[Review of Physiological Parameters Monitoring Technology in the ICU].

Physiological parameters monitoring is essential to direct medical staff to evaluate, diagnose and treat critical patients quantitatively. ECG, blood pressure, SpO2, respiratory rate and body temperature are the basic vital signs of patients in the ICU. The measuring methods are relatively mature at present, and the trend is to be wireless and more accurate and comfortable. Hemodynamics, oxygen metabolism and microcirculation should be taken seriously during the treatment of acute critical patients. The related monitoring technology has made significant progress in recent years, the trend is to reduce the trauma and improve the accuracy and usability. With the development of machine vision and data fusion technology, the identification of patient behavior and deterioration has become hot topics. This review is focused on current parameters monitoring technologies, aims to provide reference for future related research.

Studying hemispheric lateralization during a Stroop task through near-infrared spectroscopy-based connectivity.

ABSTRACT. Near-infrared spectroscopy (NIRS) is a developing and promising functional brain imaging technology. Developing data analysis methods to effectively extract meaningful information from collected data is the major bottleneck in popularizing this technology. In this study, we measured hemodynamic activity of the prefrontal cortex (PFC) during a color-word matching Stroop task using NIRS. Hemispheric lateralization was examined by employing traditional activation and novel NIRS-based connectivity analyses simultaneously. Wavelet transform coherence was used to assess intrahemispheric functional connectivity. Spearman correlation analysis was used to examine the relationship between behavioral performance and activation/functional connectivity, respectively. In agreement with activation analysis, functional connectivity analysis revealed leftward lateralization for the Stroop effect and correlation with behavioral performance. However, functional connectivity was more sensitive than activation for identifying hemispheric lateralization. Granger causality was used to evaluate the effective connectivity between hemispheres. The results showed increased information flow from the left to the right hemispheres for the incongruent versus the neutral task, indicating a leading role of the left PFC. This study demonstrates that the NIRS-based connectivity can reveal the functional architecture of the brain more comprehensively than traditional activation, helping to better utilize the advantages of NIRS.

Detection of optical neuronal signals in the visual cortex using continuous wave near-infrared spectroscopy.

Near-infrared spectroscopy (NIRS) measures slow hemodynamic signals noninvasively to indirectly infer the neuronal activity in the brain. However, it remains a controversy on whether this optical measurement technique can detect the optical neuronal signal, which reflects the optical changes directly associated with neuronal activity, within the visual cortex of human and non-human primates. By carefully reviewing the important factors in the detection of optical neuronal signals, we aim to investigate the feasibility of performing NIRS measurements of optical neuronal signals within the visual cortex in humans. To ensure a strong optical neuronal response, a full-field circular black and white reversing checkerboard stimulus was presented, and the reversal frequency was carefully chosen. We used a homemade continuous wave (CW) NIRS system with high detection sensitivity (of the order of 0.1 pW) to record a large area of the visual cortex (approximately 6 × 14 cm(2)). EEG was simultaneously acquired with the optical signal. Based on the mathematical morphology, we adapted the filter proposed by Gratton et al. to remove the influence of arterial pulsation and facilitate the detection and elimination of unknown artifacts from the data. We obtained reliable optical neuronal signals in 77% of the participants (10 out of 13). The amplitudes (latencies) of the obtained optical neuronal signals corresponding to the 785 and 850 nm wavelengths were 0.017 ± 0.003% (94.7 ± 8.4 ms) and 0.025 ± 0.006% (99.0 ± 7.7 ms), respectively. There were no significant differences between the latencies of the N75 component of the visual evoked potential (VEP) and optical neuronal signals at either wavelength. This is the first study to report optical neuronal signals within the visual cortex in the intact human brain using a CW NIRS system. These results indicate the feasibility of measuring noninvasive optical neuronal signals using a CW NIRS system with high detection sensitivity.

A fast neuronal signal-sensitive continuous-wave near-infrared imaging system.

We have developed a continuous-wave near-infrared imaging system to measure fast neuronal signals. We used a simultaneous sampling method with a separate high-speed analog-to-digital converter for each input channel, which provides a much larger point sample in a digital lock-in algorithm, higher temporal resolution, and lower crosstalk among detected channels. Without any analog filter, digital lock-in detection with a large point sample suppresses noise excellently, making the system less complex and offering better flexibility. In addition, using a custom-made collimator, more photons can reach the brain tissue due to the smaller divergence angle. Performance analysis shows high detection sensitivity (on the order of 0.1 pW) and high temporal resolution (~50 Hz, 48 channels). Simulation experiments show that intensity changes on the order of 0.01% can be resolved by our instrument when averaging over approximately 500 stimuli. In vivo experiments over the motor cortex show that our instrument can detect fast neuronal signals in the human brain.

Differences between the Vastus Lateralis and Gastrocnemius Lateralis in the Assessment Ability of Breakpoints of Muscle Oxygenation for Aerobic Capacity Indices During an Incremental Cycling Exercise.

In recent years, breakpoints (Bp) of muscle oxygenation have been measured in local muscles using near infrared spectroscopy (NIRS) to assess (predict) systemic aerobic capacity indices [lactate threshold (LT), gas exchange threshold (GET) and maximal oxygen uptake (VO2peak)]. We investigated muscular differences in the assessment (predictive) ability of the Bp of muscle oxygenation for aerobic capacity indices during incremental cycling exercise on the aerobic capacity indices. Thirty-one active college students were recruited for an incremental cycling exercise test, during which NIRS muscle oxygenation in the vastus lateralis (VL) and gastrocnemius lateralis (GL), blood lactate concentration and cardiopulmonary variables were measured simultaneously in a multi-modality approach. A linear regression model was used to analyse the relationship between the Bp of the muscle oxygenation index (OI) and the systemic aerobic capacity indices. The Bp of the muscle OI in both the VL (BpVL) and GL (BpGL) were significantly correlated with the aerobic capacity indices. Additionally, the BpVL had a better goodness-of-fit [higher coefficient of determination (R(2), p < 0.001) and lower root mean squared error (RMSE, p < 0.03)] in the linear regressions and occurred earlier than the BpGL. In conclusion, both the BpVL and the BpGL could be measured by NIRS to assess the systemic aerobic capacity indices; however, there were muscular differences in the assessment ability of the Bp of muscle oxygenation.