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Why Intubate and Ventilate ?
1. Improve Oxygenation (PaO2, SaO2).2. Improve ventilation (PaCO2).3. Relieve work of breathing.4. Unload Respiratory Muscle.
Evaluate before you sedate
The sooner the better!!!
How soon do you allow your patient to breath
spontaneously?
Does your ventilated patient appear to be struggling or uncomfortable ?
Lesson Learned!!
Conventional modes of
ventilation can not cope well with the ever-
changing patients
Ventilatory needs
The Next Generation of Synchronization Ventilatory Support
PAV+Prevent Asynchrony with
Ventilator
Ventilator Support is proportional to:Instantaneous Effort (Pmus)Pulmonary Mechanics (Resistance, Compliance)
How Does PAV+ Work?
Equation Of Motion=Pmus + Paw = (Flow x R) + (Volume x E)
PAV+ measures patient demand by monitoring flow and volume every 5 milliseconds and measures compliance and resistance every 4 to 10 breathes
Patient effort
throughout inspiration
{
Inspiratory Effort
VLUNG
PLUNG
RLUNG
CLUNG
RET
Trigger and Execute PAV
ViI
.
Pappl Ventilator
Pi E
T +
PA
TIE
NT
Pi L
UN
G-T
HO
RA
X
Sum: PiFLOW +
PiVOLUME = Pi
Y
S (ViL EL)
S (ViY * Ri
SYS)·
ViY
.
ò ViY dt =
ViL
·
PiY=S (Vi
L * RiETT)+ S (Vi
L RL) + S (ViL
Ers)
. .
Response to patient’s inspiratory effort “Mirror Image Breath
Response to patient’s inspiratory effort “Mirror Image Breath
Muscle Effort Amplifier
Results of pressure strategy with greater patient effort (PSV vs.
PAV+)
PAV+ and
Patient Control
Inspiration
How deeply to
breath?
When the breath
ends?
(A)
Patient determines when inspiration begins when Flow senses at the Wye
(B)
The ventilator will continue to provide the gas as long as the patient inspiratory effort is continuing
(C)
Because pressure is proportional to pt inspiratory effort , when effort ends pressure rapidly declines and flow stops
So How Does It Work ?
Q. How does the clinician know where to set the %Support?
1. Sound Clinical Assessment.
2. Work of Breathing (WOB) bar.
Clinical Assessment
Vital Signs ABG
Signs of Respiratory Distress:Respiratory rate > 40 breaths/minute PLUS… Marked use of accessory muscles Diaphoresis Abdominal paradox Marked complaint of dyspnea Etc…
PAV+, Understanding the WOB Bar
Proportional Assist Ventilation (PAV+),
Chasing Liberty
Literature Review
Ventilator
Pressure
Patient Effort
VC
VCV
Trigger Only
Trigger Only
Active Effortbc
Active Effort
cb
Vol
ume L
UN
G
Flo
ww
ye
Pre
ssur
e wye
Time
Time
Time
bc
Pressure Limited Ventilation (PCV, PS)
Ventilator
Pressure
Patient Effort
VC
PCV/PS
More physiologicalPAV+
Proportional assist Ventialtion and Neurally Adjusted Ventilator Assist Robert Kacmarek PhD Resp Care Feb. 2011 Vol. 56 No. 2
Physiological Mode
Levine et al., Rapid Disuse Atrophy of Diaphragm Fibers in Mechanically Ventilated Humans, NEJM 2008 358: 1327-1335
MV and Diaphragm
Complete controlled ventilation beyond 24 hours may cause Respiratory Muscle Injury and can result in:
Ventilator Induced Diaphragmatic Dysfunction
Sassoon et al (2002). Altered Diaphragm Contractile Properties with Controlled Mechanical Ventilation. J Appl Physiol 92(6): 2585-2595
Length of ICU Stay
Frequent setting changes and
increase sedation
requirements
Increase Ventilation time , possible Muscle
Atrophy and Increase Length of
stay
Asynchrony
> 25% of patients on VC and PSV had higher incidence of Asynchrony. Asynchrony Index (AI) of > 10% of respiratory efforts. Higher incidence of Asynchrony is associated with prolonged duration of MV (25 vs. 7 days, p=.005).More likely to receive Tracheostomy (33% vs 4%)
Thille et al .(2006) Intensive Care Med 32; 1515-22
PVA is common in Conventional Mode of Ventilation
Failure to Synchronize
Deleterious Effects of PVA:• Patient Fights Ventilator• Higher Work of Breathing• More Sedation Required• Muscle Fatigue• Dynamic Hyperinflation• Delayed or prolonged weaning• Longer ICU Stay• Higher Costs.
Respir Care (2005).50(2); 202-234
Potential Clinical Advantages
•The patient ‘drives’ the ventilator •Avoids ventilator over-assistance
•Less patient-ventilator asynchrony –Asynchrony associated with
•More sedation (deWit, M. Journal of Critical Care
2009:24;74-80) •Longer duration of mechanical
ventilation(Thille, A. Intensive Care Medicine 2006;
deWit, M. Crit Care Med 2009) •Disrupted sleep
(Bosma, K, Crit Care Med 2007, Fanfulla, F AJRCCM 2005)
PAV+ Increases patient safety by decreasing the risk of over-assisted
ventilation less likelihood of overventilation — With PAV+ software,
there is no minimal delivered tidal volume like with other modes. If the % Support dialed in is more than is necessary, patients will down regulate their efforts. Because with PAV+, the pressure delivered is a function of effort. When effort decreases the pressure demand will also decrease. Accordingly, this feedback mitigates the tendency for overventilation. By contrast, with other modes the ventilator will continue to give the same pressure or volume regardless of what happens to effort, so long as the effort is enough to trigger.
Also, in the case of airway artifacts like hiccups or heartbeats, no standard volume or pressure would be accidentally delivered because with PAV+, the ventilator would stop delivering gas as soon as the artifact was over. With other modes, cardiac artifacts may continue to cause frequent triggering and delivery of large volumes even when efforts cease completely.
Imanaka H. Crit Care Med. 2000;28(2):402-407.
PAV+ Increases patient safety by decreasing the risk of over-assisted
ventilation Preservation and enhancement of the patient’s
control mechanisms — With PAV+ the breath is being driven by the patient’s own control center and reflexes. One such reflex is the Hering-Breuer reflex, which causes the inhibition of inspiratory efforts when tidal volume reaches a physiologically determined threshold, thus preventing over distension of the lung. Because the ventilator ceases its pressure when inspiratory effort is terminated, stimulation of this reflex would cause the breath to cycle off.
Improved hemodynamics — Research has shown that when patients were switched from Volume Control to manual PAV+, cardiac output increased by 22% in septic patients. Patrick W, et al.. Am J Respir Crit Care Med.
1993;147:A61
PAV+ Increases patient safety by decreasing the risk of over-assisted
ventilation Weaning — The greater the reliability of ventilator rate as a measure of distress, the better the decision-making on tolerance. Because with PAV+ there are little or no ineffective efforts, ventilator rate and patient rate are the same. So, when ventilator rate increases as the assist level is reduced (e.g., during a weaning trial), it means that the patient’s rate has also increased, a sign that suggests this new level is not tolerated (distress).
With other modes in which ineffective efforts may exist (e.g., PSV, volume - cycled), ventilator rate can be considerably less than the patient’s rate. Giannouli E. Am J Respir Crit Care Med.
1999;159(6):1716-25 .Thille AW,. Intensive Care Med. 2006;32(10):1515-1522 .
Leung P. Am J Respir Crit Care Med. 1997;155(6):1940-1948 .
PAV+ Increases patient safety by decreasing the risk of over-assisted
ventilation Because the number of ineffective efforts decreases, often dramatically, as assist level is decreased, the ventilator rate frequently jumps during a weaning trial despite the fact that patient’s rate has not changed.
This can lead to the false diagnosis of weaning failure.
The PAV+ may emerge as a useful tool in weaning because with PAV+ there is less likelihood of misinterpretation of actual respiratory rate. In addition, this type of ineffective muscle contraction has been associated with muscle injury.
With PAV+, this is less likely to occur. Giannouli E. Am J Respir Crit Care Med. 1999;159(6):1716-25 .
Van Der Meulen JH,. J Appl Physiol. 1997;83(3):817-823 .Devor ST. J Appl Physiol. 1999;87(2):750-756 .
PAV+ Increases patient safety by decreasing the risk of over-assisted
ventilation Less-invasive technology.
Unlike other approaches to measuring patient demand (e.g., esophageal manometry or diaphragm EMG), there is no need for an additional invasive procedure, which could lead to complication from incorrect placement.
Cost and time are other obvious advantages to a less invasive approach.
The PAV+ takes random measurements of compliance and resistance along with rapid samples of pressure and flow to determine the support pressure via a cuffed artificial airway.
What Kind of Patient Would Benefit more from PAV?+
1. Comfort.2. Lower peak airway pressure.3. Less need for paralysis and/or
sedation.4. Less likelihood for over ventilation.5. Preservation and enhancement of
patient’s own control mechanisms such as metabolic ABG control and Hering-Breuer reflex.
6. Improved efficiency of negative pressure ventilation. M Younes. Am Rev Respir Dis
1992;145:114- 120.
12 COPD patientsUsing VASBreathing comfort was sig. with PAV
(38 vs. 11)
Wysocki et al .(2002) Crit Care Med. 30(2); 323-329
Comfort
Wrigge et al .(1999) Intensive Care Med. 25; 790-798
• 13 Ventilated COPD patients
• PAV vs. PSV
Vt Variability
Kondili et al .(2006) Intensive Care Med. 32; 692-699
WOB
Bosma et al .(2007) Crit Care Med. 35(4); 1048-1054
PVA
Settings Manipulation and Need for Sedation
Compared with PSV, PAV was associated with:
Fewer manipulations of ventilator settingsFewer changes in sedative dosing.
Careful evaluation of the patient prior to sedation may help
reduce the use of unnecessary sedation.
Siegel MD. Clin Chest Med 2003; 24 (4):713-725
Evaluate before Sedate
Probability to remain on Spontaneous Mode
RCT of 208 critically ill patients on a controlled mode randomized to either PAV or PSV.
Probability to remain on Spontaneous Mode
Failure to transition: PAV 11%, PSV 22%.Proportion of patients who developed to asynchrony: PAV 5.6%, PSV 29%.
Probability to remain on Spontaneous Mode
Proportional assist Ventialtion and Neurally Adjusted Ventilator Assist
Robert Kacmarek PhD Resp Care Feb. 2011 Vol. 56 No. 2
Background 6% of ventilated patients are prolonged
mechanically ventilated (PMV)
20% to 30% are difficult-to-wean.
Weaning tends to be delayed-Exposing the patient to unnecessary discomfort
-Increased risk of complications-Increasing the cost of care and mortality 12% vs 27% .
Time spent in the weaning process → 40–50% of the total duration of mechanical ventilation.
Intensive Care Med (2013) 39:1885–1895
DOI 10.1007/s00134-013-3014-9
Reasons contributing to weaning failure in anesthetized and critically
ill patients
Objective:
This study was designed to determine the effect of PAV+ on adult difficult-to-wean PMV patients.
Gulf Thoracic Congress March 13, 2014
Results:
13 adult Pts were included in this study. 9 of the Pts with Mean duration of MV was 53.2 days prior to PAV+ trial. On PAV+, NIF and P 0.1 measurements improved by 87% and 79% respectively from the baseline. They were successfully weaned off MV with an average weaning time of 5.8 days. 4 of the Pts were unsuccessfully weaned off MV and retained back to SIMV mode and went to be prolonged ventilator dependents.
Gulf Thoracic Congress March 13, 2014
NIF and P 0.1 measurements throughout PAV+ trails Time Spent on Conventional Weaning and PAV+
Gulf Thoracic Congress March 13, 2014
Conclusion:
PAV+ can be used safely and efficiently to wean adult difficult-to-wean PMV patients who failed multiple trails of conventional weaning. PAV+ provides opportunity for a respiratory muscle to recover and strengthen, increasing the likelihood of weaning success.
Gulf Thoracic Congress March 13, 2014
PAV vs PSV in the weaning of Pt with AECOPD
60 Pts: 30 on PAV, 30 on PSVWeaning Success PAV vs PSV 90% vs 66.7%In PAV,
less PVA 1.5 days reduction in mean days of MV2 days reduction in mean days of ICU stay1.8 days reduction in mean days of hospital stay
New Developments in PAV+
Younes M, et al. Intensive Care Med 2007; 33: 1337–1346
Kondili E, et al. Intensive Care Med 2010; 36: 648–655 .
• Recently, a new technology has been introduced that aims to monitor and improve patient– ventilator interaction.
• With PVI monitor, a signal representing an estimate of the patient’s total respiratory muscle pressure (Pmus,PVI) is calculated via the equation of motion, utilizing estimated values of resistance and elastance of the respiratory system, obtained noninvasively.
• The waveform of Pmus.PVI is continuously displayed
online on a breath-by-breath basis and can be used to trigger the ventilator. It has been shown that this triggering method may substantially shorten the triggering delay (by approximately 70%), even in patients with dynamic hyperinflation.
• Theoretically, this system should increase the efficiency of PAV+ to support critically ill patients with dynamic hyperinflation.
Why PAV+ is not Commonly Used?
PAV (1992) PAV+ (2005)
PAV+ (2005) is more accurate, safe & effective.
Failure to Knowledge Transfer??? *
Application sometimes regarded as difficult**
PAV+ had not been investigated thoroughly in weaning trails** .
**Boles, al et, Eur Respir J 2007; 29: 1033–1056
Why PAV+ is not Commonly Used?
Conclusion
PAV+– Provides assistance in PROPORTION to patient effort– Provides patient greater control of modulating VE– Reduces patient-ventilator asynchrony– Improves sleep quality for patients asynchronous on
PSV
PAV+ may help:– Preserve Respiratory Muscle Strength– Facilitate Weaning– Decrease Need for Sedation
Does all this mean extra coffee breaks for clinicians?
PAV is safe and effective mode of ventilation.There is strong evidence that PAV provides some advantages related to patient comfort and better synchrony.PAV may be helpful with difficult to wean patients (muscle fatigues, changing lung mechanics)Understanding PAV physiology and operation is essential for save use of the mode.
Conclusion
Questions Need to be Answered?
Non-invasive PAV+?PAV+ as Initial Setting Mode for Non-Fully Sedated or Paralyzed Patient?PAV+ in The Specialized Weaning Units?PAV+ in The Home Ventilators?