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

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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 onset of hypoxemia Acute onset of hypoxemia Bilateral Lung infiltrates Bilateral Lung infiltrates Absence of left atrial hypertension Absence of left atrial hypertension Risk factors: Risk factors: Pulmonary e.g. Pneumonia Pulmonary e.g. Pneumonia Non pulmonary e.g. Pancreatitis Non pulmonary e.g. Pancreatitis Acute respiratory distress syndrome Ventilatory management of ALI & ARDS

3 Other Criteria Chest Radiograph OxygenationSource 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, 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 Diagnostic Criteria for ARDS Ventilatory management of ALI & ARDS

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

5 Acute lung injury (ALI) Acute lung injury (ALI) [PaO2/FIO2] ratio<300) [PaO2/FIO2] ratio<300) Acute Respiratory distress syndrome Acute Respiratory distress syndrome (ARDS): (ARDS): (PaO2/FIO2 ratio <200) (PaO2/FIO2 ratio <200) Ventilatory management of ALI & ARDS American European consensus conference (AECC) 1994

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

7 The lung with ALI or ARDS are particularly prone to ventilator associated lung injury: (Baby lung) The lung with ALI or ARDS are particularly prone to ventilator associated lung injury: (Baby lung) Collapsed, consolidated, less compliant areas (Dependant) Collapsed, consolidated, less compliant areas (Dependant) Normal areas (non dependant) Normal areas (non dependant) Ventilatory management of ALI & ARDS

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9 Ventilator associated lung injury: Ventilator associated lung injury: High inflation pressure Barotrauma High inflation pressure Barotrauma Over distension Volutrauma Over distension Volutrauma Repetitive opening & closing of alveoli Repetitive opening & closing of alveoli Atelect-trauma Atelect-trauma SIRS & cytokines release Biotrauma. SIRS & cytokines release Biotrauma. Ventilatory management of ALI & ARDS

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

11 Brower et al, 1999 Stewart et al, 1998 Brochard et al, 1998 Amato et al, 1998 ARDSNetwork,2000 Study Participants No 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 vs vs. 60 <20 vs. unlimited 30 vs. 50 Plateau pressure, cm H2o 7.3 vs vs vs vs vs Actual intervention Tidal volume, ml_/kg 25 vs vs vs vs vs. 33 Plateau pressure, cm H2o 50 vs vs vs vs vs. 40§ Outcomes mortality, % P value

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

13 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) 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

14 Pressure & volume limitation Pressure & volume limitation Higher PEEP Higher PEEP Recruitment maneuvers (Dynamic process of reopening collapsed alveoli through increase in trans pulmonary pressure) Recruitment maneuvers (Dynamic process of reopening collapsed alveoli through increase in trans pulmonary pressure) Lung protective ventilation strategy Ventilatory management of ALI & ARDS

15 Which method of recruitment maneuvers should be Used ? Which method of recruitment maneuvers should be Used ? 1. The most well Known method of recruitment maneuver is sustained application of CPAP of Cm H2O for 30 seconds 2. Periodic recruitment with a series of traditional sigh breaths 3. Intermittently raising PEEP over several breaths 4. Extended sigh maneuver with step wise increase in PEEP while Vt is decreased 5. Intermittent application of pressure controlled ventilation with incremental high PEEP Lung protective ventilationn etiology Ventilatory management of ALI & ARDS

16 Permissive hypercapnea (acute respiratory acidosis) Permissive hypercapnea (acute respiratory acidosis) TTT: increase respiratory rate in a stepwise up to 35 TTT: increase respiratory rate in a stepwise up to 35 Bicarbonate infusion Bicarbonate infusion increase Vt increase Vt Worsened oxygenation & transient desaturation Worsened oxygenation & transient desaturation Increased sedation or analgesia Increased sedation or analgesia Hypotension & arrhythmias Hypotension & arrhythmias Barotraumas (Pneumothorax) Barotraumas (Pneumothorax) Bacterial translocation Bacterial translocation Consequences of lung protective ventilation Ventilatory management of ALI & ARDS

17 Further studies are needed to: Further studies are needed to: Inform on a clinically relevant threshold if hypercapnea, Inform on a clinically relevant threshold if hypercapnea, & acidosis both require intervention & acidosis both require intervention Increased sedation & analgesic effects (Kahn JM & colleagues, 2005 show no increase in sedation use in low tidal volume ventilation) Increased sedation & analgesic effects (Kahn JM & colleagues, 2005 show no increase in sedation use in low tidal volume ventilation) Safety of recruitment maneuvers Safety of recruitment maneuvers Ventilatory management of ALI & ARDS

18 High-frequency ventilation (jet, oscillation, and percussive ventilation) 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. HFOV allows for higher mean airway pressures & markedly reduced tidal volumes (1-3 ml/kg) Lung recruitment & reduce lung injury. Alternative Ventilatory Approaches to Lung Protection Ventilatory management of ALI & ARDS

19 Airway pressure release ventilation (APRV) 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 T high & short T low with spontaneous breathing during both. It provides two levels of airway pressure (P high & P low ) during two time periods (T high & T low ), usually a long T high & short T low with spontaneous breathing during both. Advantages: Decrease barotrauma, provide better V/P matching, cardiac filling & patient comfort. Ventilatory management of ALI & ARDS Alternative Ventilatory Approaches to Lung Protection

20 Prone positioning: 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 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) (Pelozi P et al, 2002) Adjunctive therapies to lung-protective Ventilation Ventilatory management of ALI & ARDS

21 inhaled nitric oxide : 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) Selective VD in ventilated lung units improving V/Q mismatch, decrease PaO2 & pulmonary hypertension ( no sustained clinical benefit) (Tayler RW et al, 2004) Adjunctive therapies to lung-protective Ventilation Ventilatory management of ALI & ARDS

22 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. 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

23 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 re ­ cruitment 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. Conclusions and Future Considerations Ventilatory management of ALI & ARDS

24 Thank you


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