Transcript Treatment of the Inciting Clinical Disorder in Patients

Ventilation in Special
Conditions
Mazen Kherallah, MD, FCCP
Consultant Intensivist
King Faisal Hospital & Research Center
Assistant Professor
University of North Dakota, USA
MV in Special Conditions
ARDS
COPD
Head injury
ARDS
Clinical Presentation
Acute onset (not specified)
Decreased pulmonary compliance: very heterogeneous
disease with areas of consolidation, areas of collapse
and areas of normal lung on chest CT scan
Po2/FiO2 ratio <200 (300 for ALI)
Bilateral infiltrates on chest radiograph (highly variable)
PAWP <18 mm Hg or absence of clinical evidence of
volume overload
Bernard GR et al, Am J Resp Crit Care Med. 1994;149:818-824
The Nature of Acute Lung Injury
Pulmonary events
Infection
Bleeding
Aspiration
Near drowning
Fat embolism
Chest trauma
Extrapulmonary events
Sepsis
Pancreatitis
Burns
Shock
Hypoperfusion
Trauma
Intestinal ischemia and reperfusion
Acute Inflammatory Response in the Lung
Physiologic cascades may be different
and responses to different therapies
Three Compartments of ARDS
Aerated normal lung susceptible to barotrauma
induced by inappropriate ventilation. Usually
located in the nondependent regions.
Airspaces that are filled with exudates and not
recruitable lung.
Areas that are collapsed due to interstitial
infiltration and are potentially recruitable. Usually
in the dependant lung regions.
Pathophysiology
First Phase




Intense inflammatory
response
Alveolar and
endothelial damage
Increased permeability
Increased lung water
Second Phase


Extensive fibrosis
Start 7 -10 days after
the first phase
Decline in ARDS Fatality Rate
80
60
50
40
30
20
10
Years
20
04
20
00
97
95
93
91
89
87
85
0
83
Mortality 9%)
70
Causes of Mortality in ARDS
11%
1990
6%
36%
4%
6%
15%
22%
Sepsis/MOF
CNS
Respiratory
Cardiovascular
Hepatic
GI
Others
ARDS: Physiological Abnormalities
Normal airway resistance
Low lung compliance
Decreased time constant t (t= compliance
X resistance, complete passive exhalation
requires 3-4 t; normally t is about 0.5 s)
Mostly increased ME
Severe shunting process
ARDS: Inhomogeneous
Consolidation/Atlectasis Radiopathology
ARDS: Pressure/Time
Curve
PIP
Inspiration
Pressure (cm H2O)
Plateau
Airway
Resistance
Expiration
Normal
Patient
Time (sec)
ARDS: Volume/Time Curve
(decreased t)
Volume (cm H2O)
Inspiration
0.5 s
Normal
Patient
0.35 s
Time (sec)
Expiration
ARDS: Low Lung
Compliance
Expiration
Volume (mL)
Inspiration
Deflection point
Low Compliance
Pressure (cm H2O)
ARDS: Shunting Process
FIO2
100%
Po2/FiO2 ratio <200
PO2 100 mm Hg
Indication for MV in patients with
ARDS
Increased work of breathing
Oxygenation impairment
Impending ventilatory failure
Acute ventilatory failure
ARDS: MV Objectives
Protective lung strategy: lower tidal volumes 4-6
mL/kg to provide lower alveolar pressures <30 cm
H2O and avoid barotrauma and volutrauma
Adequate oxygenation: high FiO2 and PEEP with
PaO2 targets:



ALI > 70 mm Hg
Moderate ARDS > 60 mm Hg
Severe ARDS > 50 mm Hg
High minute ventilation with acceptance of
hypercapnia
Acceptance of acidosis: pH 7.30 to 7.45
Avoid auto-PEEP (provide enough t )
Mechanical Ventilation
ARDSnet Approach


Maintaining low tidal
volume while
monitoring plateau
pressure
Set PEEP based upon
FiO2 requirement
Open Lung Approach




Pressure-controlled
ventilation
Maintaining low
plateau pressure while
monitoring tidal
volume
Use of recruitment
maneuvers
Maximize alveolar
recruitment with high
level of PEEP
Reduce Ventilator-induced Lung
Injury
End –inspiratory plateau pressure < 30 cm
H2O to prevent over-distension
Appropriate level of PEEP is maintained to
avoid the shear stress of repeatedly
opening and closing unstable lung units
ARDSNet Approach
Multicenter study of effectiveness of two
Tidal Volumes for Ventilation
ARDS network study
Prospective, randomized, multicenter study to
compare the effectiveness of 2 tidal volumes in
patients with ALI and ARDS- 12 ml/kg and 6 ml/kg

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429 subjects randomized to 12 ml/kg of ideal body
weight
Airway plateau pressure < 50 cm H2O
432 subjects randomized to 6 ml/kg of ideal body
weight
Airway plateau pressure < 30 cm H2O
NIH ARDS Network Trial
Mechanical Ventilation in ARDS
Vt=6
Vt=12
110
100
Survivals (%)
90
80
31% mortality
40% mortality
70
60
50
40
30
20
0
10
20
30
40
50
60
70
Time after onset of ARDS
80
90
100
NIH ARDS Network Trial
Mechanical Ventilation in ARDS
45
40
40
Mortality (%)
35
30
25
P = 0.0054
31
22NNT
% improvement
12 patients in
survival
20
15
10
5
0
6 ml/kg
12 ml/kg
Median # Ventilator-Free Days
14
13
12
10
8
6
6
4
2
0
6 ml/kg
ARDSnet
12 ml/kg
ARTERIAL OXYGENATION
GOAL: PaO2 55-80 mm Hg or SpO2 88-95%
Use these FiO2/PEEP combinations to achieve oxygenation goal.
FiO2 0.3 0.4 0.4 0.5 0.5 0.6 0.7 0.7 0.7 0.8 0.9 0.9 0.9 1.0
PEEP 5 5 8 8 10 10 10 12 14 14 14 16 18 20-24
ARDSnet Approach
Start
Calculate predicted body weight
CMV (A/C), VCV, Vt 8 mL/kg, then 7 mL/kg after 1 hr, then 6 mL/kg
after next 1 hr, increase inspiratory rate to maintain minute ventilation,
I:E ratio 1:2, PEEP and FiO2 per FiO2/PEEP table
Pplat <
30 cm H2O
↑ VT by 1 mL/kg
yes
no
VT 5 mL/kg
yes
yes
VT <6 mL/kg
yes
↑ VT to 7-8 mL/kg
no
VT 4 mL/kg
yes
Pplat <
25 cm H2O
Severe dyspnea
no
PaO2 55-80
SpO2 88-95
no
Adjust FiO2 or PEEP
Per FiO2/PEEP table
yes
↑ rate
Consider HCO3
↑ VT
yes
pH < 7.15
<7.30
pH
>7.45
↓ rate
FiO2 ≤ 0.4
PEEP= 8
no
↑ rate
7.30-7.45
yes
Evaluate for weaning
no
Open Lung Approach
What is a Recruitment Maneuver?
A Recruitment Maneuver is a procedure
where a sustained positive pressure is
applied, to an injured lung, over an
increment of time, to recruit, open and
keep open closed alveoli.
Why is Recruitment done?
Recruitment maneuvers are performed to help
improve oxygenation, help improve distribution
of ventilation, and improve shunts.
To try and determine the “Optimal PEEP” to
keep the lung from dynamic collapse and
alveolar de-recruitment.
*It is also done to re-recruit the lungs once there
has been a break in the ventilation circuit.*
Patient Selection
Primarily on patients with ARDS/ALI


ARDS - (PaO2/FIO2 <200) w/ bilateral infiltrates on xray.
ALI – (PaO2/FIO2 <300)
Patients in early phase ARDS, before the onset
of fibro-proliferation.
Also in non-ARDS patients.

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Patients with Alveolar Collapse.
Patients with Overnight turn lung status.
Patients with consistent Atelectasis.
Different Ways to Recruit the Lung
Use of high CPAP for short periods of
time. 40/40 rule (40 cm H2O for 40
seconds)
Increased levels of PEEP - arbitrary
Sustained inflation maneuvers
Sigh breaths
Optimal PEEP study
Injured Alveoli w/ Insufficient
Amounts of PEEP
Injured Alveoli w/ Sufficient
Amounts of PEEP
PEEP Usage
Study by A. Estaban. AJRCCM 2000;161: 14501458

PEEP usage in ICUs
31% of patients were on ZERO PEEP.
47% were on 1-5 cmH2O
18% were on 6-10 cmH2O
3% were on 11-15 cmH2O
0.2% were on greater than 15 cmH2O
How do you know it worked?
Improvements in oxygenation.

A 20% change or greater in PaO2/FIO2
Improvements in intrapulmonary shunting.
Improvements in lung mechanics.
Greater Tidal Volume for same pressure in
(PC).
Same Tidal Volume at less pressure in
(VC).
Improved compliance
Expiration
Volume (mL)
Inspiration
Pressure (cm H2O)
Potential Problems
Hemodynamic instability


Increased Pleural pressures may adversely effect pulmonary
vascular resistance and cardiac filling or performance.
Cardiac Output decreases more profoundly in patients with
pneumonia.
Caution should be used.
Decrease in Oxygenation
Cardiac arrhythmias
Pneumothorax
Regional Alveolar Overdistention
Ideal patient is deeply sedated or paralyzed.
Not indicated for awake patients.
8 step open lung picture
Recruitment Maneuver
Recruitment Maneuver
CMV (A/C), PCV to achieve VT of 4-8 mL/kg
Ti to avoid auto-PEEP, rate 20/min, FiO2 1.0,
PEEP 10 cm H2O
Start
Open Lung Approach
Recruitment maneuvers
PEEP 20
FiO2 to maintain SpO2 90-95%
Decrease PEEP to maintain SpO2 90-95%
↑ pressure control if Pplat <30 cm H2O
↑ rate (avoid auto-PEEP)
Consider accepting lower pH
<7.25
>7.45
pH
↓ pressure control
↓ rate
7.25-7.45
Recruitment maneuver
↑ PEEP
↑ FiO2
<90%
SpO2
>95%
90-95%
SpO2
Maintain ventilatory setting
<90%
Consider prone position
Consider accepting lower level of oxygenation
Consider inhaled nitric oxide
↓ FiO2
↓ PEEP if FiO2 < 0.50
Monitoring during MV of patients
with ARDS
Pulse oximetry, periodic blood gases
Central venous catheter or pulmonary
artery catheter
Presence of pneumothorax
Auto-PEEP
Tidal volume and plateau pressure
Mean airway pressure
Chronic Obstructive Pulmonary Disease
COPD: Physiological Abnormalities
High airway resistance
High lung compliance
Increased time constant (t= compliance X
resistance, complete passive exhalation requires
3-4 t; normally t is about 0.5 s)
Auto-PEEP
Increased work of breath
Ventilatory muscle dysfunction
Normal MV or increased
V/Q mismatch
Diffusion abnormalities
COPD: MV Objectives
Overcome increased resistance but keep peak alveolar
pressure <30 cm H2O
Avoid auto-PEEP by providing enough time constant t:
moderate volume 8-10 mL/kg and slower rate, minimize
Vm if auto-PEEP develops
Counter-balance auto-PEEP when present to improve
triggering
Patient-ventilator synchrony to avoid unnecessary work
and anxiety mainly with termination of inspiration
(preferred time cycled modes: PCV, VCP)
Adequate oxygenation with FiO2 is < 50% usually to
provide PaO2 of 55-75 mm Hg
Avoid hyperventilation: decrease PaCO2 to baseline
level (50-60 mm Hg and near normal pH >7.3)
Complete rest for first 48 hours
Auto-PEEP
As result of increased airway resistance and
increased compliance, time constant is
remarkable increased in COPD
That necessitate a longer expiratory time to
prevent air trapping and auto-PEEP
Since end-expiratory pressure is greater than
atmospheric pressure with auto-PEEP, a
pressure gradient sufficient to overcome autoPEEP must be established for gas to move into
the lung
The presence of auto-PEEP is a primary factor
associated with increased work of breathing in
COPD patients with acute respiratory failure
Air Trapping
Flow (L/min)
Inspiration
Normal
Patient
Time (sec)
}
Air Trapping
Auto-PEEP
Expiration
Air Trapping
Inspiration
Flow
(L/min)
Does not return
to baseline
Volume (ml)
Normal
Abnormal
Expiration
PEEP vs Auto-PEEP
+8
+8
+0
+8
+8
+8
Incidence of Auto-PEEP
“… we demonstrated that
intrinsic PEEP was present in
almost all (97%) of the patients
receiving mechanical
ventilation, even in those
patients who did not have a
history of COPD.”
Patel, Yang
CCM, 1995 Vol. 23, No. 6
1074-1079
“Undetected Effort” Due To AutoPEEP
Inspiration With Auto-PEEP
To Initiate Gas Flow, the Patient Must
Generate An Effort That Exceeds the Amount
of Auto-PEEP
+8
+8
-9
-9
What Causes AutoPEEP?
Simply ...
not enough time to exhale fully


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The Patient’s Disease
The Ventilator Settings
The Ventilator Circuitry
How Does Auto-PEEP
Increase the Patient’s
Work of Breathing?
Auto-PEEP acts as a threshold
that must be overcome at the
beginning of inspiration
0
Gradient
-5
0
-5
0
Gradient
-5 +10
Auto PEEP
Increased Work of
-15
Breath
Auto-PEEP Detection via
the Flow Waveform
Normal
--------------------------------------------------------
Flow does not
return to zero
- Auto-PEEP
Auto-PEEP
Auto-PEEP
Prolonged Inspiration/Intrinsic PEEP
Auto-PEEP
Expiratory Time
Flow
(L/m)
Flow does not
return to zero
Time (sec)
PEEP
7 cm H2O
sensitivity
-1 cm H2O
auto-PEEP
10 cm H2O
sensitivity
-1 cm H2O
auto-PEEP
3 cm H2O
PEEP
10 cm H2O
PEEP
10 cm H2O
trigger effort = 11 cm H2O
trigger effort = 4 cm H2O
Auto-PEEP should be measured with set PEEP = 0
Auto-PEEP Consequences
Increases the pressure gradient required to
inspire during spontaneous breathing
Increases the pressure gradient to trigger the
ventilator
Results in accessory muscle recruitment,
retractions, increased ventilatory drive and
dyspnea
Difference between the patient’s respiratory rate
and the ventilator response
COPD: Indications for MV
Acute on chronic ventilatory failure
Unloading work-of-breathing
Resting ventilatory muscles
Improving bronchial hygiene
Candidate
For
NPPV
yes
NPPV
yes
yes
Patient
tolerates
intubate
intubate
yes
Clinically
improved
Continue
NPPV
intubate
CMV (A/C), PCV or VCV, VT 8-10 mL/kg, Pplat <30 cm H2O, rate 10/min,
TI 0.6-1.2 s, PEEP 5 cm H2O, FiO2 for SpO2 90-95%
↑ FiO2
<55
PaO2
>75
↓ FiO2
55-75 mm Hg
no
Pplat >
30 cm H2O
>7.45
pH
<7.30
yes
↓ Rate
↑ VT
no
Auto-PEEP
yes
no
↑ PEEP, ↓ VT or ↓ rate
Auto-PEEP
no
yes
↓ VT
yes
Pplat <
30 cm H2O
Clear secretions
Administer bronchodilators
↑ rate
Administration of External PEEP
PEEP
10
Gradient
5
Auto PEEP
+10
-5
COPD: MV Monitoring
Patient-ventilator synchrony
Auto-PEEP: evaluation of expiratory flow
waveform
Peak airway pressure
Hemodynamics
Pulse oximetry and arterial blood gases
Clinical signs of cardiopulmonary distress
Head Injury
Cerebral Compliance Curve
CPP= MAP-ICP
Intracranial pressure
CPP
Intracranial volume
Cerebral Compliance Curve
PaCO2
CPP
Cerebral Blood Flow
PaO2
50
100
150
Decompressive Craniotomy
Decrease Oxygen Demand
• Prevent seizure
• Sedation
• Treat pain
• Barbiturate coma
• Avoid hyperthermia
• ? hypothermia
ICP= 10
CSF Drainage
• HOB > 30 degree
• Head in neutral
position
• Vetriculostomy
ICP =30
Vasoconstriction
Pa co2 25-30
Decrease Brain Water
•Mannitol
•Avoid D5%
•Diuretics
CPP = MAP – ICP
Avoid ↑ Intrathoracic
Pressure
Maintain adequate MAP
• Suppress Valsalva
• Adequate CO
maneuvers
Venous Return
MAP (90)= CO X
SVRinotropic Agents
• Use
• Suppress cough
• Adequate filling pressures
• ↓ Mean airway pressure
Intrathoracic Pressure (-3 cm H2O)• Avoid hypotensive agents
• Minimize use of PEEP
• Treat infection abruptly
• Treat distended abdomen
CMV (A/C), PCV or VC,
VT 4-8 mL/kg, FiO2 1, rate
20/min TI1s, PEEP 5 cm H2O
yes
Underlying lung
disease
CMV (A/C), PCV or VC,
VT 4-8 mL/kg, FiO2 1, rate
15/min TI1s, PEEP 5 cm H2O
no
Titrate FiO2 for SpO2 ≥ 92%
↑ rate
>45
PCO2
<35
Pplat > 30
no
↓ rate
yes
35-45
no
FiO2
> 0.6
<70
no
ICP <
20
PaO2
>100
↓ FiO2
70-100
yes
↑ FiO2
↓ VT
yes
FiO2 >
0.6
yes
More aggressive
Medical therapy
no
↑ PEEP
<20
Maintain
Ventilator
Setting
ICP
>20
>20
↑ rate
ICP
<20
Slowly ↓ rate to
initial setting
Head Injury: MV Monitoring
Peak alveolar pressure, airway pressure,
auto-PEEP
PaCo2 end tidal PCO2
Intracranial pressure
Jugular venous oxygen saturation
Pulse oximetry
Heart rate and systemic blood pressure
Summary
Lung Protective Ventilator Strategy

TV: 6 mL/Kg IDEAL BODY WEIGHT



Keep Plateau Pressure < 30 cmH2O
Hypercapnea and acidemia are tolerable
Use PEEP
COPD:



Obstructive diseases require adequate expiratory time
Beware of auto-PEEP
PaCO2 should be kept at patient’s baseline level
Head Injury:

Avoid increase intrathoracic pressure