientific literature, cooperation with medical colleagues, and attendance at educational meetings dedicated to the study of sleep-related disorders are essential to proper and ethical dental participation in the treatment of sleep-disordered breathing. |
Article copyright 1998 Journal of the California Dental Association.
Photographs copyright of the authors.
The Washington Post, March 5, 1997, ran a story by Leef Smith. The article read, in part:
"A Man Who Fell Asleep at Wheel Charged in Deaths of Two in Va." "A Fredericksburg, Va., man who told police that he fell asleep at the wheel of his car has been charged with hit and run and two counts of involuntary manslaughter for his role in a crash that killed two motorists in Prince William County." A follow-up story described the sentencing as follows: "Drowsy Driver Gets Five-Year Sentence" "Judge Sends Message After Reckless Act Killed Two in Pr. William" The judge said he was exceeding state sentencing guidelines, which recommend a maximum term of six months, because of the nature of the crime and to send a message. "If you're tired and falling asleep as you drive, you need to get off the road, the judge said. For drivers who may consider getting on the road when they're drowsy, he said, "the lesson from this case is you go to jail."Table 1.
The Muscles of the Pharynx and Their Actions
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Subsequent interviews with the driver's defense attorneys, the prosecutor, and the driver's wife revealed the following. Despite the fact that the driver had complained of fragmented sleep and insomnia to his primary care physician, the physician failed to diagnose obstructive sleep apnea because the patient was of average height and weight. After the accident, the driver's attorney recruited a pulmonologist who prescribed an overnight sleep study, which disclosed severe obstructive sleep apnea.
Of the general adult population in middle age, 93 percent of women and 82 percent of men with moderate to severe sleep apnea syndrome have not been clinically diagnosed. Sleep apnea is even less likely to be diagnosed in the older population.1 Unrecognized sleep-disordered breathing is linked to motor vehicle accident occurrence in the general population and may account for a significant proportion of motor vehicle accidents.2
The question then arises: Who is responsible for recognition and diagnosis of obstructive sleep apnea?
A posting was made recently to an international sleep discussion forum on the Internet by a physician asked to act as an expert witness in several malpractice cases, that read, in part:
"I am interested in experiences of other sleep physicians interacting with the legal community. I have reviewed three medical cases wherein lack of recognition of sleep apnea by the attending physician allegedly led to brain damage or death, and have been asked to state whether that lack of diagnosis constituted a breach of the standard of care in each case."Snoring, a common malady that affects people of all ages but especially middle-aged men and elderly men and women who are overweight3,4 has been identified as a risk factor for hypertension, ischemic heart disease and stroke.5 Although not all people who snore have obstructive sleep apnea, snoring is a cardinal symptom of obstructive sleep apnea and, thus, may be associated with increased morbidity and mortality. Furthermore, snoring in some patients without apnea has been associated with significant sleep disturbance and excessive sleepiness. This condition has been referred to as upper airway resistance syndrome and is characterized by repeated nocturnal arousals without recognizable hypopneas or apneas.6
Is the dentist medically qualified and legally capable of making the diagnosis of obstructive sleep apnea and upper airway resistance syndrome and differentiating between primary snoring and these conditions?
Because snoring is so common, both the medical profession and the public have regarded it as merely an annoyance to one's bed partner or as a source of humor. With the realization that an oral appliance could stop snoring, the natural assumption by the dental profession was, therefore, that treatment of snoring could be incorporated into the dental practice simply and easily. Because snoring was considered so benign, the sequela to this assumption was that a physician did not have to be involved in the diagnosis of the problem and that the dentist could exclude obstructive sleep apnea from the diagnosis of primary snoring. Recently, however, snoring has become considered as prima facie evidence of an upper airway obstruction,7 a risk factor for cardiovascular disease,7-11 and a recognized precursor of obstructive sleep apnea.12
Because of these factors, the assumption that snoring is innocuous has been proven false, and snoring is now considered one stage of a complex continuum of disease states culminating in obstructive sleep apnea. Understanding the complicated pathophysiology of obstructive sleep apnea is essential to proper treatment and underscores the necessity of dentist-physician interaction. David Rapoport of the Department of Medicine, New York University School of Medicine, stated:
"Upper airway obstruction in OSAS [obstructive sleep apnea syndrome] results from interaction between subtle anatomic airway narrowing, increased wall collapsibility due to sleep-induced loss of baseline muscle tone, and insufficient inspiratory phasic dilator muscle contraction to oppose the negative intraluminal pressure resulting from diaphragmatic contraction."13The signs and symptoms of obstructive sleep apnea and the distinction between obstructive sleep apnea and simple snoring may appear to be easily recognizable, thus tempting the dentist to treat without physician involvement. However, the pathophysiology of both snoring and obstructive sleep apnea is infinitely more complex and less well understood. Because of this, the sequelae of improperly or inadequately treated obstructive sleep apnea syndrome can have an adverse effect on the general health of the patient.
There may be several causal factors contributing to the collapse of the airway. Potentially pathogenic anatomic configurations may include overdevelopment of the soft palate and/or tongue, constriction of the lumen (especially in the bucco-pharyngeal region), and poor compliance of the pharyngeal walls to distension and rebound during the respiratory cycle. A further possible contributory factor is the existence of localized regions of turbulent or near-turbulent airflow, which could either restrict flow directly or alter the normal patterns of air pressure within the lumen and contribute to collapse.
"Balance of Pressures" Concept
According to the "balance of pressures concept" discussed by Isono and Remmers:14
"The size of the pharyngeal lumen depends on the balance between outward forces developed by actively contracting muscles and inward forces resulting from subatmospheric luminal pressure during inspiration."
Neuromuscular Factors
 Figure 1. A depiction of the action of various muscles on pharyngeal structures. The tensor palatini moves the soft palate ventrally. The genioglossus acts to displace the tongue ventrally. The geniohyoid and sternohyoid act on the hyoid bone (H) to move it.14 |
Control of the size of the upper airway and stiffness of the walls depends on the relative contraction of a host of paired muscles known as the pharyngeal dilator muscles (Table 1). Contraction of these muscles promotes ventral movement of the soft palate, mandible, tongue, and hyoid bone as shown in Figure 1. It is generally accepted that inspiratory motor output to the muscles of the pharynx and related structures stiffens the pharynx and enlarges its lumen. The activity of the pharyngeal muscles is highly dependent upon a variety of factors within the central nervous system, particularly on the brain stem level. Wakefulness conveys a supervisory function that ensures airway patency. Sleep onset and pharmacologic agents that depress the brain stem respiratory network interact with the dilating effects produced by the musculature thus implicating the nervous system as a secondary contributor to the development of obstructive sleep apnea and hypopnea.14
Anatomic Factors
The size and configuration of the upper airway plays a major role in determining whether the patient will have obstructive sleep apnea. Gain or loss of fat in the pharyngeal and/or related areas like the tongue can lead to a change in size or configuration of the passive pharyngeal airway. According to Isono and Remmers,14 anatomic and structural abnormalities compromise the size of the pharyngeal airway in patients with obstructive sleep apnea (Figures 2 and 3).
 Figure 2. Sagittal view. Visual Human Project. The posterior border of the tongue makes upper the anterior wall of the pharynx. This portion of the upper airway is collapsible. An enlarged tongue also forces the soft palate and uvula toward the posterior wall of the pharynx and further obstructs the upper airway. |
 Figure 3. Coronal View. Visible Human Project. This view is taken at the floor of the mouth. Clearly visible are the lingual tonsils and the airway. |
Mechanical Factors Influencing Upper Airway Closure
Mechanical factors that influence upper airway closure depend upon complex mathematical formulae beyond the scope of this discussion. The comments that follow are included to paint a complete picture of the complexity of the situation and intended to illustrate that multiple theories and multiple causative factors are involved when discussing why a pharynx collapses and why obstructive apnea occurs. For a more complete discussion, the reader is referred to Isono and Remmers' chapter in Principles and Practice of Sleep Medicine14 and the numerous references provided.
* Compliance. The compliance of the pharynx is defined as the ratio of change in the cross-sectional area of the pharynx to change in the transmural pressure (Ptm), which is the difference between the luminal and tissue pressure ( Ptm = Pl - Pti). Using this definition, it has been demonstrated that multiple collapsible segments exist in the passive pharynx of patients with obstructive sleep apnea and that the nasopharynx is more compliant than the oropharynx and hypopharynx in many of these patients.
* Surface adhesive forces. Surface adhesive forces between opposed luminal surfaces may contribute to airway closure. These same forces may also make re-establishment of a patent pharynx more difficult. As the pharyngeal airway narrows, the mucous film lining the airway thickens and further narrows the airway.
* Pharyngeal luminal pressure. Two types of physical phenomena cause a reduction in the luminal pressure as gas flows through a tube. These are loss of energy by work done in overcoming flow resistive aspects of the upper airway and conversion of energy from static to kinetic caused by increase in the velocity of airflow when lumen size decreases.
* Effects of geometry of the pharynx on pressure and flow. This discussion adopts a fluid mechanical approach to the airflow in the pharynx. This allows one, according to Isono and Remmers, to infer that the true driving force for fluid flow between two points is not the difference in pressure but the difference in total fluid energy. This fluid mechanical approach could account for the mechanisms of pharyngeal narrowing extending downward during inspiration.
* Site and patterns of pharyngeal narrowing. Using endoscopic methods of evaluation, Remmers has determined that there are primary and secondary sites of pharyngeal narrowing, and 75 percent of patients had more than one site of narrowing. The soft palate is the most common site of narrowing in the pharynx of patients with obstructive sleep apnea. A posterior movement of the tongue and uvula causes narrowing of the oropharynx. Primary narrowing of the hypopharynx is rare in obstructive sleep apnea patients.14
Study of the pathophysiology of snoring and obstructive sleep apnea is not included in the dental curriculum of any accredited dental school as yet, nor is the subject of sleep disorders and the diagnosis and treatment of sleep-disordered breathing included in the dental practice act of any state. Despite dentistry's ability to offer a treatment modality -- oral appliance therapy -- that often provides the patient with a necessary solution to his or her medical problem, the diagnosis and prescription for that treatment still remains the prerogative of the medical community.
The sequelae of undiagnosed and incompletely treated sleep apnea are medical in nature and are disease states with which the dentist is unprepared to cope. In addition to an increased rate of motor vehicle accidents among the sleep apneic population,15 systemic hypertension has been reported in up to 50 percent of patients with sleep apnea.16 In fact, mean morning blood pressure has been shown to increase almost linearly with an increasing severity of obstructive sleep apnea in both obese and non-obese patients.17
Bradycardic arrhythmias have been associated with sleep apnea and ventricular tachycardia has been noted with severe hypoxemia.18 Myocardial ischemia has been noted in patients with underlying coronary artery disease. The infarction may be triggered by the hypoxemia and the concurrent bradycardia and hypertension.19 There is also evidence that there is an increased risk of stroke in patients who snore, have a history of observed apneas, or present with daytime sleepiness.20 A summary of the sequelae of sleep-disordered breathing is shown in Figure 4.
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The fact that the diagnosis and treatment of sleep apnea is beyond the licensure limitations of dentistry has prompted a dental malpractice insurance carrier to make the following ruling:
"Dentists providing sleep apnea therapy to patients (including Snore Guard therapy) are required by [the] insurance underwriter to ascertain that the patient has seen a physician about the problem and that the physician has determined that a dental appliance is the proper course of action."
As an alternative, the underwriter has requested that any dentist working with patients without physician referral should present the protocol followed to the underwriter for approval. (Personal communication -- CNA Insurance -- 1998).
"A simple, cost-effective screening tool for obstructive sleep apnea is a goal that many investigators are seeking but have not as yet achieved."
"Several features of obstructive sleep apnea suggest that it may be an appropriate disease for screening programs for general populations and more specific high-risk groups. Preliminary data suggest that obstructive sleep apnea represents an important health problem in terms of high prevalence, increased levels of morbidity and mortality, and increased public safety risk. Furthermore, the chronicity of the disease and the relatively low levels of recognition of the disorder in the medical community suggest a potential for lead-time gains for screening programs. Specific groups that might be considered for screening programs include commercial vehicle operators, hazardous duty personnel, and certain groups of medical patients. The purpose of this clinical commentary is to consider the issues of population and specific group screening for obstructive sleep apnea by reviewing the general principles of screening for chronic disease and then applying these principles specifically in the case of obstructive sleep apnea. More extensive outcomes data relating levels of severity of the disorder to its potential adverse outcomes are needed and will assist in tailoring appropriate screening programs and determining the cost-effectiveness of screening various populations."21
Because snoring was once considered so harmless, an oral appliance manufacturer might suggest and a dentist might assume that a medical history would be sufficient to distinguish between primary snoring and obstructive sleep apnea. Based on this assumption, the dentist might decide to treat his or her snoring patient with an oral appliance without consulting a physician or ordering a sleep test, which would then be reviewed by a physician. A number of studies22-29 state that while a detailed medical history may be an excellent screening tool, it is an insufficient instrument on which to base a final diagnosis and treatment plan. In this instance, the malpractice insurer quoted above might well refuse malpractice coverage for the dentist while he or she utilizes oral appliances for the treatment of snoring and obstructive sleep apnea.
The protocol of one appliance suggests that a dentist can screen for obstructive sleep apnea utilizing detailed medical histories and an overnight pulse oximetry reading, consulting with a physician only after treatment has been instituted. The use of pulse oximetry alone as a screening tool is still controversial31 as interpretation of the findings is difficult and should be approached by only those trained and experienced in interpreting the results. Furthermore, the levels of oxygen desaturation do not always correlate linearly with the severity of the apneas.
"The consequence of using screening oximetry was that a significant number of patients with sleep disorders that cause excessive sleepiness would remain undiagnosed and untreated. ... Screening oximetry was most successful in detecting patients with a high likelihood of having OSA [obstructive sleep apnea]... or those with more severe disease. ... In patients with milder disease, normal results of nocturnal oximetry did not mean the absence of SDB [sleep-disordered breathing]."31
The author continued by quoting other researchers on the same subject:
"Three other studies evaluated oximetry vs. PSG [polysomnography] with respect to severity of disease and found that oximetry was a suitable screen for patients with moderate and severe OSA but was inadequate for patients with milder cases. Only one study looked specifically at patients with milder forms of disease, including UARS [upper airway resistance syndrome]. ... [ In this study] oximetry detected all patients with moderate and severe OSA. However, 30 percent of the patients who were diagnosed normal by oximetry were found to have UARS on PSG. ... They concluded that oximetry was a poor screening tool since normal results did not rule out disease and all abnormal results required further PSG study."31In the patient base that dentists are likely to see -- those with mild to moderate obstructive sleep apnea -- pulse oximetry is the least accurate. Since both the medical sequelae and the results of excessive daytime sleepiness, that is, drowsy driving, can occur in mild to moderate disease; utilization of pulse oximetry as a tool to determine necessity of medical consultation leaves the dentist liable for missed diagnosis and, consequently, inadequate treatment.
Once one assumes responsibility for the diagnosis and treatment of a patient with a medical problem, one must also be prepared to deal with the diagnosis and treatment of a wide array of peripheral causative factors and sequelae to the original disease state. The cardiac ramifications as well as the results of excessive daytime sleepiness have been discussed previously. In the case of obstructive sleep apnea, there are other medical problems that must be managed coincident with the management of the obstructive sleep apnea per se.
* Weight management. Weight gain is associated with narrowing of the pharyngeal aperture as fat lines the pharynx. In addition, increased upper body fat contributes to difficulty in breathing.
* General fitness. Accompanying the loss of muscle tone with aging, the muscles of the pharynx weaken and are less able to maintain pharyngeal dilation opposing the factors discussed that tend to narrow the airway.
* Smoking cessation. The doctor who assumes care of the patient with primary snoring or obstructive sleep apnea must be prepared to counsel and treat that patient for smoking addiction as well as to be prepared to diagnose or refer for evaluation of the sequelae of cigarette smoking, including respiratory disease, coronary heart disease, and cancer.
* Alcohol consumption. While moderate levels of alcohol consumption have been reported in the media as being healthful, alcohol consumption before bed can lead to relaxation of the pharyngeal musculature and the development of obstructive sleep apnea.
* Nasal obstruction. Congestion from upper respiratory disease or allergic reaction may account for the development of transient snoring and obstructive sleep apnea; however, nasal polyps and tumors can block the air passage as well. The doctor who assumes care of the patient with obstructive sleep apnea must be prepared to diagnose and treat or refer for treatment patients with tumors of the nasal passage and adenoids.
* Pharyngeal tumors. These can include tumors of the tonsils and pharynx whose presence must be eliminated in the diagnosis of primary snoring and obstructive sleep apnea.
* Gastroesophageal reflux. Increasing thoracic pressure due to efforts to breathe against a closed airway can cause regurgitation of stomach contents into the oral cavity.
* Iatrogenic factors. Prescription medications including tranquilizers, sedatives, and muscle relaxants can increase the chance as well as the intensity of obstructive sleep apnea. Control of medication becomes a primary responsibility for the doctor treating obstructive sleep apnea.
Once one assumes care of a patient with a medical problem, one is bound by the standard of care, which is defined as:
"The uniform standard of behavior upon which the theory of negligence is based. The standard of care requires the actor to do what the ">reasonable person of ordinary prudence' would do in the actor's place. ... If the actor's conduct falls below the standard that a reasonable person would conform to under the circumstances, the actor may be liable for injuries or damages resulting from his or her conduct."32The most common definition of standard of care is "how similarly qualified practitioners would have managed the patient's care under the same or similar circumstances."33
Negligence refers to conduct that falls below the standard established by law for the protection of others against unreasonable risk of harm.32 The dentist who chooses to diagnose and treat primary snoring and obstructive sleep apnea without the participation of a medical colleague must ask himself or herself whether he or she is violating the standard of care.
According to legal experts:
"The medical malpractice plaintiff must establish the appropriate standard of care. In theory, establishing the standard of care and establishing the breach of that standard are legally separate. In reality, unless there is a factual question about what the defendant did, the proof of the standard of care also proves the defendant's breach. For example, assume that the defendant admits that she did not counsel the patient about prenatal testing. If the patient can establish that the standard of care was to offer this testing, the defendant breached the standard."33The parallels to the situation wherein a dentist treats a patient's snoring or apnea with an oral appliance without consulting a physician about the necessary sleep testing are obvious, leaving the dentist negligent.
Would a reasonable person assume the responsibility for the diagnosis and treatment of a medical problem for which he or she was not educated or licensed to treat?
The use of oral appliances for the treatment of sleep-disordered breathing can be an exciting adjunct to the practice of general dentistry. The ability to participate in the treatment of a potentially life-endangering disease provides a sense of satisfaction unmatched by other aspects of dentistry. Cooperation with colleagues in the medical community is essential before undertaking this challenging new aspect of dental practice. Additionally, the dentist must be willing to commit to the study of oral appliance therapy for sleep-disordered breathing with the same intensity and integrity as is applied to the rest of one's practice.
Accepting dentistry's position as part of a treatment team, ongoing review of scientific literature, participation with sleep specialists in sleep laboratories, and attendance at educational meetings dedicated to the study of sleep-related disorders are essential to proper and ethical practice.
Author
Laurence I. Barsh, DMD, is a general dentist and past president of the Sleep Disorders Dental Society, a member of the American Sleep Disorders Association and has served on the Board of Directors of the American Sleep Apnea Association.
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To request a printed copy of this article, please contact/Laurence I. Barsh, DMD, 30 W. 61st St., Suite 11D, New York, NY 10023.
