| Background: Noninvasive positive pressure ventilation(NPPV)is a ventilation method that connects to a patient through a nasal mask,nasal pillow,or interface without establishing an invasive artificial airway.Noninvasive ventilation has been widely used in clinical and family rehabilitation.Since being developed,noninvasive ventilation has played an important role in treating acute and chronic respiratory failure.Compared with invasive mechanical ventilation,it has the advantage of being implemented at any time according to the requirements of the disease.In addition,ventilator-associated pneumonia and other serious complications are significantly reduced.However,poor human-machine synchronization is one of the major reasons why patients are reluctant to undergo noninvasive ventilation,which affects clinical application of the technique.There are many factors that affect human-machine synchronization,but the factors with clinical significance are patient factors,ventilator performance,respiratory parameters,ventilation mode,and leakage.we found that condensate in piezometric tube can influence patient-ventilator synchrony during non-invasive mechanical ventilation.This research is to investigate the impacts of condensate in piezometric tube of non-invasive mechanical ventilation circuit on patient-ventilator synchrony and explore the strategies.Objective: 1.To investigate the impacts of condensate in piezometric tube of non-invasive mechanical ventilation circuit on patient-ventilator synchrony.2.To investigate the effect of connecting a waterproof device in the noninvasive ventilation circuit on pressure transmission and human-machine synchronization.3.To investigate the effect of connecting a airbag in the noninvasive ventilation circuit on pressure transmission and human-machine synchronization and search the best size and filling state of the airbag.Part One:Impacts of condensate in piezometric tube of non-invasive positive pressure ventilation circuit on patient-ventilator synchronySubject: 11 subjects who works in the First Affiliated Hospital of Guangzhou Medical University and 9 COPD patients who need NPPV in hospital were recruited for the study.Methods: In test 1,Eleven normal healthy subjects received non-invasive positive pressure ventilation.During the process,different volume of distilled water was gradually injected into the mid-piezometric tube of the ventilation circuit until the subjects could not trigger the ventilator or the total volume of distilled water reached 1.5 ml.The dynamic changes of the pressure inside the mask(Pmask),pressure at the piezometric tube near the mask(Ppro),pressure at the piezometric tube near the ventilator(Pdis),and the respiratory flow(Flow)were determined.In test 2,9 COPD patients received non-invasive positive pressure ventilation.During the process,0.1ml distilled water was injected into the piezometric tube.The changes of the pressure inside the mask and inside the piezometric tube near the ventilator were determined.Results: In test 1,(1)According to the Pmask,the trigger time,trigger pressure and trigger work were increased from 0.09(0.07-0.11)S,0.26(0.15-0.33)cm H2 O and 0.02(0.01-0.03)cm H2O*S at the baseline to the maximum of 0.31(0.22-0.39)S,2.29(1.76-3.09)cm H2 O and 0.55(0.41-0.68)cm H2O*S respectively.The invalid trigger increased from 0 time/minto the maximum of 9 times/min.The spurious trigger increased from 0 time/min to the maximum of 33 times/min.(2)After distilled water injection,the plateau pressures measured by Pmask and Ppro were higher than the preset parameters,which were increased from(9.74±0.34)and(9.80±0.31)cm H2 O at the baseline to the maximum of(15.79±3.10)and(15.44±3.47)cm H2 O,respectively.The plateau pressure measured by Pdis was(9.85±0.29)cm H2 O at the baseline,and to the maximum of(12.58±2.64)cm H2 O after distilled water injection.(3)After distilled water injection,the baseline pressures measured by Pmask and Ppro were increased from(3.67±0.36)and(3.71±0.32)cm H2 O to the maximum of(8.40±3.22)and(8.13±3.55)cm H2 O,respectively.The baseline pressure measured by Pdis was increased from(3.77±0.32)cm H2 O to(5.36±1.25)cm H2 O.(4)After distilled water injection,the fluctuation of the ventilated pressure was significant.The plateau pressure measured by Pmask was increased from 0.60(0.48-0.71)cm H2 O to the maximum of 7.94(7.11-8.63)cm H2 O.The frequency of the single respiratory cycle of the plateau pressure fluctuation increased from 0 time to the maximum of 7 times.(5)After distilled water injection and the ventilator was triggered by inspiration,the time of Pdis reached to the plateau pressure was delayed compared with that of Pmask and Ppro,which was delayed to the maximum of 0.11(0.08-0.12)S.In test 2,(1)The triggering time is prolonged,the triggering pressure and the triggering work is increased.(2)The platform pressure in the tube was lowered to the pressure in the mask,and the difference was(1.495±0.301)cm H2O;the baseline pressure was higher than that in the mask,and the difference was(0.647± 0.756)cm H2 O.(3)The platform pressure of mask exceeds preset parameters,and the difference is(1.053±0.405)cm H2O;the baseline pressure is lower than the preset parameter,and the difference is(0.868 ± 0.638)cm H2 O.Part Two: Effect of a waterproof device in the noninvasive ventilation circuit on human-machine synchronizationSubject:10 subjects who works in the First Affiliated Hospital of Guangzhou Medical University and 11 COPD patients who need NPPV in hospital were recruited for the study.Method: In test 1,the waterproof device connected the piezometric tube and in a closed container,and the pressure inside the container was varied to observe the corresponding pressure change in the piezometric tube.In test 2,10 volunteers received noninvasive ventilation,the waterproof device connected the piezometric tube,the dynamic changes of the pressure inside the mask(Pmask)and piezometric tube(Ptube)could be measured.In test 3,11 COPD patients received noninvasive ventilation,the waterproof device connected the piezometric tube,the dynamic changes of the pressure inside the mask and piezometric tube could be measured.Results: In test 1,when the pressure in the container was gradually increased to 50 cm H2 O and then decreased to 0,the pressure inside the piezometric tube changed synchronously with the pressure inside the container,with no statistically significant difference between the pressures(0.009 ± 0.138)cm H2 O.In test 2,there was no significant difference in triggering time,pressure,or power as measured by Pmask after connecting the waterproof device at the front end of the piezometric tube.There was no significant difference in the platform pressure and baseline pressure as measured by Pmask,before and after connecting the waterproof device.Finally,there was no significant difference in the platform pressure and baseline pressure between the Pmask and Ptube after connecting the waterproof device.In test 3,COPD patients received noninvasive ventilation,the waterproof device connected the piezometric tube(1)the triggering time,the triggering pressure and the triggering work did not change.(2)the pressure in the piezometric tube is consistent with the pressure in the mask.(3)the mask pressure is consistent with the preset parameters.Part Three :Effect of connecting airbag at the front end of piezometric tube in noninvasive ventilation circuit on man-machine synchronizationSubject: 12 subjects who works in the First Affiliated Hospital of Guangzhou Medical University and 6 COPD patients who need NPPV in hospital were recruited for the study.Method: In test 1,the airbag connected the piezometric tube and in a closed container,the filling state of the airbag was regulated,and the pressure inside the container was varied,to observe the corresponding pressure change in the piezometric tube.In test 2,Connecting airbag in different filling state at the front end of piezometric tube in noninvasive ventilation circuit.12 subjects were connected to the ventilator such that dynamic changes of the pressure inside the mask(Pmask)and piezometric tube(Ptube)could be measured.In test 3,middling airbag filled 3/5 connecting at the front end of piezometric tube in noninvasive ventilation circuit.6 COPD patients were connected to the ventilator such that dynamic changes of the pressure inside the mask and piezometric tube could be measured.Results: In test 1,When big airbag filled 1/5,2/5,4/5;middling airbag filled 3/5,4/5,5/5;small airbag filled 4/5,the pressure inside the piezometric tube changed synchronously with the pressure inside the container with no statistically significant difference(P>0.05).In test 2,(1)Set up respiratory ventilation parameters on 10/4 cm H2O-30/14 cm H2 O,connecting airbag at the front end of piezometric tube in noninvasive ventilation circuit,when big airbag filled 1/5,2/5,3/5,4/5 and middling airbag filled 2/5,3/5,4/5,the pressure difference between Pmask and Ptube is less than 0.5 cm H2 O,which is acceptable in clinic.(2)when big airbag filled 1/5,2/5,3/5 and middling airbag filled 2/5,3/5,there was no significant difference in trigger work before and after connecting the airbag at the front end of the piezometric tube.In test 3,middling airbag filled 3/5 connecting at the front end of piezometric tube during NPP in COPD patients :(1)without increasing the triggering pressure,but the triggering time,the triggering work were slightly increased.(2)the platform pressure in the mask is slightly higher than that in the piezometric tube.The baseline pressure is slightly lower than that in the piezometric tube,and the pressure difference between the mask and the piezometric tube is less than 0.5 cm H2 O.(3)the pressure of mask keep in line with the preset parameters.Conclusion: 1.During non-invasive ventilation,condensate in piezometric tube can influence patientventilator synchrony.To ensure high patient-ventilator synchronicity during non-invasive mechanical ventilation,condensate in the piezometric tube should be avoided.2.Connecting the waterproof device at the front end of the piezometric tube can prevent condensate from entering the tube without affecting pressure transmission or human-machine synchronization.3.Connecting the airbag at the front end of the piezometric tube can avoid the forming of condensate in piezometric tube.The airbag own good properties of pressure conductivity under ideal size and filling state. |
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