Recognizing Obstructive Sleep Apnea

/ Med-Peds Forum, General Med-Peds, Pulmonology / By

Case

Lee is a 55yo with h/o asthma (no issues since childhood) and tobacco use (quit 10 years ago) presenting with dyspnea.

  • 6 months of persistent but stable mild dyspnea on exertion
  • ROS reveals 10lbs weight gain over this time period and difficulty concentrating at work, his partner notes significant fatigue at the end of the workday, difficulty staying asleep, and new snoring
  • No current medications
  • VS within normal range; BMI 32 today (previously 29 at last visit 2 years ago)

Lee’s partner is concerned that Lee may have depression.

  • PHQ9 scores positive on sleep and cognitive scales. Upon further questioning, you learn they go to sleep at 10pm every night, don’t feel they have difficulty falling asleep, and use the bathroom 3 times per night. Lee’s partner adds that she wakes up and nudges Lee to stop snoring throughout the night
  • Lee adds that multiple times the past few months their boss has caught them sleeping at work, especially while reading long manuscripts

Definitions & Terminology

  • Obstructive sleep apnea (OSA) = disorder characterized by obstructive apneas, hypopneas, and/or respiratory effort-related arousals caused by repetitive collapse of the upper airway during sleep
  • Obesity hypoventilation syndrome (OHS) = disorder characterized by elevated awake PaCO2 levels in patients with obesity in whom alternative causes of hypercapnia and hypoventilation have been excluded
  • Polysomnogram (PSG) = a procedure that utilizes EEG, electro-oculogram, electromyogram, ECG, and pulse oximetry, as well as airflow and respiratory effort, to evaluate for underlying causes of sleep disturbances
  • Home sleep apnea testing (HSAT) = out-of-center sleep testing (aka portable monitoring)
  • Bed partner = inclusive term to describe the person likely to have collateral information
  • Apnea = Breathing cessation for ≥10 seconds
  • Hypopnea = Breathing flow reduction for ≥10 seconds accompanied by either a ≥3% oxyhemoglobin desaturation or by arousal from sleep
  • Apnea-Hypopnea Index (AHI) = Frequency of of apneas and hypopneas per hour of sleep

Clinical Presentation

“The signs, symptoms and consequences of OSA are a direct result of the derangements that occur due to repetitive collapse of the upper airway: sleep fragmentation, hypoxemia, hypercapnia, marked swings in intrathoracic pressure, and increased sympathetic activity.”

Epstein et al. Clinical guideline for the evaluation, management and long-term care of obstructive sleep apnea in adults. J Clin Sleep Med. 2009

OSA is characterized by several symptoms:

  • Common:
    • Excessive daytime sleepiness
    • Observed events during sleep (snoring, gasping, choking, apneas)
      • Best elicited from bed partner
      • Snoring has 80-90% sensitivity but poor specificity; choking/gasping are less sensitive but more specific
  • Less common:
    • Sleep maintenance insomnia (30%)
    • Morning headaches (10-20%)
    • Other: decreased concentration, memory loss, decreased libido

Note that sleepiness is the inability to remain fully awake/alert during the wakefulness portion of the sleep-wake cycle (versus fatigue, which is a subjective lack of physical or mental energy that interferes with one’s usual activities.)

  • To describe sleepiness, patients may use words like fatigue, low energy, lack of focus, decreased energy, etc.
  • The Epworth Sleepiness Scale is a 1-page questionnaire that asks respondents to estimate their likelihood of falling asleep in 8 sedentary situations, scored from 0 to 3; scores ≥10 are considered abnormal and suggest excessive daytime sleepiness

Fun fact: Only about 1 in 50 patients with symptoms suggestive of OSA are evaluated and treated for the disease!

Potential exam findings in patients with OSA:

Who To Test

Interestingly, no screening tool has been shown to be superior to history and physical examination. For instance, the STOP-BANG questionnaire has high sensitivity but low specificity for OSA; the quality of evidence for the use of this screening test varies across different cutoffs.

As such, AASM guidelines advocate testing patients who have excessive daytime sleepiness on most days and the presence of at least 2 clinical features of OSA (e.g., loud snoring, witnessed apnea or gasping/choking during sleep, and HTN.)

  • Patients at high risk for OSA include those with obesity (especially BMI ≥35), family history of OSA, retrognathia, HF, afib, refractory HTN, T2DM, pulmonary hypertension, stroke, etc.

So, should we screen for OSA?

  • AASM: “Questions to be asked during a routine health maintenance evaluation should include a history of snoring and daytime sleepiness and an evaluation for the presence of obesity, retrog- nathia, or HTN. Positive findings on this OSA screen should lead to a more comprehensive sleep history and physical examination.”
  • AAFP: insufficient evidence
  • ACP: screen those with risk factors or high-risk jobs
  • USPSTF: insufficient evidence

How To Test

OSA is not a clinical diagnosis—objective testing must be performed for diagnosis.

PSG is the gold standard for confirming the diagnosis of OSA.

  • AHI is the key metric used to stratify OSA severity:

If there’s a suspicion for uncomplicated OSA, with a moderate-severe pretest probability, then HSAT is reasonable.

  • Complicated OSA refers to the presence of medical conditions that could potentially affect respiration during sleep and create additional respiratory abnormalities over and above those associated with OSA.

When clinicians suspect that symptoms are due to a nonrespiratory sleep disorder or that a nonrespiratory sleep disorder coexists with or contributes to OSA, PSG should be performed.

PSG should be performed in patients who have a job in which falling asleep would have major negative consequences (e.g., airline pilots, bus / taxi / truck / ride-sharing drivers, train operators, police, security, military posts, astronauts, etc.)

For patients with suspected OSA who do not fit the definition of high pretest probability of moderate-severe OSA per the AASM criteria, PSG is the preferred test. However, many insurers request that providers perform HSAT first, and if negative and the suspicion for OSA remains, then proceed to PSG.

Take-Home Points!

  • Recognizing OSA is our responsibility as PCPs
  • Important to distinguish between sleepiness and fatigue when considering OSA
  • No screening tool for OSA has been shown to be superior to history and physical examination
  • OSA is not a clinical diagnosis—refer patients with risk factors for confirmatory testing

Blog post based on Med-Peds Forum talk by Anu Goel, PGY2

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