The use of ENT-prescribed home sleep studies for patients with suspected obstructive sleep apnea.

Abstract

Sleep disordered breathing, including obstructive sleep apnea, is a common and morbid health problem. Traditionally, sleep disordered breathing is diagnosed by complex sleep studies. However, newer, easy-to-use, highly sensitive, and highly specific home sleep study equipment is now available. The present study was undertaken to determine whether an otolaryngologist could easily and effectively dispense home sleep equipment from the office. We used a portable AutoSet home sleep machine. Our experience with the first 100 consecutively presenting patients was recorded and analyzed under institutional review board approval.

Ninety-nine of the 100 tests were completed successfully on the first attempt; the one failure was successful on the second attempt. Our results were consistent with those reported from in-house polysomnogram sleep studies; 71% of our patients had an apnea-hypopnea index (AHI) of 15 or higher, and 93% had an AHI of at least 5. We conclude that an otolaryngologist, using state-of-the-art home sleep testing equipment, can accurately and cost-effectively prescribe home sleep studies.

Introduction

Sleep disordered breathing (SDB) is a serious public health problem, affecting 40 million adult Americans. [1-3] Most of these patients suffer from a particular form of SDB known as obstructive sleep apnea (OSA). OSA is characterized by episodic cessations of breathing during sleep because of the collapse or blockage of the upper airway, which causes oxygen desaturations, fluctuations in heart rate and blood pressure, frequent arousals from sleep, decreases in growth and immune modulators, and excessive daytime sleepiness.

Using the most liberal definition of OSA--an apnea-hypopnea index (AHI) of 5 events per hour--one landmark study found that up to 24% of men and 9% of women had OSA. [4] Using a stricter diagnostic criteria--an AHI of at least 15 events per hour plus a history of daytime hypersomnolence--the same study reported that 4% of men and 2% of women suffered from OSA.

Making the diagnosis is imperative because when OSA is left untreated, it is associated with significant mortality and morbidity brought on by hypertension, obesity, transient ischemic attacks, stroke, congestive heart failure, and myocardial infarction. [5] Because the diagnosis cannot be made by clinical history or physical examination alone, [6,7] detection has traditionally involved the measurement of the AHI by polysomnography (PSG). PSG entails monitoring at least seven parameters during an overnight sleep study in a laboratory, with a technician present throughout the entire study. The seven main parameters are electroencephalography (EEG), electro-oculography (EOG), chin electromyography (EMG), electrocardiography (ECG), airflow, respiratory effort, and oxygen saturation.

Although PSG results remain the gold standard for the diagnosis of OSA, its high cost and limited availability make the portable, unattended sleep monitoring system an increasingly attractive alternative. Portable monitors have been validated in numerous studies. [8-16] They measure different parameters depending on the model. Home monitors hold some advantages over PSG: they allow for wider access to sleep studies, they do so at a lower cost, and they allow patients to sleep in their normal environment, thus minimizing the "first-night effect" often associated with PSG. [15]

Moreover, because the data from these portable devices are relatively easy to interpret and have a high degree of sensitivity and specificity, [8] more physicians have the capability to evaluate patients who present with a history suggestive of OSA. This is especially important for otolaryngologists, who can use these devices not only to evaluate snoring and OSA, but to monitor postsurgical AHIs as well. This latter fact might hold significant prognostic implications. For example, He et al found that the incidence of mortality from SDB following uvulopalatopharyngoplasty remained high. [5] He expressed concern that some of these patients might have been cured of their snoring and had lost an important symptom of SDB, which went undetected because the snoring had been eliminated. The result was that these patients remained at significant risk for morbidity and mortality.

As otolaryngologists continue to exhibit more interest in sleep medicine and surgery [2]--including procedures such as phase I/II surgery, [17] laser-assisted uvuloplasty, [18-20] and most recently radio-frequency surgery [21]-and as cost-effective sleep tests become available in many parts of the country and the world, there is a great need for sleep testing capabilities in the ENT office.

Materials and methods

We studied 100 consecutively presenting adults, 83 men and 17 women (mean age: 52), who were suspected of having sleep apnea syndrome and who were referred to the ENT clinic at the Centre for Healthcare, a private clinic in the San Diego suburb of Rancho Bernardo, Calif. The patients' mean body mass index (BMI) was 32 kg/[m.sup.2] (normal:25), their mean neck circumference was 43 cm (17 in), and their mean blood pressure was 129/81 mm Hg.

A history (figure 1), including ascertainment of the Epworth sleepiness scale score, [22,23] and a physical examination (figure 2) were performed on all patients. Each patient was instructed on how to operate a multichannel portable sleep monitoring device (AutoSet Recorder, ResMed Corp., San Diego). The AutoSet device measures respiration via nasal cannulae and oxygen saturation via finger pulse oximetry. This machine defines an apneic event as a cessation of nasal airflow for 10 seconds or longer and a hypopneic event as a 50% reduction in nasal ventilation. The AutoSet has diagnostic and continuous positive airway pressure (CPAP) titration capabilities and has been validated. [8-10, 16, 24] Patients self-administer the sleep study at home and return the machine the following morning for data analysis by the otolaryngologist. Data analysis includes interpretation of tracings of oxygen saturation, snoring, nasal ventilation, apneas, and hypopneas (figures 3, 4).

A positive diagnosis of OSA is based on an AHI of 15 or more events per hour. For patients who have an AHI of less than 15 but a strong suspicion of OSA, a tentative diagnosis of OSA or upper airway resistance syndrome is made. Patients who are diagnosed with OSA are advised to undergo CPAP titration. Titration involves an additional unattended home sleep study wherein the patient wears a nasal CPAP mask connected to the AutoSet, which is programmed in its titration mode. The AutoSet monitors, records, and adjusts pressure in response to snoring, apneas, and hypopneas. Medical and surgical treatment paradigms are then discussed with the patient and the referring physicians. We devised a clinical algorithm to summarize our general approach (figure 5).

Results

The results of the home sleep studies on our 100 patients are shown in the table. Regression analysis indicated that there was no correlation between AHI and BMI, neck circumference, sleep symptoms, or Epworth sleepiness scale score.

The sleep data show that 71% of our patients had an AHI of 15 or higher, 84% had an AHI of 10 or higher, and 93% had an AHI of at least 5. Among the 100 tests, 99 were completed successfully on the first attempt. The failure had to be repeated because of a patient error in performing the study; this patient completed the test successfully on the second attempt.

Discussion

Otolaryngologists can now easily, cost-effectively, and accurately obtain sleep-study information to evaluate patients with OSA. Snorers who do not have OSA can be identified as such, and can therefore be treated surgically without fear of camouflaging OSA. Patients who do have OSA can be prescribed nasal CPAP. Patients who fail CPAP therapy can be provided information on surgical options.

The otolaryngologist plays an important role in the evaluation of patients with SDB. Transnasal fiberoptic laryngoscopy can reveal obstructive abnormalities that are not detected by headlight or flashlight examination. This examination is important in evaluating and treating patients with OSA, particularly those who have failed CPAP therapy. Anecdotal evidence of the value of transnasal fiberoptic laryngoscopy following CPAP failure includes reports of its detection of nasal polyps, obstructive adenoidal hypertrophy, and undiagnosed oropharyngeal neoplasms. In addition, an otolaryngologist who is experienced in performing transnasal fiberoptic examinations of patients with OSA develops a "clinical sense" in terms of identifying correctable anatomic abnormalities that should be considered for surgery (figure 6). Conversely, patients who have little anatomic obstruction are poor surgical candidates, and they should be encouraged to master CPAP or consider tracheostomy.

In summary, we believe our study answers the question of whether or not otolaryngologists can confidently prescribe and administer multichannel home sleep studies. With a state-of-the-art machine, these studies were easily performed and the results were easily recorded and interpreted. Our results were similar to those reported in laboratory sleep studies by sleep-trained physicians. We conclude that with the use of the AutoSet portable monitor, an otolaryngologist can cost-effectively prescribe multichannel home sleep studies, thereby greatly enhancing the ENT evaluation and treatment of sleep disordered breathing.

Acknowledgement

Acknowledgement is extended to Dr. Davidson's assistant, Barbara Stribling, for her outstanding effort in preparing and finalizing this manuscript.

From the Department of Otolaryngology-Head and Neck Surgery, University of California, San Diego, School of Medicine and the VA San Diego Healthcare System (Dr. Davidson), the University of California, San Diego, School of Medicine (Ms. Do), and the Centre for Healthcare, Rancho Bernardo, Calif. (Ms. Justus).

Reprint requests: Terence M. Davidson, MD, VA San Diego Healthcare System (112C), 3350 La Jolla Village Dr., San Diego, CA 92161. Phone: [phone], ext. 3405; fax: [phone]; e-mail: [e-mail]

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Mean values for 100 patients tested for obstructive sleep apnea with a
multichannel home sleep machine
Patient characteristics
  Age                        52.0 yr ([plus or minus] 13.0)
  Neck circumference         43.0 cm ([plus or minus] 5.0)
  Body mass index            32.0 kg/[m.sup.2] ([plus or minus] 8.0)
  Systolic BP               129.0 mm Hg ([plus or minus] 19.0)
  Diastolic BP               81.0 mm Hg ([plus or minus] 12.0)
Pretest symptom scores
  Snoring                    2.5 ([plus or minus] 0.9)
  Witnessed apneic episodes  2.3 ([plus or minus] 1.6)
  Daytime hypersomnolence    3.0 ([plus or minus] 1.3)
  Morning headache           1.2 ([plus or minus] 1.4)
  Arm/leg movements          2.0 ([plus or minus] 1.6)
  Epworth sleepiness score  12.0 ([plus or minus] 6.0; normal:[less than]11)
Sleep study results
  Study duration             7.3 hr ([plus or minus] 1.4)
  Lowest oxygen saturation  83.0% ([plus or minus] 9)
  Longest apneic event      42.0 sec ([plus or minus] 15.0)
  Apnea index               19.0 events/hr ([plus or minus] 19.0)
  Apnea-hypopnea index      27.0 events/hr ([plus or minus] 19.0)