Presentation on theme: "Ventilatory management pf acute lung injury & acute respiratory distress syndrome By Sherif G. Anis M.D."— Presentation transcript:
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 & ARDSAcute respiratory distress syndromeAcute onset of hypoxemiaBilateral Lung infiltratesAbsence of left atrial hypertensionRisk factors:Pulmonary e.g. PneumoniaNon pulmonary e.g. Pancreatitis
3 Diagnostic Criteria for ARDS Ventilatory management of ALI & ARDSDiagnostic Criteria for ARDSOther CriteriaChest RadiographOxygenationSourceImpaired pulmonarycomplianceMarked difference in inspired vs. arterial oxygen tensionsDiffuse alveolarinfiltrates on frontalchest radiographCyanosis refractoryto oxygen therapyPetty andAshbau,1971PEEP and respiratorysystem compliance(by quintiles)Preexisting direct orindirect lung injury Nonpulmonary organ dysfunctionNo. of quadrantsof alveolarconsolidationon frontal chestradiographHypoxemia (PaO2/FIO2),by quintilesMurray et al,1988
4 Diagnostic Criteria for ARDS Ventilatory management of ALI & ARDSDiagnostic Criteria for ARDSOther CriteriaChest RadiographOxygenationSourcePCWP <18 mm Hgif measured orno clinical evidenceof left atrial hypertensionBilateral infiltrates onfrontal chestradiographyALI:PaO2/FIO2 <300,regardless of PEEP levelARDS, PaO2/FIO2 <200,Bernard et al,1994
5 Acute lung injury (ALI) [PaO2/FIO2] ratio<300) Ventilatory management of ALI & ARDSAmerican European consensus conference (AECC) 1994Acute 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 & ARDSMechanical Ventilation in ARDSInjurious ventilator associated lung injuryNecessary to reverse Hypoxaemia
7 Collapsed, consolidated, less compliant areas (Dependant) Ventilatory management of ALI & ARDSThe 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)
9 Ventilator associated lung injury: Ventilatory management of ALI & ARDSVentilator associated lung injury:High inflation pressure BarotraumaOver distension VolutraumaRepetitive opening & closing of alveoliAtelect-traumaSIRS & cytokines release Biotrauma.
10 Lung protective ventilation in comparison with conventional approaches Ventilatory management of ALI & ARDSLung protective ventilation in comparison with conventional approachesEvidence Synthesis
11 Target intervention Tidal volume, mL/kg Brower et al, 1999Stewart et al, 1998Brochard et al, 1998Amato et al, 1998ARDSNetwork,2000Study Participants5212011653861No.49595735Mean age, y≤8 vs PBW≤8 vs IBW6-10 vs DBW≤6 vs. 12 ABW6 vs. 12 PBWTarget intervention Tidal volume, mL/kg≤30 vs. ≤45-55≤30 vs. ≤5025-30 vs.≤ 60<20 vs. unlimited≤30 vs.≤ 50Plateau pressure, cm H2o7.3 vs. 10.27.0 vs. 10.77.1 vs. 10.3384 vs.768 ‡6.2 vs. 11.8Actual intervention Tidal volume, ml_/kg25 vs. 3122 vs. 2726 vs. 3230 vs. 3725 vs. 33Plateau pressure, cm H2o50 vs. 4650 vs. 4747 vs. 3838 vs. 71.31 vs. 40§Outcomes mortality, %0.610.720.380.0010.007P value
12 3 Meta analysis of these 5 clinical trials have been performed: Ventilatory management of ALI & ARDS3 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 & ARDSLung protective ventilation strategyPressure & volume limitationHigher PEEPRecruitment maneuvers (Dynamic process of reopening collapsed alveoli through increase in trans pulmonary pressure)
15 Lung protective ventilationn etiology Ventilatory management of ALI & ARDSLung protective ventilationn etiologyWhich 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 secondsPeriodic recruitment with a series of traditional sigh breathsIntermittently raising PEEP over several breathsExtended sigh maneuver with step wise increase in PEEP while Vt is decreasedIntermittent application of pressure controlled ventilation with incremental high PEEP
16 Consequences of lung protective ventilation Ventilatory management of ALI & ARDSConsequences of lung protective ventilationPermissive hypercapnea (acute respiratory acidosis)TTT: increase respiratory rate in a stepwise up to 35Bicarbonate infusionincrease VtWorsened oxygenation & transient desaturationIncreased sedation or analgesiaHypotension & arrhythmiasBarotraumas (Pneumothorax)Bacterial translocation
17 Further studies are needed to: Ventilatory management of ALI & ARDSFurther studies are needed to:Inform on a clinically relevant threshold if hypercapnea,& acidosis both require interventionIncreased 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 & ARDSAlternative Ventilatory Approaches to Lung ProtectionHigh-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 & ARDSAlternative Ventilatory Approaches to Lung ProtectionAirway 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 & ARDSAdjunctive therapies to lung-protective VentilationProne 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 & ARDSAdjunctive therapies to lung-protective Ventilationinhaled 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 & ARDSConclusions and Future Considerationsmechanical ventilation, although life saving, can contribute to patient morbidity and mortalityVolume and pressure limited ventilation clearly leads to improved patient survivalThe role of recruitment maneuvers, higher levels of PEEP, or both remain controversialAt 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.