3D Camera and Pulse Oximeter for Respiratory Events Detection

Objective:
The purpose of this study was to derive a respiratory movement signal from a 3D time-of-flight camera and to investigate if it can be used in combination with SpO
₂
to detect respiratory events comparable to polysomnography (PSG) based detection.
Methods:
We derived a respiratory signal from a 3D camera and developed a new algorithm that detects reduced respiratory movement and SpO
₂
desaturation to score respiratory events. The method was tested on 61 patients’ synchronized 3D video and PSG recordings. The predicted apnea-hypopnea index (AHI), calculated based on total sleep time, and predicted severity were compared to manual PSG annotations (manualPSG). Predicted AHI evaluation, measured by intraclass correlation (ICC), and severity classification were performed. Furthermore, the results were evaluated by 30-second epoch analysis, labelled either as respiratory event or normal breathing, wherein the accuracy, sensitivity, specificity and Cohen's kappa were calculated.
Results:
The predicted AHI scored an ICC
r
= 0.94 (0.90 – 0.96 at 95% confidence interval,
p
< 0.001) compared to manualPSG. Severity classification scored 80% accuracy, with no misclassification by more than one severity level. Based on 30-second epoch analysis, the method scored a Cohen's kappa = 0.72, accuracy = 0.88, sensitivity = 0.80, and specificity = 0.91.
Conclusion:
Our detection method using SpO
₂
and 3D camera had excellent reliability and substantial agreement with PSG-based scoring.
Significance:
This method showed the potential to reliably detect respiratory events without airflow and respiratory belt sensors, sensors that can be uncomfortable to patients and susceptible to movement artefacts.