The colour of the silicone enclosure of an implantable reflectance-based optical probe plays a critical role in sensor performance. Red-coloured probes that are highly reflective to near-infrared light have been found to increase photodetector power by a factor of 6 for wavelengths between 660 and 950 nm and triple the magnitude of measured cardiac pulsations compared to traditional black probes. The increase in photodetector power and cardiac pulsation magnitude is presumably due to increased spatial range resulting from a higher magnitude of superficial tissue scattering. Conversely, probes with highly absorbent colours such as black and blue result in more stable signals and are expected to have higher spatial resolution and depth of penetration.

No abstract

Sudden cardiac arrest (SCA) is a leading cause of mortality worldwide. Outcomes highly depend on the SCA-to-resuscitation interval, highlighting the clinical need for quick and reliable SCA detection. Near-infrared spectroscopy (NIRS), a noninvasive optical technique, may have utility for SCA detection. We investigated the ability of hindlimb transcutaneous NIRS to detect changes with pentobarbital-induced cardiac arrest in eight Yucatan miniature pigs. NIRS measurements during cardiac arrest were compared to invasively acquired carotid blood pressure and spinal cord tissue partial oxygen pressure (PO2). We observed statistically significant decreases in mean arterial pressure (MAP) 64.68 mmHg ± 13.08, p = 0.016), spinal cord PO2 (38.16 mmHg ± 20.04, p = 0.016), and NIRS-derived tissue oxygen saturation (TSI%) (14.50% ± 3.80, p = 0.0078) from baseline to 5 minutes after pentobarbital administration. Euthanasia-to-first change in hemodynamics for MAP and TSI (%) were similar [MAP (10.43 ± 4.73 sec) vs TSI (%) (12.04 ± 1.85 sec), p = 0.605]. No significant difference was detected between NIRS and blood pressure-derived pulse rates during baseline periods (p > 0.99) and following pentobarbital administration (p = 0.97). Similar to invasive indices, transcutaneous NIRS demonstrated marked changes with cardiac arrest and was able to rapidly identify hemodynamic changes. Transcutaneous NIRS monitoring may present a novel and noninvasive approach to SCA detection.

Sudden cardiac arrest (SCA) is a leading cause of mortality worldwide. The SCA-to-resuscitation interval is a key determinant of patient outcomes, highlighting the clinical need for reliable and timely detection of SCA. Near-infrared spectroscopy (NIRS), a non-invasive optical technique, may have utility for this application. We investigated transcutaneous NIRS as a method to detect pentobarbital-induced changes during cardiac arrest in eight Yucatan miniature pigs. NIRS measurements during cardiac arrest were compared to invasively acquired carotid blood pressure and partial oxygen pressure (PO2) of spinal cord tissues. We observed statistically significant decreases in mean arterial pressure (MAP) 64.68 mmHg ± 13.08, p < 0.0001), spinal cord PO2 (38.16 mmHg ± 20.04, p = 0.0028), and NIRS-derived tissue oxygen saturation (TSI%) (14.50% ± 3.80, p < 0.0001) from baseline to 5 min after pentobarbital administration. Euthanasia-to-first change in hemodynamics for MAP and TSI (%) were similar [MAP (10.43 ± 4.73 s) vs TSI (%) (12.04 ± 1.85 s), p = 0.3714]. No significant difference was detected between NIRS and blood pressure-derived pulse rates during baseline periods (p > 0.99) and following pentobarbital administration (p = 0.97). Transcutaneous NIRS demonstrated the potential to identify rapid hemodynamic changes due to cardiac arrest in periods similar to invasive indices. We conclude that transcutaneous NIRS monitoring may present a novel, non-invasive approach for SCA detection, which warrants further investigation.