The goal of this study is to determine if the investigators can use the STOP-BANG score to identify those patients at risk for worsening Obstructive Sleep Apnea (OSA) symptoms in the early postoperative period after major surgery.

Hypotheses:

1. - Postoperative sleep apnea parameters will be worse when compared to baseline in patients with higher scores on the STOP-BANG.
2. - A higher STOP-BANG score will be predictive of worsening sleep apnea parameters in patients undergoing Total Knee Arthroscopy (TKA).

Obstructive sleep apnea (OSA) is associated with increased morbidity and mortality after total knee arthroplasty (TKA). Up to 30% of surgical patients have undiagnosed OSA; however, many patients are unable to obtain a sleep study prior to surgery. In recent years the STOP-BANG questionnaire (8 yes-no questions; ≥3 high-risk OSA) has become one of the most common tools used in the preoperative period to identify patients at high-risk for OSA. However, further research is needed to determine if the STOP-BANG is predictive of worsening of sleep apnea parameters in patients undergoing TKA.

The purpose of this prospective observational cohort study is to determine in TKA patients if the score on the STOP-BANG (<3, ≥3 to <5, or ≥5) is predictive of worsening sleep apnea parameters (AHI, time with SPO2 <90% & 85% [T90 & T85], lowest oxygen saturation [LSAT], & number of central apneas) during the first three days after surgery. The investigators propose to enroll N = 168 patients undergoing TKA at NMCSD who are receiving multimodal anesthesia/analgesia for surgery. Patients will complete a baseline unattended sleep study prior to surgery then again for the first three days after surgery. Patients will be categorized into three groups based on their STOP-BANG score (<3, ≥3 to <5, or ≥5) and the investigators will first compare the groups to identify if there are differences between baseline and postoperative sleep apnea parameters based on the STOP-BANG groups (<3, ≥3 to <5, or ≥5). If differences are found the investigators will use multiple regression analysis to determine if the STOP-BANG scores or categories and/or other covariates (i.e., comorbidity index, total morphine equivalents) are predictive of worsening sleep apnea during the first three days after surgery.

Results of this study may help improve patient safety by allowing us to identify which group of TKA patients with undiagnosed OSA may require more intensive postoperative monitoring and therapy (i.e, ICU admission, need for continuous end-tidal CO2 monitoring, postoperative positive airway pressure therapy) or change in the analgesic plan.

Inclusion Criteria:

• Age 18-90
• Scheduled for primary or revision TKA
• Able to read and understand the consent
• Able to complete an unattended OSA PM examination at home 1-60 days prior to surgery and for three days postoperatively

Exclusion Criteria:

• Polysomnography confirmed OSA
• Significant comorbid medical conditions that may degrade the accuracy of PM (moderate to severe pulmonary disease, neuromuscular disease, or congestive heart failure)

The subject population will be N = 168 patients scheduled for primary or revision TKA between the ages of 18-90, at Naval Medical Center San Diego.