1. Ventilatory management pf acute lung injury & acute respiratory distress syndrome
By Sherif G. Anis M.D.

2. Acute respiratory distress syndrome
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

3. Diagnostic Criteria for ARDS
Ventilatory management of ALI & ARDS
Diagnostic Criteria for ARDS
Other Criteria
Chest Radiograph
Oxygenation
Source
Impaired pulmonary
compliance
Marked difference in inspired vs. arterial oxygen tensions
Diffuse alveolar
infiltrates on frontal
chest radiograph
Cyanosis refractory
to oxygen therapy
Petty and
Ashbau,
1971
PEEP and respiratory
system compliance
(by quintiles)
Preexisting direct or
indirect lung injury Nonpulmonary organ dysfunction
No. of quadrants
of alveolar
consolidation
on frontal chest
radiograph
Hypoxemia (PaO2/FIO2),
by quintiles
Murray et al,
1988

4. Diagnostic Criteria for ARDS
Ventilatory management of ALI & ARDS
Diagnostic Criteria for ARDS
Other Criteria
Chest Radiograph
Oxygenation
Source
PCWP <18 mm Hg
if measured or
no clinical evidence
of left atrial hypertension
Bilateral infiltrates on
frontal chest
radiography
ALI:
PaO2/FIO2 <300,
regardless of PEEP level
ARDS, PaO2/FIO2 <200,
Bernard et al,
1994

5. Acute lung injury (ALI) [PaO2/FIO2] ratio<300)
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)

6. Mechanical Ventilation in ARDS
Ventilatory management of ALI & ARDS
Mechanical Ventilation in ARDS
Injurious ventilator associated lung injury
Necessary to reverse Hypoxaemia

7. Collapsed, consolidated, less compliant areas (Dependant)
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)

8. Ventilatory management of ALI & ARDS

9. Ventilator associated lung injury:
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.

10. Lung protective ventilation in comparison with conventional approaches
Ventilatory management of ALI & ARDS
Lung protective ventilation in comparison with conventional approaches
Evidence Synthesis

11. Target intervention Tidal volume, mL/kg
Brower et al, 1999
Stewart et al, 1998
Brochard et al, 1998
Amato et al, 1998
ARDS
Network,
2000
Study Participants 52
120
116 53
861
No. 49 59 57 35
Mean age, y
≤8 vs PBW
≤8 vs IBW
6-10 vs DBW
≤6 vs. 12 ABW
6 vs. 12 PBW
Target intervention Tidal volume, mL/kg
≤30 vs. ≤45-55
≤30 vs. ≤50
25-30 vs.≤ 60
<20 vs. unlimited
≤30 vs.≤ 50
Plateau pressure, cm H2o
7.3 vs. 10.2
7.0 vs. 10.7
7.1 vs. 10.3
384 vs.
768 ‡
6.2 vs. 11.8
Actual intervention Tidal volume, ml_/kg
25 vs. 31
22 vs. 27
26 vs. 32
30 vs. 37
25 vs. 33
Plateau pressure, cm H2o
50 vs. 46
50 vs. 47
47 vs. 38
38 vs. 71.
31 vs. 40§
Outcomes mortality, %
0.61
0.72
0.38
0.001
0.007
P value

12. 3 Meta analysis of these 5 clinical trials have been performed:
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)

13. 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)

14. Lung protective ventilation strategy
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)

15. Lung protective ventilationn etiology
Ventilatory management of ALI & ARDS
Lung protective ventilationn etiology
Which method of recruitment maneuvers should be Used ?
The most well Known method of recruitment maneuver is sustained application of CPAP of 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

16. Consequences of lung protective ventilation
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

17. Further studies are needed to:
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

18. Alternative Ventilatory Approaches to Lung Protection
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.

19. Alternative Ventilatory Approaches to Lung Protection
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.

20. Adjunctive therapies to lung-protective Ventilation
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)

21. Adjunctive therapies to lung-protective Ventilation
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)

22. 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.

23. Conclusions and Future Considerations
Ventilatory management of ALI & ARDS
Conclusions and Future Considerations
mechanical ventilation, although life saving, can 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.

24. Thank you