T&A Triage with or without Preoperative Polysomnography Clinical Pathway – Inpatient and Outpatient Specialty Care

Review Polysomnography Results (if applicable)

A polysomnography is a test used to diagnose sleep disorders. The test records brain waves, oxygen level in the blood, heart rate and breathing, as well as eye and leg movements. When interpreting results the Apnea/Hypopnea Index (AHI) and oxygen desaturation levels are used to indicate the severity of obstructive sleep apnea.

Interpreting Polysomnography Results

Apnea/Hypopnea Index (AHI)

Number of events per hour, calculated as: Apneas (no airflow for 10 seconds or longer) + Hypopneas (shallow breathing where airflow reduced by at least 50%, lasting 10 seconds or longer). Normal AHI is < 1.5/hr.

Gas Exchange

Preoperative SpO₂ nadir < 80% or peak CO₂ > 60 mmHg are more consistent predictors of postoperative respiratory complications than apnea hypopnea indices.

Oxygen nadir is the lowest oxygen saturation a patient drops to (normal oxygen nadir (SpO₂) > 92). C0₂ peak < 55 mmHg or >50 mmHg for no more than 25% total sleep time (the latter is a better measure as CO₂ can peak after a single sigh)

Graphs show the percentage of patients with respiratory complications at: (A) each level of apnea hypopnea index, (B) arterial oxygen saturation nadir, and (C) peak end-tidal CO₂.

Graphs courtesy of Predictors of Perioperative Complications in Higher Risk Children after Adenotonsillectomy for Obstructive Sleep Apnea: A Prospective Study. Otolaryngology - Head and Neck Surgery December 2014 151: 1046-1054, first published on October 9, 2014