Pulsed-jet propulsion of a squid-inspired swimmer at high ...
Getting Inspired by High Frequency Jet Ventilation Clinical Applications and Optimization.
-
Upload
candice-hamilton -
Category
Documents
-
view
216 -
download
0
Transcript of Getting Inspired by High Frequency Jet Ventilation Clinical Applications and Optimization.
Getting Inspired by High Frequency Jet
Ventilation
Clinical Applications
and Optimization
Ventilation Facts• The least traumatic ventilation occurs in the
mid-portion of the P/V curve.
• Lungs are most vulnerable to injury during the recruitment phase.
• A 5 cc/kg VT may not prevent over-expansion and lung injury
• Apply L.O.V.E.
Goals of Assisted Ventilation
• Achieve uniform lung inflation
• Minimize over and under inflation
• Minimize FiO2
• Early appropriate extubation
How should HFV be used with newborn infants?
Potential HFV Applications
1. Prevent Lung Injury
a. Non-homogeneous Lung Disorders
b. Air Leaks (PIE, PTX, etc.)
c. Whenever small VT and Low Paw helps
a. Must use early
b. Must avoid hyperventilation
c. Optimizing PEEP offers huge advantages
2. Treat Lung Injury (Rescue)
2 Trials: Early Use of HFV for RDS
244 65 65254
0.9 1.0 1.00.9
2.7 8 82.7
CV HFJVHFOVSIMV
p = 0.037p = 0.046
Number
Birth Weight, kg
Randomization Age, hrs
Alive w/o CLD at 36 wks
13156%
3148%
4468%
11747%
• Effective frequencies
• Determinants of PaO2
• Determinants of PaCO2
P drop down airways
HFJV vs. HFOVSimilarities
Why does one need HFJV?
Sick lungs aren’t always homogeneous.
We like to think that the lungs look like
this…
with lots of surface area for gas exchange.
Courtesy of Professor Louis De Vos
http://www.ulb.ac.be/sciences/biodic/index.html
Premature lungs look more like
this:
The Premature Lung
• Alveoli have yet to be fully formed
• Surfactant is not yet being adequately produced
• Terminal bronchioles make up the most compliant area of the lungs
Ventilating Premature Lungs
Distal airway rather than primitive alveolus is the most compliant part of the respiratory tract.
Distal airway disruption :
• PIE
• Pneumothorax
• Pneumo- this and that
What we would like to happen:
What really happens:
Ventilating Premature Lungs
Thar she blows!!
Airleaks Originate in Terminal Airways
Positive pressure ventilation damages premature lungs
• Inflammation
• Inhibited alveolar development
• PIE and other airleaks
• Smooth muscle growth in small airways and alveoli
Using small tidal volumes to treat lung injuries is critically
important!
How those small tidal volumes are delivered is also
critically important!
The Jet squirts gas into the lungs faster than any other ventilator.
So what?
High velocity gas shoots right past upper airway leaks!
Using HFJV to Treat BPF
Squirting gas into lungs very rapidly enables the Jet to ventilate Non-Homogenous lung disorders.
PIE RDSHigh airway resistanceupstream of injuryrestricts Jet gas,promotes healing
Raw
Problem
More ventilation since small VTs not
affected by atelectasis, low lung compliance
C L
Problem
HFJV Gas Distribution in Non-Homogeneous Lung Disease
HFJV: less gas to injuries, more gas for RDS!
A Non-Homogeneous Disorder
Interstitial gasincreases airway resistance upstream from leak site.
Tension PIE restricts alveolar expansion.
Pulmonary Interstitial Emphysema
The principal manifestations of injury in premature lungs are
airway narrowing andalveolar disruption.
If we can reduce mechanical ventilation of injured areas of premature lungs, they can heal
and grow new lung parenchyma.
HFJV decreases ventilation where airway resistance is
increased, so injured alveoli can heal and multiply.
• The Jet relies on the lungs for passive exhalation.
• Passive exhalation helps the patient in two ways.
Passive Exhalation
Mucociliary Clearance
CO 2
CO 2
CO
2
CO 2
CO 2Exhaled gas swirls out along airway walls, facilitating mucociliary clearance.
Passive exhalation also enables the Jet to work at lower Paw.
Three Ventilators, Same Blood Gases
HFJV
HFOV
CV
10
15
20
5
Tra
chea
l P
ress
ure
, cm
H2O
seconds0.80.60.40.2
Time
00
Paw
Boros, et al. Ped Pulm. 1989; 7:35-41
PRESSURE WAVEFORM COMPARISON
CHOKE POINTS may develop when:• airways lack structural strength• the chest is squeezed• gas is sucked out of the airway
++
+
+
++
+
+
PEEP
Back-pressure (higher PEEP/Paw) splints airways open, allowing gas to enter and exit.
Consequences of Active Exhalation
1. A limit to how much Paw can be reduced.
2. Possible interference with venous return, cardiac output.
When is the Jet the HFV of choice?
• Hemodynamic Compromise (e.g., PPHN, cardiac anomalies)
• Air Leak Syndromes
(particularly PIE, Ptx)
• Excessive Secretions (e.g., some pneumonias, MAS)
HFJV vs. HFOV
• Non-Homogeneous Lung Disorders (e.g., when HFOV fails)
Other Conditions When Jet is the HFV of choice:
• Difficult to Wean Patients (e.g., BPD, Chronic Lung Disease)
The “Jet”
Operating instructions: www.bunl.com
“Patient Box”
LifePort ET tube adapter
ET Tube Connector
Jet Port Cap
Jet Injection Port
15-mm Connector
Pressure Monitoring Line
The LifePort Adapter
JetPort
Inspired gas is injected down the ETT in high velocity spurts.
PIP is measured here and filtered to estimate PIP at the tip of ETT.
PressureMonitoring
Port
• Sensitive to changes in patient’s condition
• Help you maintain optimal lung volume without xrays
HFJV Monitoring and Alarms
• Servo Pressure
• Mean Airway Pressure
Monitoring HFJV with High – Low Alarms
The Importance of Servo Pressure
• Servo Pressure = Automatically controlled driving pressure• Servo Pressure changes as perceived lung volume changes
PerceivedLung Volume
Servo Pressure
PerceivedLung Volume
Servo Pressure
Observing Servo Pressure can facilitate patient management
• Improved compliance and/or resistance
• Airleak
• Disconnected Tubing
• Extubation
Servo Increases
Servo Decreases
• Worsened compliance and/or resistance
• Obstruction of ET Tube
• Tension pneumothorax
• Patient needs suctioning
• High Alarm (usually good news):
o improved lung mechanics (compliance or resistance)
o tubing leaks, etc.
Servo Pressure
Servo Pressure
• Low Alarm (always bad news): o degradation of lung mechanics
o atelectasis
o accumulation of secretions
o tension pneumothorax
o right mainstem intubation
o etc.
Mean Airway Pressure
• High Alarm: inadvertent PEEP, gas trapping.
• Low Alarm: tubing leaks or disconnects, inadvertent changes in CV settings, etc.
PIP
PEEP
Paw
Adjusting Airway Pressures to Optimize Arterial Blood Gases
Higher P
Higher Paw
Hypocapnia
Good PaO2
Lower P
Lower Paw
Good PaCO2
Hypoxemia
Higher P
Higher Paw
Hypocapnia
Good PaO2
Lower P
Higher Paw
Good PaCO2
Good PaO2
P
How much PEEP should one use with HFJV?
Start with PEEP appropriate for IMVIMV Rate = 5-10 bpm
Note current SaO2 on pulse oximeter
PEEP may be high enoughNO
PEEP is too low
YES
Flip IMV to CPAP mode
Finding Optimal PEEP During HFJV *
* Don’t be surprised if PEEP = 6-10.
Does SaO2 drop?(1- 5 min.)
Flip back to IMVRate = 5 - 10 bpm
Increase PEEP by 1-2
Wait for SaO2 to returnto acceptable value
(It may take >30 min.)
Does FiO2 need increased?
(15-30 min.)
Flip back to IMV if desired(rate = 1-3 bpm)
NO
Keep PEEP at this leveluntil FiO2 < 0.40
YES
5
10
15
20
30
0.0 2.00.5 1.51.0
seconds
cm H2O
CRITICAL "LEAKING" PRESSURE
Raise PEEP to oxygenatePIE Patients
Other Patient Management Strategies
for HFJV
The Jet in Tandem with CV
JetCV
LifePort adapter
VentilationOxygenation
PEEP Valve
2CO2
V f x VT
HFV ∆P is key to controlling PaCO2
Drazen JM, et al. Physiol. Rev. 64: 505, 1984.Fredberg, JJ. Acta Anaesthesiol. Scand. 33: 170, 1989.
Step Two
Step One
• Recruit collapsed alveoli with IMV when atelectasis is present.
Oxygenation: 2-Step Process
• Stabilize alveoli with adequate PEEP.
PIPPEEP
I-time .020
FiO2 100% 100%
Rate 420
CVHFJVCPAP
--4 4
20 --
HIGH LUNG VOLUME STRATEGY
Meanlung
volume
time
PaO2 < 50 no sustained recruitment
PIPPEEP
I-time .020
FiO2 100% 100%
Rate 420
CVHFJV
x3
2.04 4
20 30
LOW PEEP STRATEGY
Meanlung
volume
time
no sustained recruitment
PEEP is too low!
PIPPEEP
I-time .020
FiO2 100% 100%
Rate 420
CVHFJV
5 - 10
0.58 8
20 20
gradual recruitment
LUNG VOLUME STRATEGY
Meanlung
volume
time
PEEP is the key!
Lung V
time P
PEEP
Low Optimal
4 6 20
V
VVLung
time P
PEEPLow Optimal
4 6 20
Using IMV to recruit collapsed alveoli is a temporary maneuver.
Do not continue to use high CV rate with high PEEP once oxygenation
improves!
Combining CV & HFJV doesn’t have to be Complicated
• Only Jet PIP requires adjustment, to control PCO2.
• CV PEEP is the main determinant of Paw and PO2.
HFJV + CV = Versatility
CV breaths can:
• Recruit collapsed alveoli.
• Dilate or open collapsed airways.
• And, you can add them with or without HFJV breaths.
HFJV + CV: Keep It Simple
• CV settings are usually minimized, except for PEEP
• IMV Rate: 10 bpm zero (CPAP)
• PIP and I-time settings should be set in proportion to Rate.
Summary…
Why HFJV?
1. Very Gentle (prevent CLD?)• Small Tidal Volumes• Low Airway Pressures
2. Easy to Use, Like Conventional Ventilation
• Same principles of gas exchange
• Same setting changes produce same blood gas changes
3. Combined HFJV / CV = Great Versatility
4. Works great with non-homogeneous lung disorders.
• Hemodynamic Compromise
• Air Leak Syndromes
• Excessive Secretions
When is the Jet the HFV of choice?
• Non-Homogeneous Lung Disorders
• Difficult to Wean (BPD, CLD) Patients
Are you Inspired?
• Read the handout
• Website: www.bunl.com
• Call the Hotline: 1-800-800-HFJV
INO via HFJV
Jet Circuit
LifePort adapter
"Y"connector
JetCV
Sampling line to analyzer
INOvent injector module
"T" intoGAS OUT
tubing
INOvent*
Nitric Oxide + HFJV works well for PPHN