Ventilatory management pf acute
lung injury & acute respiratory
distress syndrome
By Sherif G. Anis M.D.
Ventilatory management of ALI & ARDS
Acute respiratory distress syndrome
•
•
•
•
Acute onset of hypoxemia
Bilateral Lung infiltrates
Absence of left atrial hypertension
Risk factors:
Pulmonary e.g. Pneumonia
Non pulmonary e.g. Pancreatitis
Ventilatory management of ALI & ARDS
Diagnostic Criteria for ARDS
Source Oxygenation
Chest
Radiograph
Other Criteria
Petty and Cyanosis refractory
to oxygen therapy
Ashbau,
1971
Diffuse alveolar
Impaired pulmonary
infiltrates on frontal compliance
chest radiograph
Marked difference in
inspired vs. arterial
oxygen tensions
Murray et Hypoxemia
al,
(PaO2/FIO2),
1988
by quintiles
No. of quadrants
of alveolar
consolidation
on frontal chest
radiograph
PEEP and respiratory
system compliance
(by quintiles)
Preexisting direct or
indirect lung injury
Nonpulmonary organ
dysfunction
Ventilatory management of ALI & ARDS
Diagnostic Criteria for ARDS
Source Oxygenation
Chest
Radiograph
Other Criteria
Bernard
et al,
1994
Bilateral infiltrates
on
frontal chest
radiography
PCWP <18 mm Hg
if measured or
no clinical evidence
of left atrial
hypertension
ALI:
PaO2/FIO2 <300,
regardless of PEEP
level
ARDS, PaO2/FIO2
<200,
regardless of PEEP
level
Ventilatory management of ALI & ARDS
American European consensus
conference (AECC) 1994
• Acute lung injury (ALI)
[PaO2/FIO2] ratio<300)
• Acute Respiratory distress syndrome
(ARDS):
(PaO2/FIO2 ratio <200)
Ventilatory management of ALI & ARDS
Mechanical Ventilation in ARDS
Necessary to
reverse Hypoxaemia
Injurious ventilator
associated lung injury
Ventilatory management of ALI & ARDS
• The lung with ALI or ARDS are
particularly prone to ventilator
associated lung injury: (Baby lung)

Collapsed, consolidated, less compliant
areas (Dependant)
 Normal areas (non dependant)
Ventilatory management of ALI & ARDS
Ventilatory management of ALI & ARDS
• Ventilator associated lung injury:
 High inflation pressure
Barotrauma
 Over distension
Volutrauma
 Repetitive opening & closing of alveoli
Atelect-trauma
 SIRS & cytokines release
Biotrauma.
Ventilatory management of ALI & ARDS
• Lung protective ventilation in
comparison with conventional
approaches
Evidence Synthesis
Study
Participants
ARDS
Network,
2000
Amato et al ,
1998
Brochard et
al1998 ,
Stewart et al ,
1998
Brower et al ,
1999
No.
861
53
116
120
52
Mean age, y
52
35
57
59
49
Target
intervention
Tidal volume,
mL/kg
6 vs. 12 PBW
≤6 vs. 12 ABW
6-10 vs. 10-15
DBW
≤8 vs. 10-15 IBW
≤8 vs. 10-12 PBW
Plateau
pressure, cm
H2o
30≤vs.50 ≤
20<vs. unlimited
30-25vs.60 ≤
30≤vs.50≤
30≤vs.55-45≤
Actual
intervention
Tidal volume,
ml/_kg
6.2vs. 11.8
384 vs.
‡ 768
7.1vs. 10.3
7.0vs. 10.7
7.3vs. 10.2
Plateau
pressure, cm
H2o
25vs. 33
30vs. 37
26vs. 32
22vs. 27
25vs. 31
Outcomes
mortality% ,
31vs. 40§
38vs. 71 .
47vs. 38
50vs. 47
50vs. 46
P value
0.007
0.001
0.38
0.72
0.61
Ventilatory management of ALI & ARDS
• 3 Meta analysis of these 5 clinical trials
have been performed:
 One analysis shows that there is no reflection of the
standard of care, in addition low tidal volumes may
be harmful, in the intervention group of the 2 trials
showing survival advantage. (Eichacker PQ et al,
2002)
 2 subsequent meta analyses suggested that volume
limited ventilation, particularly in the setting if
elevated plateau pressure > 30 cmH2O, has a short
term survival benefit. (Petruccin et al, 2004) (Moran
Jl et al, 2005)
Ventilatory management of ALI & ARDS
 One meta analysis also concluded that
decreased tidal volume may be advantageous
below a threshold level (<7.7 ml/Kg BW)
(Moran Jl et al, 2005)
Ventilatory management of ALI & ARDS
Lung protective ventilation strategy
 Pressure & volume limitation
 Higher PEEP
 Recruitment maneuvers (Dynamic process of
reopening collapsed alveoli through increase in
trans pulmonary pressure)
Ventilatory management of ALI & ARDS
Lung protective ventilationn etiology
 Which method of recruitment maneuvers
should be Used ?
1.
2.
3.
4.
5.
The most well Known method of recruitment maneuver is
sustained application of CPAP of 30- 50 Cm H2O for 30
seconds
Periodic recruitment with a series of traditional sigh
breaths
Intermittently raising PEEP over several breaths
Extended sigh maneuver with step wise increase in PEEP
while Vt is decreased
Intermittent application of pressure controlled ventilation
with incremental high PEEP
Ventilatory management of ALI & ARDS
Consequences of lung protective ventilation
 Permissive hypercapnea (acute respiratory acidosis)
TTT: increase respiratory rate in a stepwise up to 35
Bicarbonate infusion
increase Vt
 Worsened oxygenation & transient desaturation
 Increased sedation or analgesia
 Hypotension & arrhythmias
 Barotraumas (Pneumothorax)
 Bacterial translocation
Ventilatory management of ALI & ARDS
• Further studies are needed to:
 Inform on a clinically relevant threshold if hypercapnea,
& acidosis both require intervention
 Increased sedation & analgesic effects (Kahn JM &
colleagues, 2005 show no increase in sedation use in low
tidal volume ventilation)
 Safety of recruitment maneuvers
Ventilatory management of ALI & ARDS
Alternative Ventilatory Approaches to
Lung Protection
• High-frequency ventilation (jet,
oscillation, and percussive
ventilation)
HFOV allows for higher mean airway
pressures & markedly reduced tidal
volumes (1-3 ml/kg)
Lung
recruitment & reduce lung injury.
Ventilatory management of ALI & ARDS
Alternative Ventilatory Approaches to
Lung Protection
• Airway pressure release ventilation
(APRV)
It provides two levels of airway pressure
(P high & P low) during two time periods (T
high & T low) , usually a long Thigh & short
Tlow with spontaneous breathing during
both.
Advantages: Decrease barotrauma, provide
better V/P matching, cardiac filling &
patient comfort.
Ventilatory management of ALI & ARDS
Adjunctive therapies to lung-protective
Ventilation
 Prone positioning:
recruitment of dorsal (nondependent)
atelectatic lung units, improved respiratory
mechanics, decreased ventilation- perfusion
mismatch, increased secretion drainage, reduced
and improved distribution of injurious
mechanical forces
(Pelozi P et al, 2002)
Ventilatory management of ALI & ARDS
Adjunctive therapies to lung-protective
Ventilation
inhaled nitric oxide :
Selective VD in ventilated lung units
improving V/Q mismatch, decrease PaO2
& pulmonary hypertension ( no sustained
clinical benefit) (Tayler RW et al, 2004)
Ventilatory management of ALI & ARDS
• Irrespective of this controversy as to whether
the exact ARDSNet protocol should be adopted,
the existing evidence supports that clinicians
should change their practice and adopt volume
and pressure limited ventilation for patients with
ALI or ARDS. As additional evidence emerges,
ongoing reassessment and evolution of these
protocols will be necessary.
Ventilatory management of ALI & ARDS
Conclusions and Future Considerations
1. mechanical ventilation, although life saving, can
2.
3.
4.
contribute to patient morbidity and mortality
Volume and pressure limited ventilation clearly leads to
improved patient survival
The role of recruitment maneuvers, higher levels of
PEEP, or both remain controversial
At this time, use of alternative modes of ventilation
(e.g., HFOV) and adjunctive therapies (e.g., inhaled
nitric oxide and prone positioning) should be limited to
future clinical trials and rescue therapy for patients
with ALI or ARDS with life threatening hypoxemia
failing maximal conventional lung protective
ventilation.
Thank you