In this post I link to and excerpt from the Curbsiders‘ [Link is to the episode list] #123 Sleep Apnea Pearls and Pitfalls [Link is to the podcast and show notes] NOVEMBER 5, 2018 By CYRUS ASKIN.
Here is the podcast:
Written and produced by: Cyrus Askin MD
CME questions by: Cyrus Askin MD
Editor: Chris Chiu MD & Matthew Watto MD
Hosts: Cyrus Askin MD & Matthew Watto MD
Guest: Barbara Phillips, MD
Cover-Art & Infographic – Beth Garbitelli, MS1
The sleep apnea episode that won’t put you to sleep. Become a sleep apnea guru with incredible insights from Barbara Phillips MD, MSPH, FCCP an expert in pulmonary medicine, critical care and sleep medicine who is also a past president of CHEST! We discuss high-yield topics in the world of obstructive sleep apnea including: home sleep studies vs in-lab polysomnography, the importance of oxygen saturation (the T90 and ODI) when interpreting sleep study results, tricks to improve CPAP adherence, and alternatives therapies for obstructive sleep apnea. ACP members can visit https://acponline.org/curbsiders to claim free CME-MOC credit for this episode and show notes (goes live 0900 EST).
- Metabolic syndrome and obstructive sleep apnea (OSA) are dangerous bedfellows: Estimates suggest at least 60% of folks with the metabolic syndrome have OSA, although, Dr. Phillips suggests the association could be as high as 80+%! (Parish et al. Journal of Clinical Sleep Medicine, 2007 & Drager et al. PLoS One, 2010)
- STOP ordering sleep studies on patients who CLEARLY have sleep apnea, if there is anyway to avoid it! In patients with metabolic syndrome who have other signs or symptoms consistent with obstructive sleep apnea (excessive daytime sleepiness, morning headaches, resistant hypertension, large neck diameter) with or without high scores on the STOP-BANG questionnaire or Epworth Sleepiness Scale, the pre-test probability that they have sleep apnea and would benefit from therapy is high enough to obviate the need for time consuming, expensive testing when we have autotitrating CPAP (continuous positive airway pressure). – Dr Phillips
- The apnea-hypopnea index (AHI) is not the be-all-and-end-all: The ODI (oxygen desaturation index) and the T90 (time spent, during a sleep study, with an oxygen saturation at-or-lower than 90%) have been shown to be very useful adjuncts to the AHI when evaluating a patient for OSA. Data suggests that it is not the number of hypopneas/apneas but rather the time spent hypoxemic that is most strongly related to the sequelae of sleep apnea. (Chung et al. Anesthesia and Analgesia 2012 & Dr. Phillips)
- The data for Home Sleep Testing (HST) is growing: Dr. Phillips cited studies to suggest the data from HSTs is non-inferior to traditional lab-run polysomnography. There is also data that suggests adherence to therapy and improvement in sleepiness is equivalent (if not superior) for patients diagnosed and treated with HSTs and auto-titrating CPAP. (Chai-Coetzer et al. Annals of Internal Medicine 2017, Chai-Coetzer at al. American Journal of Respiratory & Critical Care Medicine & Berry et al. Journal of Clinical Sleep Medicine 2014)
- While HST is great, it’s not for everyone: Per the AASM, in lab polysomnography rather than home sleep testing is recommended for patients with “significant cardiorespiratory disease, potential respiratory muscle weakness due to neuromuscular condition, awake hypoventilation or suspicion of sleep related hypoventilation, chronic opioid medication use, history of stroke or severe insomnia.” (Kapur et al. Journal of Clinical Sleep Medicine 2017)
- Mild OSA may NOT require treatment: Careful reading of the AASM and ATS guidelines on OSA treatment suggests it is reasonable to defer CPAP therapy for patients with mild OSA who DO NOT endorse excessive daytime sleepiness. Asymptomatic patients with mild OSA who are started on CPAP and have bad experiences may be much more difficult to reach in the future should their disease worsen. (Kushida et al. AASM 2006 & Chowdhuri et al. ATS 2016)
- The cost of OSA on society is tremendous: According to the AASM, undiagnosed (and untreated OSA) cost the United States nearly 150 billion dollars in 2015. Of this, 26.2 billion dollars were spent due to car accidents related to sleepiness in the setting of undiagnosed OSA. Nearly 30% of car accidents in the US are associated with drowsy driving which is well-known to be seen in those with sleep apnea. Fortunately, according to the AASM, there is data to suggest that those treated for their OSA are at lower risk. (Hidden Health Crisis Costing America Billions – AASM & AASM Infographic)
- OSA is a primary care problem: There are not enough sleep medicine doctors to diagnose, treat and manage all the OSA that is out there. Thus, it is a problem that all primary care doctors need to be comfortable with. After all, OSA is not only a potential cause of morbidity and mortality for the patient, but for those the share highways and roadways with them – especially if they go untreated. – Dr. Phillips
Sleep Apnea Show Notes
More pearls from Dr. Phillips
Sleep Apnea – Why should we care?
Dr. Phillips clearly makes the point that OSA is a disease that affects many patients and undiagnosed OSA is a significant public health risk. Diagnosis of OSA, with the emergence of home sleep testing (HST) is easier to achieve than ever and there are many manual and autotitrating CPAP options along with many mask options to better treat patients.
Red flags when screening for obstructive sleep apnea.
Dr. Phillips mentioned excessive daytime fatigue and morning headaches may be suggestive of underlying sleep apnea. A neck circumference of greater than or equal to 17 inches in males and 16 inches in females is an independent risk factor for OSA.
Polycythemia may be seen in patients with OSA, however, this is more indicative of concomitant obesity hypoventilation syndrome as it is suggestive of daytime desaturation events.
Sleep apnea demographics
Not everyone with OSA is obese or has the metabolic syndrome. Dr. Phillips reminds us that individuals with hypothyroidism, a receding chin, Down syndrome, Treacher-Collins, folks with a genetic predisposition (such as Chinese populations) and post-menopausal women (due to tissue laxity caused by decreased serum estrogen) are all at higher risk for OSA regardless of their BMI.
Home sleep study
Although there are indications for inpatient sleep studies, the HST is a great option for many. Lab polysomnography is useful for patients with different pre-existing conditions (see above). However, HST offers certain noteworthy benefits! HST is an inexpensive, fast and easily administered test which uses desaturation events as the primary measurement. The oxygen desaturation index, as well as the T90 (time with oxygen saturation less-than or equal-to 90%) can be determined via an HST and have been shown in the literature to be very useful indicators of disease severity, particularly by the Spanish Sleep Society. Check it! – Consider setting a patient’s auto-titrating CPAP pressure range to 8cm – 16cm H2O as this will capture virtually the full spectrum of potential pressure needs.
Sleep Study Interpretation
The AHI represents the number of times a patient has an episode of complete apnea (stops breathing for 10 or more seconds) + episodes of hypopnea (the definition of which varies) / hour. An AHI < 5 is normal, 6-14 is mild OSA, 15-29 represents moderate OSA and 30+ represents severe OSA. That said, based on data out of the Spanish Sleep Study and other places, the ODI and the T90 may be more clinically useful indicators of disease severity. The ODI* represents the number of times oxygen a patient’s oxygen saturation drops from baseline by 4% or more / hour. The T90 which, according to Dr. Phillips, is most predictive of incident cancer and heart disease, is the number of minutes during a night of sleep where the patient’s oxygen saturation is 90% or lower.
*ODI – Oxygen Desaturation Index
**T90 – total sleep time spent with arterial oxygen saturation (SaO2) < 90% 
Alternative to CPAP for OSA treatment
Dr. Phillips discussed interventions for OSA other than conventional, non-invasive positive pressure therapy. Mandibular advancement devices, custom made by a dentist, can help with the symptoms of sleep apnea in a patient who is resistant to CPAP. These can be difficult to obtain (i.e. costly and time consuming). Other airway adjuncts, such as those that are commercially available, have not shown to be effective. With respect to surgery, bariatric surgery and tracheostomy certainly can benefit a patient with OSA. Outside of these surgeries, other surgical options do not appear to be as beneficial. Dr. Phillips briefly mentioned medications and in doing so, stated that modafinil does have an FDA-approval for residual sleepiness in patients treated for their OSA with CPAP, but it is not an alternative to CPAP.