eMedicine Specialties > Pulmonology > Sleep-Related Disorders

Obstructive Sleep Apnea: Differential Diagnoses & Workup

Author: Ralph Downey III, PhD, DABSM, FAASM, Associate Professor of Medicine, Pediatrics, and Neurology, Loma University School of Medicine; Adjunct Associate Professor, Department of Psychology, University of California at Riverside; Chief, Sleep Medicine, Loma Linda University Medical Center and the Loma Linda University Children's Hospital
Coauthor(s): Philip M Gold, MD, Professor of Medicine, Chief of Pulmonary and Critical Care Medicine, Medical Director of Respiratory Care, Loma Linda University Medical Center; Himanshu Wickramasinghe, MD, MBBS, Attending Physician; Pulmonary, Critical Care, and Sleep Medicine; Henry Mayo Newhall Memorial Hospital, Valencia, California
Contributor Information and Disclosures

Updated: Jul 30, 2009

Differential Diagnoses

Asthma
Chronic Obstructive Pulmonary Disease
Depression
Hypothyroidism
Obstructive Sleep Apnea-Hypopnea Syndrome
Sleep Disorders

Other Problems to Be Considered

Workup

Laboratory Studies

  • Routine laboratory tests usually are not helpful in obstructive sleep apnea (OSA) unless a specific indication is present.
  • Consider obtaining a thyrotropin hormone level if clinically indicated, particularly in elderly individuals.
  • An arterial blood gas determination should be obtained if obesity hypoventilation syndrome is suspected.
  • If clinically indicated, consider PSG using end-tidal carbon dioxide measurements for a continuous measurement of carbon dioxide pressures as a function of OSA and associated sleep states and by position. Data analysis help determine if OSA versus sleep state is an independent or an interacting factor (eg, REM sleep vs non-REM sleep), and data analysis help determine if OSA versus sleeping body position is an independent or an interacting factor (eg, supine sleep position vs lateral decubitus vs semi-Fowler). A single PSG probably will not be definitive to determine, out of all of these variables, a specific variable that may be a singular cause of hypercapnia; however, it is better than a daytime arterial blood gas determination for determining if OSA is a cause of hypercapnia or not.

Imaging Studies

  • Modalities available for identifying the site of obstruction include lateral cephalometry, endoscopy, fluoroscopy, CT scanning, MRI, and radiography.
  • The accuracy of these methods for identifying the sites of obstruction is not clear. At present, UA imaging is used primarily as a research tool. Routine radiographic imaging of the UA is not performed.
  • See Snoring and Obstructive Sleep Apnea, Upper Airway Evaluation for additional details about UA imaging.

Other Tests

Standard diagnostic nocturnal PSG

The AASM has published standards and guidelines for performing PSG (see American Academy of Sleep Medicine). The AASM has the highest standards to which the top-level American sleep disorders centers adhere. Unfortunately, more unaccredited sleep disorders centers exist than accredited sleep disorders centers. Having a patient studied at an AASM-accredited sleep disorders center is important to ensure the highest quality care. AASM-accredited sleep disorders centers adhere to standards that have been established by the AASM. This includes the criterion standard test for sleep disorders: the sleep disorders center PSG. A PSG is necessary to accurately diagnose OSA and to assess treatment benefit.
 
AASM standard SRDB  definitions14

  • Apnea is defined as the cessation of airflow for 10 seconds or longer.
  • Hypopnea is defined as a recognizable transient reduction (but not complete cessation) of breathing for 10 seconds or longer, a decrease of greater than 50% in the amplitude of a validated measure of breathing, or a reduction in amplitude of less than 50% associated with oxygen desaturation of 4% or more. An arousal is unnecessary to score a hypopnea.
  • Obstructive apneas and hypopneas are typically distinguished from central events by the detection of respiratory efforts during the event.
  • The RDI is defined as the number of obstructive apneas, hypopneas, and respiratory event–related arousals (RERAs) per hour. The RDI is preferred over the AHI because it includes flow-limitation events that end with arousals. The RDI is best suited to meet the new AASM diagnostic criteria for OSA, as discussed below.
  • An RERA is an event characterized by increasing respiratory effort for 10 seconds or longer leading to an arousal from sleep but one that does not fulfill the criteria for a hypopnea or apnea. The criterion standard to measure RERAs is esophageal manometry, as the AASM recommends. However, esophageal manometry is uncomfortable for patients and impractical to use in most sleep centers.
  • A reliable and valid way to measure RERAs is with the use of a nasal cannula and pressure transducer. Results obtained with this transducer are reliable (intraclass correlation of 0.96). With regard to the diagnosis of OSA, this method does not differ from esophageal manometry in a clinically significant manner. With either method, the RDI is greater than 5 and the normal RDI cutoff is greater than 15.
  • According to the International Classification of Sleep Disorders: Diagnostic and Coding Manual, Second Edition,14 at least 1 of the following criteria must apply for OSA to be diagnosed:
    • The patient reports daytime sleepiness, unrefreshing sleep, fatigue, insomnia, and/or unintentional sleep episodes during wakefulness. The patient awakens with breath holding, gasping, or choking. The patient's bed partner reports loud snoring, breathing interruptions, or both during the patient's sleep.
    • PSG shows more than 5 scoreable respiratory events (eg, apneas, hypopneas, RERAs) per hour of sleep and/or evidence of respiratory effort during all or a portion of each respiratory event.
    • PSG shows more than 15 scoreable respiratory events (eg, apneas, hypopneas, RERAs) per hour of sleep and/or evidence of respiratory effort during all or a portion of each respiratory event.
    • Another current sleep disorder, medical or neurologic disorder, medication use, or substance use does not better account for the patient's condition.

Standard PSG-measured  parameters
The  PSG is a multichannel recording of sleep and breathing and usually involves in-laboratory measurement of sleep architecture and EEG arousals, eye movements, chin movements, airflow, respiratory effort, oximetry, ECG tracings, body position, snoring, and leg movements (see Media File 3).

Segment of a nocturnal polysomnogram shows an epi...

Segment of a nocturnal polysomnogram shows an episode of central apnea. Airflow and respiratory movements have both ceased.

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Segment of a nocturnal polysomnogram shows an epi...

Segment of a nocturnal polysomnogram shows an episode of central apnea. Airflow and respiratory movements have both ceased.


Data are collected in the laboratory in the presence of a qualified technician (ie, full PSG with attended monitoring). This protocol provides the opportunity to directly observe a variety of sleep-associated disturbances (eg, apneas, periodic leg movements, seizures, REM behavior disorder). Patients who regularly work night shifts should undergo PSG during the day to match their normal sleep-wake cycle.

Arousals detected on PSG are important for the evaluation of the degree of sleep fragmentation. They may be the only clue to UA resistance syndrome in a patient with daytime hypersomnolence if esophageal pressure is not monitored. Monitoring of esophageal pressure is not routinely performed in most laboratories because of the invasive nature of the procedure.

The following PSG findings are characteristic of OSA:

  • Apneic episodes occur in the presence of respiratory muscle effort (see Media File 2).
  • Apneic episodes lasting 10 seconds or longer are considered clinically significant. Apneic episodes are usually approximately 20-40 seconds and rarely last several minutes. 
  • Apneic episodes are most prevalent during REM sleep. In some patients, they may occur exclusively during REM sleep.
  • Patients may have a combination of apneas and hypopneas, or they may have one or the other exclusively. 
  • Mixed apneas may occur. Mixed apneas are a combination of central sleep apnea and OSA in a single apneic episode (see Media File 2).
  • Sleep disruption due to arousals is usually seen at the termination of an episode of apnea.
Segment of a nocturnal polysomnogram shows an epi...

Segment of a nocturnal polysomnogram shows an episode of mixed apnea. The initial portion of the apnea is central in origin, with cessation of both airflow and respiratory movements. The latter part of the apnea is obstructive, with an absence of airflow despite the resumption of respiratory movements.

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Segment of a nocturnal polysomnogram shows an epi...

Segment of a nocturnal polysomnogram shows an episode of mixed apnea. The initial portion of the apnea is central in origin, with cessation of both airflow and respiratory movements. The latter part of the apnea is obstructive, with an absence of airflow despite the resumption of respiratory movements.


AASM guidelines for split-night PSG studies
Patients with an RDI of greater than 40 during the first 2 hours of diagnostic PSG should undergo a split-night PSG study. The final portion of the study is used for titrating the CPAP device. Split-night studies may be considered for patients with an RDI of 20-40, as based on clinical observations (eg, prolonged obstructive events, marked oxygen desaturation). A minimum of 3 hours of sleep is preferred to adequately titrate the CPAP device after this treatment is started.

Split-night studies require recording and analysis of the same parameters as those evaluated in standard diagnostic PSG. A single split-night study may not permit adequate titration of CPAP therapy. If treatment does not control symptoms, additional full-night CPAP titration may be required. 

Repeat PSG

Repeat PSG if symptoms persist despite adequate compliance with prescribed CPAP treatment. PSG can be used to assess response to UA surgical procedures and to assess response to OA therapy. If sustained weight change of greater than 15% occurs, PSG should be repeated. If results of the first PSG are of poor quality, a repeat study is indicated. Patients who stop REM sleep–suppressant medications should be restudied, if symptomatic on treatment, because OSA is most prevalent in REM sleep the OSA that occurs during REM sleep should be examined  whenever possible to avoid undertreatment of the OSA or a false-negative diagnosis on a diagnostic study.

Home monitoring

Tonelli de Oliveira et al indicate that in-home respiratory monitoring can be used to diagnose obstructive sleep apnea syndrome. They suggest that most previous studies did not use the best standards for evaluating the accuracy of in-home respiratory monitoring. They report on the use of all available comparison methods to evaluate efficacy and further suggest in-home respiratory monitoring is an effective diagnostic tool.25

More on Obstructive Sleep Apnea

Overview: Obstructive Sleep Apnea
Differential Diagnoses & Workup: Obstructive Sleep Apnea
Treatment & Medication: Obstructive Sleep Apnea
Follow-up: Obstructive Sleep Apnea
Multimedia: Obstructive Sleep Apnea
References
Further Reading
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Keywords

obstructive sleep apnea, OSA, sleep apnea, apnea, sleep disorder, snoring, sleep-related disorder, sleep disordered breathing, SDB, central apnea, obstructive apnea, mixed apnea, hypopnea, upper airway resistance syndrome, UARS, nasal continuous positive airway pressure, nasal CPAP, CPAP, apnea index, AI respiratory disturbance index, RDI, apnea-hypopnea index, AH, PSG, polysomnography, pickwickian syndrome, excessive daytime sleepiness, EDS, uvulopalatopharyngoplasty, UPPP, respiratory event–related arousal, RERA, oral appliance, OA, bilevel positive airway pressure, BiPAP, sleep-related breathing disorder, SRBD

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Contributor Information and Disclosures

Author

Ralph Downey III, PhD, DABSM, FAASM, Associate Professor of Medicine, Pediatrics, and Neurology, Loma University School of Medicine; Adjunct Associate Professor, Department of Psychology, University of California at Riverside; Chief, Sleep Medicine, Loma Linda University Medical Center and the Loma Linda University Children's Hospital
Ralph Downey III, PhD, DABSM, FAASM is a member of the following medical societies: American Academy of Sleep Medicine
Disclosure: Nothing to disclose.

Coauthor(s)

Philip M Gold, MD, Professor of Medicine, Chief of Pulmonary and Critical Care Medicine, Medical Director of Respiratory Care, Loma Linda University Medical Center
Philip M Gold, MD is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, American Federation for Clinical Research, American Heart Association, American Lung Association, American Medical Association, American Thoracic Society, Association of Subspecialty Professors, California Medical Association, California Thoracic Society, Society of Critical Care Medicine, and Undersea and Hyperbaric Medical Society
Disclosure: Glaxo-Smith-Kline Honoraria Speaking and teaching; Covidien Honoraria Speaking and teaching; Boeringer-Ingleheim Honoraria Speaking and teaching

Himanshu Wickramasinghe, MD, MBBS, Attending Physician; Pulmonary, Critical Care, and Sleep Medicine; Henry Mayo Newhall Memorial Hospital, Valencia, California
Himanshu Wickramasinghe, MD, MBBS is a member of the following medical societies: American College of Chest Physicians and American Thoracic Society
Disclosure: Nothing to disclose.

Medical Editor

Sat Sharma, MD, FRCPC, Professor and Head, Division of Pulmonary Medicine, Department of Internal Medicine, University of Manitoba; Site Director, Respiratory Medicine, St Boniface General Hospital
Sat Sharma, MD, FRCPC is a member of the following medical societies: American Academy of Sleep Medicine, American College of Chest Physicians, American College of Physicians-American Society of Internal Medicine, American Thoracic Society, Canadian Medical Association, Royal College of Physicians and Surgeons of Canada, Royal Society of Medicine, Society of Critical Care Medicine, and World Medical Association
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: eMedicine Salary Employment

Managing Editor

Daniel R Ouellette, MD, FCCP, Associate Professor of Medicine, Wayne State University School of Medicine; Consulting Staff, Pulmonary Disease and Critical Care Medicine Service, Henry Ford Health System
Daniel R Ouellette, MD, FCCP is a member of the following medical societies: American College of Chest Physicians and American Thoracic Society
Disclosure: Boehringer Ingleheim Honoraria Speaking and teaching; Pfizer Honoraria Speaking and teaching

CME Editor

Timothy D Rice, MD, Associate Professor, Departments of Internal Medicine and Pediatrics and Adolescent Medicine, Saint Louis University School of Medicine
Timothy D Rice, MD is a member of the following medical societies: American Academy of Pediatrics and American College of Physicians
Disclosure: Nothing to disclose.

Chief Editor

Zab Mosenifar, MD, Director, Division of Pulmonary and Critical Care Medicine, Director, Women's Guild Pulmonary Disease Institute, Executive Vice Chair, Department of Medicine, Cedars Sinai Medical Center; Professor of Medicine, David Geffen School of Medicine at UCLA
Zab Mosenifar, MD is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, American Federation for Medical Research, and American Thoracic Society
Disclosure: Nothing to disclose.

 
 
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