ABSTRACT
In order to effectively treat respiratory diseases, a non-invasive positive pressure ventilator system is designed, the overall structure design of the system is proposed, and the hardware construction is completed. The breathing state of the patient is identified by the threshold triggering method of the flow rate of change, and the calculation of the flow rate of change is realized by the least squares method. At the same time, the breathing parameters are calculated in real time according to the flow-time and pressure-time characteristic curves. In addition, CMV, CPAP, BiPAP and PSV ventilation modes are also implemented. Finally, the parameter measurement accuracy and ventilation mode setting tests are carried out. The results show that the calculation of key breathing parameters provided by the system meets the relevant standards, and supports the stable output of 4 ventilation modes at the same time, provides breathing treatment for patients, and meets the basic functional requirements of the ventilator.
Subject(s)
Humans , Ventilators, Mechanical , RespirationABSTRACT
Objective To compare and determine the reproducibility of apparent diffusion coefficient (ADC)values of the normal liver parenchyma in respiratory-triggered,breath-hold,and free-breathing diffusion weighted magnetic resonance imaging (DWI). Methods 11 volunteers did three times of breath-hold (excitation number is 1,at the end of the expiration,thickness/gapping=5 mm/1 mm), respiratory-triggered (excitation number is 2,at the end of the expiration,thickness/gapping=5 mm/1 mm),free-breathing (excitation number is 4,thickness/gapping=5 mm/1 mm)and for a total of nine axial liver DWI,the gradient factor was 800 s/mm2 .Then they were all coronally reconstructed (thickness/gapping=8 mm/1 mm).The nonparametric test was used to compare all axial and coronally reconstructed liver ADC values;and the Bland-Altman method was used to evaluate the ADC values’repeatability in coronally reconstructed images.Results The breath-hold DWI’s mean ADC value was (1.09±0.07)×10-3 mm2/s significantly lower than the respiratory-triggered DWI(1.16± 0.09)×10-3 mm2/s and the free-breathing DWI(1.19±0.10)×10-3 mm2/s(P<0.005),the axial and coronal images’results were similar.The ADC values’average difference and scope of consistency of coronal image were (-0.09 to -0.01±0.09 to 0.48)for breath-hold DWI,(-0.04 to 0.01±0.11 to 0.17)for respiratory-triggered DWI,(-0.07 to -0.02±0.11 to 0.18)for free-breathing DWI,respectively.Conclusion The breath-hold DWI’s ADC value of normal liver parenchyma is lower than the respiratory-triggered and free-breathing DWI,and showed more poorer repeatability.It is suggested that the measurement of ADC values of the liver parenchyma should be done within the respiratory-triggered or free-breathing DWI.