Comparison of frequency-domain and continuous-wave near-infrared spectroscopy devices during the immediate transition

Abstract

Background: Non-invasive monitoring of cerebral tissue oxygen saturation (rcSO₂) during transition is of growing interest. Different near-infrared spectroscopy (NIRS) techniques have been developed to measure rcSO₂. We compared rcSO₂ values during the immediate transition in preterm neonates measured with frequency-domain NIRS (FD-NIRS) with those measured with continuous-wave NIRS (CW-NIRS) devices in prospective observational studies.

Methods: We compared rcSO₂ values measured with an FD-NIRS device during the first 15 min after birth in neonates with a gestational age ≥ 30 weeks but < 37 weeks born at the Erasmus MC- Sophia Children's Hospital, Rotterdam, the Netherlands, with similar values measured with a CW-NIRS device in neonates born at the Medical University of Graz, Austria. Mixed models were used to adjust for repeated rcSO₂ measurements, with fixed effects for time (non-linear), device, respiratory support and the interaction of device and respiratory support with time. Additionally, parameters such as total haemoglobin concentration and oxygenated and deoxygenated haemoglobin concentrations measured by FD-NIRS were analysed.

Results: Thirty-eight FD-NIRS measurements were compared with 58 CW-NIRS measurements. The FD-NIRS rcSO₂ values were consistently higher than the CW-NIRS rcSO₂ values in the first 12 min, irrespective of respiratory support. After adjustment for respiratory support, the time-dependent trend in rcSO₂ differed significantly between techniques (p < 0.01).

Conclusion: As cerebral saturation measured with the FD-NIRS device differed significantly from that measured with the CW-NIRS device, differences in absolute values need to be interpreted with care. Although FD-NIRS devices have technical advantages over CW-NIRS devices, FD-NIRS devices may overestimate true cerebral oxygenation and their benefits might not outweigh the usability of the more clinically viable CW-NIRS devices.

Keywords: Continuous-wave; Frequency-domain; Near-infrared spectroscopy; Preterm neonate; Transition.

Fig. 1

Graphic representation of the emitted and detected light beam for the CW-NIRS and FD-NIRS techniques. The dark blue line represents the light entering the tissue; the light blue line represents the light that is detected at the detector. a, Intensity of emitted and detected light of the CW-NIRS technique. b, Intensity of the modulated light beam and measured parameters. Image adapted from OxiplexTS™ brochure with the courtesy of ISS, Champaign, Illinois, USA

Fig. 2

Effect plots of rcSO₂ and SpO₂ stratified by the need for respiratory support Symbols represent the estimated means of rcSO₂ and SpO₂ with associated 95% confidence intervals for all difference time points based on a mixed model including (non-linear) time, technique, respiratory support and their interaction with time. a, Effect plot of rcSO₂ for neonates not requiring respiratory support. b, Effect plot of rcSO₂ for neonates requiring respiratory support. c, Effect plot of SpO₂ for neonates not requiring respiratory support. d, Effect plot of SpO₂ for neonates requiring respiratory support.

Fig. 3

Effect of variance in phase-shift occurrences on cerebral saturation during a single frequency-domain measurement. a, Raw data of a single cerebral saturation measurement (dark blue line) and percentiles based on the recalculation of the cerebral saturation measurements based on all phase-shift pair occurrences (light blue ranges). b, Raw phase-shift values for 684 nm and 828 nm wavelengths

Fig. 4

Effect plots of haemoglobin concentration measurements. a, Total haemoglobin concentration (THb); b, oxygenated haemoglobin concentration (O₂Hb); and c, deoxygenated haemoglobin concentration (HHb). THb, O₂Hb and HHb are presented as per μM. Symbols represent the estimated means with associated 95% confidence intervals for all difference time points, based on a mixed model including (non-linear) time, respiratory support and their interaction