Current haemodynamic monitoring is mainly aimed at the macrocirculation. Multiple studies have demonstrated the importance of the microcirculation in relation to the patient’s condition and impact of treatment strategies. However, continuous monitoring of the microcirculation is not yet possible in the neonatal field. A novel dynamic light scattering (DLS) sensor technology for continuous monitoring of the microcirculation was investigated in the neonatal population. Thirty-one haemodynamically stable infants were included. Sequential measurements at the forehead, upper extremity, thorax, abdomen and lower extremity were conducted with the DLS sensor. For analyses stable measurements were selected. The DLS parameters, total blood flow (TBF) and relative blood velocity (RBV), were compared between measurement locations. Changes in relative haemodynamic indices (relHIs), indicating the distribution of blood flow in the microcirculatory blood vessels, were associated with heart rate decelerations. Measurements performed at the forehead had significantly lower TBF levels, compared to measurements at other locations. Early changes in relHIs around a heart rate deceleration were recorded a median (IQR) of 22.0 (13.5–27.0) s before the onset. Measurement of the currently unavailable parameters TBF, RBV and relHIs is possible with DLS technology. Validation of the DLS technology is needed for clinical implementation.

Sepsis is a severe systemic condition due to an extreme response of the body to an infection. It is responsible for a significant number of deaths worldwide, and is still difficult to diagnose early. In this study, a system was developed for exhaled breath sampling in mechanically ventilated patients at the intensive care unit (ICU), together with a custom-made electronic nose (e-Nose) device for detecting sepsis in exhaled breath. The diagnostic performance of this system was evaluated in an animal sepsis model. Ten pigs (LPS group) were administered lipopolysaccharide (LPS) to induce a systemic inflammatory response. Nine other pigs received a placebo solution (control group). Exhaled breath samples were collected in Nalophan^TM bags and stored for temperature and humidity equilibration before e-Nose analysis. Measurements were corrected for the effects of different fractions of inspired oxygen (FiO₂) on e-Nose sensors. Two classification models using e-Nose and physiological measurements were developed and compared. One hour after LPS administration, the e-Nose data model with FiO₂ correction showed a higher accuracy (76.2% (95% confidence interval (CI) [58.0, 94.2])) than the physiological data model (59.0% (95% CI [39.5, 79.5])), indicating the potential of the early detection of sepsis with an e-Nose.

Dynamic light scattering (DLS) is a promising but currently uncalibrated technology for non-invasive measurements of total blood flow (TBF) and relative blood velocity (RBV) at the skin surface in critically ill patients. This study aimed to calibrate DLS flow measurements against reference blood flow measured in the tubing of a heart-lung machine (HLM) during an in vitro setup and during minimally invasive cardiac surgery (MICS). For both setups, calibration curves between HLM flow and TBF and between HLM flow and RBV were described, differentiating for haemoglobin (Hb) levels. TBF and RBV values were lower at higher Hb levels and in the clinical setting. DLS parameters were not affected by ambient light or intravenous dyes, however, Hb concentration and blood temperature influenced the obtained HLM-TBF and HLM-RBV relationships. No correlation was found between HLM flow and skin TBF or RBV measurements at the lower extremities. In conclusion, a clear relation between DLS flow measurements and blood flow in an extracorporeal circulation was found. Future studies should further evaluate DLS technology in critically ill patients with a defective microcirculation.

Sepsis is a severe condition and the major cause of mortality in the ICU. Prompt intervention decreases mortality, and non-invasive systems for early diagnosis in ICU patients are necessary. This work presents a customized e-Nose system based on non-selective chemical sensors for exhaled breath analysis. The system comprises two units: a sampling device able to collect exhaled breath from mechanically ventilated patients and an e-Nose in which the gas is analyzed. Preliminary results from a porcine model support the possibility of discriminating between healthy and sepsis subjects.

Introduction: Early detection of microcirculatory failure in septic patients has the potential to improve clinical outcomes. The microcirculation regulates the oxygen (O ₂ ) supply and carbon dioxide (CO ₂ ) washout in tissues and changes early during severe inflammation and sepsis. Transcutaneous blood gas sensors measure tissue O ₂ and CO ₂ levels at the skin surface, or when warmed use the vasodilatory response to approximate arterial levels. In addition to differences in measured O ₂ and CO ₂ values, systemic inflammation is likely to affect this vasodilatory effect of skin warming. This study investigated whether continuous comparison of heated and unheated transcutaneous blood gas monitoring could early detect microcirculatory changes using a porcine lipopolysaccharide (LPS) model of systemic inflammation. Methods: Thirty female Yorkshire x Norwegian Landrace pigs were subdivided into three study groups (control, LPS, and LPS with fluid resuscitation) and received LPS or saline control. Transcutaneous CO ₂ (tcPCO ₂ ) and O ₂ (tcPO ₂ ) were continuously and simultaneously measured using a heated (43 °C) and unheated (37 °C) transcutaneous sensor (Sentec OxiVenT™) at the porcine ear. Arterial blood gas measurements (PaCO ₂ and PaO ₂ ) were performed at baseline and 1, 2, and 3 h after LPS administration. At each time point, tcPCO ₂ , tcPO ₂ , and differences between transcutaneous and arterial blood gas measurements were determined. In addition, the unheated-heated tcPCO ₂ difference and the ratio between heated tcPCO ₂ and tcPO ₂ (tcPCO ₂ /tcPO ₂ ) were calculated. Results: After LPS administration, a significant increase in heated tcPCO ₂ and a significant decrease in tcPO ₂ and tcPO ₂ /tcPCO ₂ were observed. This resulted in a significant decrease in the unheated-heated tcPCO ₂ difference from 22.1 [18.8–33.2] to 0.7 [−8.3–8.8] mmHg in the LPS group, and from 23.0 [16.9–23.9] to −1.2 [−6.6–2.0] mmHg in the resuscitation group, while it remained 6.5 [3.1–9.8] mmHg in the control group. PaCO ₂ and PaO ₂ did not show large changes. Conclusion: Heated tcPCO ₂ , tcPO ₂ , unheated-heated tcPCO ₂ , and tcPO ₂ /tcPCO ₂ as observed using transcutaneous blood gas monitoring are promising parameters for early detection of microcirculatory changes during severe infections. In future studies, simultaneous heated and unheated transcutaneous measurements should be further explored in both healthy and septic patients.