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OBJECTIVE@#To find out the circuit pressure and flow at the trigger point by observing the characteristics of the inspiratory trigger waveform of the ventilator, confirm the intra-alveolar pressure as the index to reflect the effort of the trigger according to the working principle of the ventilator combined with the laws of respiratory mechanics, establish the related mathematical formula, and analyze its influencing factors and logical relationship.@*METHODS@#A test-lung was connected to the circuit in a PB840 ventilator and a SV600 ventilator set in pressure-support mode. The positive end-expiratory pressure (PEEP) was set at 5 cmH2O (1 cmH2O ≈ 0.098 kPa), and the wall of test-lung was pulled outwards till an inspiratory was effectively triggered separately in slow, medium, fast power, and separately in flow-trigger mode (sensitivity VTrig 3 L/min, 5 L/min) and pressure-trigger mode (sensitivity PTrig 2 cmH2O, 4 cmH2O). By adjusting the scale of the curve in the ventilator display, the loop pressure and flow corresponding to the trigger point under different triggering conditions were observed. Taking intraalveolar pressure (Pa) as the research object, the Pa (called Pa-T) needed to reach the effective trigger time (TT) was analyzed in the method of respiratory mechanics, and the amplitude of pressure change (ΔP) and the time span (ΔT) of Pa during triggering were also analyzed.@*RESULTS@#(1) Corresponding relationship between pressure and flow rate at TT time: in flow-trigger mode, in slow, medium and fast trigger, the inhalation flow rate was VTrig, and the circuit pressure was separately PEEP, PEEP-Pn, and PEEP-Pn' (Pn, Pn', being the decline range, and Pn' > Pn). In pressure-trigger mode, the inhalation flow rate was 1 L/min (PB840 ventilator) or 2 L/min (SV600 ventilator), and the circuit pressure was PEEP-PTrig. (2) Calculation of Pa-T: in flow-trigger mode, in slow trigger: Pa-T = PEEP-VTrigR (R represented airway resistance). In medium trigger: Pa-T = PEEP-Pn-VTrigR. In fast trigger: Pa-T = PEEP-Pn'-VTrigR. In pressure-trigger mode: Pa-T = PEEP-PTrig-1R. (3) Calculation of ΔP: in flow trigger mode, in flow trigger: without intrinsic PEEP (PEEPi), ΔP = VTrigR; with PEEPi, ΔP = PEEPi-PEEP+VTrigR. In medium trigger: without PEEPi, ΔP = Pn+VTrigR; with PEEPi, ΔP = PEEPi-PEEP+Pn+VTrigR. In fast trigger: without PEEPi, ΔP = Pn'+VTrigR; with PEEPi, ΔP = PEEPi-PEEP+Pn'+VTrigR. In pressure-trigger mode, without PEEPi, ΔP = PTrig+1R; with PEEPi, ΔP = PEEPi-PEEP+PTrig+1R. (4) Pressure time change rate of Pa (FP): FP = ΔP/ΔT. In the same ΔP, the shorter the ΔT, the greater the triggering ability. Similarly, in the same ΔT, the bigger the ΔP, the greater the triggering ability. The FP could better reflect the patient's triggering ability.@*CONCLUSIONS@#The patient's inspiratory effort is reflected by three indicators: the minimum intrapulmonary pressure required for triggering, the pressure span of intrapulmonary pressure, and the pressure time change rate of intrapulmonary pressure, and formula is established, which can intuitively present the logical relationship between inspiratory trigger related factors and facilitate clinical analysis.
Subject(s)
Humans , Respiration, Artificial/methods , Positive-Pressure Respiration , Lung , Ventilators, Mechanical , Respiratory MechanicsABSTRACT
As a non-physiological way of ventilation, mechanical ventilation has a great effect on the respiratory mechanics. The biggest problem of artificial airway is that it brings extra airway resistance to the respiratory tract. For different parts of the lung, positive pressure ventilation could cause different mechanic states. We can find the formation and influencing factors of transpulmonary pressure, transchest wall pressure, trans-lung-chest pressure, trans-diaphragmatic pressure, trans-pulmonary-diaphragmatic pressure, intrapleural pressure, plateau pressure and driving pressure, by analyzing the mechanic state in a unit area of the chest or diaphragm position in the way of basic mechanics. It is obviously different in the pulmonary pressure gradient caused by inspiratory driving between in spontaneous breathing and in mechanical ventilation. The pressure is transmitted from the periphery to the center in spontaneous breathing in physiological state, playing a traction role for lung tissue. The pressure is transmitted from the center to the periphery in positive pressure ventilation without spontaneous breathing, playing a pushing role for lung tissue. It can be divided into two stages in positive pressure ventilation with spontaneous breathing. The first stage is from inspiratory trigger effort to trigger sensitivity. It is similar to spontaneous inspiration in physiological state. The pressure gradient in this stage is from the peripheral to center. But the period is very short. The second stage is the positive pressure ventilation progress after the trigger sensitivity. The pressure gradient is caused by the pulling of the patient's spontaneous inhalation and the pushing of the positive pressure ventilation of the ventilator. There is a certain complementarity in the distribution and transmission of pressure, especially for non-physiological positive pressure ventilation. Therefore, through these basic mechanical analysis, clinical medical staff can better understand the impact of mechanical ventilation on respiratory mechanics.
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Objective To design a mathematical calculation model for better understanding and grasping the logical problem of replacement fluid and citric acid anticoagulant infusion in continuous veno-venous hemofiltration (CVVH). Methods ① Parameter definition: A, B, and T were respectively called the main part of pre-replacement fluid, 5% sodium bicarbonate solution, and 4% sodium citrate infused before filter. And a and b were respectively called the main part of post-replacement fluid, and 5% sodium bicarbonate solution infused after filter. ② Logic conversion:The liquid in back terminal (Z) was artificially divided into two parts. One (X) was the original residual plasma after filtration. The second (Y) was the part excluding the plasma, including the left part of pre-replacement fluid with sodium citrate, and the post-replacement fluid. ③The mathematical formulas of liquid volume and electrolyte concentration at X, Y and Z in unit time were listed according to the principle of CVVH and the screening coefficient of filter for different substances. ④The calculation formulas were entered into Excel form, and a mathematical calculation model was made, and a simulation calculation with examples was carried out. Results An Excel model was established by inserting the calculation formulas of volume, electrolyte, and total calcium at X, Y and Z. And it was found that the concentration of Na+, K+, Cl-, HCO3- at Y point remained unchanged only when A, B and (or) a, b was kept in same side and proportion even with the change of blood flow and other parameters without sodium citrate as anticoagulant. Once any of the parameters (such as blood flow, replacement fluid volume, etc.) were adjusted in other infusion methods (such as different ratios, different directions of the same year, etc.), the calculation results at Y would vary, and the electrolyte concentration at Z would change accordingly. A change of dilution model or parameter would result in the change of the electrolyte concentration at Y and Z with sodium citrate as anticoagulant. The concentration of total calcium scarcely changed no matter in what model and parameters. Conclusions All kinds of infusion ways could be included in the Excel model. The infusion results of all kinds of infusion matching could be intuitively evaluated. It is helpful for the medical staff to make a logical analysis and risk prediction in CVVH.
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Objective@#To better understand the significance of the pressure-time curve and flow-time curve from the perspective of PB840 ventilator working principle.@*Methods@#① Mechanical principle: flow supply valves (air valve and oxygen valve) and exhalation valve in PB840 ventilator were controlled to achieve the ventilation target (volume or pressure) by the central processing unit according to the monitoring data from pressure sensors (P1 at the supply side, P2 at the exhalation side) and flow sensors (Q1 at the air side, Q2 at the oxygen side, Q3 at the exhalation side). ② The essence of curve: each point means a value of pressure or flow at a certain time measured by the sensors or calculated by the system. ③ The respiratory process could be divided into inspiratory part, expiratory part, and the connection part from expiratory to inspiratory. The air running state and the respiratory mechanics relationship at the three parts could be inferred according to the form of curves.@*Results@#① Inspiratory process: at volume-controlled and constant flow ventilation: there should be a relationship "Pc-Pa = XR" between alveolar pressure (Pa) and circuit pressure (Pc) according to Ohm law. So, the Pc curve (pressure-time curve) could indirectly reflect the Pa curve with the flow (X) and resistance (R) being constant. At pressure-set ventilation: it is the goal of ventilator to maintain the Pc at the target level. So, the stability of the target pressure line in pressure-time curve reflects the matching ability of the flow supply valves and the exhalation valve. ② Expiratory process: it could be divided into pre-expiratory [without basic flow (Ba) or bias flow (Bi)] and post-expiratory (with Ba or Bi), where Ba or Bi is equal to "Q1+Q2". So, the mathematical function are "X(t) = Q3t" in pre-part, and "X(t) = Q3t-(Q1t+Q2t)" in post-part. The relationship between pressure and flow at peak expiratory flow point: it could be found that there is an obvious time span and area formation under the curve from 0 to peak point (Fpeak) after stretching the abscissa axis of flow-time curve. It means that some gas have been discharged from the lung when it arrives at the peak point. So, the alveolar pressure should be lower than the platform pressure at the point (Pplat). The circuit pressure is significantly higher than positive end expiratory pressure (PEEP) at the point in the stretching axis diagram. So, it means that the formula "RE = (Pplat-PEEP)/Fpeak" to calculate the expiratory resistance (RE) is unreasonable in the angle of Ohm law. ③ The process from exhalation to inspiratory: according to the difference of the starting point of the conversion, it could be divided into two cases: one is that the inspiratory started from the ending of exhalation. Here, the inhaling starting point is lying in the abscissa axis. The other is that the inspiratory started before the ending of exhalation (with endogenous positive end expiratory pressure). Here, the starting point is lying below the abscissa axis, and the slope of the following curve is obviously larger than the slope of natural expiratory curve. According to the difference of results from the starting point to the end of the inhalation triggering effort, it could be divided into two cases: one is that it reach the trigger point. Here, the expiratory curve extends upward from or below the horizontal axis until an effective air supply is triggered. The other is that it could not reach the trigger point. Here, the expiratory curve extends upward from or below the horizontal axis, but then runs downward (meaning exhaling).@*Conclusion@#It is helpful to analyze the ventilation state, ventilation failure, and the causes of man-machine confrontation with understanding the ventilation principle and the air route map of the ventilator.
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Objective To better understand the significance of the pressure-time curve and flow-time curve from the perspective of PB840 ventilator working principle. Methods ① Mechanical principle: flow supply valves (air valve and oxygen valve) and exhalation valve in PB840 ventilator were controlled to achieve the ventilation target (volume or pressure) by the central processing unit according to the monitoring data from pressure sensors (P1 at the supply side, P2 at the exhalation side) and flow sensors (Q1 at the air side, Q2 at the oxygen side, Q3 at the exhalation side). ② The essence of curve: each point means a value of pressure or flow at a certain time measured by the sensors or calculated by the system. ③ The respiratory process could be divided into inspiratory part, expiratory part, and the connection part from expiratory to inspiratory. The air running state and the respiratory mechanics relationship at the three parts could be inferred according to the form of curves. Results ① Inspiratory process: at volume-controlled and constant flow ventilation: there should be a relationship "Pc-Pa = XR" between alveolar pressure (Pa) and circuit pressure (Pc) according to Ohm law. So, the Pc curve (pressure-time curve) could indirectly reflect the Pa curve with the flow (X) and resistance (R) being constant. At pressure-set ventilation: it is the goal of ventilator to maintain the Pc at the target level. So, the stability of the target pressure line in pressure-time curve reflects the matching ability of the flow supply valves and the exhalation valve. ② Expiratory process: it could be divided into pre-expiratory [without basicflow (Ba) or bias flow (Bi)] and post-expiratory (with Ba or Bi), where Ba or Bi is equal to "Q1+Q2". So, the mathematical function are "X(t) = Q3t" in pre-part, and "X(t) = Q3t-(Q1t+Q2t)" in post-part. The relationship between pressure and flow at peak expiratory flow point: it could be found that there is an obvious time span and area formation under the curve from 0 to peak point (Fpeak) after stretching the abscissa axis of flow-time curve. It means that some gas have been discharged from the lung when it arrives at the peak point. So, the alveolar pressure should be lower than the platform pressure at the point (Pplat). The circuit pressure is significantly higher than positive end expiratory pressure (PEEP) at the point in the stretching axis diagram. So, it means that the formula "RE = (Pplat-PEEP)/Fpeak" to calculate the expiratory resistance (RE) is unreasonable in the angle of Ohm law. ③ The process from exhalation to inspiratory: according to the difference of the starting point of the conversion, it could be divided into two cases: one is that the inspiratory started from the ending of exhalation. Here, the inhaling starting point is lying in the abscissa axis. The other is that the inspiratory started before the ending of exhalation (with endogenous positive end expiratory pressure). Here, the starting point is lying below the abscissa axis, and the slope of the following curve is obviously larger than the slope of natural expiratory curve. According to the difference of results from the starting point to the end of the inhalation triggering effort, it could be divided into two cases: one is that it reach the trigger point. Here, the expiratory curve extends upward from or below the horizontal axis until an effective air supply is triggered. The other is that it could not reach the trigger point. Here, the expiratory curve extends upward from or below the horizontal axis, but then runs downward (meaning exhaling). Conclusion It is helpful to analyze the ventilation state, ventilation failure, and the causes of man-machine confrontation with understanding the ventilation principle and the air route map of the ventilator.
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Objective? To? analyze? the? ineffective? triggering? caused? by? nebulization? in? the? way? of?respiratory?mechanics.? Methods? A?test-lung?and?an?oxygen-driven?jet?nebulizer?were?connected?to?the?circuit?in?a?PB840?ventilator.?The?test-lung?was?pulled?outwards?in?manual?way?till?an?inspiration?was?effectively?triggered?separately?in?different?flow-trigger?modes?[flow-trigger?sensitivity?(VTrig)?3?L/min?and?5?L/min]?and?pressure-trigger?modes?[pressure-trigger?sensitivity?(PTrig)?2?cmH2O?and?4?cmH2O,?1?cmH2O?=?0.098?kPa]?with?the?nebulizer?being?closed?and?opened?in?turn.?The?corresponding?relationship?and?characteristics?between?the?flow?and?pressure?in?the?circuit?under?different?triggering?conditions?were?observed?by?adjusting?the?curve?amplitude?in?the?screen.?The?minimum?alveolar?pressure?(Pa)?which?could?cause?an?effective?triggering?and?the?variation?span?of?Pa?during?the?triggering?period?were?analyzed?in?respiratory?mechanics.? Results? ①?In?flow-trigger?mode:?Pa?was?pulled?down? from? positive? end-expiratory? pressure? (PEEP)? or? intrinsic? positive? end-expiratory? pressure? (PEEPi)? to?"PEEP－VTrigR"?(R?meant?airway?resistance)?without?nebulization,?and?the?span?of?Pa?was?"VTrigR"?or?"PEEPi－PEEP+VTrigR".?Pa?was?pulled?down?from?PEEP?or?PEEPi?to?"PEEP－(VTrig+N)?R"?(N?meant?nebulization?airflow)?with?nebulization,?and?the?span?of?Pa?was?"(VTrig+N)?R"?or?"PEEPi－PEEP+(VTrig+N)?R".?②?In?pressure-trigger?mode:?Pa?was?pulled?down?from?PEEP?or?PEEPi?to?"PEEP－PTrig－1R"?without?nebulization,?and?the?span?of?Pa?was?"PTrig+1R"?or?"PEEPi－PEEP+PTrig+1R".?Pa?was?pulled?down?from?PEEP?or?PEEPi?to?"PEEP－PTrig－(N+1)?R"?with?nebulization,?and?the?span?of?Pa?was?"PTrig+(N+1)?R"?or?"PEEPi－PEEP+PTrig+(N+1)?R".? ?Conclusions? Nebulization?airflow?increases?the?difficulty?of?inspiratory?triggering?in?mechanical?ventilation.?PEEPi?makes?it?more?difficult.
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ObjectiveTo establish a mathematical formula for choosing the manner of replacement fluid infusion in continuous renal replacement therapy (CRRT), so as to provide the basis for improving the treatment effect. Methods A mathematical formula for choosing the manner of replacement fluid infusion with continuous veno-venous hemofiltration (CVVH) was taken as an example, and it was compared with the result of standard replacement fluid in order to analyze the effect of different manners of infusion.① Comparison parameters: the plasma volume (Vreturn) and some electrolyte concentration (Creturn) in back way of CRRT (if other thing was solute, filter coefficient should be 1.0).② Research objects: the actual replacement fluid (for example, the most complex should be sorted into A and B type) mode (pre or post) was compared with the standard replacement fluid (the A and B in one).③ Based on the formula of standard replacement, four equations in different conditions were derived: pre-dilution and post-dilution mode; same direction and same ratio; same direction and different ratio; different direction and same ratio; different direction and different ratio.Results The calculated results of Vreturn (except hematocrit) and Creturn were same to the standard only following the rule of same direction and ratio for A and B no matter pre-dilution mode or post-dilution mode, and it was different from the standard in others. In pre-dilution mode and post-dilution mode, it showed:① A and B in same direction and different ratio: Vreturn and Creturn were different from the standard for the alterative ratio of B.② A and B in different direction and same ratio: Vreturn was same to the standard, but Creturn was different from the standard for the completely different and more complex computational formula.③ A and B in different direction and different ratio: both Vreturn and Creturn were different from the standard. The different Vreturn was due to the different ratio of B. The different Creturn was caused by different ratio of B and the completely different computational formula.Conclusions① For parts of replacement fluid which must be separated ( for example, bicarbonate formula ), the result is same to the standard, and is predicted and mastered only following the rule of same direction and ratio. Otherwise, we need to calculate the two parameters over and over again. The result will run out of our judgment. The wrongness of losing water and electrolyte disorders maybe come out.② Accordingly,the formula could be used to analyze the same case like the separated replacement infusion, for example, a large number of citrates as regional anticoagulation were infused only in the front of filter, while the replacement fluid can be done in varied forms.
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Objective To prove with mathematical formula that the patient's blood electrolyte concentration shows a tendency to approach that of replacement-fluid after continuous renal replacement therapy (CRRT).Methods Electrolyte concentration of plasma,replacement-fluid and returning fluid were compared,and they were labeled as Cblood,Cnom,and Creturn respectively.The Creturn was calculated,and the relationship among them was demonstrated with comparison by mathematical formula.At last,according to their relationship,plasma change towards to the replacement fluid was analyzed.Results It was showed that Cblood＜Creturn＜Cnom or Cblood＞Creturn＞ Cnom,and according the relationship,it was derive that the trend of change in Cblood after circulation for m unit time was Cblood1 ＞Cblood2 ＞Cblood3 ＞ … ＞Cbloodm ＞Cblood or Cblood1 ＜ Cblood2 ＜Cblood3 ＜ … ＜Cbloodm ＜Cnom.The plasma electrolyte concentration would close to that of replacement fluid infinitely with the continue of CRRT.Conclusions With mathematical model,it is proved that the replacement fluid electrolyte concentration is the final target of the plasma.We must make up the replacement fluid correctly.And this results provide the basis for CRRT treatment of electrolyte disorder.
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Obiective To develop an integration profile for hospital clinical system and medical image information system, and discuss relative problems on regional medical image sharing based on the Cross-Enterprise Document Sharing Integration Profile (XDS). Methods As medical image constitutes important information of the patient health record, it is logical to extend the XDS integration profile to include images. The new integration profile for sharing images and image reports between multiple enterprises and the XDS for Imaging(XDS-I) was used. Results The XDS-I profile can be used in medical image sharing system in multiple enterprises. Conclusion The IHE XDS-I can give references for medical imaging regional sharing.
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Objective To develop an integration profile for hospital clinical system and medical image information system, and discuss relative problems on regional medical image sharing based on the Cross -Enterprise Document Sharing Integration Profile (XDS). Methods As medical image constitutes important information of the patient health record, it is logical to extend the XDS integration profile to include images. The new integration profile for sharing images and image reports between multiple enterprises and the XDS for Imaging(XDS-I) was used. Results The XDS-I profile can be used in medical image sharing system in multiple enterprises. Conclusion The IHE XDS-I can give references for medical imaging regional sharing.
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Objective To focus on the expressiveness and flexibility of OpenSDE: an application that supports recording of structured narrative data. Methods OpenSDE enabled data entry with (customizable) forms based on trees of medical concepts. The relevant scope for data entry could be tailored per medical domain by construction of a domain-specific tree. OpenSDE was intended for structuring narrative data to make these available for both care and research. Results The OpenSDE application was used at two departments in aspects of radiology, neurology, pediatrics, and child psychiatry. Conclusion OpenSDE is superior to traditional text entry method in aspects of correct and full expression and clinical decision support.
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Based on the analysis of dataflow and workflow of hospital HIS?RIS and PACs,this article projects a system integration model in the digital hospital construction.By the design of a typical hospital information system,a method of all the information system workflow integration is proposed and validated,which is based on the HL7 and DICOM.
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Objective To explore the application ways of IHE XDS technology in electronic medical record (EMR) system and develop application system of clinical EMR integration. Methods The clinical EMR integration plan was worked out based on IHE XDS technical framework. Results A EMR solution based on IHE XDS was presented. It was consisted of the components of the clinical Data Entry, XDS Registry, clinical document Repository, EMR application server and the i-node accessing server. The system was tested and the result indicated that the system was effective and scalable. Conclusion IHE XDS profile can be not only used to realize the sharing of EMR documents across multiple hospital, but also support the collection clinical data within a hospital clinical system integration.
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Objective To further develop SDE for structured documentation of clinical data based on medical ontology. Methods OpenSDE was customized for the broad domain of medical ontology: medical concepts and its descriptors from history taking and physical examination were modeled into a tree structure. Results An expandable EMR system with structured data entry was developed. Conclusion Structured data entry is significant to clinical decision based on EMR.