Managing Patient-Ventilator Interaction in Pediatrics Robert L. Chatburn, MHHS, RRT-NPS, FAARC Clinical Research Manager - Section of Respiratory Therapy Professor of Medicine Case Western Reserve University
Disclaimer All views expressed are my own opinion and not necessarily those of the Cleveland Clinic.
Disclosure I have affiliations with, special interests, or have conducted business with the following companies that in context with this presentation might possibly constitute a real or perceived conflict of interest: : Breathe Technologies CareFusion Covidien Dräger Hamilton IngMar Newport
Overview Straigtening out the Nomenclature Volume control vs pressure control CMV, IMV, CSV Targeting schemes Literature review What modes to use (literature review) Demonstrating Patient Ventilator Interaction Comparison of modes
Key Terminology Mode: predetermined pattern of patient-ventilator interaction Mode name: arbitrary name coined by vendor Mode tag: classification of mode using a taxonomy Trigger: to start inspiration Cycle: to end inspiration Spontaneous: inspiration is patient triggered and cycled Mandatory: inspiration is machine triggered or cycled CMV: continuous mandatory ventilation spontaneous breaths not allowed between mandatory breaths IMV: intermittent mandatory ventilation spontaneous breaths possible between mandatory breaths CSV: continuous spontaneous ventilation all breaths are spontaneous
Volume/Flow Control Inspiration Expiration Pressure Control Inspiration Expiration Pressure Paw Paw Volume P lung Flow 0 Time (s) 0 Time (s)
Defining the Targeting Schemes 1. Set-point (s) all parameters are operator pre-set 2. Servo (r) inspiratory pressure proportional to effort NAVA and PAV 3. Adaptive (a) ventilator adjusts target with changing patient condition Volume Guarantee Pressure Regulated Volume Control Volume Assured Pressure Support CMV with AutoFlow Volume Control Plus
Literature Review
Early Human Development 2005;81:957 RCTs generally for RDS and severe RF Meta-analyses show no benefit of patient triggered ventilation or HFO Need more, better studies Need better understanding of how ventilator work Many modes Many variations of ventilator design
Meta-analyses using the Cochrane statistical package Eighteen trials met inclusion criteria Arch Dis Child Fetal Neonatal Ed 2013 No evidence that VolTarg modes reduced mortality VolTarg modes did reduce bronchopulmonary dysplasia (RR 0.61) duration of ventilation and oxygen (2 days, 1.7 days) intraventricular hemorrhage (RR 0.65) pneumothorax (RR 0.56)
Respir Care 2014;59(2):159 169 366 eligible preterm infants were randomly assigned to treatment with HFOV or PC-SIMV PC-SIMV with PS Death or BPD was higher HFOV Duration of mechanical ventilation less Hospitalization was shorter Incidence of surfactant requirement lower Retinopathy of prematurity lower
The Cochrane Library 2014, Issue 9 Meta-analyses using the Cochrane statistical package Determine the effect NIPPV compared with NCPAP on the need for additional ventilatory support NIPPV reduces extubation failure more effectively than NCPAP No effect on chronic lung disease or mortality Synchronisation and device design may be important
Ventilating the Neonate
Case Presentation: Classic RDS 1,500 grams, male, 30 weeks gestation Apgar scores 1 @ 3 min, 1 @ 5 min Tachypnea, retractions, cyanosis
General Pattern of Ventilation Ventilator Settings low rate hi volume BPD hi rate low volume RDS Ventilatory Rate (breaths/min) 20-40 40-60 PIP (cm H 2 O) 20-30 10-20 PEEP (cm H 2 O) 4-8 4-5 Insp. Time (seconds) 0.4 0.7 0.25 0.4 Tidal Volume (ml/kg) 5-8 3-6 Semin Perinatol 2006 30:192-199
Appropriate Ventilator Settings Goal: minimize further lung damage by ventilator Lower tidal volume to minimize stretch Higher frequency to achieve gas exchange Tolerated because of short time constant t = R C = 0.12 cm H 2 O/mL/s 0.4 ml/ cm H 2 O = 0.05 s
General Blood Gas Targets Parameter RDS BPD SpO 2 87-92 89-94 ph 7.25 7.35 7.25 7.35 PaO 2 40-60 50-70 PaCO 2 45-55 55+ relatively lower relatively higher Semin Perinatil 2006 30:192-199
Goals of Ventilation 1. Promote safety (do no harm) Provide adequate gas exchange Optimize V/Q relation Protect the lung Optimize P/V relation ventilation perfusion 2. Promote patient comfort Optimize WOB vent vs WOB patient 3. Liberate as soon as possible Optimize weaning experience
How do we select the best mode based on graphic analysis?
What you see today will amaze and astound you! Be prepared to re-examine your beliefs
But first a confession..
I Cheated!! Ingmar Medical ASL 5000
Volume Pressure Flow Unassisted Breathing Freq. 50 I:E 1:3 P mus 20 R 120 C 0.5 V T 5 airway pressure muscle pressure
What will happen to V T on CPAP? A. Increase B. Decrease C. Stay the same Remember that lung simulator mechanics will not change
Volume Pressure Flow CPAP = 5 (intubated, on ventilator) 2 cm H 2 O inadvertent pressure support Freq. 50 I:E 1:3 P mus 20 R 120 C 0.5 V T 5.5 V T FRC
What happens when we apply the time honored PC-IMV?
Volume Pressure Flow PC-IMV inspiration time triggered not patient triggered Freq. 30 I:E 1:2 PIP 25 PEEP 5 P AW 12 V T 17 Why? in sycn unassisted out of sync
How would SIMV improve synchrony? A. Every breath would be assisted B. Mandatory tidal volumes would all be the same size C. There would be a consistent pattern of mandatory and spontaneous breaths
Volume Pressure Flow Answer: B consistent mandatory V T inspiratory time too long Freq. 30 I:E 1:2 PIP 25 PEEP 5 P AW 12 V T 17 What is wrong? missed breath unassisted consistent tidal volumes
What happens if we decrease inspiratory time and increase rate? A. Every breath will be assisted (will entrain patient spontaneous rate) B. All tidal volumes will be the same C. Asyncrhony may get worse
Volume Pressure Flow Answer: C asynchrony worsens missed breath Freq. 50 I:E 1:2 PIP 15 PEEP 5 P AW 8 V T 11 in phase out of phase
OK, let s try PC-CMV (assist/control) Surely that will solve the problem?
Volume Pressure Flow PC-CMV patient triggered ventilation inspiratory time too long Freq. 28 I:E 1:2 PIP 15 PEEP 5 P AW 10 V T 11 What is wrong? missed breaths unassisted
Volume Pressure Flow PC-CMV inspiratory time OK Freq. 50 I:E 1:1 PIP 15 PEEP 5 P AW 9 V T 9 every breath is assisted
What if we switch to pressure support? A. Consistent tidal volumes B. Automatic adjustment of inspiratory time C. Lower mean airway pressure
Volume Pressure Flow Answer: A, B, and C all true inspiratory time shorter than PC-CMV Freq. 50 I:E 1:1 PIP 15 PEEP 5 P AW 7 V T 9 Why? every breath is assisted but mean airway pressure is lower by 2 cm H 2 O
What happens if we use VC-IMV? A. All mandatory breaths are the same size B. Every breath is assisted C. PIP is higher but mean airway pressure is lower
Volume Pressure Flow Answer: C PIP higher, mean lower Inconsistent volume delivery Freq. 30 I:E 1:2 PIP 20 PEEP 5 P AW 6 V T 11 What? That s not what I learned in school! Volume control means consistent tidal volumes, doesn t it?
High power graphic analysis!!
Volume Pressure Flow Why VC is not VC inspiratory time too long trigger is out of sync Freq. 30 I:E 1:2 PIP 20 PEEP 5 P AW 6 V T 11 patient out vent in patient in vent in unassisted missed breaths
Volume Pressure Flow Why VC is not VC asynchrony causes increased PIP Freq. 30 I:E 1:2 PIP 20 PEEP 5 P AW 6 V T 11 increased PIP compresses more volume in patient circuit
OK, IMV is old school Let s use VC-CMV Surely that will fix all the problems?
Volume Pressure Flow VC-CMV inspiratory time too long Freq. 40 I:E 1:2 PIP 20 PEEP 5 P AW 6 V T 9 Why in sync missed breath out of sync
Volume Pressure Flow VC-CMV inspiratory time OK Freq. 50 I:E 1:2 PIP 16 PEEP 5 P AW 7 V T 9 every breath is assisted
What about Pressure Control with Adaptive Targeting? also known as: Pressure Regulated Volume Control Volume Control Plus AutoFlow Volume Support Volume Targeted Pressure Control Dual Control
Volume Pressure Flow PC-CMVa (pressure regulated volume control) inspiratory time too long Freq. 40 I:E 1:2 PIP 16 PEEP 5 P AW 6 V T 10 in sync out of sync missed breath
Volume Pressure Flow PC-CMVa (pressure regulated volume control) inspiratory time OK Freq. 50 I:E 1:2 PIP 15 PEEP 5 P AW 7 V T 9 every breath is assisted
Why not use PC-CSVa adaptive pressure support (eg, Volume Support) to let the patient determine timing?
Volume Pressure Flow PC-CSVa (volume assist) inspiratory time OK automatically Freq. 50 I:E 1:2 PIP 15 PEEP 5 P AW 7 V T 9 every breath is assisted
Volume Pressure Flow Adapts to acute resistance drop resistance drop after suctioning Freq. 50 I:E 1:2 PIP 15 PEEP 5 P AW 7 V T 9 volume too high initially PIP drops volume OK
Volume Pressure Flow Adapts to acute compliance increase compliance increase after surfactant Freq. 50 I:E 1:2 PIP 15 PEEP 5 P AW 7 V T 9 volume too high PIP drops tidal volume moves to target
Ventilator WOB WOB Comparison Volume Control? Pressure Control? Proportional Assist/NAVA? PAV, NAVA PC VC, PCadaptive Patient WOB
Neurally Adjusted Ventilatory Assist ideal NAVA other modes Sinderby in: Tobin. Principles and Practice of Mechanical Ventilation 3 rd edition 2012
Classification of Mode Called NAVA Neurally Adjusted Ventilatory Assist 1. Control Variable = Pressure Inspiratory pressure is proportional to diaphragmatic EMG, called the Edi signal Edi is measured using a naso-gastiric catheter 2. Breath Sequence = Continuous Spontaneous Ventilation All breaths are triggered by Edi (adjustable sensitivity) All breaths are cycled at 70% peak Edi 3. Targeting Scheme = Servo Inspiratory pressure is proportional effort
NAVA Compared to Other Modes Respir Care 2012;57(12):2138-2150
Edi Volume Flow Pressure How Does Edi Control the Ventilator? trigger rise in Edi adjustable sensitivity Sinderby in: Tobin. Principles and Practice of Mechanical Ventilation 3 rd edition 2012.
Edi Volume Flow Pressure How Does Edi Control the Ventilator? assist pressure proportional to Edi Sinderby in: Tobin. Principles and Practice of Mechanical Ventilation 3 rd edition 2012.
Edi Volume Flow Pressure How Does Edi Control the Ventilator? cycle drop to 70% peak Edi not user adjustable Sinderby in: Tobin. Principles and Practice of Mechanical Ventilation 3 rd edition 2012.
NAVA PCV PSV good synchrony bad neural synchrony inspiratory time trigger delay delayed cycling bad synchrony trigger delay
Take-Home Messages Most infants are still ventillated like 35 years ago There is no way to guarantee perfect synchrony with PC-SIMV (patient rate variable, vent rate constant) Even with VC-CMV tidal volume is inconsistent With any mode delivering mandatory breaths, proper tuning of inspiratory time is essential Pressure support automates the synchrony issue PC-CSVa automates synchrony and lung protection Leaks can defeat the targeting system NAVA provides best synchrony and lung protection Leaks irrelevant Weaning is still a challenge no consensus