Effects Of BiPAP Ventilation At Different Pressure On Respiratory Mechanics And Neural Respiratory Drive In Patients With Stable Chronic Obstructive Pulmonary Disease

[Background]Chronic obstructive pulmonary disease(COPD)is a common chronic respiratory disease that is now the fourth leading cause of death worldwide.Due to chronic inflammation,patients often suffer from small airway dysfunction,increased airway resistance and functional residual capacity,which results in dynamic pulmonary hyperinflation(DPH)and intrinsic positive end-expiratory pressure(PEEPi).The deterioration of physiological indicators was mainly manifested by an increase in the neural respiratory drive and a decrease in ventilation efficiency.As the disease progresses,respiratory failure eventually occurs.In recent years,there has been increasing attention to comprehensive management based on pulmonary rehabilitation.Reasonable pulmonary rehabilitation can reduce the clinical symptoms of patients,improve exercise tolerance and quality of life.Noninvasive positive pressure ventilation(NPPV)is an important pulmonary rehabilitation strategy.Studies have shown that NPPV using Bi-level positive airway pressure(BiPAP)mode in COPD patients with respiratory failure can reduce rehospitalization and carbon dioxide retention,thus improving prognosis of patients.We suppose that for patients who is in stable condition,have obvious clinical symptoms and without respiratory failure,early use of BiPAP ventilation for pulmonary rehabilitation may lead to an improvement in physiological indicators,reducing DPH,offsetting the adverse effects of PEEPi,reducing respiratory muscle load,improving the breath and delaying the progression of the disease.However,there is few research report on the early implementation of BiPAP ventilation in patients with stable COPD without respiratory failure,neither is study on the relevant respiratory mechanics.[Objective]To observe the effects of BiPAP ventilation at different pressure levels on respiratory mechanics and neural respiratory drive in patients with COPD during stable non-respiratory failure,to provide a theoretical basis for early intervention of COPD patients with non?invasive positive pressure ventilation.[Methods]Patients with stable COPD who were admitted to the respiratory medicine clinic of Zhujiang Hospital of Southern Medical University from January 2017 to December 2017 were selected.After the inclusion,the basline data collection was first carried out,including demographic characteristics,smoking history,history of acute exacerbation in the previous year,and evaluation of the lung function,respiratory muscle strength,exercise capacity,symptom performance,quality of life,and nutritional status.Before the test,the patient completed the sniff manoeuvre(Sniff)action,maximum inspiratory pressure(MIP)action,totel lung capacity(TLC)action and recorded the maximal inspiratory pressure(Plmax),the maximum esophageal pressure(Pesmax),the maximum gastric pressure(Pgamax),and the maxinun transdiaphragmatic pressure(Pdimax)under the guidance of the operator.And the maximum Root mean square(RMSmax)of Diaphragm electromyogram(EMGdi)was calculated.At the start,no pressure was set first,then the BiPAP mode was adopted.The inspiratory positive airway pressure(IPAP)was gradually increased from 10cmH2O to 24cmH2O,and each time 2mH2O was added,the espiratory positive airway pressure(EPAP)remained unchanged at 4cmH2O.Each pressure level was maintained for at least 5 minutes.During the no-pressure and different pressure ventilation,the changes of respiratory physiological indexes was recorded such as respiratory pressure(mouth pressure(Pmo),esophageal pressure(Pes),gastric pressure(Pga),transdiaphragmatic pressure(Pdi)),flow(Flow),and EMGdi,and the patient was directed to perform corresponding Breathing action.After the test,the respiratory physiology indexes were calculated using the LabChart software of the PowerLab system.Statistical analysis was performed using SPSS 20.0 software.The respiratory physiological indexes measured before BiPAP,different pressure levels,high pressure and low pressure were compared by repeated measures analysis of variance.The LSD method was used to compare the two indicators.The effect of BiPAP ventilation on respiratory physiological parameters of COPD patients with different inspiratory muscle strength was analyzed by covariance analysis.Respiratory parameters between the normal muscle strength group and the low muscle strength group were compared using two independent sample t-tests.All statistical values were statistically significant using a two-sided test P<0.05.[Results]1.Basic information of COPD patientsA total of 10 patients with stable COPD participated in the study and completed the trial,and all subjects were male.The average age was 65.20±9.31(years),the number of hospitalizations in the previous year was 0.50±0.71(times),and the average smoking index was 30.60±24.48(package/year).The body mass index(BMI)was 21.65±2.97,and the fat-free body mass index(FFMI)was 16.22±2.46.In terms of lung function index,after inhaling bronchodilator,FEV1 was 1.17±0.31(L),FEV1%predicted was 47.80±15.24(%),FVC was 2.26±0.78(L),and FEV1/FVC was 53.64±10.54(%).The 6-minute walk test distance(6MWD)was 479.60±93.89(m),the chronic obstructive pulmonary disease assessment test(CAT)score was 11.80±6.41,and the modified British Medical Research Council Dyspnea Scale(mMRC)averaged 1.50±0.85,the St.George Respiratory Questionnaire(SGRQ)average score of 22.10 ± 7.91.The average PImax was 66.41±17.03(CmH2O)and PEmax was 68.94±15.89(cmH2O).Blood gas analysis showed an average PH of 7.41± 0.02,PaO2 of 79.57±10.06(cmH2O),and PaCO2 of 35.58±3.77(cmH2O).Grouping according to 2019GOLD,group A 4(40%),group B 2(20%),group C 1(10%),group D 3(30%),and graded according to lung function,GOLD1 0(0%),GOLD2 4(40%),GOLD3 5(50%),GOLD4 1(10%).2.Determination of respiratory physiological indexes in patients with COPD during calm breathingIn the state of calm breathing,the average dynamic intrinsic positive end-expiratory pressure(PEEPidyn)was 1.35±0.73 emH2O,and the airway resistance(Raw)was 9.27±2.19 cmH2O/L/s.The mean respiratory cycle(Ttot)was 3.24± 0.86 s.The average inspiratory tidal volume(VTi)was 0.58 ± 0.16 L,and the minute ventilation(Ve)was 11.21 ± 3.20 L/min.In terms of pressure,the mean Pmo of all subjects was 0.72±0.35 cmH2O,Peso was-13.30±4.55 cmH2O,and the Pga was 17.72±4.87 cmH2O.The Pdi was 29.66±6.35 cmH2O,and the average RMS of all subjects was 70.42±13.71?V,and the Ve/RMS was 0.17±0.06L/min./?V,the Pdi/RMS was 0.44±0.13 cmH2O/?V.All subjects were able to complete the Sniff,MIP,and TLC actions.The Pesmax was-56.73±18.99cmH2O,the Pgamax was 71.73±23.44 cmH2O,and the Pdimax was 94.50±33.26.cmH2O,the RMSmax was 193.09±20.85?V.3.Effects of BiPAP ventilation at different pressure on respiratory physiological parameters in patients with COPDEffects on Breathing patternAs the pressure increased,Ttot,inspiratory time(Ti)and exspiratory time(Te)showed a gradual increase trend,respiratory rate(RR)gradually decreases,but there was no statistically significant difference between Ttot and Ti in rest condition and various pressure(P>0.05).Compared with the time of calm breathing,VTi,and Ve gradually increased with the increase of pressure,and the difference between most pressure levels was statistically significant(P<0.05).Effects on respiratory pressureThe change in Pmo is the same as that of the ventilator.As the pressure gradually increased,the absolute value of Peso gradually decreased,and the difference between each pressure and calm breathing was statistically significant(P<0.05).Pga increased with the increase of pressure,but there was no statistical difference between the levels(P>0.05).Because the esophageal pressure has a tendency to become positive from negative,Pdi gradually decreases with the increase of the pressure,and the all pressure levels are statistically different compared with the calm breathing(P<0.05).Effects on of inspiratory workBoth esophageal pressure time product(PTPes)and diaphragm pressure time product(PTPdi)decreased with the increase of pressure,and the difference between each pressure level and calm breathing was statistically significant(P<0.05).Similarly,when the pressure rose to 16cmH2O,PTPes and PTPdi both approached 0,no significant change(P>0.05),reflecting a significant decrease in respiratory muscle work compared to calm breathing.Effects on lung capacity,PEEPidynThe inspiratory capacity(IC)increased with the increase of the pressure level.Compared with the calm breathing,the increase of each pressure level was statistically significant(P<0.05),and the corresponding AEELV also showed a similar trend.However,PEEPidyn showed a trend of decreasing first and then increasing with the increase of pressure level.Compared with calm breathing,only the 10-14cmH2O showed significant statistical difference(P<0.05).Effect on airway resistance and TTdiAs the pressure increased,Raw showed a trend of decreasing first and then slightly increasing.The measured values of each pressure level were significantly different from those of calm breathing(P<0.05).The the diaphragmatic muscle tension time index(TTdi)showed a decreasing trend with the increase of pressure level,and there were statistical differences compared with calm breathing(P<0.05).Effect on neural respiratory drive and neural respiratory drive couplingWith the increase of pressure level,RMS gradually decreased,and each pressure levels were statistically different from calm breathing(P<0.05).When the pressure was greater than 16cmH2O,the RMS remained basically stable and no significant decline occurred.A similar trend has emerged with RMS/RMSmax.Ve/RMS and Pdi/RMS showed an increasing trend with the increase of pressure,but Pdi/RMS showed no statistical difference between the pressure(P>0.05).Effect on Borg score,SpO2,PetCO2As the pressure increased,the Borg score reflecting the degree of dyspnea gradually increased and reached the maximum at the highest pressure(P<0.05).At the same time,SpO2 also showed an upward trend with the increase of pressure level.Except for 10cmH2O,each pressure was statistically different compared with calm breathing(P<0.05).In addition,PetCO2 also showed a trend of decreasing with increasing pressure.4.Effects of BiPAP ventilation with high pressure and low pressure on respiratory physiological parameters in patients with COPDEffect on tidal volume and minute ventilationWith the increase of pressure level,VTi and Ve at low pressure and high pressure level were significantly higher than those without pressure(P<0.05),and the increase was more significant at high pressure(P<0.05).Effect on inspiratory workWith the increase of the pressure,the work of the respiratory muscles at low pressure and high pressure was reduced significantly(P<0.05),and the decrease was more significant at high pressure(P<0.05).Effect on IC,PEEPidynIC increased with increasing pressure,which was statistically significant compared with calm breathing(P<0.05),but there was no statistically significant difference between high pressure ventilation and low pressure(P>0.05).In addition,low pressure ventilation can reduce PEEPidyn to some extent(P<0.05).Effect on Raw,TTdiRaw at low and high pressures were significantly lower than those without pressure(P<0.05),but there was no statistical difference between the two levels(P>0.05).Low pressure and high pressure ventilation significantly reduced TTdi(P<0.05)and decreased significantly at high pressure(P<0.05).Effect on neural repiratory driveThe low and high positive pressure ventilation can significantly reduce RMS,RMS/RMSmax(P<0.05),and the high pressure is more obvious(P<0.05),while the ventilation efficiency was further improved(P<0.05).In terms of the mechanical contraction efficiency of the diaphragm,although the low pressure and high pressure level ventilation can increase the Pdi/RMS numerically,there is no statistically significant difference between the two(P>0.05).Effect on Borg score and PetCO2Positive pressure ventilation increased the subject's Borg score(P<0.05),and the increase was more significant at high pressure(P<0.05).At the same time,ventilation reduced PetCO2(P<0.05)and decreased significantly at high pressures(P<0.05).5.Effects of BiPAP ventilation at different pressure on respiratory physiological parameters in patients with different inspiratory muscle strength(COPD)Effect on breathing workAs the pressure increased,both PTPes and PTPdi showed a downward trend.At level of 12 cmH2O,the PTPes in the normal muscle strength group were significantly lower than those in the low muscle strength group(P<0.05).There was no significant difference in other levels between the normal muscle strength group and the low muscle strength group(P>0.05).Effect on neural respiratory drive and TTdiWith the increase of pressure,the RMS and RMS/RMSmax of the normal muscle strength and the low muscle strength showed a gradual decline,but there was no difference between the groups at each level(P>0.05).The Ve/RMS of the normal muscle group and the low muscle strength group showed an increasing trend with increasing pressure,but no difference between groups was observed in each pressure(P>0.05).At the same time,the TTdi of the normal muscle strength group and the low muscle strength group decreased with the increase of pressure,but also did not show the difference between the groups(P>0.05).[Conclusion]1.For stable COPD patients,non-invasive positive pressure ventilation in BiPAP mode can increase the patient's ventilation,reduce the inspiratory muscle load,and improve ventilation efficiency.2.compared with the calm breathing and low pressure ventilation,high pressure ventilation can further increase the patient's tidal volume,minute ventilation,reduce respiratory muscle work,improve ventilation efficiency,but also cause increased breathing difficulties,resulting in human-machine incoordination.3.For stable COPD patients,the pressure of IPAP less than 16cmH2O may be suitable.4.There were no significant differences in respiratory physiological parameters between patients with COPD with different inspiratory muscle strength in BiPAP ventilation.