TABLE OF CONTENTSIntroductionNAVA WorkflowTroubleshootingReferences for NAVA Study GuideNAVA STUDY GUIDETable of ContentsNAVA Neurally Adjusted Ventilatory Assist is an optional mode of ventilation f ID: 876400
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1 SERVO EducationNAVA STUDY GUIDE TABLE OF
SERVO EducationNAVA STUDY GUIDE TABLE OF CONTENTSIntroductionNAVA WorkflowTroubleshootingReferences for NAVA Study GuideNAVA STUDY GUIDETable of Contents NAVA Neurally Adjusted Ventilatory Assist is an optional mode of ventilation for the SERVO-iventilator. NAVA delivers assist in proportion to and in sync
2 hrony with the patients Edi signal A sp
hrony with the patients Edi signal A spontaneous breath starts with an impulsegenerated by the respiratory center. Theimpulse is transmitted via the phrenic nerves,which excites the diaphragm. Before themechanical effect is achieved, the signal ismodulated and the muscle response isdownwards, creating a neg
3 ative alveolarpressure, and gas flows in
ative alveolarpressure, and gas flows into the lung.All muscles, including the diaphragm and other respiratory muscles, generate electrical activityto excite muscle contraction: this electrical excitation is controlled by nerve stimuli.NAVA STUDY GUIDE 1.1 NEUROVENTILATORY COUPLING HealthDisease The efficacy
4 of the respiratory muscles and the degr
of the respiratory muscles and the degree of respiratory demand will determinethe degree of respiratory center output. In a healthy subject, the low amplitude of diaphragmexcitation reflects the fact that neuroventilatory coupling is highly efficient and that only aboutNAVA STUDY GUIDE In disease, muscle pe
5 rformance may not be up to expectation,
rformance may not be up to expectation, leading to an increased outputfrom the respiratory center with the aim of recruiting additional motor units in the diaphragm. In this example, the increased signal seen inCOPD and post-polio patients thus reflectsthe fact that a larger part of the muscularreserve is us
6 ed. Only 5-8% of maximumIf the diaphragm
ed. Only 5-8% of maximumIf the diaphragm becomes weaker and/or the inspiratory loadincreases, the diaphragm´s electrical activation must increase toThe electrical activity of the diaphragm (Edi) is measured in µV (micro volt). 1 µV = 10V, thus1,000,000 µV = 1V.NAVA STUDY GUIDE 1.2 RESPIRATORY CONTROLThere ar
7 e three important components in mechanic
e three important components in mechanical ventilation:The timing with which breaths are delivered i.e. the frequency and inspiratory time forassist delivery.The magnitude of the delivered breaths, i.e. the pressure or volume needed to ventilateThe magnitude of pressure on expiration, which prevents the lung
8 s from derecruitingbetween inspirations,
s from derecruitingbetween inspirations, i.e. the required PEEP level.Conventional ventilator technology uses a pressure drop or flow reversal to initiate the assistdelivered to the patient (as shown on the right-hand side of the picture). This is the last stepof the signal chain leading to inhalation and is
9 subject to disturbances such as intrins
subject to disturbances such as intrinsic PEEP, The earliest signal that can be registered witha low degree of invasivity is the excitation ofof the picture).proportional to the integrated output of therespiratory center and thus controls the depthand cycling of the breath. The excitation ofproblems associa
10 ted with pneumatic triggeringAdapted fro
ted with pneumatic triggeringAdapted from C. Sinderby, Nature Medicine, 1999NAVA STUDY GUIDE By following diaphragm excitation and adjusting the support level in synchrony with the riseand fall of the electrical discharge, the ventilator and the diaphragm will work with the samesignal input. In effect, this
11 allows the ventilator to function as an
allows the ventilator to function as an extra muscle, unloading extrarespiratory work induced by the disease process.The electrical discharge of the diaphragm is captured by an Edi Catheter fitted with an electrodearray. The Edi Catheter is positioned in the esophagus. 1.Edi Catheter2.Esophageal wall3.Diaphr
12 agm4.StomachSince NAVA uses the Edi to c
agm4.StomachSince NAVA uses the Edi to control the ventilator, it is important to understand what the signalrepresents. All muscles (including the diaphragm and other respiratory muscles) generateNAVA STUDY GUIDE The electrical excitation is controlled by nerve stimulus and controlled in magnitude by adjusti
13 ngthe stimulation frequency (rate coding
ngthe stimulation frequency (rate coding) or the number of nerves sending the stimulus (nervefiber recruitment). Both rate coding and nerve fiber recruitment will be transmitted into musclefiber motor unit action potentials which will be summed up both in time and space to producethe intensity of electrical
14 activity measured in the muscle, in this
activity measured in the muscle, in this case the Edi. By means of theEdi signal, NAVA delivers pressure in response to the patients respiratory drive.To reduce the influence of external noise, the measurement of muscle electrical activity isperformed by bipolar differential recordings, where the signal dif
15 ference between two singleelectrodes is
ference between two singleelectrodes is measured.Patients with chronic respiratory insufficiency may demonstrate signals 5-7 times stronger tocompensate for this insufficiency. Due to the differential recording and low signal amplitude,measurement of Edi is sensitive to electrode filtering, external noise, a
16 nd cross-talk from othermuscles, e.g. th
nd cross-talk from othermuscles, e.g. the heart which produces electrical amplitudes about 10-100 times that of thediaphragm. Since the Edi must always be present to initiate a contraction of the diaphragm,it should however always be possible to record the signal in healthy subjects.1.3 NAVA ACCESSORIESParts
17 needed for NAVA are: 1.NAVA software op
needed for NAVA are: 1.NAVA software option - if notpre-installed, the software is installed witha PC Card.2.Edi Module3.Edi Cable4.Edi CatheterNAVA STUDY GUIDE 1.4 EDI CATHETERThe Edi Catheter is a single-use gastric feeding tube with an electrode array of ten electrodes.One electrode is a reference electr
18 ode and nine are measuring electrodes. T
ode and nine are measuring electrodes. The electrodes are 80757065605550 235 1.Connection to Edi cable2.Nutrition feed3.Evacuation (only 12 and 16 Fr)4.Reference electrode5.Electrodes (9)6.Holes for nutrition/evacuation7.Inter Electrode Distance (IED)8.Lumen for electrodes9.Sump lumen (only 12 and 16 Fr)10.F
19 eeding lumen11.Barium strip for X-ray id
eeding lumen11.Barium strip for X-ray identification12.Coating for easier insertion and betterpicture with light blue)13.Scale in centimeters from the tipOn the right-hand side of the picture, a cross-section of the Edi Catheter is displayed. OnlyEdi Catheter that are 12 Fr and 16 Fr have a sump lumen for ev
20 acuation.NAVA STUDY GUIDE 1.5 EDI MODULE
acuation.NAVA STUDY GUIDE 1.5 EDI MODULE that is interchangeable between differentSERVO-i´sThe SERVO-i receives several signals from theEdi Catheter and the signals are filtered andfurther processed to retrieve four ECGThe picture illustrates how the recorded raw signals detected by the electrodes duringelec
21 trodes and one reference electrodeare us
trodes and one reference electrodeare used.filtered signals (e.g. filtered from the ECGsignal). The marked parts indicate wherethe Edi signal is strongest. The locationof the strongest Edi signal movesdownwards as the patient makes astrongest Edi.Square (RMS) of the signal in waveformAdapted from C. Sinderby
22 , Nature Medicine, 1999NAVA STUDY GUIDE
, Nature Medicine, 1999NAVA STUDY GUIDE 2 NAVA WORKFLOWTABLE OF CONTENTS NAVA WorkflowMeasure NEXVerify Edi Catheter positionSecure the Edi CatheterSet initial NAVA levelSelect NAVA mode set parametersExample of setting the NAVA levelNAVA STUDY GUIDENAVA Workflow 2.2 EDI MODULE FUNCTION CHECK Insert the
23 Edi Module into a free slot in the Make
Edi Module into a free slot in the Make sure it clicks into place. Connect the Edi Cable to the Edi Module. Remove the cap from the test plug andstart automatically. Wait until the dialog Edi Module testpassed appears on the display.-If the test fails, replace the Edi Cableand/or Edi Module and re-run the
24 test. To remove the Edi Cable, hold the
test. To remove the Edi Cable, hold the ribbedrelease. Press OK, remove the test plug and replace2.3 POSITIONING OF THE EDI CATHETER CALCULATE THE INSERTIONDISTANCE packed sterile. Follow hospital routines forhandling the Edi Catheter. Verify by visual inspection that the packageand the Edi Catheter are un
25 damaged. If a guide wire is used, only u
damaged. If a guide wire is used, only use aguide wire from MAQUET.NAVA STUDY GUIDENAVA Workflow 2.5 INSERT EDI CATHETER INTO PATIENT conductivity. IMPORTANT: water to the Edi Catheter. Other substances (lubricants,gels or any other solvents) might destroy the coatingand disturb the contact with the electrod
26 es. Insert the Edi Catheter through the
es. Insert the Edi Catheter through the nostril or through the mouth until the calculated insertiondistance (Y) is reached.NAVA STUDY GUIDENAVA Workflow 2.6 VERIFY EDI CATHETER POSITION Connect the Edi Catheter to the Edi Cable. Open the "Neural access" menu NAVA STUDY GUIDENAVA Workflow 2.7 SECURE THE EDI C
27 ATHETER correct position of the marking
ATHETER correct position of the marking on the Edi Catheter;-appearance of the ECG waveforms;-appearance of the blue highlights on the waveforms.If this does not produce a satisfactory result, refer to the Troubleshooting chapter. Secure the Edi Catheter. Ensure that the Edi Catheter is not secured to the en
28 dotracheal IMPORTANT: Follow hospital ro
dotracheal IMPORTANT: Follow hospital routines to check the position of the Edi Catheter when used2.8 SET INITIAL NAVA LEVEL Press " NAVA preview In the uppermost waveform, two curves are presented simultaneously. The gray curve showsthe estimated pressure based on Edi and the set NAVA level, the yellow curv
29 e is the currentpatient airway pressure
e is the currentpatient airway pressure in the selected conventional mode. with a negative pressure deflection. If this is not the case, refer to the Troubleshootingchapter.NAVA STUDY GUIDENAVA Workflow Press "NAVA level" and use the Main rotary dial to set the NAVA level. As a guide, the firstNAVA level to
30 be tried should be the same or a little
be tried should be the same or a little below the pressure used in the current Press to save the NAVA level. The NAVA level will be transferred to the NAVAventilation mode window. Note that the patient is still being ventilated in the conventionalmode and that this is an estimate of the pressure to be deliv
31 ered with NAVA.2.9 SELECT NAVA MODE SE
ered with NAVA.2.9 SELECT NAVA MODE SET PARAMETERS "Select Ventilation Mode"NAVA" "Set Ventilation mode" NAVA STUDY GUIDENAVA Workflow 2.10 EXAMPLE OF SETTING THE NAVA LEVEL The NAVA Ppeak pressure is calculated according to the formula:NAVA Ppeak = NAVA level x (Edi peak Edi min) + PEEPIn the above exam
32 ple, NAVA Ppeak est. in the "Set Ventila
ple, NAVA Ppeak est. in the "Set Ventilation Mode" window is calculatedSee the next chapter for more information on NAVA level.NAVA STUDY GUIDENAVA Workflow TABLE OF CONTENTS NAVA levelTrigger levelNAVA Respiration CycleRunning in NAVA modeSuctioning/disconnection in NAVANeuro Ventilatory Tool (NVT)NAVA back
33 up functionNAVA (PS)Switching to NAVA (P
up functionNAVA (PS)Switching to NAVA (PS)Switching back from NAVA (PS) toNAVAAlarm for asynchronyBack to NAVANAVA STUDY GUIDE The NAVA trigger detects increases in Edi and should be set to a level where random variabilityin the background noise does not exceed the trigger level. The variable background no
34 ise istypically less than 0.5 µV, which
ise istypically less than 0.5 µV, which is the default value for Trigg. Edi. TimeTrigger levelabove Edi min It is important to emphasize that NAVA is triggered by an increase in Edi from the Edi min ratherAs a secondary source NAVA also employs the pneumatic trigger, based on flow or pressure,NAVA STUDY GUID
35 E 3.3 NAVA RESPIRATION CYCLE When the pa
E 3.3 NAVA RESPIRATION CYCLE When the patient triggers a breath, gas flowinto the lungs at a varying pressureproportional to the patient's Edi. The maximum available pressure level is 5O below the preset upper pressure When the Edi decreases below 70% for If the pressure increases 3 cmHthe inspiratory target
36 pressure; If the upper pressure limit i
pressure; If the upper pressure limit is exceeded. NAVA STUDY GUIDE " window, it is possible to adjust values and still see the curves. NAVA STUDY GUIDE 3.5 RUNNING IN NAVA MODEInspiratory support is delivered in proportion to the Edi signal (inspiratory trigger, size and cycleoff). The patient triggers the
37 assisted inspiration in NAVA accordingt
assisted inspiration in NAVA accordingto the first-come-first-served principle (Edi, flow or pressure In the User Interface, there are different trigger colorsdepending on how the inspiration is triggered (for NAVA - lightpink, see picture; flow pressure - purple). In the User Interface,there are direct acc
38 ess knobs for adjustment of NAVA level,N
ess knobs for adjustment of NAVA level,NAVA STUDY GUIDE Edi monitoring is available in all modes of ventilation, invasive and non invasive. In Stand-by,it is possible to monitor the Edi signal in the positioning window. NAVA STUDY GUIDE 4 TROUBLESHOOTING4.1 LOW OR NO EDI SIGNAL Verify the Edi Catheter positi
39 oning. Verify that the effects of muscle
oning. Verify that the effects of muscle relaxants have worn off. Verify the patient's sedation level. The apneic threshold might be higher due to CNSdepressant drugs. Verify, by means of blood gas or end tidal COthis may affect the Edi. Too high a PEEP level and/or too high support pressures may diminish di
40 aphragm electricalactivity to a level wh
aphragm electricalactivity to a level where it is difficult to detect. In this case, reduction of these levels mayrestore Edi and diaphragm activity. NAVA STUDY GUIDETroubleshooting 4.2 THE EDI SIGNAL IS PRESENT, BUT THERE ARE NO BLUE HIGHLIGHTSON THE ECG WAVEFORMSA certain amount of time (up to 30 s) is oft
41 en required before the blue highlight ap
en required before the blue highlight appears. In the picture, the Edi Catheter is probablyinserted too far and a signal from an expiratoryrepositioning of the Edi Catheter is needed. NEX measurement The calculation of the Y (see tables below) Verify that P and QRS waves are present indecrease in QRS amplitu
42 de in the lower Insertion distance Y for
de in the lower Insertion distance Y for oral insertionCalculation of YFr/cmNEX cm x 0.8 + 18 =Y cm16 FrNEX cm x 0.8 + 15 =Y cm12 FrNEX cm x 0.8 + 18 =Y cm8 Fr 125 cmNEX cm x 0.8 + 8 = Y cm8 Fr 100 cmNEX cm x 0.8 + 3.5 =Y cm6 Fr 50 cmNEX cm x 0.8 + 2.5 =Y cm6 Fr 49 cm insertionCalculation of YFr/cmNEX cm x 0
43 .9 + 18 =Y cm16 FrNEX cm x 0.9 + 15 =Y c
.9 + 18 =Y cm16 FrNEX cm x 0.9 + 15 =Y cm12 FrNEX cm x 0.9 + 18 =Y cm8 Fr 125cmNEX cm x 0.9 + 8 =Y cm8 Fr 100cmNEX cm x 0.9 + 3.5 =Y cm6 Fr 50 cmNEX cm x 0.9 + 2.5 =Y cm6 Fr 49 cm NAVA STUDY GUIDETroubleshooting TABLE OF CONTENTS Alarm for asynchronyBack to NAVANAVA STUDY GUIDEAlarms 5.1 ALARM FOR ASYNCHRONY
44 without sounding an alarm until one of
without sounding an alarm until one of the The ventilator has been in NAVA (PS) formore than 80 s. There have been six switches from NAVAto NAVA (PS) in the last 5 minutes5.1.1 BACK TO NAVA If the asynchrony alarm is activated, theventilator will search for synchrony indices. Assoon as synchrony is re-estab
45 lished, themessage Pneumatic Edi synch
lished, themessage Pneumatic Edi synch restored isdisplayed. Press the OK button, or wait 10s, then the ventilator will switch back to NAVA.NAVA STUDY GUIDEAlarms will be shown when the Edi Catheter detects the strongest signalat either end of the electrode array, i.e. the upper or lower electrode. The
46 picture displays an example where only t
picture displays an example where only the upper ECG waveform has blue highlights. This situation indicates that the Edi Ca Check that the Edi Catheter is still inserted according to the final marking. If the blue highlights are in the top or bottom leads, fine tune the Edi Catheter position by-If the top le
47 ads are highlighted in blue, pull out th
ads are highlighted in blue, pull out the Edi Catheter in steps correspondingto the IED until the blue highlight appears in the centre. Do not pull out more than 4 times-If the bottom leads are highlighted in blue, insert the Edi Catheter further in stepscorresponding to the IED until the blue highlight appe
48 ars in the center. Do not insert moreNAV
ars in the center. Do not insert moreNAVA STUDY GUIDEAlarms 6 REFERENCES FOR NAVA STUDY GUIDE1. Sinderby C, Beck J. Neurally Adjusted Ventilatory Assist (NAVA): An Update and Summaryof Experiences. Neth J Crit Care 2007:11(5): 243-252.2. Sinderby C, Beck J, Spahija J, de Marchie M, Lacroix J, Navalesi P, Slu
49 tsky AS. Inspiratorymuscle unloading by
tsky AS. Inspiratorymuscle unloading by neurally adjusted ventilatory assist during maximal inspiratory efforts in3. Beck J, Campoccia F, Allo JC, Brander L, Brunet F, Slutsky AS, Sinderby C. Improvedsynchrony and respiratory unloading by neurally adjusted ventilatory assist (NAVA) in lung-injured4. Allo JC,
50 Beck JC, Brander L, Brunet F, Slutsky A
Beck JC, Brander L, Brunet F, Slutsky AS, Sinderby CA. Influence of neurally adjustedventilatory assist and positive end-expiratory pressure on breathing pattern in rabbits withacute lung injury. Crit Care Med 2006; 34(12): 2997-3004.5. Emeriaud G, Beck J,Tucci M, Lacroix J, Sinderby C. Diaphragm electrical
51 activity during6. Beck J, Gottfried SB,
activity during6. Beck J, Gottfried SB, Navalesi P, SkrobikY, Comtois N, Rossini M. Sinderby C. Electricalactivation of the diaphragm during pressure support ventilation in acute respiratory failure. AmJ Respir Crit Care Med 2001; 164(3): 419-4247. Sinderby C, Spahija, J, Beck J, Kaminski D,Yan S. Comtois N
52 , Sliwinski P. Diaphragmactivation durin
, Sliwinski P. Diaphragmactivation during exercise in chronic obstructive pulmonary disease. Am J Respir Crit Care8. Sinderby C, Navalesi P, Beck J, SkrobikY, Comtois N, Friberg S, Gottfried SB, LindstromL. Neural control of mechanical ventilation in respiratory failure. Nat Med 1999; 5(12): 1433-1436.NAVA S