Marta Zanoletti

SignificanceThe hybrid diffuse optical system (hDOS) is a fully automated platform designed to bring advanced optical monitoring closer to clinical practice. Many existing systems lack automation, multiparametric output, and operator independence, limiting their use in demanding environments such as intensive care. hDOS integrates time-domain near-infrared spectroscopy, diffuse correlation spectroscopy, and pulse oximetry to assess both tissue oxygenation and perfusion. Although initially developed in the context of vascular occlusion tests, its modular design makes it suitable for broader applications, including trauma, surgery, anesthesia, and studies in healthy subjects.AimIt aims to design and validate hDOS, focusing on precision, repeatability, and usability for peripheral microvascular monitoring in both clinical and research settings.ApproachValidation included test-retest measurements, a 7-month clinical deployment in the critical care, and a comparison with a commercial continuous wave NIRS device (INVOS 5100C).ResultsThe device underwent extensive validation, accumulating over 200 h of usage across ∼150 measurement sessions. The system showed high precision (test-retest CV <1.2% for oxygenation, <13% for perfusion), stable long-term performance, and lower variability than INVOS. It has also detected statistically significant differences during VOTs and detected hemodynamic impairment in ICU patients (n=100) compared with healthy volunteers (n=37).ConclusionshDOS performed well in both bench and clinical settings, offering a unique combination of parameters in a fully automated, self-contained platform.

Significance: A new platform/device is presented that advances hybrid diffuse optical monitors closed to clinical practice, bridging the gap between research-grade optical systems and practical bedside applications. Traditional devices often lack automation, multi-parameter functionality, and operator independence, hence, limiting their usability in demanding clinical environments. By offering automation, user-friendly operation, and overcoming the typical limitations of continuous-wave near-infrared spectroscopy, the hybrid diffuse optical platform (hDOS) provides a more accurate and reliable assessment of both oxygenation and perfusion. This innovation is particularly valuable for monitoring critically ill patients, where precise real-time measurements can directly influence patient management and outcomes. Aim: To design, validate, and characterize the platform hDOS that integrates time-domain near-infrared spectroscopy, diffuse correlation spectroscopy, and a pulse oximeter with an automated vascular occlusion test (VOT). The platform aims to support continuous monitoring and the assessment of peripheral microvascular, and metabolic functions in both clinical and field settings. Approach: The validation strategy for the hDOS device follows a comprehensive approach that goes beyond conventional optical performance assessments. Rather than solely verifying fundamental system parameters, the evaluation comprises of real-world usability, operator and patient safety, and clinical implementation. The device’s precision and usability were rigorously tested in vivo through test-retest measurements and comparisons with a commercially available device (INVOS 5100C). This was subsequently followed by a seven-month clinical evaluation at Parc Taulí Hospital Universitari. Results: The device underwent extensive validation, accumulating over 200 hours of usage across approximately 150 measurement sessions. The hDOS device exhibited two-fold lower inter-subject and intra-subject variability in baseline tissue oxygen saturation compared to the INVOS 5100C. Furthermore, during a a vascular occlusion challenge, statistically significant differences were observed between the two systems across all extracted parameters. Finally, as a proof of concept, hDOS successfully detected differences in the microvasculature between a general mixed ICU patient cohort ( n = 100) and a healthy control group ( n = 37). Conclusions: Overall, hDOS device has performed well in both bench-top and realistic clinical applications on patients in vivo . hDOS device provides a unique combination of parameters, available for the first time in a fully automated, self-contained platform.

Fluid therapy is essential in hemodynamic resuscitation, but not all patients benefit. Passive leg raising predicts fluid responsiveness, necessitating reliable cardiac output (CO) monitoring. Here, we present a complementary approach using hybrid diffuse optics as a surrogate for CO monitoring.

We assessed in 14 healthy volunteers and 10 intensive care unit (ICU) patients low and very low frequency oscillations in hemodynamic parameters of thenar eminence by studying their power spectral density exploiting time domain near-infrared and diffuse correlation spectroscopies.

Thyroid vascularization and hemodynamics become altered in thyroid pathologies and could thus inform diagnostics, therapy planning, and follow-up. However, the current non-invasive monitoring methods available in clinics lack the necessary sensitivity and/or are impractical for large-scale deployment. As a step towards proposing a new modality, we applied the first platform, to our knowledge, designed to do simultaneous measurements of neck anatomy and thyroid microvascular hemodynamics and metabolism in a single probe placement, integrating state-of-the-art near-infrared spectroscopy techniques and clinical ultrasound. A rich dataset was formed with sixty-five subjects (forty-eight females), including eighteen healthy volunteers and forty-seven patients with thyroid nodules, characterizing thyroid tissue and the effects of demographic and anatomical variables while preserving the standard clinical workflow. We have found marked reductions with age and body mass index in thyroid total hemoglobin concentration (THC), tissue oxygen saturation (StO₂), and blood flow index (BFi), among others. Patients showed lower THC and BFi than healthy subjects, and the limited sample of malignant nodules showed a higher StO₂ than the benign. These findings support the need for personalized clinical approaches.

We present preliminary in-vivo validation of VASCOVID device, a hybrid diffuse optical platform designed for automatized microvasculature health assessment in the intensive care. The in-vivo validation was run on more than hundred subjects.

In this work, we used a hybrid time domain near-infrared spectroscopy (TD-NIRS) and diffuse correlation spectroscopy (DCS) device to retrieve hemoglobin and blood flow oscillations of skeletal muscle microvasculature. We focused on very low (VLF) and low-frequency (LF) oscillations (i.e., frequency lower than 0.145 Hz), that are related to myogenic, neurogenic and endothelial activities. We measured power spectral density (PSD) of blood flow and hemoglobin concentration in four muscles (thenar eminence, plantar fascia, sternocleidomastoid and forearm) of 14 healthy volunteers to highlight possible differences in microvascular hemodynamic oscillations. We observed larger PSDs for blood flow compared to hemoglobin concentration, in particular in case of distal muscles (i.e., thenar eminence and plantar fascia). Finally, we compared the PSDs measured on the thenar eminence of healthy subjects with the ones measured on a septic patient in the intensive care unit: lower power in the endothelial-dependent frequency band, and larger power in the myogenic ones were observed in the septic patient, in accordance with previous works based on laser doppler flowmetry.

The non-invasive monitoring of the hemodynamics and metabolism of the sternocleidomastoid muscle (SCM) during respiration became a topic of increased interest partially due to the increased use of mechanical ventilation during the COVID-19 pandemic. Near-infrared diffuse optical spectroscopies were proposed as potential practical monitors of increased recruitment of SCM during respiratory distress. They can provide clinically relevant information on the degree of the patient’s respiratory effort that is needed to maintain an optimal minute ventilation, with potential clinical application ranging from evaluating chronic pulmonary diseases to more acute settings, such as acute respiratory failure, or to determine the readiness to wean from invasive mechanical ventilation. In this paper, we present a detailed characterization of the optical properties (wave-length dependent absorption and reduced scattering coefficients) and hemodynamic properties (oxy-, deoxy- and total hemoglobin concentrations, blood flow, blood oxygen saturation and metabolic rate of oxygen extraction) of the human SCM, obtained by measuring sixty-five subjects through ultrasound-guided near-infrared time-resolved and diffuse correlation spectroscopies. We provide detailed tables of the results related to SCM baseline (i.e. muscle at rest) properties, and reveal significant differences on the measured parameters due to variables such as side of the neck, sex, age, body mass index and thickness of the overlaying tissues, allowing future clinical studies to take into account such dependencies.

Diffuse optics (DO) encompasses a range of photonics tools based on the study of random photon migration in highly scattering media—biological tissues in particular. Due to its unique features, DO is emerging as a powerful means for clinical or homecare diagnostics.¹ The basic physics of DO is related to the detection of temporal or spatial alteration in photon distribution re-emitted on the tissue surface.² Due to the low power (typically few mW) of injected near-infrared light (600- to 1100-nm range), DO is inherently noninvasive. The photon temporal (or spatial) distribution carries information on the absorption—ultimately related to tissue chemical composition, such as water, lipid, collagen content, oxy- and deoxy-hemoglobin concentration, cytochrome c-oxidase³—and scattering properties—linked to tissue microstructure. Further, DO is one of the few noninvasive modalities capable of providing functional information, e.g., brain or muscle activation.⁴ It can be operated noncontact through remote light illumination and collection.⁵ It explores the tissue well below the skin at depths of up to 2 to 4 cm. It can provide quantitative operator-independent assessment of the tissue status, such as hemoglobin oxygenation level in the brain. Finally, it is highly scalable, sharing the same technology from large clinical tomographic systems down to wearable devices or homecare appliances.⁶ For all these aspects, DO is attracting more and more interest in many fields, such as monitoring vital signs like brain oxygenation in critical care or during interventions,⁷ tumor diagnostics as for breast cancer,⁸ investigating the impact of lifestyle and nutrition on our body,⁹ or other fields such as neuroscience and psychology,¹⁰ sports, and leisure.¹¹ Even further, the operator independence, the depth sensitivity, and the scalability in addition to noninvasiveness make this option attractive for telemedicine and homecare of patients remotely.

VASCOVID project is developing and testing a hybrid diffuse optical monitor for evaluating endothelial function and metabolism in intensive care including COVID-19.