Ventilatory management pf acute lung injury

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Ventilatory management pf acute lung injury
acute respiratory distress syndrome

• By Sherif G. Anis M.D.

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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

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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
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Ventilatory management of ALI ARDS
Diagnostic Criteria for ARDS
Other Criteria Chest Radiograph Oxygenation Source
PCWP lt18 mm Hg if measured or no clinical evidence of left atrial hypertension Bilateral infiltrates on frontal chest radiography ALI PaO2/FIO2 lt300, regardless of PEEP level ARDS, PaO2/FIO2 lt200, regardless of PEEP level Bernard et al, 1994
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Ventilatory management of ALI ARDS
American European consensus conference (AECC)
1994

• Acute lung injury (ALI)
• PaO2/FIO2 ratiolt300)
• Acute Respiratory distress syndrome
• (ARDS)
• (PaO2/FIO2 ratio lt200)

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Ventilatory management of ALI ARDS

• Mechanical Ventilation in ARDS

Injurious ventilator associated lung injury
Necessary to reverse Hypoxaemia
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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)

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Ventilatory management of ALI ARDS

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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.

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Ventilatory management of ALI ARDS

• Lung protective ventilation in comparison with
  conventional approaches
• Evidence Synthesis

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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 52 Mean age, y
8 vs. 10-12 PBW 8 vs. 10-15 IBW 6-10 vs. 10-15 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 lt20 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
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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 gt 30 cmH2O, has a
  short term survival benefit. (Petruccin et al,
  2004) (Moran Jl et al, 2005)

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Ventilatory management of ALI ARDS

• One meta analysis also concluded that decreased
  tidal volume may be advantageous below a
  threshold level (lt7.7 ml/Kg BW) (Moran Jl et al,
  2005)

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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)

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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 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

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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

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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

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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.

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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.

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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)

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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)

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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.

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Ventilatory management of ALI ARDS
Conclusions and Future Considerations

1. mechanical ventilation, although life saving, can
   contribute to patient
   morbidity and mortality
2. Volume and pressure limited ventilation clearly
   leads to improved patient survival
3. The role of recruitment maneuvers, higher levels
   of PEEP, or both remain controversial
4. 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.

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Thank you