Significant Delay in the Detection of Desaturation between Finger Transmittance and Earlobe Reflectance Oximetry Probes during Fiberoptic Bronchoscopy: Analysis of 104 Cases

Purpose: There is clinical significance to a delay in response time for detecting desaturation by pulse oximetry. Our aim in this study was to compare the response time of the reflectance and transmittance saturation probes during fiberoptic bronchoscopy (FOB) under monitored anesthesia care. Methods: A prospective study included 104 patients scheduled for FOB. Patients were monitored with transmittance (finger) and reflectance (ear) oximetry probes. The response time was evaluated during desaturation and resaturation. We also acquired blood tests for arterial oxygen saturation to assess the agreement with the oximetry probes. Results: Ninety patients had a desaturation episode during FOB and were included in the final analysis. Mean time difference between the reflectance ear probe (reference probe) and transmittance finger probe for the detection of desaturation (SpO2 = 90%) was + 36 s (CI 27.0–45.0, P < 0.001). The time difference between probes at end of desaturation episode (SpO2 = 95%) was + 31 s (CI 19.0–43.0; P < 0.001). A significant difference in response time was evident throughout the episode in all saturation values. The reflectance ear probe showed better agreement with arterial blood gases. The bias (and precision) for the earlobe and finger oximeters were of 0.24 (1.04) and 2.31 (3.37), respectively. Conclusion: The data displayed by a centrally located reflectance probe are more accurate and allows for earlier identification, treatment, and resolution of desaturation events. In light of these data and the added value of the reflectance probe ability to measure transcutaneous PCO ₂ , we recommend monitoring bronchoscopy by a reflectance oximetry probe.