Sleep apnea is insidious, and patients are often unaware of their associated symptoms. As a result, it often goes undiagnosed or is first noticed by others due to habitual loud snoring combined with daytime sleepiness.
If OSA is suspected, the clinical approach to diagnosis should begin with an assessment of the likelihood of disease, the symptoms present and any relevant coexisting conditions (Veasey & Rosen, 2019). There are several steps that should be taken along the diagnostic pathway:
1. Carry out a sleep test/questionnaire
Getting patients to answer a sleep questionnaire, possibly with the help of their partner, is an important first stage to ascertain if sleep apnea could in fact be a problem. The Epworth Sleepiness Scale is also often used to determine the likelihood of a patient’s dozing in different settings as an indicator of inadequate restorative night-time sleep. The scores range from 0‒24, with more than 10 being indicative of excessive sleepiness. Specific to OSA is the STOP-BANG score:
S - snoring
T - tired
O - observed apnea
P - blood pressure
B - BMI over 35
A - older than 50 years old
N - large neck size
G - gender male
If there are ≥3 positive answers, the patient is considered at high risk of sleep apnea. Alternatively, the Berlin questionnaire can be used to evaluate the presence, loudness and frequency of snoring, apneas, daytime sleepiness, hypertension and obesity to help predict a high or low likelihood of sleep apneas (Slowik & Collen, 2019). It should be noted, however, that not every patient with OSA perceives sleepiness or has been informed of their snoring (Veasey & Rosen, 2019).
2. Refer the patient to a sleep specialist
A sleep specialist will be able to determine the best screening or diagnostic test. Polysomnography (PSG) is the gold standard for diagnosing sleep disordered breathing in a sleep laboratory. During a PSG study, both neurophysiological and respiratory parameters are measured such as brain wave activity (electroencephalogram, EEG), cardiac activity (electrocardiogram, ECG), eye movements (electro-occulogram, EOG) or chin activity, nasal and oral airflow, respiratory efforts, body position, oxygen saturation, snoring and leg movements. PSG interpretation, made by the sleep physician or a qualified sleep technician, will help to quantify sleep time, differentiate sleep stages, assess sleep fragmentation and evaluate the sleep disordered breathing severity by measuring the apnea hypopnea index (AHI) or the respiratory disturbance index (RDI) (Ibáñez et al., 2018).
Apnea is defined as complete obstruction (airflow reduction by more than 90%) of the upper airways lasting for at least 10 seconds.
Hypopnea is defined as airflow restriction of more than 30% for at least 10 seconds, with at least a 3% oxygen desaturation and/or an arousal (AASM, 2013).
Disease severity is assessed by measuring the AHI which represents the number of apneas and hypopneas per hour of sleep (table 2).
Table 2. Apnea-hypopnea index (AHI) classification (Veasey & Rosen, 2019, American Sleep Apnea Association, 2017).
The AHI is also used to assess positional obstructive sleep apnea (POSA). POSA is defined in adults as an AHI greater than 5 and an AHI in the supine position twice as high or more when compared with AHI in non-supine positions, together with subjective complaints (Cartwright et al., 1991):
To diagnose exclusive POSA (ePOSA), the AHI in the non-supine position should be ≤5/hour (Mador et al., 2005).
Due to inter night variability, AHI can be influenced by weight, sleeping position, age, alcohol and medications and medical comorbidities (Veasey & Rosen, 2019).
A simplified Home Sleep Testing (HST) consists of measuring respiratory parameters such as airflow (nasal, oral or both), respiratory efforts, pulse oximetry, body position, snoring and heart rate, but in the convenience of a patient’s own home (figure 10). However, HST does not measure sleep, and as respiratory events (including apneas and hypopneas) are measured for the entire recording time, these tests may underestimate the severity of OSA (Veasey & Rosen, 2019).
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