Split Night versus Full Night Polysomnography Section in Obstructive Sleep Apnoea Syndrome: A Retrospective Study

Introduction: Obstructive Sleep Apnoea (OSA) is traditionally evaluated using a diagnostic Polysomnography (PSG) which is then followed by a PSG with Continuous Positive Airway Pressure (CPAP) titration. Split Night PSG (SN-PSG) includes the diagnostic and titration study in a single night. Split Night PSG is a better technique however, the requirements for CPAP titration are too strict.

Aim: To assess the accuracy of different duration of split night compared to a Full Night PSG (FN-PSG) in OSA Syndrome.

Materials and Methods: A retrospective observational study was performed in the Department of Pulmonary Medicine at VMMC and Safdarjung Hospital, from January 2019 to May 2019 at Safdarjung Hospital was done. Apnoea-Hypopnea Index (AHI) was assessed at the 1 hour, 2 hour, 3 hour and 4 hour from analysis of SN-PSG data obtained from FN-PSG. Using the Area Under Receiver Operating Characteristic (AUROC) curve, it was compared to the FN-PSG. Calculations were made to validate the diagnosis by a 2 hour PSG using different AHI cut-off points (5/hour to 15/hour).

Results: Data from 20 PSG recordings was processed. A stronger correlation of FN-AHI was demonstrated with AHI at 2 hour (p-value <0.0001) (r value=0.902). At 2 hours of study, with an AHI cut-off of 5 hour, the sensitivity and specificity was 92.9% and 83.3%, respectively. The Positive Predictive Value (PPV) was 100% and Negative Predictive Value (NPV) was 83.3% (AUROC=0.976; p-value <0.0001). At 2 hours, AHI cut-off of 15 hour, the sensitivity and specificity was 71.4% and 100%, respectively. The PPV was 100% and NPV was 86.7% (AUROC=1.000; p-value <0.0001).

Conclusion: Split-night PSG is effective for diagnosing severe OSA. A lower cut-off of AHI may be used to qualify patients for CPAP titration.