Automatic Measurement of Loop Gain Based on Pseudorandom Binary Sequence CO2 Stimulation.

OBJECTIVE: Measurement of loop gain in patients with obstructive sleep apnea (OSA) is of great importance for determining the cause of OSA and realizing precision medicine. In this study, automatic measurement of loop gain is carried out during wakefulness based on the pseudorandom binary sequence (PRBS) CO2 stimulation method. METHODS: A respiratory data acquisition platform is designed and constructed to automate the processes of gas configuration, ventilatory stimulation with CO2 and data acquisition. The respiratory data are substituted into the model of the ventilatory control system for parameter identification, and the loop gain values are calculated and then compared with the apnea-hypopnea index (AHI) measured in a hypoxia chamber. RESULTS: A positive correlation is found between loop gain and AHI measured in the hypoxia chamber, with the linear correlation coefficient of approximately 0.65. CONCLUSION: The feasibility of automatic measurement of loop gain using the respiratory data acquisition platform based on the PRBS CO2 stimulation method is validated, and the measured loop gain values can be used to assess the stability of ventilatory control. SIGNIFICANCE: This study provides an automated, rapid, and instrumented solution for loop gain measurement, laying the foundation for wide-scale clinical application of the PRBS CO2 stimulation method.

Sprayable chitosan nanogel with nitric oxide to accelerate diabetic wound healing through bacteria inhibition, biofilm eradication and macrophage polarization.

Bacterial infection and chronic inflammation are two major risks in diabetic wound healing, which increase patient mortality. In this study, a multifunctional sprayable nanogel (Ag-G@CS) based on chitosan has been developed to synergistically inhibit bacterial infection, eradicate biofilm, and relieve inflammation of diabetic wounds. The nanogel is successfully crafted by encapsulating with a nitric oxide (NO) donor and performing in-situ reduction of silver nanoparticles (Ag). The released NO enhances the antibacterial efficacy of Ag, nearly achieving complete eradication of biofilms in vitro. Upon application on both normal or diabetic chronic wounds, the combination effects of released NO and Ag offer a notable antibacterial effect. Furthermore, after bacteria inhibition and biofilm eradication, the NO released by the nanogel orchestrates a transformation of M1 macrophages into M2 macrophages, significantly reducing tumor necrosis factor α (TNF-α) release and relieving inflammation. Remarkably, the released NO also promotes M2a to M2c macrophages, thereby facilitating tissue remodeling in chronic wounds. More importantly, it upregulates the expression of vascular endothelial growth factor (VEGF), further accelerating the wound healing process. Collectively, the formed sprayable nanogel exhibits excellent inhibition of bacterial infections and biofilms, and promotes chronic wound healing via inflammation resolution, which has excellent potential for clinical use in the future.