AAO-HNSF Primary Care Otolaryngology Handbook

INTRODUCTION TO CLINICAL ROTATION AND PHYSICAL EXAM OBSTRUCTIVE LEEP APNEA

• Oxygen saturation • EKG rhythm strip—electrocardiography • Nasal pressure tranducer • Oronasal thermister • Effort of breathing (via chest and abdominal belts)

• Snoring recording • Video monitoring

The PSG is recorded digitally and must be read by an experienced practi- tioner. Onset of sleep can be determined via the EEG and EMG. The recordings are reviewed in 30-second snapshots called epochs. Each epoch is scored to determine the stage of sleep. The other parameters recorded are used to determine apneas or hypopneas. If no flow is detected through the nose or mouth with respiratory effort, an apnea is recorded. If there is reduced airflow with respiratory effort and a corre- sponding drop in the partial pressure of oxygen, a hypopnea is noted. The number of apneas and hypopneas divided by the number of hours of sleep determines the apnea–hypopnea index or AHI. The PSG can be a full-night recording or can be split. If the patient has documented OSA after two or three hours of sleep, continuous positive airway pressure (CPAP) can be applied and tested for the remainder of the night. The split study can both diagnose and assess treatment in one night. Home Sleep Testing Another form of sleep testing to assess for OSA in adults is HST, which has traditionally consisted of four channels of recording that must include ventilation, oximetry, EKG, and heart rate. Other home testing equipment is available that uses peripheral arterial tonometry to measure sleep- disordered breathing as well. HST generally does not record actual sleep; rather, it records test time. Because the patient may not be asleep the entire time of testing, the number of events per hour may be underesti- mated. This decreased sensitivity makes the PSG a better test for patients with a low suspicion of OSA. OSA is quantified by the number of apneas and hypopneas per hour of sleep. This is divided into mild (5–15/hour), moderate (15–30/hour), and severe (>30/hour).

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