Patient Ventilator Interaction Revised.ppsx

ventilator waveforms are graphical representation of pulmonary physiology, mechanics and patient ventilator interaction. optimal patient ventilator interaction is needed to balance two goals of mechanical ventilation, safety and comfort.

1. PATIENT VENTILATOR INTERACTION
Dr. Ubaidur Rahaman
M.D. (General Medicine), EDIC
Senior Consultant Critical Care Medicine
Meenakshi Mission Hospital and Research Center
Madurai, Tamilnadu

2. “The world will ask you who you are,
and if you don’t know,
the world will tell you”
-Carl Gustav Jung

3. APPROACH
1.WHAT IS PATIENT VENTILATOR INTERACTION (PVI)
2.WHY IT IS IMPORTANT TO UNDERSTAND
3.HOW TO UNDERSTAND
1.READ VENTILATOR WAVEFORMS
1. IDENTIFY TAG (TAXONOMY ATTRIBUTE GROUPING) FOR MODE OF VENTILATION
2. BASIC PHYSIOLGY OF PATIENT VENTILATOR INTERACTION (PVI)
3. DIAGNOSE PATIENT VENTILATOR INTERACTION (PVI)
4.REVERSE TRIGGER
5.REAL PATIENT SCENARIOS

4. PATIENT VENTILATOR INTERACTION
Central controller
•Respiratory center
RESPIRATORY CONTROL APPERATUS
•ventilator
Input
•Sensors-
•PaO2, PaCO2, pH,
•sensation of stiffness,
irritation from lung/ chest
wall
•Effect of drugs
Effector pumps
•Respiratory muscle
•inspiratory muscle
•expiratory muscle

5. PATIENT VENTILATOR INTERACTION
Pulmonary mechanics
Metabolic demand
Neural drive
Mode of MV

6. PATIENT VENTILATOR ASYNCHRONY (PVA)
CONSEQUENCE WHERE PVI IS NOT OPTIMAL
DELIVERY OF GAS BY VENITLATOR
•does not correspond in timing, quantity or pattern to what patient wants
INCIDENCE
•25% patients on mechanical ventilation
•80% patients on NIV
IT MAY BE
•innocuous in relation to safety and comfort of ventilation
•have disastrous consequence
SIGNS OF PVA MAY BE LESS OBVIOUS CLINICALLY BUT
•very obvious in ventilator graphics

7. •ineffective ventilation
•dynamic hyperinflation
•increased WoB
•Respiratory muscle dysfunction
•patient discomfort
•Confusion with respect to readiness for weaning
•overuse of sedatives and NMB agents
•Prolong mechanical ventilation
•distress for family members at bedside
•conflict among team members
PATIENT VENTILATOR ASYNCHRONY (PVA)-CONSEQUENCES

8. PATIENT VENTILATOR ASYNCHRONY (PVA)-CONSEQUENCES

9. COMFORT
•optimal patient ventilator
interaction
SAFTETY
•optimal gas exchange
•Minimizing VILI/ PSILI
LIBERATION
•shorter duration of
mechanical ventilation and
minimizing complications
PATIENT CAN NOT BE MADE
•to conform to ventilator performance
RATHER VENTILATOR SHOULD MATCH PATIENT'S DEMAND
THUS, ONUS IS ON PHYSICIAN
•to optimize mechanical ventilation setting to reach a
consensus between SAFETY and COMFORT
WHAT IS THE SOLUTION?
AIM
Of
MV
PATIENT SHARED VENTILATOR

10. Who is the Boss?
WHAT IF VENTILATOR SETTING CAN NOT BE OPTIMIZED?
INCREASED VENTILATORY DEMAND:
•increased dead dead space,
•increased neurogenic drive,
•increased metabolic demand
DERANGED PULMONARY MECHANICS:
•ARDS,
•OAD, neuromechanical uncoupling,
HEMODYNAMIC COMPROMISE
•DHI, acute corpulmonale
PATIENT SHARED VENTILATOR
Acute Phase Recovery Phase

11. CALMING CENTRAL CONTROLLER-TO DO OR NOT TO DO
Central controller
•Respiratory center
inactive respiratory muscle
•VIDD-ventilator induced
diaphragmatic dysfunction
•oxidative stress
•Altered gene expression
•ultrastructural changes
•contractile dysfunction
•atrophy
•CONSEQUENCES OF NMB
•CINM
consequences of patient ventilator asynchrony
•ineffective ventilation
•dynamic hyperinflation
•increased WoB
•Respiratory muscle dysfunction-disease related,
use of NMB and steroid
•patient discomfort, fighting ventilator
•Confusion with respect to readiness for weaning
•overuse of sedatives and NMB agents
•Prolong mechanical ventilation
•distress for family members at bedside
•conflict among team members
PATIENT SHARED VENTILATOR

12. WHAT TO DO?
•IDENTIFY THE PROBLEM,
HOW TO IDENTIFY THE PROBLEM?
PATIENT VENTILATOR INTERACTION RECOGNITION IS BASED ON
•PATTERN RECOGNITION
•multiple trigger, double trigger, false/ pseudo double trigger
•ETIOLOGY
•reverse trigger, pseudo reverse trigger, flow asynchrony
•OUTCOME
•breath stacking,
NO STANDARD VOCABULARY TO DESCRIBE THIS
•Rather different names and definitions further confuse us.

13. HOW TO IDENTIFY THE PROBLEM?
•READ VENTILATOR WAVEFORM,
HOW TO READ VENTILATOR WAVEFORM?
•THIS IS WHAT WE GOING TO DISCUSS,

15. READING VENTILATOR WAVEFORMS-3 STEPS
1.Identify TAG (Taxonomy attribute grouping) for mode of ventilation
2. Understand Basic physiology of Patient Ventilator Interaction (PVI)
3. Diagnose Patient Ventilator Interaction (PVI)

16. STEP 1
IDENTIFY TAG FOR MODE OF VENTILATION
READING VENTILATOR WAVEFORMS

17. IDENTIFY TAG FOR MODE OF VENTILATION
CONTROL VARIABLE
PRESSURE
VOLUME
BREATH SEQUENCE
CMV
CSV
IMV
VENTILATORY
PATTERN
PC-CMV
VC-CMV
PC-CSV
PC-IMV
VC-IMV
TARGETING SCHEMES
SET POINT
DUAL
BIO-VARIABLE
SERVO
ADAPTIVE
OPTIMAL
INTELLIGENT
VENTILATOR
MODE

18. IDENTIFY TAG FOR MODE OF VENTILATION
COMMON MODES
PC A/C
•PC-CMVs
VC-A/C
•VC-CMV:
•constant flow-set point or adaptive,
•de accelerating flow: set point
•In macquetservo I, constant flow set Point, flow is dual
targeted
PC-SIMV
•PC-IMVss
VC-SIMV WITH PS
•VC-IMVss
PRVC
•PC-CMVa
PRVC-SIMV
•PC-IMVas

19. STEP 2
BASIC PHYSIOLOGY
PATIENT VENTILATOR INTERACTION
READING VENTILATOR WAVEFORMS

20. BASIC PHYSIOLOGY OF PATIENT VENTILATOR INTERACTION
Pressure (P) delivered to the respiratory system at any given time is equal to
1. Elastic recoil pressure (product of tidal volume and elastance of respiratory system-V
T×E
RS)-Elastic load
2. Resistive pressure (product of airway resistance and inspiratory flow-R
AW×F)-Resistive load and
3. Applied PEEP.
EQUATION OF MOTION
P
mus+Pvent=??????
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P=??????
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????????????× ??????+????????????????????????

21. VC MODES
•1. pressure is dependent variable, which is determined by
respiratory system mechanics (compliance and resistance).
Therefore PVI is seen in Pressure waveform,
•3. Ventilators are excellent in controlling flow, so VT and flow
waveform configuration will be unaffected by Pmusfor VC
set point targeting,
P
mus+Pvent=??????
�×??????
��+??????
????????????× ??????+????????????????????????
BASIC PHYSIOLOGY OF PATIENT VENTILATOR INTERACTION
VC MODE
•constant flow, set point targeting
•constant flow with flow adaptation
•De accelerating/ descending ramp flow with set point
targeting

22. PC MODES,
•1. flow and tidal volume are dependent variable, determined
by respiratory system mechanics (C/R).
•Thus, PVI is visible in flow waveform,
•3. As ventilators are poor in controlling pressure, compared
to flow, effect of Pmus(PVI) is also seen in pressure
waveform in PC modes.
P
mus+Pvent=??????
�×??????
��+??????
????????????× ??????+????????????????????????
BASIC PHYSIOLOGY OF PATIENT VENTILATOR INTERACTION
PC MODE
•set point targeting
•adaptive targeting-PRVC, autoflow

23. PRESSURE
FLOW
TIME
TIME
initial rapid rise in pressure is result of resistive load,
once tidal volume starts to be delivered
•pressure is function of both resistive and elastic load
once flow stops, resistive load becomes zero,
•therefore pressure drops as it overcomes elastic load
only
BASIC PHYSIOLOGY OF PATIENT VENTILATOR INTERACTION
VC-CMV, CONSTANT FLOW, SET POINT TARGETING

24. SLOPE OF PRESSURE RISE IS LINEAR, CONSIDERING CONSTANT ELASTANCE,
SLOPE OF PRESSURE WAVEFORM MAY BE CURVED BECAUSE OF
•PVI-patient effort (Pmus) or
•changing compliance (recruitable/ overdistention of ARDS lung-stress
index)
STRESS INDEX
•upward concavity-overdistention,
•downward concavity-recruitment,
PRESSURE
TIME
PRESSURE
TIME
PRESSURE
TIME
BASIC PHYSIOLOGY OF PATIENT VENTILATOR INTERACTION
VC-CMV, CONSTANT FLOW, SET POINT TARGETING

25. PRESSURE
FLOW
TIME
TIME
PmusMAY ADD TO OR SUBTRACT FROM Pvent, AND
•deform pressure waveform
INSPIRATORY Pmus WILL
•deflect pressure waveform towards baseline (upward
concave), we will further explore in later slides
EXPIRATORY MUSCLE ACTIVITY-
•we will explore in later slides
BASIC PHYSIOLOGY OF PATIENT VENTILATOR INTERACTION
VC-CMV, CONSTANT FLOW, SET POINT TARGETING

26. PRESSURE
FLOW
TIME
TIME
INSPIRATORY PmusWILL
•deflect pressure waveform towards baseline (upward
concave),
VENTILATORS ALLOWS EXTRA FLOW DESIRED BY PATIENT,
•flow waveform is deformed with upward convexity,
•Tidal volume also increases,
BASIC PHYSIOLOGY OF PATIENT VENTILATOR INTERACTION
VC-CMV, CONSTANT ADAPTIVE FLOW

27. PRESSURE
FLOW
TIME
TIME
VOLUME
TIME
INITIAL RAPID RISE IN PRESSURE IS RESULT OF RESISTIVE LOAD,
ONCE TIDAL VOLUME STARTS TO BE DELIVERED
•pressure is function of both resistive and elastic load
IF FLOW GOES TO ZERO BEFORE CYCLING,
•resistive load becomes zero, therefore pressure drops as it overcomes
elastic load only,
BASIC PHYSIOLOGY OF PATIENT VENTILATOR INTERACTION
VC-CMV, DESCENDING RAMP FLOW, SET POINT TARGETING

28. Pmusmay add to or subtract from Pvent, and deform pressure waveform
inspiratory Pmuswill deflect pressure waveform towards baseline (upward
concave)
BASIC PHYSIOLOGY OF PATIENT VENTILATOR INTERACTION
VC-CMV, DESCENDING RAMP FLOW, SET POINT TARGETING
FLOW TIME

29. PRESSURE
FLOW
TIME
TIME
VOLUME
TIME
CONSTANT PRESSURE CREATES
•pressure difference between airway opening and alveoli,
•starting flow which decays exponentially a function of compliance and
resistance
RATE OF EXPONENTIAL DECAY IN FLOW IN BOTH INSPIRATION AND EXPIRATION IS
DETERMINED BY
•time constant of respiratory system,
TC= C ×R
BASIC PHYSIOLOGY OF PATIENT VENTILATOR INTERACTION
PC-SET POINT TARGETING

30. PmusTHEORETICALLY DEFORMS ONLY FLOW WAVEFORM,
•but practically distorts pressure waveform also
INSPIRATORY FLOW MOVING AWAY FROM BASELINE (INCREASING FLOW),
•indicates inspiratory effort (Pmus)-flow index
•pressure waveform deflects towards baseline (upward concave)
INSPIRATORY FLOW MOVING TOWARDS BASELINE (DECREASING FLOW),
•indicates ventilator flow is more than patient's demand-
•we will explore in later slide-flow index
BASIC PHYSIOLOGY OF PATIENT VENTILATOR INTERACTION
PC-SET POINT TARGETING

31. EXPIRATORY PHASE
EXPIRATORY PHASE CAN DEMONSTRATE
•PVI (failed trigger and early cycle) and
•EXPIRATORY WORK
WILL DISCUSS IN LATER SLIDES

32. STEP 3
DIAGNOSE PATIENT VENTILATOR INTERACTION
READING VENTILATOR WAVEFORMS

33. DIAGNOSE PATIENT VENTILATOR INTERACTION
TIMING
•trigger
•Cycle
•expiration
SYNCHRONY
QUANTITY
•inspiratory
flow,
•tidal volume
WORK SHIFT
PATTERN
•Tirise,
•PIFR
•PEFR,
•expiratory
flow
WORK SHIFT
P
mus+Pvent=??????
�×??????
��+??????
????????????× ??????+????????????????????????

34. DIAGNOSE PATIENT VENTILATOR INTERACTION
PATIENT VENTILATOR
INTERACTION
•SYNCHRONY
•WORK SHIFTING
BREATH PHASES
•TRIGGER
•INSPIRATION
•CYCLE
•EXPIRATION
MODE OF VENTILATION
•PC-CMV/IMV/CSV-
TARGETING SCHEME
•VC-CMV/IMV/CSV-
TARGETING SCHEME

35. DIAGNOSE PATIENT VENTILATOR INTERACTION
SYNCHRONY
•a near zero phase difference between patient signal and ventilator response (beginning of flow/ cyling/
expiration)
ASYNCHRONY
•absence of ventilator response to a patient signal or vice versa
•Failed trigger, false trigger
DYSYNCHRONY
•a clinically important phase difference in timing between patient signal and ventilator response (beginning of
flow/ cycling/ expiration)
WORK SHIFTING
•when both Pventand Pmusare active, portion of work shifted from ventilator to patient

36. PRESSURE
FLOW
TIME
TIME
DIAGNOSE PATIENT VENTILATOR INTRACTION
TRIGGER
TRIGGER DELAY
•PRESSURE TRIGGER
•Duration between drop in pressure below baseline (PEEP) to
return to baseline (PEEP) and beginning of inspiration (flow)
•FLOW TRIGGER
•Duration between rise in flow above base line (PEEP) and
beginning of inspiration (flow)
CLASSIFICATION
•NORMAL TRIGGER
•LATE TRIGGER
•EARLY TRIGGER
•FAILED TRIGGER
•FALSE TRIGGER

37. NORMAL TRIGGER (SYNCHRONY)
•clinically unimportant (near zero) trigger delay-less than 100 msec
LATE TRIGGER
•clinically important delay between patient trigger (Pmus) and beginning of inspiration (flow)-more than 100 msec
•delayed pressurization may mimic late trigger
•inappropriate slow inspiratory rise time does not matches patient effort
•Both late trigger and delayed pressurization increase WoB(work shifting)
•Causes-trigger threshold set too high, slow ventilator response time
EARLY TRIGGER
•machine triggered breath (mandatory breath) precedes patient trigger
•patient trigger may occur during inspiration or early expiration
•patient trigger (Pmus) is detected after start of inspiration (mandatory breath), patient trigger may or may not trigger
another breath
•defined as REVERSE TRIGGER as it is reverse of normal situation (machine breath-P vent is followed by Pmus)
•Causes-deep sedation, brain injury, pleural irritation
DIAGNOSE PATIENT VENTILATOR INTRACTION
TRIGGER

38. PRESSURE
FLOW
TIME
TIME
Normal Trigger Late Trigger Early Trigger
PRESSURE TRIGGER
DIAGNOSE PATIENT VENTILATOR INTRACTION
TRIGGER

39. PRESSURE
FLOW
TIME
TIME
Normal Trigger Late Trigger Early Trigger
FLOW TRIGGER
DIAGNOSE PATIENT VENTILATOR INTRACTION
TRIGGER

40. DIAGNOSE PATIENT VENTILATOR INTRACTION
TRIGGER

41. PATIENT VENTILATOR INTERACTION
TRIGGER
FALSE TRIGGER
•inspiration is trigger by non Pmusactivity
•secretions in circuit/ endotracheal tube/ airway
•Cardiac oscillations
•Leak in patient circuit
•Hiccups
FAILED TRIGGER
•patient effort (Pmus) fails to initiate inspiration
•expiratory waveform deflection towards baseline that does not reach zero
•Causes
•Auto PEEP, DHI
•trigger threshold set to high
•In case of trigger threshold set to high, expiratory deflection towards baseline will reach zero but could not
trigger breath (initiate inspiration)

42. PRESSURE
FLOW
TIME
TIME
FALSE TRIGGER
DIAGNOSE PATIENT VENTILATOR INTRACTION
TRIGGER

43. PRESSURE
FLOW
TIME
TIME
FAILED TRIGGER
DIAGNOSE PATIENT VENTILATOR INTRACTION
TRIGGER

44. PATIENT VENTILATOR INTERACTION
INSPIRATION
WORK SHIFTING
•Presuming increased WoBshould be dome by ventilator, portion of work shifted
from ventilator to patient, is defined as WORK SHIFTING,
PATTERN OF WORK SHIFTING IS AFFECTED BY MODE AND TARGETING SCHEME
•in VC and PC with adaptive targeting scheme, relationship of work shifting is
inverse
•more patient effort will shift more work from ventilator to patient (work shifting
increases)
•in PC with set point targeting, work output of ventilator remains constant
irrespective of patient effort, though total WoBincreases proportionate to patient's
demand
•in servo targeting schemes, work shifting decreases in proportion to patient's effort
(Pmus)
Ventilator Patient
WoB WoB

45. PATIENT VENTILATOR INTERACTION
INSPIRATION: WORK SHIFTING AND MODES OF MV
Pmus
(Patient demand)
Pvent
(Patient delivered)
Zero
Highest
Highest
PC-CSVr(PAV, NAVA)
PC-CMVs (Pressure control)
PC-CSVs (Pressure support)
PC-IMVs,s(PC/PC)
VC-CMVs (Volume control)
PC-CMVa(PRVC, autoflow)
PC-CSVa(volume support)

46. VC with set point targeting-deflection in Pressure waveform
•as Pmusincreases, inspiratory pressure waveform deflects towards baseline
with upward concavity
•total WoBremains constant, as VT and total pressure (Pmus+Pvent) remains
constant
•Work shifting occurs from ventilator to patient
•FLOW STARVATION-extreme case of work shifting, where patient generates
very high Pmus, Pventdecreases below baseline (PEEP)
•in this case patient is doing work on ventilator
Ventilator Patient
PATIENT VENTILATOR INTERACTION
INSPIRATION: WORK SHIFT

47. PRESSURE
FLOW
TIME
TIME
VC WITH SET POINT TARGETING-DEFLECTION IN PRESSURE WAVEFORM
FLOW STARVATION
(extreme work shifting)
VOLUME
PATIENT VENTILATOR INTERACTION
INSPIRATION: WORK SHIFT

48. PATIENT VENTILATOR INTERACTION
INSPIRATION: WORK SHIFT
PC with set point targeting-deflection in Flow waveform
•Patient effort (Pmus) increases inspiratory flow and tidal volume
•as total driving pressure (Pvent+Pmus) increases and tidal volume increases,
total WoBincreases at the cost of WoBof patient (ventilator WoBis constant)
•increasing Pmus, flow deflects away from baseline (increasing flow)
•pressure waveform deflects towards baseline,
Ventilator Patient
WoB WoB

49. PRESSURE
FLOW
TIME
TIME
VOLUME
PATIENT VENTILATOR INTERACTION
INSPIRATION: WORK SHIFT
PC WITH SET POINT TARGETING-DEFLECTION IN FLOW and PRESSURE WAVEFORM

50. PC with adaptive targeting
•as Pmusincreases, Pventdecreases, to maintain target VT
similar to VC-set point targeting
•but compared to VC with set point targeting, WoBin not
constant, as VT can be larger than set target
•with high Pmuspatient may be breathing at PEEP level with
little assistance from ventilator and larger VT than target
•work shifting may be severe to deflect Pressure below
baseline
Ventilator Patient
PATIENT VENTILATOR INTERACTION
INSPIRATION: WORK SHIFT

51. PRESSURE
FLOW
TIME
TIME
VOLUME
PC WITH SET ADAPTIVE TARGETING DEFLECTION IN FLOW and PRESSURE WAVEFORM
PATIENT VENTILATOR INTERACTION
INSPIRATION: WORK SHIFT

52. PATIENT VENTILATOR INTERACTION
CYCLE
Synchrony between cycle and end of patient’s inspiratory effort (Pmus)
NORMAL CYCLE
LATE CYCLE
•neural Tishorter than set ventilator Ti
•set Titoo long, flow cycle threshold set too low
EARLY CYCLE
•neural Tilonger than set ventilator Ti
•set Titoo short, flow cycle threshold set too high
FALSE CYCLE
•early cycle but not related to timing
•Pmax
FAILED CYCLE
•late cycle but not related to time, patient signal fail to cycle ventilator
•RUN AWAY PHENOMENON in PAV-ventilator continues to assist in spite of
patient terminating inspiratory effort due to ventilator's inaccurate estimation
of lung mechanics

53. PATIENT VENTILATOR INTERACTION
CYCLE
VC mode
•observe Pressure waveform and expiratory flow waveform
PC mode
•observe inspiratory flow waveform, expiratory flow waveform and pressure waveform

54. PATIENT VENTILATOR INTERACTION
CYCLE
NORMAL CYCLE
•inspiration ends within clinically acceptable time near Pmuspeak
LATE CYCLE
•inspiration ends with clinically important delay after Pmuspeak
•Late cycling becomes relevant when there is expiratory effort before cycling
•VC mode-upward (positive) deflection in pressure waveform
•PC mode-
•downward (towards baseline) deflection in flow waveform, reaching baseline or crossing into negative
flow (below baseline) before ventilator cycles
•Upward (positive) deflection in pressure waveform

55. PRESSURE
FLOW
TIME
TIME
VOLUME
TIME
NORMAL CYCLE
LATE CYCLE
PATIENT VENTILATOR INTERACTION
CYCLE-PC MODE

56. PRESSURE
FLOW
TIME
TIME
VOLUME
TIME
PATIENT VENTILATOR INTERACTION
CYCLE-PC MODE
NORMAL CYCLE LATE CYCLE
evidence of expiratory muscle
before cycle

57. PRESSURE
FLOW
TIME
TIME
VOLUME
PATIENT VENTILATOR INTERACTION
CYCLE-VC MODE
LATE CYCLE NORMAL CYCLE
evidence of expiratory muscle
before cycle

58. PATIENT VENTILATOR INTERACTION
CYCLE: EARLY CYCLE
INSPIRATION END WITHIN CLINICALLY IMPORTANT TIME BEFORE PmusPEAK (BEFORE PATIENT'S EFFORT CEASES)
INSPIRATORY FLOW MAY NOT COME TO ZERO IN PATIENT’S WITH LONG TC AT THE END OF INSPIRATION (OAD),
•but if there is no continued inspiratory effort, after cycling, it is not a synchrony problem
RELEVANT IF EVIDENCE OF INSPIRATORY EFFORT AFTER CYCLING
•Recognized in expiratory flow waveform in both PC and VC modes
•Distortion of peak expiratory flow and disruption of normal smooth exponential decay of expiratory flow
•Deflection of expiratory flow towards baseline
MAY ALSO OCCUR BECAUSE OF
•False cycling -safety feature (Pmax) setting
•erroneous setting like in CSV, flow cycle threshold reaching rapidly in short TC (low compliance)-high peak
followed by rapid decay in flow)

59. PRESSURE
FLOW
TIME
TIME
VOLUME
TIME
NORMAL CYCLE EARLY CYCLE
PATIENT VENTILATOR INTERACTION
CYCLE-PC MODE

60. PRESSURE
FLOW
TIME
TIME
VOLUME
TIME
PATIENT VENTILATOR INTERACTION
CYCLE
NORMAL CYCLE EARLY CYCLE
evidence of inspiratory muscle
after cycle

61. PRESSURE
FLOW
TIME
TIME
VOLUME
PATIENT VENTILATOR INTERACTION
CYCLE
NORMAL CYCLE EARLY CYCLE
evidence of inspiratory muscle
after cycle

62. FLOW TIME
EXPIRATORY FLOW IN VENTILATOR IS
•always pressure controlled with set point targeting (target being PEEP),
•irrespective of mode (PC or VC),
THAT IS DURING EXPIRATION
•ventilator controls the pressure, by operator set PEEP
AS EXPIRATION IS PASSIVE (NO Pmus)
•expiratory flow waveform and volume waveform displays smooth exponential decay
PATIENT VENTILATOR INTERACTION
EXPIRATORY PHASE

63. Expiratory phase can demonstrate
•Normal expiration-exponential decay of expiratory flow waveform
•EXPIRATORY WORK
•Patient's expiratory effort (expPmus) will deflect expiratory flow
waveform away from baseline (negative direction)
•may be normal, as during coughing or exercising
•may indicate high resistive load (obstructive airway disease),
acidosis, pain, anxiety
•PVI (failed trigger and early cycle)-distortion of PEF and or deflection
of expiratory flow towards baseline-inspiratory effort
PATIENT VENTILATOR INTERACTION
EXPIRATORY PHASE
Normal Expiration
Expiratory effort
Failed trigger
Early cycle

64. PATIENT VENTILATOR INTERACTION-CONFUSION
Flow dyssynchrony-inspiration PVI-work shifting
double trigger-early cycle,, inspiration PVI, reverse trigger
multiple trigger-false trigger, inspiration PVI, early cycle
breath stacking-consequence of double/ multiple trigger
reverse trigger-Trigger PVI-early trigger

65. PATIENT VENTILATOR INTERACTION-CONFUSION
double trigger: two consecutive breaths delivered by ventilator in response to
patient’s respiratory muscle effort
•Patient triggered breath followed by ventilator trigger breath
patient trigger breath may be preceded by ventilator trigger breath
•RT-false or pseudo double trigger
Double trigger-patient (DT-P): patient triggered breath followed by ventilator
triggered breath
Double trigger-Vent (DT-V): patient triggered breath preceded by ventilator
triggered breath: RT
Double trigger-auto (DT-A): patient triggered breath preceded by auto triggered
breath (false triggered breath)

66. PATIENT VENTILATOR INTERACTION-CONFUSION
DT-V
•REVERSE TRIGGER:
•due to entrainment
•PSEUDO REVERSE TRIGGER
•due to high ventilatory demand
Double trigger, Reverse triggering and pseudo-Reverse-Triggering, Jose Antonio Benitez Lozano, Jose Manuel serrano Simon, Arch Med Case Rep. 2020, vol2, issue 1

67. PATIENT VENTILATOR INTERACTION-VOLUME WAVEFORM
AT THE BEGINNING OF BREATH (BOTH PATIENT TRIGGERED OR MACHINE TRIGGERED)
•ventilator resets volume waveform to zero so that inspiratory tidal volume displayed is accurate
IF THERE IS DIFFERENCE BETWEEN INSPIRATORY AND EXPIRATORY TIDAL VOLUME,
•volume waveform is displayed as a sharp drop (reset) prior to next breath-square root sign
THIS SQUARE ROOT SIGN HAS 4 CAUSES-
•LEAK FROM CIRCUIT, AIRWAY OR LUNG, airway or lung-leaked volume is falsely detected as flow trigger
and another breath is triggered
•ACTIVE EXPIRATION DURING INSPIRATION-some ventilators do not account for VT exhaled during
inspiration
•AIR TRAPPING-patient has not been able to exhale the inhaled VT and another breath is delivered
•FLOW SENSOR MALFUNCTION

68. PRESSURE
FLOW
TIME
TIME
VOLUME
TIME
SQUARE ROOT SIGN
PATIENT VENTILATOR INTERACTION-VOLUME WAVEFORM
1. LEAK FROM CIRCUIT, AIRWAY OR LUNG,
2. ACTIVE EXPIRATION DURING INSPIRATION
3. AIR TRAPPING
4. FLOW SENSOR MALFUNCTION

69. STANDARDIZED VENTILATOR WAVEFORM ANALYSIS
1. Define TAG
•PC-CMVs, PC-CMVa, VC-CMVs, PC-IMVs,s, PC-IMVa,s, VC-IMVs,s, PC-CSVa, PC-CSVr
Define PVI
•Trigger-normal, early, late, false, failed
•Inspiration-normal, work shifting, severe work shifting
•Cycle-normal, early, late
•Expiration-normal, expiratory work
•Intervention
•Main goal-safety, comfort, liberation
•Adjusted setting: which?..............................................
•Changed mode: to what?.............................................
•None
•Other………………………………………………………………………...

70. REVERSE TRIGGER

71. PATIENT VENTILATOR INTERACTION-CONFUSION
DT-V: EARLY TRIGGER
•REVERSE TRIGGER:
•due to entrainment
•PSEUDO REVERSE TRIGGER
•due to high ventilatory demand, early cycle
Double trigger, Reverse triggering and pseudo-Reverse-Triggering, Jose Antonio Benitez Lozano, Jose Manuel serrano Simon, Arch Med Case Rep. 2020, vol2, issue 1

72. accidental observation in a patient with a continuous oesophageal pressure (Pes) recording, inspiratory efforts
occurred near the end of each mechanical inspiration in a repetitive and consistent manner.
First description of respiratory entrainment in critically ill patient
2013; 143(4):927–938
REVERSE TRIGGER instead of patient triggering ventilator to deliver breath, time triggered ventilator
breath triggered neural effort (patient trigger)
muscular effort (diaphragmatic contraction lagged behind time triggered ventilator
breath
reversal of normal relationship between patient trigger and machine delivered breath

73. REVERSE TRIGGER
Entrainment was defined as a pattern in which the inspiratory efforts of the patient occurred over a specific and repetitive phase of
the ventilator cycle, therefore, with a minimal variability of their neural respiratory time (Ttotneu).
Ability of the brain stem to entrain the respiratory rhythm to periodic mechanical inflations is considered a normal phenomenon
steadily reproduced experimentally in vagally intact humans and animals.
It seems to reflect the ability of the central controller to adapt its output to afferent information. In addition, the positiveimpact of
wakefulness to 1:1 entrainment has been interpreted by Simon et al as an adaptive strategy to avoid discomfort during mechanical
ventilation.
On the other hand, respiratory entrainment indicates a loss of breathing variability. Preservation of breathing variability has been
linked to improvement of oxygenation and weaning success. Prospective studies are needed to investigate the prognostic
significance of entrainment in patients in the ICU.
The consequences of this asynchrony are potentially large. This may indeed continuously induce pliometriccontractions of the
diaphragm. These contractions are associated with muscle cytokine release and muscle fiberdamage. They also induce increased
respiratory muscle work and oxygen consumption, may contribute to cardiovascular instability, and make monitoring of the plateau
pressure very misleading. Moreover, reverse-triggered efforts may generate higher plateau pressure in VAC and large Vt and
transpulmonary pressure swings during pressure assist control. In a study by Papazian et al, the administration of neuromuscular
blocking agents early in the course of severe ARDS was associated with improved survival and more ventilator-free days.
CHEST / 143 / 4 / APRIL 2013
Mechanical Ventilation-Induced Reverse-Triggered Breaths A Frequently Unrecognized Form of Neuromechanical Coupling
EvangeliaAkoumianaki, MD ; AissamLyazidi, PhD ; Nathalie Rey , MD ; DimitriosMatamis, MD ; Nelly Perez-Martinez , MD ; Raphael Giraud , MD ;
Jordi Mancebo, MD; Laurent Brochard, MD; and Jean Christophe Marie Richard, MD, PhD

75. RESPIRATORY ENTRAINMENT
Entrainment of respiratory rhythm to the ventilator rate implies a fixed, repetitive, temporal relationship
between the onset of respiratory muscle contraction and the onset of a mechanical breath.80–82 Human subjects
exhibit one-to-one entrainment over a considerable range above and below the spontaneous breathing
frequency.83,84 Cortical influences (learning or adaptation response) and the Hering-Breuer reflex are postulated
as the predominant mechanisms of entrainment. Theoretically, one-to-one entrainment should facilitate
patient–ventilator synchrony, but studies of the entrainment response in critically ill patients are lacking.
GeorgopoulosD . Effects of Mechanical ventilation on control of breathing . In: Tobin MJ , ed.
Principles and Practice of Mechanical Ventilation . New York, NY : Mc Graw-Hill ; 2006 : 715 -728 .
Entrainment was defined as a pattern in which the inspiratory efforts of the patient occurred over a specific
and repetitive phase of the ventilator cycle, therefore, with a minimal variability of their neural respiratory
time (Ttotneu).

76. ENTRAINMENT
INTERACTION OF TWO RHYTHMIC PROCESS
•adjustment and locking in common phase and or periodicity
DOMINANT PROCESS: ENTRAINING RHYTHM, RECESSIVE PROCESS: ENTRAINED RHYTHM
LOCKING IN PHASE: SYNCHRONOUS
LOCKING IN PERIODICITY: SYNCHRONOUS OR ASYNCHRONOUS

77. ENTRAINMENT

78. ENTRAINMENT
Oscillator 1
Oscillator 2

79. ENTRAINMENT-Frequency locking with phase synchrony
Oscillator 1
Oscillator 2

80. ENTRAINMENT-Frequency locking with phase asynchrony
Oscillator 1
Oscillator 2
Oscillator 1
Oscillator 2

81. 1
2
ENTRAINMENT-Phase angle
1
2
1
2
PHASE ANGLE 0
PHASE ANGLE 90 PHASE ANGLE 180

82. ENTRAINMENT-Frequency locking: Entrainment ratio
Oscillator 1
Oscillator 2
Oscillator 1
Oscillator 2

83. ENTRAINMENT-Frequency locking-Entrainment ratio
Oscillator 1
Oscillator 2
Oscillator 1
Oscillator 2

84. ENTRAINMENT-Frequency locking-Entrainment ratio
Oscillator 1
Oscillator 2
Oscillator 1
Oscillator 2

85. PATIENT-VENTILATOR SYNCHRONY
•Entrainment with phase synchronization-narrow phase angle
PATIENT-VENTILATOR DYS SYNCHRONY
•Lack of entrainment
•Complex entrainment ration-neural effort: machine breath ration 2:1 or more
•Entrainment with wide phase angle
ENTRAINMENT

87. REAL PATIENT SCENARIOS
FROM OUR ICU

107. KEEP LEARNING, UNLEARNING AND RELEARNING…….
“A wise man once said that which is simple is rarely seen,
and that which is seen is seldom understood.
What to say about that which is complicated?”

108. KEEP LEARNING, UNLEARNING AND RELEARNING…….