The Design,Development,Characteristics And Performance Of A New Separate-breathing Valve For Noninvasive Ventilation

?Background?Chronic obstructive pulmonary disease(COPD)as know a type of lung disease characterized by airflow limitation.The airflow limitation is not fully reversible and usually progressive over time,and COPD has accompanied by the lungs to toxic gases or particles that cause abnormal inflammatory reaction.The main respiratory mechanics of abnormality of COPD includes: airflow limitation,increased hyperinflation,increased lung volume significantly at the end expiratory phase,increased the dead space and imbalance of gas transfer.COPD is a major cause of chronic illness and death,is the fourth leading cause of death in our world,moreover,the prevalence and mortality of COPD will rise further in the next few decades.According to our country and the World Health Organization recommendations,after COPD diagnosed,it is necessary to provide a positive intervention,treatment and management for a COPD patient.Besides drug intervention,exercise rehabilitation in patients with COPD is an important treatment approach.Nowadays,many clinical studies had showed that noninvasive positive pressure ventilation(NIPPV)as a assistant rehabilitation therapy has been becoming an important way for the treatment on moderate and severe COPD patients in stable stage.Previous studies showed that SEV as a traditional expiratory device may cause CO2 retention when using NIPPV to treat COPD with respiratory failure patients,and led to rebreathing because of insufficient exhalation.A recent study showed that enough exhalation on PEV can be met need with COPD patient while at the resting state.However,a study showed while using NIPPV to do rehabilitation exercise on COPD patients,large amount of exhalation could not be discharged effectively,hence led to retention of carbon dioxide and rebeathing.PEV could not meet the clinical requirement to discharge gas.The above-mentioned two kinds of valve are short of their design structure,can not effectively solve the problem of exhalation for rehabilitation exercise in patients with COPD.In addition,the existing literature research mostly in the study of NIPPV has concerned leakage and carbon dioxide retention at mask;there are few researches on the expirtory valve.Therefore,design and development of a new kind of expiratory valve to discharge a large amount of exhalation will be needed;it has an important clinical significance for rehabilitation exercise in patients with COPD while using NIPPV.The concept firstly is put forward to separate inhale route and exhale route on NIPPV ventilator.Design of SBV is based on Bemoulli principle,and the principles of fluid mechanics.The use of NIPPV ventilator has a characteristics with a single limb circuit,by the aid of referencing the current expiratory valve structure and its exhalation mode at home and abroad,A new kind of expiratory valve(our designed SBV)was created.Its aim to solve the problem that current expiratory valve has a shortage for insufficient exhalation while COPD do rehabilitation exercise.By separating inhale and exhale gas,reduce leak during inspiration,increase the exhalation volume during expiration at the same time.In order to make the gas exhaled by the patient discharge,so reduce the probability of carbon dioxide retention.Part1.Design of adjustable(SBV)Design of adjustable SBV is based on Bemoulli Principle,the ball inside SBV is due to the impact of Bemoulli effect,traveling to the specified line to move,which can blocks the outlet and inlet in the inspiratory phase and expiratory phase respectively,therefore ensure to separates the inhaled and exhaled gas;in addition,with regulating EPAP by the spring,to control the EPAP,to meet the patient's need of EPAP.E.Buckingham theorem of dimensional analysis is used for the design of SBV.The ball movement of SBV is deduced in the pipeline,and the functional relationship between the thrush F and the by gas velocity,density,small ball and SBV pipeline gap,the important basis for the design of-ball journey applies the Newton's laws of motion to calculate.Prototype SBV is self-designed,and manual made of by using of available existing parts.It consists of three parts: SBV main part,EPAP adjusting device,oblique ventilating tube.The main part is composed of the upper and lower sealing rings-air inlet valve seat,diaphragm,SBV ball and spring.Through up and down movement of SBV,the air vents of up and down were closed,so as to achieve to separate inhale gas and exhaled gas.Adjusting EPAP device by adjusting knob to change the spring pressure,to control the opening pressure of regulating valve ball,and to ensure gas unobstructed discharge in different EPAP;Oblique ventilating tube supply gas from the circuit of Ventilator into the oronasal mask.A signal hole is provided in SBV housing and the air inlet valve seat.When the inspiratory and expiratory phase conversed,small changes in the signal flow,pressure can be transmitted to ventilator through the signal hole,therefore Ventilator can make corresponding reaction.Part2.Comparison test of healthy volunteers on Separate Breathing Valve?Objectives?To test three kinds of expiratory valves through 10 healthy volunteers;to compare SBV exhalation volume in expiratory phase and leak volume in inspiratory phase with other two kinds of expiratory valves;to evaluate the performance of SBV.?Subjects and Methods?Subject: 10 cases of healthy volunteers(mean age 34.40 + 10.18 years old,(FEV1%predicted 91.12.+ 0.56%).Method : Compare self-designed SBV to with other two kinds of expiratory valves1.Apparatus and equipments: Powerlab 16/35 multi-channel recorder,biomedical amplifier,pressure monitoring catheter,pressure transducer,spirometer(Fleich No 2pneumotachgraph),calibrator for volume and pressure,i Mac computer,noninvasive ventilator(Res MED H5i+S9).oranasal mask(Mirage Mask),Lung function test instrument2.Test methods and recorded parameters:Subjects performed pulmonary function tests first.The ventilation circuit was connected according to following order : ventilator?single-limb circuit?flow detector(F1)?pressure transducer(P1)?PEV/SEV/SBV?pressure transducer(P2)?flow detector2(F2)?oronal mask.After wearing mask comfortably,the ventilator parameters were set: ST mode.Then recorded the changes in breathing pattern,flow and pressure,exhalation volume in expiratory phase and leak volume in inspiratory phase in every breathing cycleSpecific process: in ST mode,pressure and flow were measured in the mode after EPAP was adjusted to 4,IPAP,corresponded to adjust to 8,10,12,14,16,20,24 cm H2O respectively;EPAP: was adjusted to 6cm H2 O,IPAP: corresponding to10,12,14,16,20,24 cm H2O respectively;EPAP: was adjusted to 8cm H2 O,IPAP: 12,corresponding to 14,16,20,24 cm H2O respectively;according above mentioned order PEV,SEV,SBV to test.Signals of amplification by Powerlab16 were recorded;Data were analyzed with Chart 7.2.3 for i Mac.?Results?When ventilator connected to SEB,then adjusted EPAP to 4 cm H2 O,6 cm H2 O,8cm H2 O,10 cm H2 O respectively,the average exhalation volume in expiratory phase were 254ml/s,309 ml/s,341 ml/s,368 ml/s respectively.While adjusted EPAP to 4cm H2 O,6 cm H2 O,8 cm H2 O,10 cm H2 O,leak volume in inspiratory phase were about327-494 ml/s,392-552 ml/s,431-538 ml/s,456-561 ml/s,changes of leak volume in inspiratory phase was positively related to changes IPAP(P < 0.01).When ventilator connected to PEV,adjusted EPAP to 4 cm H2 O,6 cm H2 O,8 cm H2 O,10 cm H2 O respectively,the average exhalation volume in expiratory phase: 469ml/s,465 ml/s,479 ml/s,484 ml/s respectively;While adjusted EPAP to 4 cm H2 O,6cm H2 O,8 cm H2 O,10 cm H2 O respectively,leak volume in inspiratory phase were429-454 ml/s,403-439 ml/s,410-437 ml/s,402-417 ml/s respectively,to changes of leak volume in inspiratory phase was no correlation with IPAP changes(P > 0.05).When ventilator connected to SBV,adjusted EPAP to 4 cm H2 O,6 cm H2 O,8 cm H2 O,10 cm H2 O,respectively,the average exhalation volume in expiratory phase:were563ml/s,639 ml/s,657 ml/s,676 ml/s respectively;While adjusted EPAP to 4 cm H2 O,6 cm H2 O,8 cm H2 O,10 cm H2 O respectively,leak volume in inspiratory phase were325-360 ml/s,336-355 ml/s,340-372 ml/s,356-347 ml/s,respectively,which was lower than ones the same set conditions on the PEV(all P < 0.01).The changes of leak volume in inspiratory phase were no correlation with IPAP changes(P > 0.05).In addition,IPAP droved by ventilator through SBV,and transmitted into the mouth unchangfully.SBV had a good safety on clinical use.?Conclusion?1.leak volume in inspiratory phase in SEV was greater than exhalation volume in expiratory phase.With the increase IPAP,exhalation volume in SEV was insufficient,it may cause carbon dioxide retention.2.Exhalation volume in expiratory phase.in PEV is greater than leak volume in inspiratory phase,but exhalation volume is limited,when doing exercise caused ventilation volume increases,once beyond PEV exhalation range,it may cause carbon dioxide retention.3.As PEV,Exhalation volume in expiratory phase.in SBV is greater than leak volume in inspiratory phase,Because of separate paths for inhaled gas and exhaled gas.a small amount of leakage occurred,and avoided leak compensation.in addition,Exhalation volume in expiratory phase.in SBV is more than the one of PEV in the same phase,therefore meet the clinical demand while using ventilation aid to exercise training.4.SBV applied in health volunteers showed clinical safetyPart 3 Comparison Test of patients with COPD on Separate Breathing Valve?Objectives?To test two kinds of expiratory valves(SBV,PEV)through four COPDers;to compare exhalation volume in expiratory phase on SBV and leak volume in inspiratory phase with PEV;therefore evaluate the performance of SBV.?Subjects and Methods?Subject: 4 COPDers,3 males,1 female,(mean age 67.00±7.46 years old).Method : Compare self-designed SBV with PEV by respiratory mechanics.1,Apparatus and equipments: Powerlab 16/35 multi-channel recorder,biomedical amplifier,pressure monitoring catheter,pressure transducer,spirometer(Fleich No 2pneumotachgraph),calibrator for volume and pressure,i Mac computer,noninvasive ventilator(Res MED H5i+S9).oranasal mask(Mirage Mask),Lung function test instrument.2 Test methods and recorded parameters:Subjects performed pulmonary function tests first.The ventilation circuit was connected according to following order : ventilator?single-limb circuit?flow detector(F1)?pressure transducer(P1)?PEV/SBV?pressure transducer(P2)?flow detector(F2)? oronal mask.After wearing mask comfortably,the ventilator parameters were set to ST mode.Then real-time recorded the changes in breathing pattern;flow and pressure,exhalation volume in expiratory phase and leak volume in inspiratory phase in every breathing cycleSpecific process: in ST mode,pressure and flow were measured in the mode.(1)after EPAP was adjusted to 4,IPAP,corresponded to adjust to 12,16,20,cm H2 O respectively;(2)EPAP was adjusted to 6cm H2 O,IPAP: corresponding to 12,16,20 cm H2O respectively,according above mentioned order PEV,SEV,SBV to test.Signals of amplification by Powerlab16 were recorded;Data were analyzed with Chart 7.2.3 for i Mac.?Results?When ventilator connected to PEV,adjusted EPAP to 4 cm H2 O,6 cm H2 O respectively,the average exhalation volume in expiratory phase were: 488 ml/s?,472ml/s respectively;While adjusted EPAP to 4 cm H2 O,6 cm H2 O,respectively,leak volume in inspiratory phase were 474-485 ml/s?474-478 ml/s respectively,to changes of leak volume in inspiratory phase was no correlation with IPAP changes(P >0.05).When ventilator connected to SBV,adjusted EPAP to 4 cm H2 O,6 cm H2 O,8 cm H2 O,10 cm H2 O,respectively,the average exhalation volume in expiratory phase: were597ml/s ? 759 ml/s respectively;While adjusted EPAP to 4 cm H2 O,6 cm H2 O respectively,leak volume in inspiratory phase were 347-362 ml/s ? 325-346 ml/s respectively,which was lower than ones the same set conditions on the PEV(all P <0.01).The changes of leak volume in inspiratory phase were no correlation with IPAP changes(P > 0.05).In addition,IPAP droved by ventilator through SBV,and transmitted into the mouth unchangfully.patients had a good endurance to SBV.?Conclusion?1 In patients with COPD,leak volume in inspiratory phase in SBV was less than exhalation volume in expiratory phase in PEV.2 In patients with COPD,exhalation volume in expiratory phase in PEV is less than exhalation volume in expiratory phase in SBV.3 Pressures can be keep stable on ventilator when used SBV.4 SBV applied in patients with COPD showed good endurance.